{-# LANGUAGE BangPatterns #-}
{-# LANGUAGE DeriveFunctor #-}
{-# LANGUAGE DeriveGeneric #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE DeriveDataTypeable #-}
{-# LANGUAGE NoImplicitPrelude #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE RecordWildCards #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE TupleSections #-}
{-# LANGUAGE MultiWayIf #-}
module Pantry.Types
  ( PantryConfig (..)
  , HackageSecurityConfig (..)
  , Storage (..)
  , HasPantryConfig (..)
  , BlobKey (..)
  , PackageName
  , Version
  , PackageIdentifier (..)
  , Revision (..)
  , ModuleName
  , CabalFileInfo (..)
  , PrintWarnings (..)
  , PackageNameP (..)
  , VersionP (..)
  , ModuleNameP (..)
  , PackageIdentifierRevision (..)
  , pirForHash
  , FileType (..)
  , BuildFile (..)
  , FileSize (..)
  , TreeEntry (..)
  , SafeFilePath
  , unSafeFilePath
  , mkSafeFilePath
  , safeFilePathtoPath
  , hpackSafeFilePath
  , TreeKey (..)
  , Tree (..)
  , renderTree
  , parseTree
  , parseTreeM
  , SHA256
  , Unresolved
  , resolvePaths
  , Package (..)
  , PackageCabal (..)
  , PHpack (..)
  -- , PackageTarball (..)
  , RawPackageLocation (..)
  , PackageLocation (..)
  , toRawPL
  , RawPackageLocationImmutable (..)
  , PackageLocationImmutable (..)
  , toRawPLI
  , RawArchive (..)
  , Archive (..)
  , toRawArchive
  , Repo (..)
  , RepoType (..)
  , parsePackageIdentifier
  , parsePackageName
  , parsePackageNameThrowing
  , parseFlagName
  , parseVersion
  , parseVersionThrowing
  , packageIdentifierString
  , packageNameString
  , flagNameString
  , versionString
  , moduleNameString
  , OptionalSubdirs (..)
  , ArchiveLocation (..)
  , RelFilePath (..)
  , CabalString (..)
  , toCabalStringMap
  , unCabalStringMap
  , parsePackageIdentifierRevision
  , Mismatch (..)
  , PantryException (..)
  , FuzzyResults (..)
  , ResolvedPath (..)
  , HpackExecutable (..)
  , WantedCompiler (..)
  --, resolveSnapshotLocation
  , snapshotLocation
  , defaultSnapshotLocation
  , SnapName (..)
  , parseSnapName
  , RawSnapshotLocation (..)
  , SnapshotLocation (..)
  , toRawSL
  , parseHackageText
  , parseRawSnapshotLocation
  , RawSnapshotLayer (..)
  , SnapshotLayer (..)
  , toRawSnapshotLayer
  , RawSnapshot (..)
  , Snapshot (..)
  , RawSnapshotPackage (..)
  , SnapshotPackage (..)
  , parseWantedCompiler
  , RawPackageMetadata (..)
  , PackageMetadata (..)
  , toRawPM
  , cabalFileName
  , SnapshotCacheHash (..)
  , getGlobalHintsFile
  , bsToBlobKey
  , warnMissingCabalFile
  ) where

import RIO
import qualified Data.Conduit.Tar as Tar
import qualified RIO.Text as T
import qualified RIO.ByteString as B
import qualified RIO.ByteString.Lazy as BL
import RIO.List (intersperse)
import RIO.Time (toGregorian, Day, UTCTime)
import qualified RIO.Map as Map
import qualified RIO.HashMap as HM
import qualified Data.Map.Strict as Map (mapKeysMonotonic)
import qualified RIO.Set as Set
import Data.Aeson (ToJSON (..), FromJSON (..), withText, FromJSONKey (..))
import Data.Aeson.Types (ToJSONKey (..) ,toJSONKeyText, Parser)
import Pantry.Internal.AesonExtended
import Data.Aeson.Encoding.Internal (unsafeToEncoding)
import Data.ByteString.Builder (toLazyByteString, byteString, wordDec)
import Database.Persist
import Database.Persist.Sql
import Pantry.SHA256 (SHA256)
import qualified Pantry.SHA256 as SHA256
import qualified Distribution.Compat.CharParsing as Parse
import Distribution.CabalSpecVersion (CabalSpecVersion (..), cabalSpecLatest)
import Distribution.Parsec (PError (..), PWarning (..), showPos, parsec, explicitEitherParsec, ParsecParser)
import Distribution.Types.PackageName (PackageName, unPackageName, mkPackageName)
import Distribution.Types.VersionRange (VersionRange)
import Distribution.PackageDescription (FlagName, unFlagName, GenericPackageDescription)
import Distribution.Types.PackageId (PackageIdentifier (..))
import qualified Distribution.Pretty
import qualified Distribution.Text
import qualified Hpack.Config as Hpack
import Distribution.ModuleName (ModuleName)
import Distribution.Types.Version (Version, mkVersion, nullVersion)
import Network.HTTP.Client (parseRequest)
import Network.HTTP.Types (Status, statusCode)
import Data.Text.Read (decimal)
import Path (Path, Abs, Dir, File, toFilePath, filename, (</>), parseRelFile)
import Path.IO (resolveFile, resolveDir)
import Data.List.NonEmpty (NonEmpty)
import qualified Data.List.NonEmpty as NE
import Casa.Client (CasaRepoPrefix)

-- | Parsed tree with more information on the Haskell package it contains.
--
-- @since 0.1.0.0
data Package = Package
  { packageTreeKey :: !TreeKey
  -- ^ The 'TreeKey' containing this package.
  --
  -- This is a hash of the binary representation of 'packageTree'.
  --
  -- @since 0.1.0.0
  , packageTree :: !Tree
  -- ^ The 'Tree' containing this package.
  --
  -- @since 0.1.0.0
  , packageCabalEntry :: !PackageCabal
  -- ^ Information on the cabal file inside this package.
  --
  -- @since 0.1.0.0
  , packageIdent :: !PackageIdentifier
  -- ^ The package name and version in this package.
  --
  -- @since 0.1.0.0
  }
  deriving (Show, Eq)

data PHpack = PHpack
    {
      phOriginal :: !TreeEntry, -- ^ Original hpack file
      phGenerated :: !TreeEntry, -- ^ Generated Cabal file
      phVersion :: !Version -- ^ Version of Hpack used
    } deriving (Show, Eq)

data PackageCabal = PCCabalFile !TreeEntry -- ^ TreeEntry of Cabal file
                  | PCHpack !PHpack
                  deriving (Show, Eq)

cabalFileName :: PackageName -> SafeFilePath
cabalFileName name =
  case mkSafeFilePath $ T.pack (packageNameString name) <> ".cabal" of
    Nothing -> error $ "cabalFileName: failed for " ++ show name
    Just sfp -> sfp

-- | The revision number of a package from Hackage, counting upwards
-- from 0 (the original cabal file).
--
-- See caveats on 'CFIRevision'.
--
-- @since 0.1.0.0
newtype Revision = Revision Word
    deriving (Generic, Show, Eq, NFData, Data, Typeable, Ord, Hashable, Display, PersistField, PersistFieldSql)

-- | Represents a SQL database connection. This used to be a newtype
-- wrapper around a connection pool. However, when investigating
-- <https://github.com/commercialhaskell/stack/issues/4471>, it
-- appeared that holding a pool resulted in overly long write locks
-- being held on the database. As a result, we now abstract away
-- whether a pool is used, and the default implementation in
-- "Pantry.Storage" does not use a pool.
data Storage = Storage
  { withStorage_ :: forall env a. HasLogFunc env => ReaderT SqlBackend (RIO env) a -> RIO env a
  , withWriteLock_ :: forall env a. HasLogFunc env => RIO env a -> RIO env a
  }

-- | Configuration value used by the entire pantry package. Create one
-- using @withPantryConfig@. See also @PantryApp@ for a convenience
-- approach to using pantry.
--
-- @since 0.1.0.0
data PantryConfig = PantryConfig
  { pcHackageSecurity :: !HackageSecurityConfig
  , pcHpackExecutable :: !HpackExecutable
  , pcRootDir :: !(Path Abs Dir)
  , pcStorage :: !Storage
  , pcUpdateRef :: !(MVar Bool)
  -- ^ Want to try updating the index once during a single run for missing
  -- package identifiers. We also want to ensure we only update once at a
  -- time. Start at @True@.
  , pcParsedCabalFilesRawImmutable :: !(IORef (Map RawPackageLocationImmutable GenericPackageDescription))
  -- ^ Cache of previously parsed cabal files, to save on slow parsing time.
  , pcParsedCabalFilesMutable ::
      !(IORef
        (Map
         (Path Abs Dir)
         (PrintWarnings -> IO GenericPackageDescription, PackageName, Path Abs File)
        )
       )
  -- ^ Cache for mutable packages. We want to allow for an optimization:
  -- deferring parsing of the 'GenericPackageDescription' until its actually
  -- needed. Therefore, we keep the filepath and the 'PackageName' derived from
  -- that filepath. When the @IO GenericPackageDescription@ is run, it will
  -- ensure that the @PackageName@ matches the value inside the cabal file, and
  -- print out any warnings that still need to be printed.
  , pcConnectionCount :: !Int
  -- ^ concurrently open downloads
  , pcCasaRepoPrefix :: !CasaRepoPrefix
  -- ^ The pull URL e.g. @https://casa.fpcomplete.com/v1/pull@
  , pcCasaMaxPerRequest :: !Int
  -- ^ Maximum blobs sent per pull request.
  , pcSnapshotLocation :: SnapName -> RawSnapshotLocation
  -- ^ The location of snapshot synonyms
  }

-- | Get the location of a snapshot synonym from the 'PantryConfig'.
--
-- @since 0.5.0.0
snapshotLocation :: HasPantryConfig env => SnapName -> RIO env RawSnapshotLocation
snapshotLocation name = do
  loc <- view $ pantryConfigL.to pcSnapshotLocation
  pure $ loc name

-- | Should we print warnings when loading a cabal file?
--
-- @since 0.1.0.0
data PrintWarnings = YesPrintWarnings | NoPrintWarnings

-- | Wraps a value which potentially contains relative paths. Needs to
-- be provided with a base directory to resolve these paths.
--
-- Unwrap this using 'resolvePaths'.
--
-- @since 0.1.0.0
newtype Unresolved a = Unresolved (Maybe (Path Abs Dir) -> IO a)
  deriving Functor
instance Applicative Unresolved where
  pure = Unresolved . const . pure
  Unresolved f <*> Unresolved x = Unresolved $ \mdir -> f mdir <*> x mdir

-- | Resolve all of the file paths in an 'Unresolved' relative to the
-- given directory.
--
-- @since 0.1.0.0
resolvePaths
  :: MonadIO m
  => Maybe (Path Abs Dir) -- ^ directory to use for relative paths
  -> Unresolved a
  -> m a
resolvePaths mdir (Unresolved f) = liftIO (f mdir)

-- | A combination of the relative path provided in a config file,
-- together with the resolved absolute path.
--
-- @since 0.1.0.0
data ResolvedPath t = ResolvedPath
  { resolvedRelative :: !RelFilePath
  -- ^ Original value parsed from a config file.
  , resolvedAbsolute :: !(Path Abs t)
  -- ^ Absolute path resolved against base directory loaded from.
  }
  deriving (Show, Eq, Generic, Ord)
instance NFData (ResolvedPath t)

-- | Location to load a package from. Can either be immutable (see
-- 'PackageLocationImmutable') or a local directory which is expected
-- to change over time. Raw version doesn't include exact package
-- version (e.g. could refer to the latest revision on Hackage)
--
-- @since 0.1.0.0
data RawPackageLocation
  = RPLImmutable !RawPackageLocationImmutable
  | RPLMutable !(ResolvedPath Dir)
  deriving (Show, Eq, Generic)
instance NFData RawPackageLocation

-- | Location to load a package from. Can either be immutable (see
-- 'PackageLocationImmutable') or a local directory which is expected
-- to change over time.
--
-- @since 0.1.0.0
data PackageLocation
  = PLImmutable !PackageLocationImmutable
  | PLMutable !(ResolvedPath Dir)
  deriving (Show, Eq, Generic)
instance NFData PackageLocation

instance Display PackageLocation where
  display (PLImmutable loc) = display loc
  display (PLMutable fp) = fromString $ toFilePath $ resolvedAbsolute fp

-- | Convert `PackageLocation` to its "raw" equivalent
--
-- @since 0.1.0.0
toRawPL :: PackageLocation -> RawPackageLocation
toRawPL (PLImmutable im) = RPLImmutable (toRawPLI im)
toRawPL (PLMutable m) = RPLMutable m

-- | Location for remote packages or archives assumed to be immutable.
-- as user specifies it i.e. not an exact location
--
-- @since 0.1.0.0
data RawPackageLocationImmutable
  = RPLIHackage !PackageIdentifierRevision !(Maybe TreeKey)
  | RPLIArchive !RawArchive !RawPackageMetadata
  | RPLIRepo    !Repo !RawPackageMetadata
  deriving (Show, Eq, Ord, Generic)

instance NFData RawPackageLocationImmutable

instance Display RawPackageLocationImmutable where
  display (RPLIHackage pir _tree) = display pir <> " (from Hackage)"
  display (RPLIArchive archive _pm) =
    "Archive from " <> display (raLocation archive) <>
    (if T.null $ raSubdir archive
       then mempty
       else " in subdir " <> display (raSubdir archive))
  display (RPLIRepo repo _pm) =
    "Repo from " <> display (repoUrl repo) <>
    ", commit " <> display (repoCommit repo) <>
    (if T.null $ repoSubdir repo
       then mempty
       else " in subdir " <> display (repoSubdir repo))

-- | Location for remote packages or archives assumed to be immutable.
--
-- @since 0.1.0.0
data PackageLocationImmutable
  = PLIHackage !PackageIdentifier !BlobKey !TreeKey
  | PLIArchive !Archive !PackageMetadata
  | PLIRepo    !Repo !PackageMetadata
  deriving (Generic, Show, Eq, Ord, Typeable)
instance NFData PackageLocationImmutable

instance Display PackageLocationImmutable where
  display (PLIHackage ident _cabalHash _tree) =
    fromString (packageNameString $ pkgName ident) <> " (from Hackage)"
  display (PLIArchive archive _pm) =
    "Archive from " <> display (archiveLocation archive) <>
    (if T.null $ archiveSubdir archive
       then mempty
       else " in subdir " <> display (archiveSubdir archive))
  display (PLIRepo repo _pm) =
    "Repo from " <> display (repoUrl repo) <>
    ", commit " <> display (repoCommit repo) <>
    (if T.null $ repoSubdir repo
       then mempty
       else " in subdir " <> display (repoSubdir repo))

instance ToJSON PackageLocationImmutable where
  toJSON = toJSON . toRawPLI

-- | Package identifier and revision with a specified cabal file hash
--
-- @since 0.1.0.0
pirForHash :: PackageIdentifier -> BlobKey -> PackageIdentifierRevision
pirForHash (PackageIdentifier name ver) (BlobKey sha size') =
  let cfi = CFIHash sha (Just size')
  in PackageIdentifierRevision name ver cfi

-- | Convert `PackageLocationImmutable` to its "raw" equivalent
--
-- @since 0.1.0.0
toRawPLI :: PackageLocationImmutable -> RawPackageLocationImmutable
toRawPLI (PLIHackage ident cfKey treeKey) = RPLIHackage (pirForHash ident cfKey) (Just treeKey)
toRawPLI (PLIArchive archive pm) = RPLIArchive (toRawArchive archive) (toRawPM pm)
toRawPLI (PLIRepo repo pm) = RPLIRepo repo (toRawPM pm)

-- | A raw package archive, specified by a user, could have no
-- hash and file size information.
--
-- @since 0.1.0.0
data RawArchive = RawArchive
  { raLocation :: !ArchiveLocation
  -- ^ Location of the archive
  --
  -- @since 0.1.0.0
  , raHash :: !(Maybe SHA256)
  -- ^ Cryptographic hash of the archive file
  --
  -- @since 0.1.0.0
  , raSize :: !(Maybe FileSize)
  -- ^ Size of the archive file
  --
  -- @since 0.1.0.0
  , raSubdir :: !Text
  -- ^ Subdirectory within the archive to get the package from.
  --
  -- @since 0.1.0.0
  }
    deriving (Generic, Show, Eq, Ord, Typeable)

instance NFData RawArchive

-- | A package archive, could be from a URL or a local file
-- path. Local file path archives are assumed to be unchanging
-- over time, and so are allowed in custom snapshots.
--
-- @since 0.1.0.0
data Archive = Archive
  { archiveLocation :: !ArchiveLocation
  -- ^ Location of the archive
  --
  -- @since 0.1.0.0
  , archiveHash :: !SHA256
  -- ^ Cryptographic hash of the archive file
  --
  -- @since 0.1.0.0
  , archiveSize :: !FileSize
  -- ^ Size of the archive file
  --
  -- @since 0.1.0.0
  , archiveSubdir :: !Text
  -- ^ Subdirectory within the archive to get the package from.
  --
  -- @since 0.1.0.0
  }
    deriving (Generic, Show, Eq, Ord, Typeable)
instance NFData Archive

-- | Convert archive to its "raw" equivalent.
--
-- @since 0.1.0.0
toRawArchive :: Archive -> RawArchive
toRawArchive archive =
  RawArchive (archiveLocation archive) (Just $ archiveHash archive)
             (Just $ archiveSize archive) (archiveSubdir archive)

-- | The type of a source control repository.
--
-- @since 0.1.0.0
data RepoType = RepoGit | RepoHg
    deriving (Generic, Show, Eq, Ord, Typeable)
instance NFData RepoType
instance PersistField RepoType where
  toPersistValue RepoGit = toPersistValue (1 :: Int32)
  toPersistValue RepoHg = toPersistValue (2 :: Int32)
  fromPersistValue v = do
    i <- fromPersistValue v
    case i :: Int32 of
      1 -> pure RepoGit
      2 -> pure RepoHg
      _ -> Left $ fromString $ "Invalid RepoType: " ++ show i
instance PersistFieldSql RepoType where
  sqlType _ = SqlInt32

-- | Information on packages stored in a source control repository.
--
-- @since 0.1.0.0
data Repo = Repo
  { repoUrl :: !Text
    -- ^ Location of the repo
    --
    -- @since 0.1.0.0
  , repoCommit :: !Text
    -- ^ Commit to use from the repo. It's strongly recommended to use
    -- a hash instead of a tag or branch name.
    --
    -- @since 0.1.0.0
  , repoType :: !RepoType
    -- ^ The type of the repo
    --
    -- @since 0.1.0.0
  , repoSubdir :: !Text
    -- ^ Subdirectory within the archive to get the package from.
    --
    -- @since 0.1.0.0
  }
    deriving (Generic, Eq, Ord, Typeable)
instance NFData Repo
instance Show Repo where
  show = T.unpack . utf8BuilderToText . display
instance Display Repo where
  display (Repo url commit typ subdir) =
    (case typ of
       RepoGit -> "Git"
       RepoHg -> "Mercurial") <>
    " repo at " <>
    display url <>
    ", commit " <>
    display commit <>
    (if T.null subdir
      then mempty
      else " in subdirectory " <> display subdir)


-- An unexported newtype wrapper to hang a 'FromJSON' instance off of. Contains
-- a GitHub user and repo name separated by a forward slash, e.g. "foo/bar".
newtype GitHubRepo = GitHubRepo Text

instance FromJSON GitHubRepo where
    parseJSON = withText "GitHubRepo" $ \s -> do
        case T.split (== '/') s of
            [x, y] | not (T.null x || T.null y) -> return (GitHubRepo s)
            _ -> fail "expecting \"user/repo\""

-- | Configuration for Hackage Security to securely download package
-- metadata and contents from Hackage. For most purposes, you'll want
-- to use the default Hackage settings via
-- @defaultHackageSecurityConfig@.
--
-- /NOTE/ It's highly recommended to only use the official Hackage
-- server or a mirror. See
-- <https://github.com/commercialhaskell/stack/issues/4137>.
--
-- @since 0.1.0.0
data HackageSecurityConfig = HackageSecurityConfig
  { hscKeyIds :: ![Text]
  , hscKeyThreshold :: !Int
  , hscDownloadPrefix :: !Text
  , hscIgnoreExpiry :: !Bool
  }
  deriving Show
instance FromJSON (WithJSONWarnings HackageSecurityConfig) where
  parseJSON = withObjectWarnings "HackageSecurityConfig" $ \o' -> do
    hscDownloadPrefix <- o' ..: "download-prefix"
    Object o <- o' ..: "hackage-security"
    hscKeyIds <- o ..: "keyids"
    hscKeyThreshold <- o ..: "key-threshold"
    hscIgnoreExpiry <- o ..:? "ignore-expiry" ..!= True
    pure HackageSecurityConfig {..}


-- | An environment which contains a 'PantryConfig'.
--
-- @since 0.1.0.0
class HasPantryConfig env where
  -- | Lens to get or set the 'PantryConfig'
  --
  -- @since 0.1.0.0
  pantryConfigL :: Lens' env PantryConfig


-- | File size in bytes
--
-- @since 0.1.0.0
newtype FileSize = FileSize Word
  deriving (Show, Eq, Ord, Typeable, Generic, Display, Hashable, NFData, PersistField, PersistFieldSql, ToJSON, FromJSON)

-- | A key for looking up a blob, which combines the SHA256 hash of
-- the contents and the file size.
--
-- The file size may seem redundant with the hash. However, it is
-- necessary for safely downloading blobs from an untrusted
-- source. See
-- <https://www.fpcomplete.com/blog/2018/07/pantry-part-2-trees-keys>.
--
-- @since 0.1.0.0
data BlobKey = BlobKey !SHA256 !FileSize
  deriving (Eq, Ord, Typeable, Generic)
instance NFData BlobKey

instance Show BlobKey where
  show = T.unpack . utf8BuilderToText . display
instance Display BlobKey where
  display (BlobKey sha size') = display sha <> "," <> display size'

blobKeyPairs :: BlobKey -> [(Text, Value)]
blobKeyPairs (BlobKey sha size') =
    [ "sha256" .= sha
    , "size" .= size'
    ]

instance ToJSON BlobKey where
  toJSON = object . blobKeyPairs
instance FromJSON BlobKey where
  parseJSON = withObject "BlobKey" $ \o -> BlobKey
    <$> o .: "sha256"
    <*> o .: "size"

newtype PackageNameP = PackageNameP { unPackageNameP :: PackageName }
  deriving (Eq, Ord, Show, Read, NFData)
instance Display PackageNameP where
  display = fromString . packageNameString . unPackageNameP
instance PersistField PackageNameP where
  toPersistValue (PackageNameP pn) = PersistText $ T.pack $ packageNameString pn
  fromPersistValue v = do
    str <- fromPersistValue v
    case parsePackageName str of
      Nothing -> Left $ "Invalid package name: " <> T.pack str
      Just pn -> Right $ PackageNameP pn
instance PersistFieldSql PackageNameP where
  sqlType _ = SqlString
instance ToJSON PackageNameP where
  toJSON (PackageNameP pn) = String $ T.pack $ packageNameString pn
instance FromJSON PackageNameP where
  parseJSON = withText "PackageNameP" $ pure . PackageNameP . mkPackageName . T.unpack
instance ToJSONKey PackageNameP where
  toJSONKey =
    ToJSONKeyText
      (T.pack . packageNameString . unPackageNameP)
      (unsafeToEncoding . getUtf8Builder . display)
instance FromJSONKey PackageNameP where
  fromJSONKey = FromJSONKeyText $ PackageNameP . mkPackageName . T.unpack

newtype VersionP = VersionP { unVersionP :: Version }
  deriving (Eq, Ord, Show, Read, NFData)
instance PersistField VersionP where
  toPersistValue (VersionP v) = PersistText $ T.pack $ versionString v
  fromPersistValue v = do
    str <- fromPersistValue v
    case parseVersion str of
      Nothing -> Left $ "Invalid version number: " <> T.pack str
      Just ver -> Right $ VersionP ver
instance PersistFieldSql VersionP where
  sqlType _ = SqlString
instance Display VersionP where
  display (VersionP v) = fromString $ versionString v
instance ToJSON VersionP where
  toJSON (VersionP v) = String $ T.pack $ versionString v
instance FromJSON VersionP where
  parseJSON =
    withText "VersionP" $
    either (fail . displayException) (pure . VersionP) . parseVersionThrowing . T.unpack

newtype ModuleNameP = ModuleNameP
  { unModuleNameP :: ModuleName
  } deriving (Eq, Ord, Show, NFData)
instance Display ModuleNameP where
  display = fromString . moduleNameString . unModuleNameP
instance PersistField ModuleNameP where
  toPersistValue (ModuleNameP mn) = PersistText $ T.pack $ moduleNameString mn
  fromPersistValue v = do
    str <- fromPersistValue v
    case parseModuleName str of
      Nothing -> Left $ "Invalid module name: " <> T.pack str
      Just pn -> Right $ ModuleNameP pn
instance PersistFieldSql ModuleNameP where
  sqlType _ = SqlString

-- | How to choose a cabal file for a package from Hackage. This is to
-- work with Hackage cabal file revisions, which makes
-- @PackageIdentifier@ insufficient for specifying a package from
-- Hackage.
--
-- @since 0.1.0.0
data CabalFileInfo
  = CFILatest
  -- ^ Take the latest revision of the cabal file available. This
  -- isn't reproducible at all, but the running assumption (not
  -- necessarily true) is that cabal file revisions do not change
  -- semantics of the build.
  --
  -- @since 0.1.0.0
  | CFIHash !SHA256 !(Maybe FileSize)
  -- ^ Identify by contents of the cabal file itself. Only reason for
  -- @Maybe@ on @FileSize@ is for compatibility with input that
  -- doesn't include the file size.
  --
  -- @since 0.1.0.0
  | CFIRevision !Revision
  -- ^ Identify by revision number, with 0 being the original and
  -- counting upward. This relies on Hackage providing consistent
  -- versioning. @CFIHash@ should be preferred wherever possible for
  -- reproducibility.
  --
  -- @since 0.1.0.0
    deriving (Generic, Show, Eq, Ord, Typeable)
instance NFData CabalFileInfo
instance Hashable CabalFileInfo

instance Display CabalFileInfo where
  display CFILatest = mempty
  display (CFIHash hash' msize) =
    "@sha256:" <> display hash' <> maybe mempty (\i -> "," <> display i) msize
  display (CFIRevision rev) = "@rev:" <> display rev

-- | A full specification for a package from Hackage, including the
-- package name, version, and how to load up the correct cabal file
-- revision.
--
-- @since 0.1.0.0
data PackageIdentifierRevision = PackageIdentifierRevision !PackageName !Version !CabalFileInfo
  deriving (Generic, Eq, Ord, Typeable)
instance NFData PackageIdentifierRevision

instance Show PackageIdentifierRevision where
  show = T.unpack . utf8BuilderToText . display

instance Display PackageIdentifierRevision where
  display (PackageIdentifierRevision name version cfi) =
    fromString (packageNameString name) <> "-" <> fromString (versionString version) <> display cfi

instance ToJSON PackageIdentifierRevision where
  toJSON = toJSON . utf8BuilderToText . display
instance FromJSON PackageIdentifierRevision where
  parseJSON = withText "PackageIdentifierRevision" $ \t ->
    case parsePackageIdentifierRevision t of
      Left e -> fail $ show e
      Right pir -> pure pir

-- | Parse a hackage text.
--
-- @since 0.1.0.0
parseHackageText :: Text -> Either PantryException (PackageIdentifier, BlobKey)
parseHackageText t =
  either (\x -> error (show x) $ const $ Left $ PackageIdentifierRevisionParseFail t) Right $
  explicitEitherParsec (hackageTextParsec <* Parse.eof) $
  T.unpack t

hackageTextParsec :: ParsecParser (PackageIdentifier, BlobKey)
hackageTextParsec = do
  ident <- packageIdentifierParsec
  _ <- Parse.string "@sha256:"

  shaT <- Parse.munch (/= ',')
  sha <- either (const mzero) pure $ SHA256.fromHexText $ fromString shaT

  _ <- Parse.char ','
  size' <- Parse.integral -- FIXME probably need to handle overflow, since unfortunately Cabal doesn't
  pure (ident, BlobKey sha (FileSize size'))

splitColon :: Text -> Maybe (Text, Text)
splitColon t' =
    let (x, y) = T.break (== ':') t'
     in (x, ) <$> T.stripPrefix ":" y

-- | Parse a 'PackageIdentifierRevision'
--
-- @since 0.1.0.0
parsePackageIdentifierRevision :: Text -> Either PantryException PackageIdentifierRevision
parsePackageIdentifierRevision t = maybe (Left $ PackageIdentifierRevisionParseFail t) Right $ do
  let (identT, cfiT) = T.break (== '@') t
  PackageIdentifier name version <- parsePackageIdentifier $ T.unpack identT
  cfi <-
    case splitColon cfiT of
      Just ("@sha256", shaSizeT) -> do
        let (shaT, sizeT) = T.break (== ',') shaSizeT
        sha <- either (const Nothing) Just $ SHA256.fromHexText shaT
        msize <-
          case T.stripPrefix "," sizeT of
            Nothing -> Just Nothing
            Just sizeT' ->
              case decimal sizeT' of
                Right (size', "") -> Just $ Just $ FileSize size'
                _ -> Nothing
        pure $ CFIHash sha msize
      Just ("@rev", revT) ->
        case decimal revT of
          Right (rev, "") -> pure $ CFIRevision $ Revision rev
          _ -> Nothing
      Nothing -> pure CFILatest
      _ -> Nothing
  pure $ PackageIdentifierRevision name version cfi

data Mismatch a = Mismatch
  { mismatchExpected :: !a
  , mismatchActual :: !a
  }

-- | Things that can go wrong in pantry. Note two things:
--
-- * Many other exception types may be thrown from underlying
--   libraries. Pantry does not attempt to wrap these underlying
--   exceptions.
--
-- * We may add more constructors to this data type in minor version
--   bumps of pantry. This technically breaks the PVP. You should not
--   be writing pattern matches against this type that expect total
--   matching.
--
-- @since 0.1.0.0
data PantryException
  = PackageIdentifierRevisionParseFail !Text
  | InvalidCabalFile
      !(Either RawPackageLocationImmutable (Path Abs File))
      !(Maybe Version)
      ![PError]
      ![PWarning]
  | TreeWithoutCabalFile !RawPackageLocationImmutable
  | TreeWithMultipleCabalFiles !RawPackageLocationImmutable ![SafeFilePath]
  | MismatchedCabalName !(Path Abs File) !PackageName
  | NoCabalFileFound !(Path Abs Dir)
  | MultipleCabalFilesFound !(Path Abs Dir) ![Path Abs File]
  | InvalidWantedCompiler !Text
  | InvalidSnapshotLocation !(Path Abs Dir) !Text
  | InvalidOverrideCompiler !WantedCompiler !WantedCompiler
  | InvalidFilePathSnapshot !Text
  | InvalidSnapshot !RawSnapshotLocation !SomeException
  | MismatchedPackageMetadata
      !RawPackageLocationImmutable
      !RawPackageMetadata
      !(Maybe TreeKey)
      !PackageIdentifier
  | Non200ResponseStatus !Status
  | InvalidBlobKey !(Mismatch BlobKey)
  | Couldn'tParseSnapshot !RawSnapshotLocation !String
  | WrongCabalFileName !RawPackageLocationImmutable !SafeFilePath !PackageName
  | DownloadInvalidSHA256 !Text !(Mismatch SHA256)
  | DownloadInvalidSize !Text !(Mismatch FileSize)
  | DownloadTooLarge !Text !(Mismatch FileSize)
  -- ^ Different from 'DownloadInvalidSize' since 'mismatchActual' is
  -- a lower bound on the size from the server.
  | LocalInvalidSHA256 !(Path Abs File) !(Mismatch SHA256)
  | LocalInvalidSize !(Path Abs File) !(Mismatch FileSize)
  | UnknownArchiveType !ArchiveLocation
  | InvalidTarFileType !ArchiveLocation !FilePath !Tar.FileType
  | UnsupportedTarball !ArchiveLocation !Text
  | NoHackageCryptographicHash !PackageIdentifier
  | FailedToCloneRepo !Repo
  | TreeReferencesMissingBlob !RawPackageLocationImmutable !SafeFilePath !BlobKey
  | CompletePackageMetadataMismatch !RawPackageLocationImmutable !PackageMetadata
  | CRC32Mismatch !ArchiveLocation !FilePath !(Mismatch Word32)
  | UnknownHackagePackage !PackageIdentifierRevision !FuzzyResults
  | CannotCompleteRepoNonSHA1 !Repo
  | MutablePackageLocationFromUrl !Text
  | MismatchedCabalFileForHackage !PackageIdentifierRevision !(Mismatch PackageIdentifier)
  | PackageNameParseFail !Text
  | PackageVersionParseFail !Text
  | InvalidCabalFilePath !(Path Abs File)
  | DuplicatePackageNames !Utf8Builder ![(PackageName, [RawPackageLocationImmutable])]
  | MigrationFailure !Text !(Path Abs File) !SomeException
  | InvalidTreeFromCasa !BlobKey !ByteString
  | ParseSnapNameException !Text

  deriving Typeable
instance Exception PantryException where
instance Show PantryException where
  show = T.unpack . utf8BuilderToText . display
instance Display PantryException where
  display (InvalidTreeFromCasa blobKey _bs) = "Invalid tree from casa: " <> display blobKey
  display (PackageIdentifierRevisionParseFail text) =
    "Invalid package identifier (with optional revision): " <>
    display text
  display (InvalidCabalFile loc mversion errs warnings) =
    "Unable to parse cabal file from package " <>
    either display (fromString . toFilePath) loc <>
    "\n\n" <>
    foldMap
      (\(PError pos msg) ->
          "- " <>
          fromString (showPos pos) <>
          ": " <>
          fromString msg <>
          "\n")
      errs <>
    foldMap
      (\(PWarning _ pos msg) ->
          "- " <>
          fromString (showPos pos) <>
          ": " <>
          fromString msg <>
          "\n")
      warnings <>

    (case mversion of
       Just version
         | version > cabalSpecLatestVersion ->
             "\n\nThe cabal file uses the cabal specification version " <>
             fromString (versionString version) <>
             ", but we only support up to version " <>
             fromString (versionString cabalSpecLatestVersion) <>
             ".\nRecommended action: upgrade your build tool (e.g., `stack upgrade`)."
       _ -> mempty)
  display (TreeWithoutCabalFile pl) = "No cabal file found for " <> display pl
  display (TreeWithMultipleCabalFiles pl sfps) =
    "Multiple cabal files found for " <> display pl <> ": " <>
    fold (intersperse ", " (map display sfps))
  display (MismatchedCabalName fp name) =
    "cabal file path " <>
    fromString (toFilePath fp) <>
    " does not match the package name it defines.\n" <>
    "Please rename the file to: " <>
    fromString (packageNameString name) <>
    ".cabal\n" <>
    "For more information, see: https://github.com/commercialhaskell/stack/issues/317"
  display (NoCabalFileFound dir) =
    "Stack looks for packages in the directories configured in\n" <>
    "the 'packages' and 'extra-deps' fields defined in your stack.yaml\n" <>
    "The current entry points to " <>
    fromString (toFilePath dir) <>
    ",\nbut no .cabal or package.yaml file could be found there."
  display (MultipleCabalFilesFound dir files) =
    "Multiple .cabal files found in directory " <>
    fromString (toFilePath dir) <>
    ":\n" <>
    fold (intersperse "\n" (map (\x -> "- " <> fromString (toFilePath (filename x))) files))
  display (InvalidWantedCompiler t) = "Invalid wanted compiler: " <> display t
  display (InvalidSnapshotLocation dir t) =
    "Invalid snapshot location " <>
    displayShow t <>
    " relative to directory " <>
    displayShow (toFilePath dir)
  display (InvalidOverrideCompiler x y) =
    "Specified compiler for a resolver (" <>
    display x <>
    "), but also specified an override compiler (" <>
    display y <>
    ")"
  display (InvalidFilePathSnapshot t) =
    "Specified snapshot as file path with " <>
    displayShow t <>
    ", but not reading from a local file"
  display (InvalidSnapshot loc e) =
    "Exception while reading snapshot from " <>
    display loc <>
    ":\n" <>
    displayShow e
  display (MismatchedPackageMetadata loc pm mtreeKey foundIdent) =
    "Mismatched package metadata for " <> display loc <>
    "\nFound: " <> fromString (packageIdentifierString foundIdent) <>
    (case mtreeKey of
       Nothing -> mempty
       Just treeKey -> " with tree " <> display treeKey) <>
    "\nExpected: " <> display pm
  display (Non200ResponseStatus status) =
    "Unexpected non-200 HTTP status code: " <>
    displayShow (statusCode status)
  display (InvalidBlobKey Mismatch{..}) =
    "Invalid blob key found, expected: " <>
    display mismatchExpected <>
    ", actual: " <>
    display mismatchActual
  display (Couldn'tParseSnapshot sl e) =
    "Couldn't parse snapshot from " <> display sl <> ": " <> fromString e
  display (WrongCabalFileName pl sfp name) =
    "Wrong cabal file name for package " <> display pl <>
    "\nCabal file is named " <> display sfp <>
    ", but package name is " <> fromString (packageNameString name) <>
    "\nFor more information, see:\n  - https://github.com/commercialhaskell/stack/issues/317\n  -https://github.com/commercialhaskell/stack/issues/895"
  display (DownloadInvalidSHA256 url Mismatch {..}) =
    "Mismatched SHA256 hash from " <> display url <>
    "\nExpected: " <> display mismatchExpected <>
    "\nActual:   " <> display mismatchActual
  display (DownloadInvalidSize url Mismatch {..}) =
    "Mismatched download size from " <> display url <>
    "\nExpected: " <> display mismatchExpected <>
    "\nActual:   " <> display mismatchActual
  display (DownloadTooLarge url Mismatch {..}) =
    "Download from " <> display url <> " was too large.\n" <>
    "Expected: " <> display mismatchExpected <> ", stopped after receiving: " <>
    display mismatchActual
  display (LocalInvalidSHA256 path Mismatch {..}) =
    "Mismatched SHA256 hash from " <> fromString (toFilePath path) <>
    "\nExpected: " <> display mismatchExpected <>
    "\nActual:   " <> display mismatchActual
  display (LocalInvalidSize path Mismatch {..}) =
    "Mismatched file size from " <> fromString (toFilePath path) <>
    "\nExpected: " <> display mismatchExpected <>
    "\nActual:   " <> display mismatchActual
  display (UnknownArchiveType loc) = "Unable to determine archive type of: " <> display loc
  display (InvalidTarFileType loc fp x) =
    "Unsupported tar filetype in archive " <> display loc <> " at file " <> fromString fp <> ": " <> displayShow x
  display (UnsupportedTarball loc e) =
    "Unsupported tarball from " <> display loc <> ": " <> display e
  display (NoHackageCryptographicHash ident) =
    "Not cryptographic hash found for Hackage package " <> fromString (packageIdentifierString ident)
  display (FailedToCloneRepo repo) = "Failed to clone repo " <> display repo
  display (TreeReferencesMissingBlob loc sfp key) =
    "The package " <> display loc <>
    " needs blob " <> display key <>
    " for file path " <> display sfp <>
    ", but the blob is not available"
  display (CompletePackageMetadataMismatch loc pm) =
    "When completing package metadata for " <> display loc <>
    ", some values changed in the new package metadata: " <>
    display pm
  display (CRC32Mismatch loc fp Mismatch {..}) =
    "CRC32 mismatch in ZIP file from " <> display loc <>
    " on internal file " <> fromString fp <>
    "\n.Expected: " <> display mismatchExpected <>
    "\n.Actual:   " <> display mismatchActual
  display (UnknownHackagePackage pir fuzzy) =
    "Could not find " <> display pir <> " on Hackage" <>
    displayFuzzy fuzzy
  display (CannotCompleteRepoNonSHA1 repo) =
    "Cannot complete repo information for a non SHA1 commit due to non-reproducibility: " <>
    display repo
  display (MutablePackageLocationFromUrl t) =
    "Cannot refer to a mutable package location from a URL: " <> display t
  display (MismatchedCabalFileForHackage pir Mismatch{..}) =
    "When processing cabal file for Hackage package " <> display pir <>
    ":\nMismatched package identifier." <>
    "\nExpected: " <> fromString (packageIdentifierString mismatchExpected) <>
    "\nActual:   " <> fromString (packageIdentifierString mismatchActual)
  display (PackageNameParseFail t) =
    "Invalid package name: " <> display t
  display (PackageVersionParseFail t) =
    "Invalid version: " <> display t
  display (InvalidCabalFilePath fp) =
    "File path contains a name which is not a valid package name: " <>
    fromString (toFilePath fp)
  display (DuplicatePackageNames source pairs') =
    "Duplicate package names (" <> source <> "):\n" <>
    foldMap
      (\(name, locs) ->
        fromString (packageNameString name) <> ":\n" <>
        foldMap
          (\loc -> "- " <> display loc <> "\n")
          locs
      )
      pairs'
  display (MigrationFailure desc fp ex) =
    "Encountered error while migrating " <> display desc <> " database:" <>
    "\n    " <> displayShow ex <>
    "\nPlease report this on https://github.com/commercialhaskell/stack/issues" <>
    "\nAs a workaround you may delete " <> display desc <> " database in " <>
    fromString (toFilePath fp) <> " triggering its recreation."
  display (ParseSnapNameException t) = "Invalid snapshot name: " <> display t

data FuzzyResults
  = FRNameNotFound ![PackageName]
  | FRVersionNotFound !(NonEmpty PackageIdentifierRevision)
  | FRRevisionNotFound !(NonEmpty PackageIdentifierRevision)

displayFuzzy :: FuzzyResults -> Utf8Builder
displayFuzzy (FRNameNotFound names) =
  case NE.nonEmpty names of
    Nothing -> ""
    Just names' ->
      "\nPerhaps you meant " <>
      orSeparated (NE.map (fromString . packageNameString) names') <>
      "?"
displayFuzzy (FRVersionNotFound pirs) =
  "\nPossible candidates: " <>
  commaSeparated (NE.map display pirs) <>
  "."
displayFuzzy (FRRevisionNotFound pirs) =
  "\nThe specified revision was not found.\nPossible candidates: " <>
  commaSeparated (NE.map display pirs) <>
  "."

orSeparated :: NonEmpty Utf8Builder -> Utf8Builder
orSeparated xs
  | NE.length xs == 1 = NE.head xs
  | NE.length xs == 2 = NE.head xs <> " or " <> NE.last xs
  | otherwise = fold (intersperse ", " (NE.init xs)) <> ", or " <> NE.last xs

commaSeparated :: NonEmpty Utf8Builder -> Utf8Builder
commaSeparated = fold . NE.intersperse ", "

-- You'd really think there'd be a better way to do this in Cabal.
cabalSpecLatestVersion :: Version
cabalSpecLatestVersion =
  case cabalSpecLatest of
    CabalSpecV1_0 -> error "this cannot happen"
    CabalSpecV1_2 -> error "this cannot happen"
    CabalSpecV1_4 -> error "this cannot happen"
    CabalSpecV1_6 -> error "this cannot happen"
    CabalSpecV1_8 -> error "this cannot happen"
    CabalSpecV1_10 -> error "this cannot happen"
    CabalSpecV1_12 -> error "this cannot happen"
    CabalSpecV1_18 -> error "this cannot happen"
    CabalSpecV1_20 -> error "this cannot happen"
    CabalSpecV1_22 -> error "this cannot happen"
    CabalSpecV1_24 -> error "this cannot happen"
    CabalSpecV2_0 -> error "this cannot happen"
    CabalSpecV2_2 -> error "this cannot happen"
    CabalSpecV2_4 -> error "this cannot happen"
    CabalSpecV3_0 -> mkVersion [3, 0]

data BuildFile = BFCabal !SafeFilePath !TreeEntry
               | BFHpack !TreeEntry -- We don't need SafeFilePath for Hpack since it has to be package.yaml file
  deriving (Show, Eq)

data FileType = FTNormal | FTExecutable
  deriving (Show, Eq, Enum, Bounded)
instance PersistField FileType where
  toPersistValue FTNormal = PersistInt64 1
  toPersistValue FTExecutable = PersistInt64 2

  fromPersistValue v = do
    i <- fromPersistValue v
    case i :: Int64 of
      1 -> Right FTNormal
      2 -> Right FTExecutable
      _ -> Left $ "Invalid FileType: " <> tshow i
instance PersistFieldSql FileType where
  sqlType _ = SqlInt32

data TreeEntry = TreeEntry
  { teBlob :: !BlobKey
  , teType :: !FileType
  }
  deriving (Show, Eq)

newtype SafeFilePath = SafeFilePath Text
  deriving (Show, Eq, Ord, Display)

instance PersistField SafeFilePath where
  toPersistValue = toPersistValue . unSafeFilePath
  fromPersistValue v = do
    t <- fromPersistValue v
    maybe (Left $ "Invalid SafeFilePath: " <> t) Right $ mkSafeFilePath t
instance PersistFieldSql SafeFilePath where
  sqlType _ = SqlString

unSafeFilePath :: SafeFilePath -> Text
unSafeFilePath (SafeFilePath t) = t

safeFilePathtoPath :: (MonadThrow m) => Path Abs Dir -> SafeFilePath -> m (Path Abs File)
safeFilePathtoPath dir (SafeFilePath path) = do
  fpath <- parseRelFile (T.unpack path)
  return $ dir </> fpath

mkSafeFilePath :: Text -> Maybe SafeFilePath
mkSafeFilePath t = do
  guard $ not $ "\\" `T.isInfixOf` t
  guard $ not $ "//" `T.isInfixOf` t
  guard $ not $ "\n" `T.isInfixOf` t
  guard $ not $ "\0" `T.isInfixOf` t

  (c, _) <- T.uncons t
  guard $ c /= '/'

  guard $ all (not . T.all (== '.')) $ T.split (== '/') t

  Just $ SafeFilePath t

-- | SafeFilePath for `package.yaml` file.
hpackSafeFilePath :: SafeFilePath
hpackSafeFilePath =
    let fpath = mkSafeFilePath (T.pack Hpack.packageConfig)
    in case fpath of
         Nothing -> error $ "hpackSafeFilePath: Not able to encode " <> (Hpack.packageConfig)
         Just sfp -> sfp

-- | The hash of the binary representation of a 'Tree'.
--
-- @since 0.1.0.0
newtype TreeKey = TreeKey BlobKey
  deriving (Show, Eq, Ord, Generic, Typeable, ToJSON, FromJSON, NFData, Display)

-- | Represents the contents of a tree, which is a mapping from
-- relative file paths to 'TreeEntry's.
--
-- @since 0.1.0.0
newtype Tree
  = TreeMap (Map SafeFilePath TreeEntry)
  -- In the future, consider allowing more lax parsing
  -- See: https://www.fpcomplete.com/blog/2018/07/pantry-part-2-trees-keys
  -- TreeTarball !PackageTarball
  deriving (Show, Eq)

renderTree :: Tree -> ByteString
renderTree = BL.toStrict . toLazyByteString . go
  where
    go :: Tree -> Builder
    go (TreeMap m) = "map:" <> Map.foldMapWithKey goEntry m

    goEntry sfp (TreeEntry (BlobKey sha (FileSize size')) ft) =
      netstring (unSafeFilePath sfp) <>
      byteString (SHA256.toRaw sha) <>
      netword size' <>
      (case ft of
         FTNormal -> "N"
         FTExecutable -> "X")

netstring :: Text -> Builder
netstring t =
  let bs = encodeUtf8 t
   in netword (fromIntegral (B.length bs)) <> byteString bs

netword :: Word -> Builder
netword w = wordDec w <> ":"

parseTreeM :: MonadThrow m => (BlobKey, ByteString) -> m (TreeKey, Tree)
parseTreeM (blobKey, blob) =
  case parseTree blob of
    Nothing -> throwM (InvalidTreeFromCasa blobKey blob)
    Just tree -> pure (TreeKey blobKey, tree)

parseTree :: ByteString -> Maybe Tree
parseTree bs1 = do
  tree <- parseTree' bs1
  let bs2 = renderTree tree
  guard $ bs1 == bs2
  Just tree

parseTree' :: ByteString -> Maybe Tree
parseTree' bs0 = do
  entriesBS <- B.stripPrefix "map:" bs0
  TreeMap <$> loop Map.empty entriesBS
  where
    loop !m bs1
      | B.null bs1 = pure m
      | otherwise = do
          (sfpBS, bs2) <- takeNetstring bs1
          sfp <-
            case decodeUtf8' sfpBS of
              Left _ -> Nothing
              Right sfpT -> mkSafeFilePath sfpT
          (sha, bs3) <- takeSha bs2
          (size', bs4) <- takeNetword bs3
          (typeW, bs5) <- B.uncons bs4
          ft <-
            case typeW of
              78 -> Just FTNormal -- 'N'
              88 -> Just FTExecutable -- 'X'
              _ -> Nothing
          let entry = TreeEntry (BlobKey sha (FileSize (fromIntegral size'))) ft
          loop (Map.insert sfp entry m) bs5

    takeNetstring bs1 = do
      (size', bs2) <- takeNetword bs1
      guard $ B.length bs2 >= size'
      Just $ B.splitAt size' bs2

    takeSha bs = do
      let (x, y) = B.splitAt 32 bs
      x' <- either (const Nothing) Just (SHA256.fromRaw x)
      Just (x', y)

    takeNetword =
      go 0
      where
        go !accum bs = do
          (next, rest) <- B.uncons bs
          if
            | next == 58 -> pure (accum, rest) -- ':'
            | next >= 48 && next <= 57 ->
                go
                  (accum * 10 + fromIntegral (next - 48))
                  rest
            | otherwise -> Nothing

    {-
data PackageTarball = PackageTarball
  { ptBlob :: !BlobKey
  -- ^ Contains the tarball itself
  , ptCabal :: !BlobKey
  -- ^ Contains the cabal file contents
  , ptSubdir :: !FilePath
  -- ^ Subdir containing the files we want for this package.
  --
  -- There must be precisely one file with a @.cabal@ file extension
  -- located there. Thanks to Hackage revisions, its contents will be
  -- overwritten by the value of @ptCabal@.
  }
  deriving Show
    -}

-- | This is almost a copy of Cabal's parser for package identifiers,
-- the main difference is in the fact that Stack requires version to be
-- present while Cabal uses "null version" as a default value
--
-- @since 0.1.0.0
parsePackageIdentifier :: String -> Maybe PackageIdentifier
parsePackageIdentifier = either (const Nothing) Just . explicitEitherParsec (packageIdentifierParsec <* Parse.eof)

packageIdentifierParsec :: ParsecParser PackageIdentifier
packageIdentifierParsec = do
  ident@(PackageIdentifier _ v) <- parsec

  -- version is a required component of a package identifier for Stack
  guard (v /= nullVersion)

  pure ident

-- | Parse a package name from a 'String'.
--
-- @since 0.1.0.0
parsePackageName :: String -> Maybe PackageName
parsePackageName = Distribution.Text.simpleParse

-- | Parse a package name from a 'String' throwing on failure
--
-- @since 0.1.0.0
parsePackageNameThrowing :: MonadThrow m => String -> m PackageName
parsePackageNameThrowing str =
  case parsePackageName str of
    Nothing -> throwM $ PackageNameParseFail $ T.pack str
    Just pn -> pure pn

-- | Parse a version from a 'String'.
--
-- @since 0.1.0.0
parseVersion :: String -> Maybe Version
parseVersion = Distribution.Text.simpleParse

-- | Parse a package version from a 'String' throwing on failure
--
-- @since 0.1.0.0
parseVersionThrowing :: MonadThrow m => String -> m Version
parseVersionThrowing str =
  case parseVersion str of
    Nothing -> throwM $ PackageVersionParseFail $ T.pack str
    Just v -> pure v

-- | Parse a version range from a 'String'.
--
-- @since 0.1.0.0
parseVersionRange :: String -> Maybe VersionRange
parseVersionRange = Distribution.Text.simpleParse

-- | Parse a module name from a 'String'.
--
-- @since 0.1.0.0
parseModuleName :: String -> Maybe ModuleName
parseModuleName = Distribution.Text.simpleParse

-- | Parse a flag name from a 'String'.
--
-- @since 0.1.0.0
parseFlagName :: String -> Maybe FlagName
parseFlagName = Distribution.Text.simpleParse

-- | Render a package name as a 'String'.
--
-- @since 0.1.0.0
packageNameString :: PackageName -> String
packageNameString = unPackageName

-- | Render a package identifier as a 'String'.
--
-- @since 0.1.0.0
packageIdentifierString :: PackageIdentifier -> String
packageIdentifierString = Distribution.Text.display

-- | Render a version as a 'String'.
--
-- @since 0.1.0.0
versionString :: Version -> String
versionString = Distribution.Text.display

-- | Render a flag name as a 'String'.
--
-- @since 0.1.0.0
flagNameString :: FlagName -> String
flagNameString = unFlagName

-- | Render a module name as a 'String'.
--
-- @since 0.1.0.0
moduleNameString :: ModuleName -> String
moduleNameString = Distribution.Text.display

data OptionalSubdirs
  = OSSubdirs !(NonEmpty Text)
  | OSPackageMetadata !Text !RawPackageMetadata
  -- ^ subdirectory and package metadata
  deriving (Show, Eq, Generic)
instance NFData OptionalSubdirs

-- | Metadata provided by a config file for archives and repos. This
-- information can be used for optimized lookups of information like
-- package identifiers, or for validating that the user configuration
-- has the expected information.
--
-- @since 0.1.0.0
data RawPackageMetadata = RawPackageMetadata
  { rpmName :: !(Maybe PackageName)
    -- ^ Package name in the cabal file
    --
    -- @since 0.1.0.0
  , rpmVersion :: !(Maybe Version)
    -- ^ Package version in the cabal file
    --
    -- @since 0.1.0.0
  , rpmTreeKey :: !(Maybe TreeKey)
    -- ^ Tree key of the loaded up package
    --
    -- @since 0.1.0.0
  }
  deriving (Show, Eq, Ord, Generic, Typeable)
instance NFData RawPackageMetadata

instance Display RawPackageMetadata where
  display rpm = fold $ intersperse ", " $ catMaybes
    [ (\name -> "name == " <> fromString (packageNameString name)) <$> rpmName rpm
    , (\version -> "version == " <> fromString (versionString version)) <$> rpmVersion rpm
    , (\tree -> "tree == " <> display tree) <$> rpmTreeKey rpm
    ]

-- | Exact metadata specifying concrete package
--
-- @since 0.1.0.0
data PackageMetadata = PackageMetadata
  { pmIdent :: !PackageIdentifier
    -- ^ Package identifier in the cabal file
    --
    -- @since 0.1.0.0
  , pmTreeKey :: !TreeKey
    -- ^ Tree key of the loaded up package
    --
    -- @since 0.1.0.0
  }
  deriving (Show, Eq, Ord, Generic, Typeable)
-- i PackageMetadata
instance NFData PackageMetadata

instance Display PackageMetadata where
  display pm = fold $ intersperse ", " $
    [ "ident == " <> fromString (packageIdentifierString $ pmIdent pm)
    , "tree == " <> display (pmTreeKey pm)
    ]

parsePackageMetadata :: Object -> WarningParser PackageMetadata
parsePackageMetadata o = do
  _oldCabalFile :: Maybe BlobKey <- o ..:? "cabal-file"
  pantryTree :: BlobKey <- o ..: "pantry-tree"
  CabalString pkgName <- o ..: "name"
  CabalString pkgVersion <- o ..: "version"
  let pmTreeKey = TreeKey pantryTree
      pmIdent = PackageIdentifier {..}
  pure PackageMetadata {..}


-- | Conver package metadata to its "raw" equivalent.
--
-- @since 0.1.0.0
toRawPM :: PackageMetadata -> RawPackageMetadata
toRawPM pm = RawPackageMetadata (Just name) (Just version) (Just $ pmTreeKey pm)
  where
    PackageIdentifier name version = pmIdent pm

-- | File path relative to the configuration file it was parsed from
--
-- @since 0.1.0.0
newtype RelFilePath = RelFilePath Text
  deriving (Show, ToJSON, FromJSON, Eq, Ord, Generic, Typeable, NFData, Display)

-- | Location that an archive is stored at
--
-- @since 0.1.0.0
data ArchiveLocation
  = ALUrl !Text
    -- ^ Archive stored at an HTTP(S) URL
    --
    -- @since 0.1.0.0
  | ALFilePath !(ResolvedPath File)
    -- ^ Archive stored at a local file path
    --
    -- @since 0.1.0.0
  deriving (Show, Eq, Ord, Generic, Typeable)
instance NFData ArchiveLocation

instance Display ArchiveLocation where
  display (ALUrl url) = display url
  display (ALFilePath resolved) = fromString $ toFilePath $ resolvedAbsolute resolved

parseArchiveLocationObject :: Object -> WarningParser (Unresolved ArchiveLocation)
parseArchiveLocationObject o =
    ((o ..: "url") >>= either (fail . T.unpack) pure . validateUrl) <|>
    ((o ..: "filepath") >>= either (fail . T.unpack) pure . validateFilePath) <|>
    ((o ..: "archive") >>= either (fail . T.unpack) pure . parseArchiveLocationText) <|>
    ((o ..: "location") >>= either (fail . T.unpack) pure . parseArchiveLocationText)

parseArchiveLocationText :: Text -> Either Text (Unresolved ArchiveLocation)
parseArchiveLocationText t =
  case validateUrl t of
    Left e1 ->
      case validateFilePath t of
        Left e2 -> Left $ T.unlines
          [ "Invalid archive location, neither a URL nor a file path"
          , "  URL error: " <> e1
          , "  File path error: " <> e2
          ]
        Right x -> Right x
    Right x -> Right x

validateUrl :: Text -> Either Text (Unresolved ArchiveLocation)
validateUrl t =
  case parseRequest $ T.unpack t of
    Left _ -> Left $ "Could not parse URL: " <> t
    Right _ -> pure $ pure $ ALUrl t

validateFilePath :: Text -> Either Text (Unresolved ArchiveLocation)
validateFilePath t =
  if any (\ext -> ext `T.isSuffixOf` t) (T.words ".zip .tar .tar.gz")
    then pure $ Unresolved $ \mdir ->
           case mdir of
             Nothing -> throwIO $ InvalidFilePathSnapshot t
             Just dir -> do
               abs' <- resolveFile dir $ T.unpack t
               pure $ ALFilePath $ ResolvedPath (RelFilePath t) abs'
    else Left $ "Does not have an archive file extension: " <> t

instance ToJSON RawPackageLocation where
  toJSON (RPLImmutable rpli) = toJSON rpli
  toJSON (RPLMutable resolved) = toJSON (resolvedRelative resolved)
instance FromJSON (WithJSONWarnings (Unresolved (NonEmpty RawPackageLocation))) where
  parseJSON v =
    ((fmap.fmap.fmap.fmap) RPLImmutable (parseJSON v)) <|>
    ((noJSONWarnings . mkMutable) <$> parseJSON v)
    where
      mkMutable :: Text -> Unresolved (NonEmpty RawPackageLocation)
      mkMutable t = Unresolved $ \mdir -> do
        case mdir of
          Nothing -> throwIO $ MutablePackageLocationFromUrl t
          Just dir -> do
            abs' <- resolveDir dir $ T.unpack t
            pure $ pure $ RPLMutable $ ResolvedPath (RelFilePath t) abs'

instance ToJSON RawPackageLocationImmutable where
  toJSON (RPLIHackage pir mtree) = object $ concat
    [ ["hackage" .= pir]
    , maybe [] (\tree -> ["pantry-tree" .= tree]) mtree
    ]
  toJSON (RPLIArchive (RawArchive loc msha msize subdir) rpm) = object $ concat
    [ case loc of
        ALUrl url -> ["url" .= url]
        ALFilePath resolved -> ["filepath" .= resolvedRelative resolved]
    , maybe [] (\sha -> ["sha256" .= sha]) msha
    , maybe [] (\size' -> ["size" .= size']) msize
    , if T.null subdir then [] else ["subdir" .= subdir]
    , rpmToPairs rpm
    ]
  toJSON (RPLIRepo (Repo url commit typ subdir) rpm) = object $ concat
    [ [ urlKey .= url
      , "commit" .= commit
      ]
    , if T.null subdir then [] else ["subdir" .= subdir]
    , rpmToPairs rpm
    ]
    where
      urlKey =
        case typ of
          RepoGit -> "git"
          RepoHg  -> "hg"

rpmToPairs :: RawPackageMetadata -> [(Text, Value)]
rpmToPairs (RawPackageMetadata mname mversion mtree) = concat
  [ maybe [] (\name -> ["name" .= CabalString name]) mname
  , maybe [] (\version -> ["version" .= CabalString version]) mversion
  , maybe [] (\tree -> ["pantry-tree" .= tree]) mtree
  ]

instance FromJSON (WithJSONWarnings (Unresolved PackageLocationImmutable)) where
    parseJSON v = repoObject v <|> archiveObject v <|> hackageObject v <|> github v
                  <|> fail ("Could not parse a UnresolvedPackageLocationImmutable from: " ++ show v)
        where
          repoObject :: Value -> Parser (WithJSONWarnings (Unresolved PackageLocationImmutable))
          repoObject = withObjectWarnings "UnresolvedPackageLocationImmutable.PLIRepo" $ \o -> do
            pm <- parsePackageMetadata o
            repoSubdir <- o ..:? "subdir" ..!= ""
            repoCommit <- o ..: "commit"
            (repoType, repoUrl) <-
                (o ..: "git" >>= \url -> pure (RepoGit, url)) <|>
                (o ..: "hg" >>= \url -> pure (RepoHg, url))
            pure $ pure $ PLIRepo Repo {..} pm

          archiveObject =
            withObjectWarnings "UnresolvedPackageLocationImmutable.PLIArchive" $ \o -> do
              pm <- parsePackageMetadata o
              Unresolved mkArchiveLocation <- parseArchiveLocationObject o
              archiveHash <- o ..: "sha256"
              archiveSize <- o ..: "size"
              archiveSubdir <- o ..:? "subdir" ..!= ""
              pure $ Unresolved $ \mdir -> do
                archiveLocation <- mkArchiveLocation mdir
                pure $ PLIArchive Archive {..} pm

          hackageObject =
             withObjectWarnings "UnresolvedPackagelocationimmutable.PLIHackage (Object)" $ \o -> do
                      treeKey <- o ..: "pantry-tree"
                      htxt <- o ..: "hackage"
                      case parseHackageText htxt of
                        Left e -> fail $ show e
                        Right (pkgIdentifier, blobKey) ->
                          pure $ pure $ PLIHackage pkgIdentifier blobKey (TreeKey treeKey)

          github value =
            withObjectWarnings "UnresolvedPackagelocationimmutable.PLIArchive:github" (\o -> do
              pm <- parsePackageMetadata o
              GitHubRepo ghRepo <- o ..: "github"
              commit <- o ..: "commit"
              let archiveLocation = ALUrl $ T.concat
                    [ "https://github.com/"
                    , ghRepo
                    , "/archive/"
                    , commit
                    , ".tar.gz"
                    ]
              archiveHash <- o ..: "sha256"
              archiveSize <- o ..: "size"
              archiveSubdir <- o ..:? "subdir" ..!= ""
              pure $ pure $ PLIArchive Archive {..} pm) value

instance FromJSON (WithJSONWarnings (Unresolved (NonEmpty RawPackageLocationImmutable))) where
  parseJSON v
      = http v
    <|> hackageText v
    <|> hackageObject v
    <|> repo v
    <|> archiveObject v
    <|> github v
    <|> fail ("Could not parse a UnresolvedRawPackageLocationImmutable from: " ++ show v)
    where
      http :: Value -> Parser (WithJSONWarnings (Unresolved (NonEmpty RawPackageLocationImmutable)))
      http = withText "UnresolvedPackageLocationImmutable.RPLIArchive (Text)" $ \t ->
        case parseArchiveLocationText t of
          Left _ -> fail $ "Invalid archive location: " ++ T.unpack t
          Right (Unresolved mkArchiveLocation) ->
            pure $ noJSONWarnings $ Unresolved $ \mdir -> do
              raLocation <- mkArchiveLocation mdir
              let raHash = Nothing
                  raSize = Nothing
                  raSubdir = T.empty
              pure $ pure $ RPLIArchive RawArchive {..} rpmEmpty

      hackageText = withText "UnresolvedPackageLocationImmutable.UPLIHackage (Text)" $ \t ->
        case parsePackageIdentifierRevision t of
          Left e -> fail $ show e
          Right pir -> pure $ noJSONWarnings $ pure $ pure $ RPLIHackage pir Nothing

      hackageObject = withObjectWarnings "UnresolvedPackageLocationImmutable.UPLIHackage" $ \o -> (pure.pure) <$> (RPLIHackage
        <$> o ..: "hackage"
        <*> o ..:? "pantry-tree")

      optionalSubdirs :: Object -> WarningParser OptionalSubdirs
      optionalSubdirs o =
        -- if subdirs exists, it needs to be valid
        case HM.lookup "subdirs" o of
          Just v' -> do
            tellJSONField "subdirs"
            subdirs <- lift $ parseJSON v'
            case NE.nonEmpty subdirs of
              Nothing -> fail "Invalid empty subdirs"
              Just x -> pure $ OSSubdirs x
          Nothing -> OSPackageMetadata
            <$> o ..:? "subdir" ..!= T.empty
            <*> (rawPackageMetadataHelper
                  <$> (fmap unCabalString <$> (o ..:? "name"))
                  <*> (fmap unCabalString <$> (o ..:? "version"))
                  <*> o ..:? "pantry-tree"
                  <*> o ..:? "cabal-file")

      rawPackageMetadataHelper
        :: Maybe PackageName
        -> Maybe Version
        -> Maybe TreeKey
        -> Maybe BlobKey
        -> RawPackageMetadata
      rawPackageMetadataHelper name version pantryTree _ignoredCabalFile =
        RawPackageMetadata name version pantryTree

      repo = withObjectWarnings "UnresolvedPackageLocationImmutable.UPLIRepo" $ \o -> do
        (repoType, repoUrl) <-
          ((RepoGit, ) <$> o ..: "git") <|>
          ((RepoHg, ) <$> o ..: "hg")
        repoCommit <- o ..: "commit"
        os <- optionalSubdirs o
        pure $ pure $ NE.map (\(repoSubdir, pm) -> RPLIRepo Repo {..} pm) (osToRpms os)

      archiveObject = withObjectWarnings "UnresolvedPackageLocationImmutable.RPLIArchive" $ \o -> do
        Unresolved mkArchiveLocation <- parseArchiveLocationObject o
        raHash <- o ..:? "sha256"
        raSize <- o ..:? "size"
        os <- optionalSubdirs o
        pure $ Unresolved $ \mdir -> do
          raLocation <- mkArchiveLocation mdir
          pure $ NE.map (\(raSubdir, pm) -> RPLIArchive RawArchive {..} pm) (osToRpms os)

      github = withObjectWarnings "PLArchive:github" $ \o -> do
        GitHubRepo ghRepo <- o ..: "github"
        commit <- o ..: "commit"
        let raLocation = ALUrl $ T.concat
              [ "https://github.com/"
              , ghRepo
              , "/archive/"
              , commit
              , ".tar.gz"
              ]
        raHash <- o ..:? "sha256"
        raSize <- o ..:? "size"
        os <- optionalSubdirs o
        pure $ pure $ NE.map (\(raSubdir, pm) -> RPLIArchive RawArchive {..} pm) (osToRpms os)

-- | Returns pairs of subdirectory and 'PackageMetadata'.
osToRpms :: OptionalSubdirs -> NonEmpty (Text, RawPackageMetadata)
osToRpms (OSSubdirs subdirs) = NE.map (, rpmEmpty) subdirs
osToRpms (OSPackageMetadata subdir rpm) = pure (subdir, rpm)

rpmEmpty :: RawPackageMetadata
rpmEmpty = RawPackageMetadata Nothing Nothing Nothing

-- | Newtype wrapper for easier JSON integration with Cabal types.
--
-- @since 0.1.0.0
newtype CabalString a = CabalString { unCabalString :: a }
  deriving (Show, Eq, Ord, Typeable)

-- I'd like to use coerce here, but can't due to roles. unsafeCoerce
-- could work, but let's avoid unsafe code.

-- | Wrap the keys in a 'Map' with a 'CabalString' to get a 'ToJSON'
-- instance.
--
-- @since 0.1.0.0
toCabalStringMap :: Map a v -> Map (CabalString a) v
toCabalStringMap = Map.mapKeysMonotonic CabalString

-- | Unwrap the 'CabalString' from the keys in a 'Map' to use a
-- 'FromJSON' instance.
--
-- @since 0.1.0.0
unCabalStringMap :: Map (CabalString a) v -> Map a v
unCabalStringMap = Map.mapKeysMonotonic unCabalString

instance Distribution.Pretty.Pretty a => ToJSON (CabalString a) where
  toJSON = toJSON . Distribution.Text.display . unCabalString
instance Distribution.Pretty.Pretty a => ToJSONKey (CabalString a) where
  toJSONKey = toJSONKeyText $ T.pack . Distribution.Text.display . unCabalString

instance forall a. IsCabalString a => FromJSON (CabalString a) where
  parseJSON = withText name $ \t ->
    case cabalStringParser $ T.unpack t of
      Nothing -> fail $ "Invalid " ++ name ++ ": " ++ T.unpack t
      Just x -> pure $ CabalString x
    where
      name = cabalStringName (Nothing :: Maybe a)
instance forall a. IsCabalString a => FromJSONKey (CabalString a) where
  fromJSONKey =
    FromJSONKeyTextParser $ \t ->
    case cabalStringParser $ T.unpack t of
      Nothing -> fail $ "Invalid " ++ name ++ ": " ++ T.unpack t
      Just x -> pure $ CabalString x
    where
      name = cabalStringName (Nothing :: Maybe a)

class IsCabalString a where
  cabalStringName :: proxy a -> String
  cabalStringParser :: String -> Maybe a
instance IsCabalString PackageName where
  cabalStringName _ = "package name"
  cabalStringParser = parsePackageName
instance IsCabalString Version where
  cabalStringName _ = "version"
  cabalStringParser = parseVersion
instance IsCabalString VersionRange where
  cabalStringName _ = "version range"
  cabalStringParser = parseVersionRange
instance IsCabalString PackageIdentifier where
  cabalStringName _ = "package identifier"
  cabalStringParser = parsePackageIdentifier
instance IsCabalString FlagName where
  cabalStringName _ = "flag name"
  cabalStringParser = parseFlagName

-- | What to use for running hpack
--
-- @since 0.1.0.0
data HpackExecutable
    = HpackBundled
    -- ^ Compiled in library
    | HpackCommand !FilePath
    -- ^ Executable at the provided path
    deriving (Show, Read, Eq, Ord)


-- | Which compiler a snapshot wants to use. The build tool may elect
-- to do some fuzzy matching of versions (e.g., allowing different
-- patch versions).
--
-- @since 0.1.0.0
data WantedCompiler
  = WCGhc !Version
  | WCGhcGit !Text !Text
  | WCGhcjs
      !Version
      !Version
    -- ^ GHCJS version followed by GHC version
 deriving (Show, Eq, Ord, Generic)

instance NFData WantedCompiler
instance Display WantedCompiler where
  display (WCGhc vghc) = "ghc-" <> fromString (versionString vghc)
  display (WCGhcjs vghcjs vghc) =
    "ghcjs-" <> fromString (versionString vghcjs) <> "_ghc-" <> fromString (versionString vghc)
  display (WCGhcGit commit flavour) =
    "ghc-git-" <> display commit <> "-" <> display flavour
instance ToJSON WantedCompiler where
  toJSON = toJSON . utf8BuilderToText . display
instance FromJSON WantedCompiler where
  parseJSON = withText "WantedCompiler" $ either (fail . show) pure . parseWantedCompiler
instance FromJSONKey WantedCompiler where
  fromJSONKey =
    FromJSONKeyTextParser $ \t ->
    case parseWantedCompiler t of
      Left e -> fail $ "Invalid WantedComiler " ++ show t ++ ": " ++ show e
      Right x -> pure x

-- | Parse a 'Text' into a 'WantedCompiler' value.
--
-- @since 0.1.0.0
parseWantedCompiler :: Text -> Either PantryException WantedCompiler
parseWantedCompiler t0 = maybe (Left $ InvalidWantedCompiler t0) Right $
  case T.stripPrefix "ghcjs-" t0 of
    Just t1 -> parseGhcjs t1
    Nothing -> case T.stripPrefix "ghc-git-" t0 of
       Just t1 -> parseGhcGit t1
       Nothing -> T.stripPrefix "ghc-" t0 >>= parseGhc
  where
    parseGhcjs t1 = do
      let (ghcjsVT, t2) = T.break (== '_') t1
      ghcjsV <- parseVersion $ T.unpack ghcjsVT
      ghcVT <- T.stripPrefix "_ghc-" t2
      ghcV <- parseVersion $ T.unpack ghcVT
      pure $ WCGhcjs ghcjsV ghcV
    parseGhcGit t1 = do
      let (commit, flavour) = T.break (== '-') t1
      pure $ WCGhcGit commit (T.drop 1 flavour)
    parseGhc = fmap WCGhc . parseVersion . T.unpack

instance FromJSON (WithJSONWarnings (Unresolved RawSnapshotLocation)) where
  parseJSON v = text v <|> obj v
    where
      text :: Value -> Parser (WithJSONWarnings (Unresolved RawSnapshotLocation))
      text = withText "UnresolvedSnapshotLocation (Text)" $ pure . noJSONWarnings . parseRawSnapshotLocation

      obj :: Value -> Parser (WithJSONWarnings (Unresolved RawSnapshotLocation))
      obj = withObjectWarnings "UnresolvedSnapshotLocation (Object)" $ \o ->
        ((pure . RSLCompiler) <$> o ..: "compiler") <|>
        ((\x y -> pure $ RSLUrl x y) <$> o ..: "url" <*> blobKey o) <|>
        (parseRawSnapshotLocationPath <$> o ..: "filepath")

      blobKey o = do
        msha <- o ..:? "sha256"
        msize <- o ..:? "size"
        case (msha, msize) of
          (Nothing, Nothing) -> pure Nothing
          (Just sha, Just size') -> pure $ Just $ BlobKey sha size'
          (Just _sha, Nothing) -> fail "You must also specify the file size"
          (Nothing, Just _) -> fail "You must also specify the file's SHA256"

instance Display SnapshotLocation where
  display (SLCompiler compiler) = display compiler
  display (SLUrl url blob) = display url <> " (" <> display blob <> ")"
  display (SLFilePath resolved) = display (resolvedRelative resolved)

-- | Parse a 'Text' into an 'Unresolved' 'RawSnapshotLocation'.
--
-- @since 0.1.0.0
parseRawSnapshotLocation :: Text -> Unresolved RawSnapshotLocation
parseRawSnapshotLocation t0 = fromMaybe (parseRawSnapshotLocationPath t0) $
  (either (const Nothing) (Just . pure . RSLCompiler) (parseWantedCompiler t0)) <|>
  (pure <$> RSLSynonym <$> parseSnapName t0) <|>
  parseGithub <|>
  parseUrl
  where
    parseGithub = do
      t1 <- T.stripPrefix "github:" t0
      let (user, t2) = T.break (== '/') t1
      t3 <- T.stripPrefix "/" t2
      let (repo, t4) = T.break (== ':') t3
      path <- T.stripPrefix ":" t4
      Just $ pure $ githubSnapshotLocation user repo path

    parseUrl = parseRequest (T.unpack t0) $> pure (RSLUrl t0 Nothing)

parseRawSnapshotLocationPath :: Text -> Unresolved RawSnapshotLocation
parseRawSnapshotLocationPath t =
  Unresolved $ \mdir ->
  case mdir of
    Nothing -> throwIO $ InvalidFilePathSnapshot t
    Just dir -> do
      abs' <- resolveFile dir (T.unpack t) `catchAny` \_ -> throwIO (InvalidSnapshotLocation dir t)
      pure $ RSLFilePath $ ResolvedPath (RelFilePath t) abs'

githubSnapshotLocation :: Text -> Text -> Text -> RawSnapshotLocation
githubSnapshotLocation user repo path =
  let url = T.concat
        [ "https://raw.githubusercontent.com/"
        , user
        , "/"
        , repo
        , "/master/"
        , path
        ]
   in RSLUrl url Nothing

defUser :: Text
defUser = "commercialhaskell"

defRepo :: Text
defRepo = "stackage-snapshots"

-- | Default location of snapshot synonyms
-- , i.e. commercialhaskell's GitHub repository.
--
-- @since 0.5.0.0
defaultSnapshotLocation
  :: SnapName
  -> RawSnapshotLocation
defaultSnapshotLocation (LTS x y) =
  githubSnapshotLocation defUser defRepo $
  utf8BuilderToText $
  "lts/" <> display x <> "/" <> display y <> ".yaml"
defaultSnapshotLocation (Nightly date) =
  githubSnapshotLocation defUser defRepo $
  utf8BuilderToText $
  "nightly/" <> display year <> "/" <> display month <> "/" <> display day <> ".yaml"
  where
    (year, month, day) = toGregorian date

-- | A snapshot synonym.
-- It is expanded according to the field 'snapshotLocation'
-- of a 'PantryConfig'.
--
-- @ since 0.5.0.0
data SnapName
    -- | LTS Haskell snapshot,
    -- displayed as @"lts-maj.min"@.
    --
    -- @since 0.5.0.0
    = LTS
        !Int -- ^ Major version 
        !Int -- ^ Minor version
    -- | Stackage Nightly snapshot,
    -- displayed as @"nighly-YYYY-MM-DD"@.
    --
    -- @since 0.5.0.0
    | Nightly !Day
    deriving (Eq, Ord, Generic)

instance NFData SnapName

instance Display SnapName where
  display (LTS x y) = "lts-" <> display x <> "." <> display y
  display (Nightly date) = "nightly-" <> displayShow date

instance Show SnapName where
  show = T.unpack . utf8BuilderToText . display

instance ToJSON SnapName where
  toJSON syn = String $ utf8BuilderToText $ display syn

-- | Parse the short representation of a 'SnapName'.
--
-- @since 0.5.0.0
parseSnapName :: MonadThrow m => Text -> m SnapName
parseSnapName t0 =
    case lts <|> nightly of
        Nothing -> throwM $ ParseSnapNameException t0
        Just sn -> return sn
  where
    lts = do
        t1 <- T.stripPrefix "lts-" t0
        Right (x, t2) <- Just $ decimal t1
        t3 <- T.stripPrefix "." t2
        Right (y, "") <- Just $ decimal t3
        return $ LTS x y
    nightly = do
        t1 <- T.stripPrefix "nightly-" t0
        Nightly <$> readMaybe (T.unpack t1)

-- | Where to load a snapshot from in raw form
-- (RSUrl could have a missing BlobKey)
--
-- @since 0.1.0.0
data RawSnapshotLocation
  = RSLCompiler !WantedCompiler
    -- ^ Don't use an actual snapshot, just a version of the compiler
    -- with its shipped packages.
    --
    -- @since 0.1.0.0
  | RSLUrl !Text !(Maybe BlobKey)
    -- ^ Download the snapshot from the given URL. The optional
    -- 'BlobKey' is used for reproducibility.
    --
    -- @since 0.1.0.0
  | RSLFilePath !(ResolvedPath File)
    -- ^ Snapshot at a local file path.
    --
    -- @since 0.1.0.0
  | RSLSynonym !SnapName
    -- ^ Snapshot synonym (LTS/Nightly).
    --
    -- @since 0.5.0.0
  deriving (Show, Eq, Ord, Generic)

instance NFData RawSnapshotLocation

instance Display RawSnapshotLocation where
  display (RSLCompiler compiler) = display compiler
  display (RSLUrl url Nothing) = display url
  display (RSLUrl url (Just blob)) = display url <> " (" <> display blob <> ")"
  display (RSLFilePath resolved) = display (resolvedRelative resolved)
  display (RSLSynonym syn) = display syn
  

instance ToJSON RawSnapshotLocation where
  toJSON (RSLCompiler compiler) = object ["compiler" .= compiler]
  toJSON (RSLUrl url mblob) = object
    $ "url" .= url
    : maybe [] blobKeyPairs mblob
  toJSON (RSLFilePath resolved) = object ["filepath" .= resolvedRelative resolved]
  toJSON (RSLSynonym syn) = toJSON syn

-- | Where to load a snapshot from.
--
-- @since 0.1.0.0
data SnapshotLocation
  = SLCompiler !WantedCompiler
    -- ^ Don't use an actual snapshot, just a version of the compiler
    -- with its shipped packages.
    --
    -- @since 0.1.0.0
  | SLUrl !Text !BlobKey
    -- ^ Download the snapshot from the given URL. The optional
    -- 'BlobKey' is used for reproducibility.
    --
    -- @since 0.1.0.0
  | SLFilePath !(ResolvedPath File)
    -- ^ Snapshot at a local file path.
    --
    -- @since 0.1.0.0
  deriving (Show, Eq, Ord, Generic)
instance NFData SnapshotLocation

instance ToJSON SnapshotLocation where
  toJSON sl = toJSON (toRawSL sl)

instance FromJSON (WithJSONWarnings (Unresolved SnapshotLocation)) where
    parseJSON v = file v <|> url v <|> compiler v
      where
        file = withObjectWarnings "SLFilepath" $ \o -> do
           ufp <- o ..: "filepath"
           pure $ Unresolved $ \mdir ->
             case mdir of
               Nothing -> throwIO $ InvalidFilePathSnapshot ufp
               Just dir -> do
                 absolute <- resolveFile dir (T.unpack ufp)
                 let fp = ResolvedPath (RelFilePath ufp) absolute
                 pure $ SLFilePath fp
        url = withObjectWarnings "SLUrl" $ \o -> do
          url' <- o ..: "url"
          sha <- o ..: "sha256"
          size <- o ..: "size"
          pure $ Unresolved $ \_ -> pure $ SLUrl url' (BlobKey sha size)
        compiler = withObjectWarnings "SLCompiler" $ \o -> do
          c <- o ..: "compiler"
          pure $ Unresolved $ \_ -> pure $ SLCompiler c

-- | Convert snapshot location to its "raw" equivalent.
--
-- @since 0.1.0.0
toRawSL :: SnapshotLocation -> RawSnapshotLocation
toRawSL (SLCompiler c) = RSLCompiler c
toRawSL (SLUrl url blob) = RSLUrl url (Just blob)
toRawSL (SLFilePath fp) = RSLFilePath fp

-- | A flattened representation of all the layers in a snapshot.
--
-- @since 0.1.0.0
data RawSnapshot = RawSnapshot
  { rsCompiler :: !WantedCompiler
  -- ^ The compiler wanted for this snapshot.
  , rsPackages :: !(Map PackageName RawSnapshotPackage)
  -- ^ Packages available in this snapshot for installation. This will be
  -- applied on top of any globally available packages.
  , rsDrop :: !(Set PackageName)
  -- ^ Global packages that should be dropped/ignored.
  }

-- | A flattened representation of all the layers in a snapshot.
--
-- @since 0.1.0.0
data Snapshot = Snapshot
  { snapshotCompiler :: !WantedCompiler
  -- ^ The compiler wanted for this snapshot.
  , snapshotPackages :: !(Map PackageName SnapshotPackage)
  -- ^ Packages available in this snapshot for installation. This will be
  -- applied on top of any globally available packages.
  , snapshotDrop :: !(Set PackageName)
  -- ^ Global packages that should be dropped/ignored.
  }

-- | Settings for a package found in a snapshot.
--
-- @since 0.1.0.0
data RawSnapshotPackage = RawSnapshotPackage
  { rspLocation :: !RawPackageLocationImmutable
  -- ^ Where to get the package from
  , rspFlags :: !(Map FlagName Bool)
  -- ^ Same as 'slFlags'
  , rspHidden :: !Bool
  -- ^ Same as 'slHidden'
  , rspGhcOptions :: ![Text]
  -- ^ Same as 'slGhcOptions'
  }

-- | Settings for a package found in a snapshot.
--
-- @since 0.1.0.0
data SnapshotPackage = SnapshotPackage
  { spLocation :: !PackageLocationImmutable
  -- ^ Where to get the package from
  , spFlags :: !(Map FlagName Bool)
  -- ^ Same as 'slFlags'
  , spHidden :: !Bool
  -- ^ Same as 'slHidden'
  , spGhcOptions :: ![Text]
  -- ^ Same as 'slGhcOptions'
  }
  deriving Show

-- | A single layer of a snapshot, i.e. a specific YAML configuration file.
--
-- @since 0.1.0.0
data RawSnapshotLayer = RawSnapshotLayer
  { rslParent :: !RawSnapshotLocation
  -- ^ The sl to extend from. This is either a specific
  -- compiler, or a @SnapshotLocation@ which gives us more information
  -- (like packages). Ultimately, we'll end up with a
  -- @CompilerVersion@.
  --
  -- @since 0.1.0.0
  , rslCompiler :: !(Maybe WantedCompiler)
  -- ^ Override the compiler specified in 'slParent'. Must be
  -- 'Nothing' if using 'SLCompiler'.
  --
  -- @since 0.1.0.0
  , rslLocations :: ![RawPackageLocationImmutable]
  -- ^ Where to grab all of the packages from.
  --
  -- @since 0.1.0.0
  , rslDropPackages :: !(Set PackageName)
  -- ^ Packages present in the parent which should not be included
  -- here.
  --
  -- @since 0.1.0.0
  , rslFlags :: !(Map PackageName (Map FlagName Bool))
  -- ^ Flag values to override from the defaults
  --
  -- @since 0.1.0.0
  , rslHidden :: !(Map PackageName Bool)
  -- ^ Packages which should be hidden when registering. This will
  -- affect, for example, the import parser in the script
  -- command. We use a 'Map' instead of just a 'Set' to allow
  -- overriding the hidden settings in a parent sl.
  --
  -- @since 0.1.0.0
  , rslGhcOptions :: !(Map PackageName [Text])
  -- ^ GHC options per package
  --
  -- @since 0.1.0.0
  , rslPublishTime :: !(Maybe UTCTime)
  -- ^ See 'slPublishTime'
  --
  -- @since 0.1.0.0
  }
  deriving (Show, Eq, Generic)

instance NFData RawSnapshotLayer

instance ToJSON RawSnapshotLayer where
  toJSON rsnap = object $ concat
    [ ["resolver" .= rslParent rsnap]
    , maybe [] (\compiler -> ["compiler" .= compiler]) (rslCompiler rsnap)
    , ["packages" .= rslLocations rsnap]
    , if Set.null (rslDropPackages rsnap)
        then []
        else ["drop-packages" .= Set.map CabalString (rslDropPackages rsnap)]
    , if Map.null (rslFlags rsnap)
        then []
        else ["flags" .= fmap toCabalStringMap (toCabalStringMap (rslFlags rsnap))]
    , if Map.null (rslHidden rsnap)
        then []
        else ["hidden" .= toCabalStringMap (rslHidden rsnap)]
    , if Map.null (rslGhcOptions rsnap)
        then []
        else ["ghc-options" .= toCabalStringMap (rslGhcOptions rsnap)]
    , maybe [] (\time -> ["publish-time" .= time]) (rslPublishTime rsnap)
    ]

instance FromJSON (WithJSONWarnings (Unresolved RawSnapshotLayer)) where
  parseJSON = withObjectWarnings "Snapshot" $ \o -> do
    _ :: Maybe Text <- o ..:? "name" -- avoid warnings for old snapshot format
    mcompiler <- o ..:? "compiler"
    mresolver <- jsonSubWarningsT $ o ...:? ["snapshot", "resolver"]
    unresolvedSnapshotParent <-
      case (mcompiler, mresolver) of
        (Nothing, Nothing) -> fail "Snapshot must have either resolver or compiler"
        (Just compiler, Nothing) -> pure $ pure (RSLCompiler compiler, Nothing)
        (_, Just (Unresolved usl)) -> pure $ Unresolved $ \mdir -> do
          sl <- usl mdir
          case (sl, mcompiler) of
            (RSLCompiler c1, Just c2) -> throwIO $ InvalidOverrideCompiler c1 c2
            _ -> pure (sl, mcompiler)

    unresolvedLocs <- jsonSubWarningsT (o ..:? "packages" ..!= [])
    rslDropPackages <- Set.map unCabalString <$> (o ..:? "drop-packages" ..!= Set.empty)
    rslFlags <- (unCabalStringMap . fmap unCabalStringMap) <$> (o ..:? "flags" ..!= Map.empty)
    rslHidden <- unCabalStringMap <$> (o ..:? "hidden" ..!= Map.empty)
    rslGhcOptions <- unCabalStringMap <$> (o ..:? "ghc-options" ..!= Map.empty)
    rslPublishTime <- o ..:? "publish-time"
    pure $ (\rslLocations (rslParent, rslCompiler) -> RawSnapshotLayer {..})
      <$> ((concat . map NE.toList) <$> sequenceA unresolvedLocs)
      <*> unresolvedSnapshotParent

-- | A single layer of a snapshot, i.e. a specific YAML configuration file.
--
-- @since 0.1.0.0
data SnapshotLayer = SnapshotLayer
  { slParent :: !SnapshotLocation
  -- ^ The sl to extend from. This is either a specific
  -- compiler, or a @SnapshotLocation@ which gives us more information
  -- (like packages). Ultimately, we'll end up with a
  -- @CompilerVersion@.
  --
  -- @since 0.1.0.0
  , slCompiler :: !(Maybe WantedCompiler)
  -- ^ Override the compiler specified in 'slParent'. Must be
  -- 'Nothing' if using 'SLCompiler'.
  --
  -- @since 0.1.0.0
  , slLocations :: ![PackageLocationImmutable]
  -- ^ Where to grab all of the packages from.
  --
  -- @since 0.1.0.0
  , slDropPackages :: !(Set PackageName)
  -- ^ Packages present in the parent which should not be included
  -- here.
  --
  -- @since 0.1.0.0
  , slFlags :: !(Map PackageName (Map FlagName Bool))
  -- ^ Flag values to override from the defaults
  --
  -- @since 0.1.0.0
  , slHidden :: !(Map PackageName Bool)
  -- ^ Packages which should be hidden when registering. This will
  -- affect, for example, the import parser in the script
  -- command. We use a 'Map' instead of just a 'Set' to allow
  -- overriding the hidden settings in a parent sl.
  --
  -- @since 0.1.0.0
  , slGhcOptions :: !(Map PackageName [Text])
  -- ^ GHC options per package
  --
  -- @since 0.1.0.0
  , slPublishTime :: !(Maybe UTCTime)
  -- ^ Publication timestamp for this snapshot. This field is optional, and
  -- is for informational purposes only.
  --
  -- @since 0.1.0.0
  }
  deriving (Show, Eq, Generic)

instance ToJSON SnapshotLayer where
  toJSON snap = object $ concat
    [ ["resolver" .= slParent snap]
    , maybe [] (\compiler -> ["compiler" .= compiler]) (slCompiler snap)
    , ["packages" .= slLocations snap]
    , if Set.null (slDropPackages snap) then [] else ["drop-packages" .= Set.map CabalString (slDropPackages snap)]
    , if Map.null (slFlags snap) then [] else ["flags" .= fmap toCabalStringMap (toCabalStringMap (slFlags snap))]
    , if Map.null (slHidden snap) then [] else ["hidden" .= toCabalStringMap (slHidden snap)]
    , if Map.null (slGhcOptions snap) then [] else ["ghc-options" .= toCabalStringMap (slGhcOptions snap)]
    , maybe [] (\time -> ["publish-time" .= time]) (slPublishTime snap)
    ]

-- | Convert snapshot layer into its "raw" equivalent.
--
-- @since 0.1.0.0
toRawSnapshotLayer :: SnapshotLayer -> RawSnapshotLayer
toRawSnapshotLayer sl = RawSnapshotLayer
  { rslParent = toRawSL (slParent sl)
  , rslCompiler = slCompiler sl
  , rslLocations = map toRawPLI (slLocations sl)
  , rslDropPackages = slDropPackages sl
  , rslFlags = slFlags sl
  , rslHidden = slHidden sl
  , rslGhcOptions = slGhcOptions sl
  , rslPublishTime = slPublishTime sl
  }

-- | An arbitrary hash for a snapshot, used for finding module names
-- in a snapshot. Mostly intended for Stack's usage.
--
-- @since 0.1.0.0
newtype SnapshotCacheHash = SnapshotCacheHash { unSnapshotCacheHash :: SHA256}
  deriving (Show)

-- | Get the path to the global hints cache file
getGlobalHintsFile :: HasPantryConfig env => RIO env (Path Abs File)
getGlobalHintsFile = do
  root <- view $ pantryConfigL.to pcRootDir
  globalHintsRelFile <- parseRelFile "global-hints-cache.yaml"
  pure $ root </> globalHintsRelFile

-- | Creates BlobKey for an input ByteString
--
-- @since 0.1.0.0
bsToBlobKey :: ByteString -> BlobKey
bsToBlobKey bs =
    BlobKey (SHA256.hashBytes bs) (FileSize (fromIntegral (B.length bs)))

-- | Warn if the package uses 'PCHpack'.
--
-- @since 0.4.0.0
warnMissingCabalFile :: HasLogFunc env => RawPackageLocationImmutable -> RIO env ()
warnMissingCabalFile loc =
  logWarn $
  "DEPRECATED: The package at " <> display loc <>
  " does not include a cabal file.\n" <>
  "Instead, it includes an hpack package.yaml file for generating a cabal file.\n" <>
  "This usage is deprecated; please see https://github.com/commercialhaskell/stack/issues/5210.\n" <>
  "Support for this workflow will be removed in the future.\n"