{-# LANGUAGE ViewPatterns #-}
{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}

-- | Template name handling.

module Stack.Types.TemplateName where

import           Control.Error.Safe (justErr)
import           Control.Applicative
import           Data.Aeson.Extended (FromJSON, withText, parseJSON)
import           Data.Aeson.Types (typeMismatch)
import           Data.Foldable (asum)
import           Data.Monoid
import           Data.Text (Text)
import qualified Data.Text as T
import           Data.Yaml (Value(Object), (.:?))
import           Language.Haskell.TH
import           Network.HTTP.Client (parseRequest)
import qualified Options.Applicative as O
import           Path
import           Path.Internal
import           Prelude

-- | A template name.
data TemplateName = TemplateName !Text !TemplatePath
  deriving (Ord,Eq,Show)

data TemplatePath = AbsPath (Path Abs File)
                  -- ^ an absolute path on the filesystem
                  | RelPath (Path Rel File)
                  -- ^ a relative path on the filesystem, or relative to
                  -- the template repository
                  | UrlPath String
                  -- ^ a full URL
  deriving (Eq, Ord, Show)

instance FromJSON TemplateName where
    parseJSON = withText "TemplateName" $
        either fail return . parseTemplateNameFromString . T.unpack

data TemplateInfo = TemplateInfo
  { author      :: Maybe Text
  , description :: Maybe Text }
  deriving (Eq, Ord, Show)

instance FromJSON TemplateInfo where
  parseJSON (Object v) = TemplateInfo <$> v .:? "author" <*> v .:? "description"
  parseJSON invalid = typeMismatch "Template Info" invalid

-- | An argument which accepts a template name of the format
-- @foo.hsfiles@ or @foo@, ultimately normalized to @foo@.
templateNameArgument :: O.Mod O.ArgumentFields TemplateName
                     -> O.Parser TemplateName
templateNameArgument =
    O.argument
        (do string <- O.str
            either O.readerError return (parseTemplateNameFromString string))

-- | An argument which accepts a @key:value@ pair for specifying parameters.
templateParamArgument :: O.Mod O.OptionFields (Text,Text)
                      -> O.Parser (Text,Text)
templateParamArgument =
    O.option
        (do string <- O.str
            either O.readerError return (parsePair string))
  where
    parsePair :: String -> Either String (Text, Text)
    parsePair s =
        case break (==':') s of
            (key,':':value@(_:_)) -> Right (T.pack key, T.pack value)
            _ -> Left ("Expected key:value format for argument: " <> s)

-- | Parse a template name from a string.
parseTemplateNameFromString :: String -> Either String TemplateName
parseTemplateNameFromString fname =
    case T.stripSuffix ".hsfiles" (T.pack fname) of
        Nothing -> parseValidFile (T.pack fname) (fname <> ".hsfiles") fname
        Just prefix -> parseValidFile prefix fname fname
  where
    parseValidFile prefix hsf orig = justErr expected
                                           $ asum (validParses prefix hsf orig)
    validParses prefix hsf orig =
        -- NOTE: order is important
        [ TemplateName (T.pack orig) . UrlPath <$> (parseRequest orig *> Just orig)
        , TemplateName prefix        . AbsPath <$> parseAbsFile hsf
        , TemplateName prefix        . RelPath <$> parseRelFile hsf
        ]
    expected = "Expected a template like: foo or foo.hsfiles or\
               \ https://example.com/foo.hsfiles"

-- | Make a template name.
mkTemplateName :: String -> Q Exp
mkTemplateName s =
    case parseTemplateNameFromString s of
        Left{} -> error ("Invalid template name: " ++ show s)
        Right (TemplateName (T.unpack -> prefix) p) ->
            [|TemplateName (T.pack prefix) $(pn)|]
            where pn =
                      case p of
                          AbsPath (Path fp) -> [|AbsPath (Path fp)|]
                          RelPath (Path fp) -> [|RelPath (Path fp)|]
                          UrlPath fp -> [|UrlPath fp|]

-- | Get a text representation of the template name.
templateName :: TemplateName -> Text
templateName (TemplateName prefix _) = prefix

-- | Get the path of the template.
templatePath :: TemplateName -> TemplatePath
templatePath (TemplateName _ fp) = fp