{-# LANGUAGE CPP, Rank2Types, ExistentialQuantification #-}
module Options.Applicative.Types (
  ParseError(..),
  ParserInfo(..),
  ParserPrefs(..),

  Option(..),
  OptName(..),
  isShortName,
  isLongName,

  OptReader(..),
  OptProperties(..),
  OptVisibility(..),
  Backtracking(..),
  ReadM(..),
  readerAsk,
  readerAbort,
  readerError,
  CReader(..),
  Parser(..),
  ParserM(..),
  Completer(..),
  mkCompleter,
  CompletionResult(..),
  ParserFailure(..),
  ParserResult(..),
  overFailure,
  Args,
  ArgPolicy(..),
  ArgumentReachability(..),
  AltNodeType(..),
  OptTree(..),
  ParserHelp(..),
  SomeParser(..),
  Context(..),
  IsCmdStart(..),

  fromM,
  oneM,
  manyM,
  someM,

  filterOptional,
  optVisibility,
  optMetaVar,
  optHelp,
  optShowDefault,
  optDescMod
  ) where

import Control.Applicative
import Control.Monad (ap, liftM, MonadPlus, mzero, mplus)
import Control.Monad.Trans.Except (Except, throwE)
import Control.Monad.Trans.Class (lift)
import Control.Monad.Trans.Reader (ReaderT, ask)
import qualified Control.Monad.Fail as Fail
import Data.Semigroup hiding (Option)
import Prelude

import System.Exit (ExitCode(..))

import Options.Applicative.Help.Types
import Options.Applicative.Help.Pretty
import Options.Applicative.Help.Chunk


data ParseError
  = ErrorMsg String
  | InfoMsg String
  | ShowHelpText (Maybe String)
  | UnknownError
  | MissingError IsCmdStart SomeParser
  | ExpectsArgError String
  | UnexpectedError String SomeParser

data IsCmdStart = CmdStart | CmdCont
  deriving Show

instance Monoid ParseError where
  mempty = UnknownError
  mappend = (<>)

instance Semigroup ParseError where
  m <> UnknownError = m
  _ <> m = m

-- | A full description for a runnable 'Parser' for a program.
data ParserInfo a = ParserInfo
  { infoParser :: Parser a    -- ^ the option parser for the program
  , infoFullDesc :: Bool      -- ^ whether the help text should contain full
                              -- documentation
  , infoProgDesc :: Chunk Doc -- ^ brief parser description
  , infoHeader :: Chunk Doc   -- ^ header of the full parser description
  , infoFooter :: Chunk Doc   -- ^ footer of the full parser description
  , infoFailureCode :: Int    -- ^ exit code for a parser failure
  , infoPolicy :: ArgPolicy   -- ^ allow regular options and flags to occur
                              -- after arguments (default: InterspersePolicy)
  }

instance Functor ParserInfo where
  fmap f i = i { infoParser = fmap f (infoParser i) }

data Backtracking
  = Backtrack
  | NoBacktrack
  | SubparserInline
  deriving (Eq, Show)

-- | Global preferences for a top-level 'Parser'.
data ParserPrefs = ParserPrefs
  { prefMultiSuffix :: String     -- ^ metavar suffix for multiple options
  , prefDisambiguate :: Bool      -- ^ automatically disambiguate abbreviations
                                  -- (default: False)
  , prefShowHelpOnError :: Bool   -- ^ always show help text on parse errors
                                  -- (default: False)
  , prefShowHelpOnEmpty :: Bool   -- ^ show the help text for a command or subcommand
                                  -- if it fails with no input (default: False)
  , prefBacktrack :: Backtracking -- ^ backtrack to parent parser when a
                                  -- subcommand fails (default: Backtrack)
  , prefColumns :: Int            -- ^ number of columns in the terminal, used to
                                  -- format the help page (default: 80)
  , prefHelpLongEquals :: Bool    -- ^ when displaying long names in usage and help,
                                  -- use an '=' sign for long names, rather than a
                                  -- single space (default: False)
  , prefHelpShowGlobal :: Bool    -- ^ when displaying subparsers' usage help,
                                  -- show parent options under a "global options"
                                  -- section (default: True)
  } deriving (Eq, Show)

data OptName = OptShort !Char
             | OptLong !String
  deriving (Eq, Ord, Show)

isShortName :: OptName -> Bool
isShortName (OptShort _) = True
isShortName (OptLong _)  = False

isLongName :: OptName -> Bool
isLongName = not . isShortName

-- | Visibility of an option in the help text.
data OptVisibility
  = Internal          -- ^ does not appear in the help text at all
  | Hidden            -- ^ only visible in the full description
  | Visible           -- ^ visible both in the full and brief descriptions
  deriving (Eq, Ord, Show)

-- | Specification for an individual parser option.
data OptProperties = OptProperties
  { propVisibility :: OptVisibility       -- ^ whether this flag is shown in the brief description
  , propHelp :: Chunk Doc                 -- ^ help text for this option
  , propMetaVar :: String                 -- ^ metavariable for this option
  , propShowDefault :: Maybe String       -- ^ what to show in the help text as the default
  , propShowGlobal :: Bool                -- ^ whether the option is presented in global options text
  , propDescMod :: Maybe ( Doc -> Doc )   -- ^ a function to run over the brief description
  }

instance Show OptProperties where
  showsPrec p (OptProperties pV pH pMV pSD pSG _)
    = showParen (p >= 11)
    $ showString "OptProperties { propVisibility = " . shows pV
    . showString ", propHelp = " . shows pH
    . showString ", propMetaVar = " . shows pMV
    . showString ", propShowDefault = " . shows pSD
    . showString ", propShowGlobal = " . shows pSG
    . showString ", propDescMod = _ }"

-- | A single option of a parser.
data Option a = Option
  { optMain :: OptReader a               -- ^ reader for this option
  , optProps :: OptProperties            -- ^ properties of this option
  }

data SomeParser = forall a . SomeParser (Parser a)

-- | Subparser context, containing the 'name' of the subparser and its parser info.
--   Used by parserFailure to display relevant usage information when parsing inside a subparser fails.
data Context = forall a. Context String (ParserInfo a)

instance Show (Option a) where
    show opt = "Option {optProps = " ++ show (optProps opt) ++ "}"

instance Functor Option where
  fmap f (Option m p) = Option (fmap f m) p

-- | A newtype over 'ReaderT String Except', used by option readers.
newtype ReadM a = ReadM
  { unReadM :: ReaderT String (Except ParseError) a }

instance Functor ReadM where
  fmap f (ReadM r) = ReadM (fmap f r)

instance Applicative ReadM where
  pure = ReadM . pure
  ReadM x <*> ReadM y = ReadM $ x <*> y

instance Alternative ReadM where
  empty = mzero
  (<|>) = mplus

instance Monad ReadM where
  return = pure
  ReadM r >>= f = ReadM $ r >>= unReadM . f

#if !(MIN_VERSION_base(4,13,0))
  fail = Fail.fail
#endif

instance Fail.MonadFail ReadM where
  fail = readerError

instance MonadPlus ReadM where
  mzero = ReadM mzero
  mplus (ReadM x) (ReadM y) = ReadM $ mplus x y

-- | Return the value being read.
readerAsk :: ReadM String
readerAsk = ReadM ask

-- | Abort option reader by exiting with a 'ParseError'.
readerAbort :: ParseError -> ReadM a
readerAbort = ReadM . lift . throwE

-- | Abort option reader by exiting with an error message.
readerError :: String -> ReadM a
readerError = readerAbort . ErrorMsg

data CReader a = CReader
  { crCompleter :: Completer
  , crReader :: ReadM a }

instance Functor CReader where
  fmap f (CReader c r) = CReader c (fmap f r)

-- | An 'OptReader' defines whether an option matches an command line argument.
data OptReader a
  = OptReader [OptName] (CReader a) (String -> ParseError)
  -- ^ option reader
  | FlagReader [OptName] !a
  -- ^ flag reader
  | ArgReader (CReader a)
  -- ^ argument reader
  | CmdReader (Maybe String) [String] (String -> Maybe (ParserInfo a))
  -- ^ command reader

instance Functor OptReader where
  fmap f (OptReader ns cr e) = OptReader ns (fmap f cr) e
  fmap f (FlagReader ns x) = FlagReader ns (f x)
  fmap f (ArgReader cr) = ArgReader (fmap f cr)
  fmap f (CmdReader n cs g) = CmdReader n cs ((fmap . fmap) f . g)

-- | A @Parser a@ is an option parser returning a value of type 'a'.
data Parser a
  = NilP (Maybe a)
  | OptP (Option a)
  | forall x . MultP (Parser (x -> a)) (Parser x)
  | AltP (Parser a) (Parser a)
  | forall x . BindP (Parser x) (x -> Parser a)

instance Functor Parser where
  fmap f (NilP x) = NilP (fmap f x)
  fmap f (OptP opt) = OptP (fmap f opt)
  fmap f (MultP p1 p2) = MultP (fmap (f.) p1) p2
  fmap f (AltP p1 p2) = AltP (fmap f p1) (fmap f p2)
  fmap f (BindP p k) = BindP p (fmap f . k)

instance Applicative Parser where
  pure = NilP . Just
  (<*>) = MultP

newtype ParserM r = ParserM
  { runParserM :: forall x . (r -> Parser x) -> Parser x }

instance Monad ParserM where
  return = pure
  ParserM f >>= g = ParserM $ \k -> f (\x -> runParserM (g x) k)

instance Functor ParserM where
  fmap = liftM

instance Applicative ParserM where
  pure x = ParserM $ \k -> k x
  (<*>) = ap

fromM :: ParserM a -> Parser a
fromM (ParserM f) = f pure

oneM :: Parser a -> ParserM a
oneM p = ParserM (BindP p)

manyM :: Parser a -> ParserM [a]
manyM p = do
  mx <- oneM (optional p)
  case mx of
    Nothing -> return []
    Just x -> (x:) <$> manyM p

someM :: Parser a -> ParserM [a]
someM p = (:) <$> oneM p <*> manyM p

instance Alternative Parser where
  empty = NilP Nothing
  (<|>) = AltP
  many = fromM . manyM
  some = fromM . someM

-- | A shell complete function.
newtype Completer = Completer
  { runCompleter :: String -> IO [String] }

-- | Smart constructor for a 'Completer'
mkCompleter :: (String -> IO [String]) -> Completer
mkCompleter = Completer

instance Semigroup Completer where
  (Completer c1) <> (Completer c2) =
    Completer $ \s -> (++) <$> c1 s <*> c2 s

instance Monoid Completer where
  mempty = Completer $ \_ -> return []
  mappend = (<>)

newtype CompletionResult = CompletionResult
  { execCompletion :: String -> IO String }

instance Show CompletionResult where
  showsPrec p _ = showParen (p > 10) $
    showString "CompletionResult _"

newtype ParserFailure h = ParserFailure
  { execFailure :: String -> (h, ExitCode, Int) }

instance Show h => Show (ParserFailure h) where
  showsPrec p (ParserFailure f)
    = showParen (p > 10)
    $ showString "ParserFailure"
    . showsPrec 11 (f "<program>")

instance Functor ParserFailure where
  fmap f (ParserFailure err) = ParserFailure $ \progn ->
    let (h, exit, cols) = err progn in (f h, exit, cols)

-- | Result of 'execParserPure'.
data ParserResult a
  = Success a
  | Failure (ParserFailure ParserHelp)
  | CompletionInvoked CompletionResult
  deriving Show

instance Functor ParserResult where
  fmap f (Success a) = Success (f a)
  fmap _ (Failure f) = Failure f
  fmap _ (CompletionInvoked c) = CompletionInvoked c

overFailure :: (ParserHelp -> ParserHelp)
            -> ParserResult a -> ParserResult a
overFailure f (Failure failure) = Failure $ fmap f failure
overFailure _ r = r

instance Applicative ParserResult where
  pure = Success
  Success f <*> r = fmap f r
  Failure f <*> _ = Failure f
  CompletionInvoked c <*> _ = CompletionInvoked c

instance Monad ParserResult where
  return = pure
  Success x >>= f = f x
  Failure f >>= _ = Failure f
  CompletionInvoked c >>= _ = CompletionInvoked c

type Args = [String]

-- | Policy for how to handle options within the parse
data ArgPolicy
  = Intersperse
  -- ^ The default policy, options and arguments can
  --   be interspersed.
  --   A `--` option can be passed to ensure all following
  --   commands are treated as arguments.
  | NoIntersperse
  -- ^ Options must all come before arguments, once a
  --   single positional argument or subcommand is parsed,
  --   all remaining arguments are treated as positionals.
  --   A `--` option can be passed if the first positional
  --   one needs starts with `-`.
  | AllPositionals
  -- ^ No options are parsed at all, all arguments are
  --   treated as positionals.
  --   Is the policy used after `--` is encountered.
  | ForwardOptions
  -- ^ Options and arguments can be interspersed, but if
  --   a given option is not found, it is treated as a
  --   positional argument. This is sometimes useful if
  --   one is passing through most options to another tool,
  --   but are supplying just a few of their own options.
  deriving (Eq, Ord, Show)

newtype ArgumentReachability = ArgumentReachability
  { argumentIsUnreachable :: Bool -- ^ If the result is a positional, if it can't be
                                  --    accessed in the current parser position ( first arg )
  } deriving (Eq, Show)

-- | This type encapsulates whether an 'AltNode' of an 'OptTree' should be displayed
-- with brackets around it.
data AltNodeType = MarkDefault | NoDefault
  deriving (Show, Eq)

data OptTree a
  = Leaf a
  | MultNode [OptTree a]
  | AltNode AltNodeType [OptTree a]
  | BindNode (OptTree a)
  deriving Show

filterOptional :: OptTree a -> OptTree a
filterOptional t = case t of
  Leaf a
    -> Leaf a
  MultNode xs
    -> MultNode (map filterOptional xs)
  AltNode MarkDefault _
    -> AltNode MarkDefault []
  AltNode NoDefault xs
    -> AltNode NoDefault (map filterOptional xs)
  BindNode xs
    -> BindNode (filterOptional xs)

optVisibility :: Option a -> OptVisibility
optVisibility = propVisibility . optProps

optHelp :: Option a -> Chunk Doc
optHelp  = propHelp . optProps

optMetaVar :: Option a -> String
optMetaVar = propMetaVar . optProps

optShowDefault :: Option a -> Maybe String
optShowDefault = propShowDefault . optProps

optDescMod :: Option a -> Maybe ( Doc -> Doc )
optDescMod = propDescMod . optProps