-- |
-- Module      :  Documentation.DocCheck
-- Copyright   :  (c) Mateusz Kowalczyk 2013,
-- License     :  GPLv3
--
-- Maintainer  :  fuuzetsu@fuuzetsu.co.uk
-- Stability   :  experimental
-- Portability :  portable

{-# LANGUAGE OverloadedStrings #-}
module Documentation.DocCheck where

import           Bag (bagToList)
import           Control.Applicative ((*>), (<$>))
import           Control.Monad (unless, liftM2)
import qualified Data.Attoparsec.Text as A (takeWhile, Parser, parseOnly)
import           Data.Text (Text, pack)
import           DynFlags (DynFlag(Opt_Haddock), getDynFlags, dopt_set)
import           FastString (unpackFS)
import           GHC (Ghc, HsDocString(..), DocDecl(..), HsDecl(..),
                      GenLocated(L), hsmodDecls, parser)
import           System.Directory (doesFileExist, doesDirectoryExist)
import           System.Directory.Tree (AnchoredDirTree(..), DirTree(..),
                                        filterDir, readDirectoryWith,
                                        flattenDir)
import           System.FilePath (takeExtension)
import           System.Exit (exitFailure)

-- | Extracts Haddock documentation from all the files provided. Note that any
-- modules that fail to parse will be reported as such. Note that the program
-- will still exit succesfully even if some files don't parse but no potential
-- warnings are found in regards to documentation.
extractDocs
  :: [(FilePath, String)] -- ^ Files and their sources to extract the docs from
     -> Ghc ([(FilePath, String)], [(FilePath, [String])])
extractDocs files = do
  dflags' <- flip dopt_set Opt_Haddock <$> getDynFlags
  let psed = map (\(f, s) -> (f, parser s dflags' f)) files
  return (failedParses psed, map stripLoc $ rightLocs psed)
  where
    -- Determine which modules failed to parse
    failedParses xs = [ (f, show $ bagToList m) | (f, Left m) <- xs ]


    -- Pull out module declarations from successful parses, drop location
    rightLocs xs = [ (f, hsmodDecls x) | (f, Right (_, L _ x)) <- xs ]

    -- Get out Haddock comment strings from amongst other module declarations
    stripLoc (f, ls) = (f, [ docDeclToString x | (L _ (DocD x)) <- ls ])

-- | Extracts a 'String' from 'DocDecl's by unpacking the 'FastString's
-- with 'unpackFs' packed in the 'HsDocString' data type.
docDeclToString :: DocDecl -> String
docDeclToString (DocCommentNext (HsDocString x)) = unpackFS x
docDeclToString (DocCommentPrev (HsDocString x)) = unpackFS x
docDeclToString (DocCommentNamed _ (HsDocString x)) = unpackFS x
docDeclToString (DocGroup _ (HsDocString x)) = unpackFS x

-- | Finds potential problems for each comment in each file and
-- formats the warning messages.
findIssues :: [(FilePath, [String])] -> [String]
findIssues fs = filter (not . null) $ map warn fs
  where
    warn :: (FilePath, [String]) -> String
    warn (p, docs) =
      case [ (d, x) |
             (d, Just x) <- map (\d' -> (d', runParsers $ pack d')) docs ] of
        [] -> []
        xs -> "Potential problems in " ++ p
              ++ " :\n" ++ unlines (map formatProblems xs)
          where
            formatProblems :: (String, [String]) -> String
            formatProblems (doc, issues) =
              unlines $ map (++ " in ‘" ++ doc ++ "’") issues

-- | Runs multiple parsers on each of the strings and collects results of any
-- parsers that succeed. Note that these results will are used as the warning
-- messages so each parser should be in form of
-- @p = someParsing *> return \\"warning message for this parser\\"@
runParsers :: Text -> Maybe [String]
runParsers d = case [ x | Right x <- map (`A.parseOnly` d) parsers ] of
  [] -> Nothing
  xs -> Just xs
  where
    parsers :: [A.Parser String]
    parsers = [escapingEmph, htmlEmph]
      where
        escapingEmph = A.takeWhile (/= '/') *> "/"
                       *> A.takeWhile (`notElem` "\n\\/") *> "\\"
                       *> return ("attempting to escape a character "
                                  ++ "inside of emphasis")
        htmlEmph = A.takeWhile (/= '/') *> "/"
                   *> A.takeWhile (`notElem` "\n&/") *> "&#"
                   *> return "HTML sequence inside of emphasis"

-- | Walks the file system looking for Haskell source files, starting from the
-- given file.
getHaskellFiles :: FilePath -> IO [FilePath]
getHaskellFiles s = do
  exists <- liftM2 (||) (doesFileExist s) (doesDirectoryExist s)
  unless exists $ putStrLn ("no such file or directory: " ++ s) >> exitFailure
  _:/tree <- readDirectoryWith return s
  return $ map flattenFiles $ filter f $ flattenDir $ filterDir myPred tree
  where
    myPred (Dir ('.':_) _) = False
    myPred (File n _) = e == ".hs" || e == ".lhs"
      where e = takeExtension n
    myPred _ = True

    f (File _ _) = True
    f _ = False

    flattenFiles (File _ path) = path
    flattenFiles x = error $ "Got non-file into flattenFiles: " ++ show x