-----------------------------------------------------------------------------
-- |
-- Module      :  Distribution.Client.Init.Heuristics
-- Copyright   :  (c) Benedikt Huber 2009
-- License     :  BSD-like
--
-- Maintainer  :  cabal-devel@haskell.org
-- Stability   :  provisional
-- Portability :  portable
--
-- Heuristics for creating initial cabal files.
--
-----------------------------------------------------------------------------
module Distribution.Client.Init.Heuristics (
    guessPackageName,
    scanForModules,     SourceFileEntry(..),
    neededBuildPrograms,
    guessMainFileCandidates,
    guessAuthorNameMail,
    knownCategories,
) where

import Prelude ()
import Distribution.Client.Compat.Prelude
import Distribution.Utils.Generic (safeHead, safeTail, safeLast)

import Distribution.Simple.Setup (Flag(..), flagToMaybe)
import Distribution.ModuleName
    ( ModuleName, toFilePath )
import qualified Distribution.Package as P
import qualified Distribution.PackageDescription as PD
    ( category, packageDescription )
import Distribution.Client.Utils
         ( tryCanonicalizePath )
import Language.Haskell.Extension ( Extension )

import Distribution.Solver.Types.PackageIndex
    ( allPackagesByName )
import Distribution.Solver.Types.SourcePackage
    ( srcpkgDescription )

import Distribution.Client.Types ( SourcePackageDb(..) )
import Data.Char   ( isLower )
import Data.List   ( isInfixOf )
import qualified Data.Set as Set ( fromList, toList )
import System.Directory ( getCurrentDirectory, getDirectoryContents,
                          doesDirectoryExist, doesFileExist, getHomeDirectory, )
import Distribution.Compat.Environment ( getEnvironment )
import System.FilePath ( takeExtension, takeBaseName, dropExtension,
                         (</>), (<.>), splitDirectories, makeRelative )

import Distribution.Client.Init.Types     ( InitFlags(..) )
import Distribution.Client.Compat.Process ( readProcessWithExitCode )

import qualified Distribution.Utils.ShortText as ShortText

-- | Return a list of candidate main files for this executable: top-level
-- modules including the word 'Main' in the file name. The list is sorted in
-- order of preference, shorter file names are preferred. 'Right's are existing
-- candidates and 'Left's are those that do not yet exist.
guessMainFileCandidates :: InitFlags -> IO [Either FilePath FilePath]
guessMainFileCandidates flags = do
  dir <-
    maybe getCurrentDirectory return (flagToMaybe $ packageDir flags)
  files <- getDirectoryContents dir
  let existingCandidates = filter isMain files
      -- We always want to give the user at least one default choice.  If either
      -- Main.hs or Main.lhs has already been created, then we don't want to
      -- suggest the other; however, if neither has been created, then we
      -- suggest both.
      newCandidates =
        if any (`elem` existingCandidates) ["Main.hs", "Main.lhs"]
        then []
        else ["Main.hs", "Main.lhs"]
      candidates =
        sortBy (\x y -> comparing (length . either id id) x y
                        `mappend` compare x y)
               (map Left newCandidates ++ map Right existingCandidates)
  return candidates

  where
    isMain f =    (isInfixOf "Main" f || isInfixOf  "main" f)
               && (isSuffixOf ".hs" f || isSuffixOf ".lhs" f)

-- | Guess the package name based on the given root directory.
guessPackageName :: FilePath -> IO P.PackageName
guessPackageName = liftM (P.mkPackageName . repair . fromMaybe "" . safeLast . splitDirectories)
                 . tryCanonicalizePath
  where
    -- Treat each span of non-alphanumeric characters as a hyphen. Each
    -- hyphenated component of a package name must contain at least one
    -- alphabetic character. An arbitrary character ('x') will be prepended if
    -- this is not the case for the first component, and subsequent components
    -- will simply be run together. For example, "1+2_foo-3" will become
    -- "x12-foo3".
    repair = repair' ('x' :) id
    repair' invalid valid x = case dropWhile (not . isAlphaNum) x of
        "" -> repairComponent ""
        x' -> let (c, r) = first repairComponent $ break (not . isAlphaNum) x'
              in c ++ repairRest r
      where
        repairComponent c | all isDigit c = invalid c
                          | otherwise     = valid c
    repairRest = repair' id ('-' :)

-- |Data type of source files found in the working directory
data SourceFileEntry = SourceFileEntry
    { relativeSourcePath :: FilePath
    , moduleName         :: ModuleName
    , fileExtension      :: String
    , imports            :: [ModuleName]
    , extensions         :: [Extension]
    } deriving Show

sfToFileName :: FilePath -> SourceFileEntry -> FilePath
sfToFileName projectRoot (SourceFileEntry relPath m ext _ _)
  = projectRoot </> relPath </> toFilePath m <.> ext

-- |Search for source files in the given directory
-- and return pairs of guessed Haskell source path and
-- module names.
scanForModules :: FilePath -> IO [SourceFileEntry]
scanForModules rootDir = scanForModulesIn rootDir rootDir

scanForModulesIn :: FilePath -> FilePath -> IO [SourceFileEntry]
scanForModulesIn projectRoot srcRoot = scan srcRoot []
  where
    scan dir hierarchy = do
        entries <- getDirectoryContents (projectRoot </> dir)
        (files, dirs) <- liftM partitionEithers (traverse (tagIsDir dir) entries)
        let modules = catMaybes [ guessModuleName hierarchy file
                                | file <- files
                                , maybe False isUpper (safeHead file) ]
        modules' <- traverse (findImportsAndExts projectRoot) modules
        recMods <- traverse (scanRecursive dir hierarchy) dirs
        return $ concat (modules' : recMods)
    tagIsDir parent entry = do
        isDir <- doesDirectoryExist (parent </> entry)
        return $ (if isDir then Right else Left) entry
    guessModuleName hierarchy entry
        | takeBaseName entry == "Setup" = Nothing
        | ext `elem` sourceExtensions   =
            SourceFileEntry <$> pure relRoot <*> modName <*> pure ext <*> pure [] <*> pure []
        | otherwise = Nothing
      where
        relRoot       = makeRelative projectRoot srcRoot
        unqualModName = dropExtension entry
        modName       = simpleParsec
                      $ intercalate "." . reverse $ (unqualModName : hierarchy)
        ext           = case takeExtension entry of '.':e -> e; e -> e
    scanRecursive parent hierarchy entry
      | maybe False isUpper (safeHead entry) = scan (parent </> entry) (entry : hierarchy)
      | maybe False isLower (safeHead entry) && not (ignoreDir entry) =
          scanForModulesIn projectRoot $ foldl (</>) srcRoot (reverse (entry : hierarchy))
      | otherwise = return []
    ignoreDir ('.':_)  = True
    ignoreDir dir      = dir `elem` ["dist", "_darcs"]

findImportsAndExts :: FilePath -> SourceFileEntry -> IO SourceFileEntry
findImportsAndExts projectRoot sf = do
  s <- readFile (sfToFileName projectRoot sf)

  let modules = mapMaybe
                ( getModName
                . drop 1
                . filter (not . null)
                . dropWhile (/= "import")
                . words
                )
              . filter (not . ("--" `isPrefixOf`)) -- poor man's comment filtering
              . lines
              $ s

      -- TODO: We should probably make a better attempt at parsing
      -- comments above.  Unfortunately we can't use a full-fledged
      -- Haskell parser since cabal's dependencies must be kept at a
      -- minimum.

      -- A poor man's LANGUAGE pragma parser.
      exts = mapMaybe simpleParsec
           . concatMap getPragmas
           . filter isLANGUAGEPragma
           . map fst
           . drop 1
           . takeWhile (not . null . snd)
           . iterate (takeBraces . snd)
           $ ("",s)

      takeBraces = break (== '}') . dropWhile (/= '{')

      isLANGUAGEPragma = ("{-# LANGUAGE " `isPrefixOf`)

      getPragmas = map trim . splitCommas . takeWhile (/= '#') . drop 13

      splitCommas "" = []
      splitCommas xs = x : splitCommas (drop 1 y)
        where (x,y) = break (==',') xs

  return sf { imports    = modules
            , extensions = exts
            }

 where getModName :: [String] -> Maybe ModuleName
       getModName []               = Nothing
       getModName ("qualified":ws) = getModName ws
       getModName (ms:_)           = simpleParsec ms



-- Unfortunately we cannot use the version exported by Distribution.Simple.Program
knownSuffixHandlers :: [(String,String)]
knownSuffixHandlers =
  [ ("gc",     "greencard")
  , ("chs",    "chs")
  , ("hsc",    "hsc2hs")
  , ("x",      "alex")
  , ("y",      "happy")
  , ("ly",     "happy")
  , ("cpphs",  "cpp")
  ]

sourceExtensions :: [String]
sourceExtensions = "hs" : "lhs" : map fst knownSuffixHandlers

neededBuildPrograms :: [SourceFileEntry] -> [String]
neededBuildPrograms entries =
    [ handler
    | ext <- nubSet (map fileExtension entries)
    , handler <- maybeToList (lookup ext knownSuffixHandlers)
    ]

-- | Guess author and email using darcs and git configuration options. Use
-- the following in decreasing order of preference:
--
-- 1. vcs env vars ($DARCS_EMAIL, $GIT_AUTHOR_*)
-- 2. Local repo configs
-- 3. Global vcs configs
-- 4. The generic $EMAIL
--
-- Name and email are processed separately, so the guess might end up being
-- a name from DARCS_EMAIL and an email from git config.
--
-- Darcs has preference, for tradition's sake.
guessAuthorNameMail :: IO (Flag String, Flag String)
guessAuthorNameMail = fmap authorGuessPure authorGuessIO

-- Ordered in increasing preference, since Flag-as-monoid is identical to
-- Last.
authorGuessPure :: AuthorGuessIO -> AuthorGuess
authorGuessPure (AuthorGuessIO { authorGuessEnv = env
                               , authorGuessLocalDarcs = darcsLocalF
                               , authorGuessGlobalDarcs = darcsGlobalF
                               , authorGuessLocalGit = gitLocal
                               , authorGuessGlobalGit = gitGlobal })
    = mconcat
        [ emailEnv env
        , gitGlobal
        , darcsCfg darcsGlobalF
        , gitLocal
        , darcsCfg darcsLocalF
        , gitEnv env
        , darcsEnv env
        ]

authorGuessIO :: IO AuthorGuessIO
authorGuessIO = AuthorGuessIO
    <$> getEnvironment
    <*> (maybeReadFile $ "_darcs" </> "prefs" </> "author")
    <*> (maybeReadFile =<< liftM (</> (".darcs" </> "author")) getHomeDirectory)
    <*> gitCfg Local
    <*> gitCfg Global

-- Types and functions used for guessing the author are now defined:

type AuthorGuess   = (Flag String, Flag String)
type Enviro        = [(String, String)]
data GitLoc        = Local | Global
data AuthorGuessIO = AuthorGuessIO {
    authorGuessEnv         :: Enviro,         -- ^ Environment lookup table
    authorGuessLocalDarcs  :: (Maybe String), -- ^ Contents of local darcs author info
    authorGuessGlobalDarcs :: (Maybe String), -- ^ Contents of global darcs author info
    authorGuessLocalGit    :: AuthorGuess,   -- ^ Git config --local
    authorGuessGlobalGit   :: AuthorGuess    -- ^ Git config --global
  }

darcsEnv :: Enviro -> AuthorGuess
darcsEnv = maybe mempty nameAndMail . lookup "DARCS_EMAIL"

gitEnv :: Enviro -> AuthorGuess
gitEnv env = (name, mail)
  where
    name = maybeFlag "GIT_AUTHOR_NAME" env
    mail = maybeFlag "GIT_AUTHOR_EMAIL" env

darcsCfg :: Maybe String -> AuthorGuess
darcsCfg = maybe mempty nameAndMail

emailEnv :: Enviro -> AuthorGuess
emailEnv env = (mempty, mail)
  where
    mail = maybeFlag "EMAIL" env

gitCfg :: GitLoc -> IO AuthorGuess
gitCfg which = do
  name <- gitVar which "user.name"
  mail <- gitVar which "user.email"
  return (name, mail)

gitVar :: GitLoc -> String -> IO (Flag String)
gitVar which = fmap happyOutput . gitConfigQuery which

happyOutput :: (ExitCode, a, t) -> Flag a
happyOutput v = case v of
  (ExitSuccess, s, _) -> Flag s
  _                   -> mempty

gitConfigQuery :: GitLoc -> String -> IO (ExitCode, String, String)
gitConfigQuery which key =
    fmap trim' $ readProcessWithExitCode "git" ["config", w, key] ""
  where
    w = case which of
        Local  -> "--local"
        Global -> "--global"
    trim' (a, b, c) = (a, trim b, c)

maybeFlag :: String -> Enviro -> Flag String
maybeFlag k = maybe mempty Flag . lookup k

-- | Read the first non-comment, non-trivial line of a file, if it exists
maybeReadFile :: String -> IO (Maybe String)
maybeReadFile f = do
    exists <- doesFileExist f
    if exists
        then fmap getFirstLine $ readFile f
        else return Nothing
  where
    getFirstLine content =
      let nontrivialLines = dropWhile (\l -> (null l) || ("#" `isPrefixOf` l)) . lines $ content
      in case nontrivialLines of
           [] -> Nothing
           (l:_) -> Just l

-- |Get list of categories used in Hackage. NOTE: Very slow, needs to be cached
knownCategories :: SourcePackageDb -> [String]
knownCategories (SourcePackageDb sourcePkgIndex _) = nubSet
    [ cat | pkg <- maybeToList . safeHead =<< (allPackagesByName sourcePkgIndex)
          , let catList = (PD.category . PD.packageDescription . srcpkgDescription) pkg
          , cat <- splitString ',' $ ShortText.fromShortText catList
    ]

-- Parse name and email, from darcs pref files or environment variable
nameAndMail :: String -> (Flag String, Flag String)
nameAndMail str
  | all isSpace nameOrEmail = mempty
  | null erest = (mempty, Flag $ trim nameOrEmail)
  | otherwise  = (Flag $ trim nameOrEmail, Flag mail)
  where
    (nameOrEmail,erest) = break (== '<') str
    (mail,_)            = break (== '>') (safeTail erest)

trim :: String -> String
trim = removeLeadingSpace . reverse . removeLeadingSpace . reverse
  where
    removeLeadingSpace  = dropWhile isSpace

-- split string at given character, and remove whitespace
splitString :: Char -> String -> [String]
splitString sep str = go str where
    go s = if null s' then [] else tok : go rest where
      s' = dropWhile (\c -> c == sep || isSpace c) s
      (tok,rest) = break (==sep) s'

nubSet :: (Ord a) => [a] -> [a]
nubSet = Set.toList . Set.fromList

{-
test db testProjectRoot = do
  putStrLn "Guessed package name"
  (guessPackageName >=> print) testProjectRoot
  putStrLn "Guessed name and email"
  guessAuthorNameMail >>= print

  mods <- scanForModules testProjectRoot

  putStrLn "Guessed modules"
  mapM_ print mods
  putStrLn "Needed build programs"
  print (neededBuildPrograms mods)

  putStrLn "List of known categories"
  print $ knownCategories db
-}
