{-# LANGUAGE DeriveDataTypeable    #-}
{-# LANGUAGE FlexibleContexts      #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE OverloadedStrings     #-}
{-# LANGUAGE PatternGuards         #-}
{-# LANGUAGE RankNTypes            #-}
{-# LANGUAGE ScopedTypeVariables   #-}
{-# LANGUAGE TemplateHaskell       #-}
{-# LANGUAGE TupleSections         #-}
{-# LANGUAGE PackageImports        #-}
{-# LANGUAGE ViewPatterns          #-}

-- | Functionality for downloading packages securely for cabal's usage.

module Stack.Fetch
    ( unpackPackages
    , unpackPackageIdents
    , fetchPackages
    , resolvePackages
    , resolvePackagesAllowMissing
    , ResolvedPackage (..)
    , withCabalFiles
    , withCabalLoader
    ) where

import qualified Codec.Archive.Tar              as Tar
import qualified Codec.Archive.Tar.Check        as Tar
import qualified Codec.Archive.Tar.Entry        as Tar
import           Codec.Compression.GZip         (decompress)
import           Control.Applicative
import           Control.Concurrent.Async       (Concurrently (..))
import           Control.Concurrent.MVar.Lifted (modifyMVar, newMVar)
import           Control.Concurrent.STM         (TVar, atomically, modifyTVar,
                                                 newTVarIO, readTVar,
                                                 readTVarIO, writeTVar)
import           Control.Exception              (assert)
import           Control.Monad                  (join, liftM, unless, void,
                                                 when)
import           Control.Monad.Catch
import           Control.Monad.IO.Class
import           Control.Monad.Logger
import           Control.Monad.Reader           (asks, runReaderT)
import           Control.Monad.Trans.Control
import "cryptohash" Crypto.Hash                 (SHA512 (..))
import           Data.ByteString                (ByteString)
import qualified Data.ByteString                as S
import qualified Data.ByteString.Lazy           as L
import           Data.Either                    (partitionEithers)
import qualified Data.Foldable                  as F
import           Data.Function                  (fix)
import           Data.IORef                     (newIORef, readIORef,
                                                 writeIORef)
import           Data.List                      (intercalate)
import           Data.List.NonEmpty             (NonEmpty)
import qualified Data.List.NonEmpty             as NE
import           Data.Map                       (Map)
import qualified Data.Map                       as Map
import           Data.Maybe                     (maybeToList, catMaybes)
import           Data.Monoid                    ((<>))
import           Data.Set                       (Set)
import qualified Data.Set                       as Set
import qualified Data.Text                      as T
import           Data.Text.Encoding             (decodeUtf8)
import           Data.Typeable                  (Typeable)
import           Data.Word                      (Word64)
import           Network.HTTP.Download
import           Path
import           Path.IO
import           Prelude -- Fix AMP warning
import           Stack.GhcPkg
import           Stack.PackageIndex
import           Stack.Types
import qualified System.Directory               as D
import           System.FilePath                ((<.>))
import qualified System.FilePath                as FP
import           System.IO                      (IOMode (ReadMode),
                                                 SeekMode (AbsoluteSeek), hSeek,
                                                 withBinaryFile)
import           System.PosixCompat             (setFileMode)
import           Text.EditDistance              as ED

type PackageCaches = Map PackageIdentifier (PackageIndex, PackageCache)

data FetchException
    = Couldn'tReadIndexTarball FilePath Tar.FormatError
    | Couldn'tReadPackageTarball FilePath SomeException
    | UnpackDirectoryAlreadyExists (Set FilePath)
    | CouldNotParsePackageSelectors [String]
    | UnknownPackageNames (Set PackageName)
    | UnknownPackageIdentifiers (Set PackageIdentifier) String
    deriving Typeable
instance Exception FetchException

instance Show FetchException where
    show (Couldn'tReadIndexTarball fp err) = concat
        [ "There was an error reading the index tarball "
        , fp
        , ": "
        , show err
        ]
    show (Couldn'tReadPackageTarball fp err) = concat
        [ "There was an error reading the package tarball "
        , fp
        , ": "
        , show err
        ]
    show (UnpackDirectoryAlreadyExists dirs) = unlines
        $ "Unable to unpack due to already present directories:"
        : map ("    " ++) (Set.toList dirs)
    show (CouldNotParsePackageSelectors strs) =
        "The following package selectors are not valid package names or identifiers: " ++
        intercalate ", " strs
    show (UnknownPackageNames names) =
        "The following packages were not found in your indices: " ++
        intercalate ", " (map packageNameString $ Set.toList names)
    show (UnknownPackageIdentifiers idents suggestions) =
        "The following package identifiers were not found in your indices: " ++
        intercalate ", " (map packageIdentifierString $ Set.toList idents) ++
        (if null suggestions then "" else "\n" ++ suggestions)

-- | Fetch packages into the cache without unpacking
fetchPackages :: (MonadIO m, MonadBaseControl IO m, MonadReader env m, HasHttpManager env, HasConfig env, MonadThrow m, MonadLogger m, MonadCatch m)
              => EnvOverride
              -> Set PackageIdentifier
              -> m ()
fetchPackages menv idents = do
    resolved <- resolvePackages menv idents Set.empty
    ToFetchResult toFetch alreadyUnpacked <- getToFetch Nothing resolved
    assert (Map.null alreadyUnpacked) (return ())
    nowUnpacked <- fetchPackages' Nothing toFetch
    assert (Map.null nowUnpacked) (return ())

-- | Intended to work for the command line command.
unpackPackages :: (MonadIO m, MonadBaseControl IO m, MonadReader env m, HasHttpManager env, HasConfig env, MonadThrow m, MonadLogger m, MonadCatch m)
               => EnvOverride
               -> FilePath -- ^ destination
               -> [String] -- ^ names or identifiers
               -> m ()
unpackPackages menv dest input = do
    dest' <- resolveDir' dest
    (names, idents) <- case partitionEithers $ map parse input of
        ([], x) -> return $ partitionEithers x
        (errs, _) -> throwM $ CouldNotParsePackageSelectors errs
    resolved <- resolvePackages menv (Set.fromList idents) (Set.fromList names)
    ToFetchResult toFetch alreadyUnpacked <- getToFetch (Just dest') resolved
    unless (Map.null alreadyUnpacked) $
        throwM $ UnpackDirectoryAlreadyExists $ Set.fromList $ map toFilePath $ Map.elems alreadyUnpacked
    unpacked <- fetchPackages' Nothing toFetch
    F.forM_ (Map.toList unpacked) $ \(ident, dest'') -> $logInfo $ T.pack $ concat
        [ "Unpacked "
        , packageIdentifierString ident
        , " to "
        , toFilePath dest''
        ]
  where
    -- Possible future enhancement: parse names as name + version range
    parse s =
        case parsePackageNameFromString s of
            Right x -> Right $ Left x
            Left _ ->
                case parsePackageIdentifierFromString s of
                    Left _ -> Left s
                    Right x -> Right $ Right x

-- | Ensure that all of the given package idents are unpacked into the build
-- unpack directory, and return the paths to all of the subdirectories.
unpackPackageIdents
    :: (MonadBaseControl IO m, MonadIO m, MonadReader env m, HasHttpManager env, HasConfig env, MonadThrow m, MonadLogger m, MonadCatch m)
    => EnvOverride
    -> Path Abs Dir -- ^ unpack directory
    -> Maybe (Path Rel Dir) -- ^ the dist rename directory, see: https://github.com/fpco/stack/issues/157
    -> Set PackageIdentifier
    -> m (Map PackageIdentifier (Path Abs Dir))
unpackPackageIdents menv unpackDir mdistDir idents = do
    resolved <- resolvePackages menv idents Set.empty
    ToFetchResult toFetch alreadyUnpacked <- getToFetch (Just unpackDir) resolved
    nowUnpacked <- fetchPackages' mdistDir toFetch
    return $ alreadyUnpacked <> nowUnpacked

data ResolvedPackage = ResolvedPackage
    { rpCache :: !PackageCache
    , rpIndex :: !PackageIndex
    }

-- | Resolve a set of package names and identifiers into @FetchPackage@ values.
resolvePackages :: (MonadIO m, MonadReader env m, HasHttpManager env, HasConfig env, MonadLogger m, MonadBaseControl IO m, MonadCatch m)
                => EnvOverride
                -> Set PackageIdentifier
                -> Set PackageName
                -> m (Map PackageIdentifier ResolvedPackage)
resolvePackages menv idents0 names0 = do
    eres <- go
    case eres of
        Left _ -> do
            updateAllIndices menv
            go >>= either throwM return
        Right x -> return x
  where
    go = r <$> resolvePackagesAllowMissing idents0 names0
    r (missingNames, missingIdents, idents)
      | not $ Set.null missingNames  = Left $ UnknownPackageNames       missingNames
      | not $ Set.null missingIdents = Left $ UnknownPackageIdentifiers missingIdents ""
      | otherwise                    = Right idents

resolvePackagesAllowMissing
    :: (MonadIO m, MonadReader env m, HasHttpManager env, HasConfig env, MonadLogger m, MonadThrow m, MonadBaseControl IO m, MonadCatch m)
    => Set PackageIdentifier
    -> Set PackageName
    -> m (Set PackageName, Set PackageIdentifier, Map PackageIdentifier ResolvedPackage)
resolvePackagesAllowMissing idents0 names0 = do
    caches <- getPackageCaches
    let versions = Map.fromListWith max $ map toTuple $ Map.keys caches
        (missingNames, idents1) = partitionEithers $ map
            (\name -> maybe (Left name ) (Right . PackageIdentifier name)
                (Map.lookup name versions))
            (Set.toList names0)
        (missingIdents, resolved) = partitionEithers $ map (goIdent caches)
                                  $ Set.toList
                                  $ idents0 <> Set.fromList idents1
    return (Set.fromList missingNames, Set.fromList missingIdents, Map.fromList resolved)
  where
    goIdent caches ident =
        case Map.lookup ident caches of
            Nothing -> Left ident
            Just (index, cache) -> Right (ident, ResolvedPackage
                { rpCache = cache
                , rpIndex = index
                })

data ToFetch = ToFetch
    { tfTarball :: !(Path Abs File)
    , tfDestDir :: !(Maybe (Path Abs Dir))
    , tfUrl     :: !T.Text
    , tfSize    :: !(Maybe Word64)
    , tfSHA512  :: !(Maybe ByteString)
    , tfCabal   :: !ByteString
    -- ^ Contents of the .cabal file
    }

data ToFetchResult = ToFetchResult
    { tfrToFetch         :: !(Map PackageIdentifier ToFetch)
    , tfrAlreadyUnpacked :: !(Map PackageIdentifier (Path Abs Dir))
    }

-- | Add the cabal files to a list of idents with their caches.
withCabalFiles
    :: (MonadThrow m, MonadIO m, MonadReader env m, HasConfig env)
    => IndexName
    -> [(PackageIdentifier, PackageCache, a)]
    -> (PackageIdentifier -> a -> ByteString -> IO b)
    -> m [b]
withCabalFiles name pkgs f = do
    indexPath <- configPackageIndex name
    liftIO $ withBinaryFile (toFilePath indexPath) ReadMode $ \h ->
        mapM (goPkg h) pkgs
  where
    goPkg h (ident, pc, tf) = do
        hSeek h AbsoluteSeek $ fromIntegral $ pcOffset pc
        cabalBS <- S.hGet h $ fromIntegral $ pcSize pc
        f ident tf cabalBS

-- | Provide a function which will load up a cabal @ByteString@ from the
-- package indices.
withCabalLoader
    :: (MonadThrow m, MonadIO m, MonadReader env m, HasConfig env, MonadLogger m, HasHttpManager env, MonadBaseControl IO m, MonadCatch m)
    => EnvOverride
    -> ((PackageIdentifier -> IO ByteString) -> m a)
    -> m a
withCabalLoader menv inner = do
    icaches <- getPackageCaches >>= liftIO . newIORef
    env <- ask

    -- 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
    updateRef <- liftIO $ newMVar True

    runInBase <- liftBaseWith $ \run -> return (void . run)

    -- TODO in the future, keep all of the necessary @Handle@s open
    let doLookup :: PackageIdentifier
                 -> IO ByteString
        doLookup ident = do
            cachesCurr <- liftIO $ readIORef icaches
            eres <- lookupPackageIdentifierExact ident env cachesCurr
            case eres of
                Just bs -> return bs
                -- Update the cache and try again
                Nothing -> do
                    let fuzzy = fuzzyLookupCandidates ident cachesCurr
                        suggestions = case fuzzy of
                            Nothing ->
                              case typoCorrectionCandidates ident cachesCurr of
                                  Nothing -> ""
                                  Just cs -> "Perhaps you meant " <>
                                    orSeparated cs <> "?"
                            Just cs -> "Possible candidates: " <>
                              commaSeparated (NE.map packageIdentifierString cs)
                              <> "."
                    join $ modifyMVar updateRef $ \toUpdate ->
                        if toUpdate then do
                            runInBase $ do
                                $logInfo $ T.concat
                                    [ "Didn't see "
                                    , T.pack $ packageIdentifierString ident
                                    , " in your package indices.\n"
                                    , "Updating and trying again."
                                    ]
                                updateAllIndices menv
                                clearPackageCaches
                                caches <- getPackageCaches
                                liftIO $ writeIORef icaches caches
                            return (False, doLookup ident)
                        else return (toUpdate,
                                     throwM $ UnknownPackageIdentifiers
                                       (Set.singleton ident) suggestions)
    inner doLookup

lookupPackageIdentifierExact
  :: HasConfig env
  => PackageIdentifier
  -> env
  -> PackageCaches
  -> IO (Maybe ByteString)
lookupPackageIdentifierExact ident env caches =
    case Map.lookup ident caches of
        Nothing -> return Nothing
        Just (index, cache) -> do
            [bs] <- flip runReaderT env
                  $ withCabalFiles (indexName index) [(ident, cache, ())]
                  $ \_ _ bs -> return bs
            return $ Just bs

-- | Given package identifier and package caches, return list of packages
-- with the same name and the same two first version number components found
-- in the caches.
fuzzyLookupCandidates
  :: PackageIdentifier
  -> PackageCaches
  -> Maybe (NonEmpty PackageIdentifier)
fuzzyLookupCandidates (PackageIdentifier name ver) caches =
  let (_, zero, bigger) = Map.splitLookup zeroIdent caches
      zeroIdent         = PackageIdentifier name $(mkVersion "0.0")
      sameName  (PackageIdentifier n _) = n == name
      sameMajor (PackageIdentifier _ v) = toMajorVersion v == toMajorVersion ver
  in NE.nonEmpty . filter sameMajor $ maybe [] (pure . const zeroIdent) zero
         <> takeWhile sameName (Map.keys bigger)

-- | Try to come up with typo corrections for given package identifier using
-- package caches. This should be called before giving up, i.e. when
-- 'fuzzyLookupCandidates' cannot return anything.
typoCorrectionCandidates
  :: PackageIdentifier
  -> PackageCaches
  -> Maybe (NonEmpty String)
typoCorrectionCandidates ident =
  let getName = packageNameString . packageIdentifierName
      name    = getName ident
  in  NE.nonEmpty
    . Map.keys
    . Map.filterWithKey (const . (== 1) . damerauLevenshtein name)
    . Map.mapKeys getName

-- | Figure out where to fetch from.
getToFetch :: (MonadThrow m, MonadIO m, MonadReader env m, HasConfig env)
           => Maybe (Path Abs Dir) -- ^ directory to unpack into, @Nothing@ means no unpack
           -> Map PackageIdentifier ResolvedPackage
           -> m ToFetchResult
getToFetch mdest resolvedAll = do
    (toFetch0, unpacked) <- liftM partitionEithers $ mapM checkUnpacked $ Map.toList resolvedAll
    toFetch1 <- mapM goIndex $ Map.toList $ Map.fromListWith (++) toFetch0
    return ToFetchResult
        { tfrToFetch = Map.unions toFetch1
        , tfrAlreadyUnpacked = Map.fromList unpacked
        }
  where
    checkUnpacked (ident, resolved) = do
        dirRel <- parseRelDir $ packageIdentifierString ident
        let mdestDir = (</> dirRel) <$> mdest
        mexists <-
            case mdestDir of
                Nothing -> return Nothing
                Just destDir -> do
                    exists <- doesDirExist destDir
                    return $ if exists then Just destDir else Nothing
        case mexists of
            Just destDir -> return $ Right (ident, destDir)
            Nothing -> do
                let index = rpIndex resolved
                    d = pcDownload $ rpCache resolved
                    targz = T.pack $ packageIdentifierString ident ++ ".tar.gz"
                tarball <- configPackageTarball (indexName index) ident
                return $ Left (indexName index, [(ident, rpCache resolved, ToFetch
                    { tfTarball = tarball
                    , tfDestDir = mdestDir
                    , tfUrl = case d of
                        Just d' -> decodeUtf8 $ pdUrl d'
                        Nothing -> indexDownloadPrefix index <> targz
                    , tfSize = fmap pdSize d
                    , tfSHA512 = fmap pdSHA512 d
                    , tfCabal = S.empty -- filled in by goIndex
                    })])

    goIndex (name, pkgs) =
        liftM Map.fromList $
        withCabalFiles name pkgs $ \ident tf cabalBS ->
        return (ident, tf { tfCabal = cabalBS })

-- | Download the given name,version pairs into the directory expected by cabal.
--
-- For each package it downloads, it will optionally unpack it to the given
-- @Path@ (if present). Note that unpacking is not simply a matter of
-- untarring, but also of grabbing the cabal file from the package index. The
-- destinations should not include package identifiers.
--
-- Returns the list of paths unpacked, including package identifiers. E.g.:
--
-- @
-- fetchPackages [("foo-1.2.3", Just "/some/dest")] ==> ["/some/dest/foo-1.2.3"]
-- @
--
-- Since 0.1.0.0
fetchPackages' :: (MonadIO m,MonadReader env m,HasHttpManager env,HasConfig env,MonadLogger m,MonadThrow m,MonadBaseControl IO m)
               => Maybe (Path Rel Dir) -- ^ the dist rename directory, see: https://github.com/fpco/stack/issues/157
               -> Map PackageIdentifier ToFetch
               -> m (Map PackageIdentifier (Path Abs Dir))
fetchPackages' mdistDir toFetchAll = do
    connCount <- asks $ configConnectionCount . getConfig
    outputVar <- liftIO $ newTVarIO Map.empty

    runInBase <- liftBaseWith $ \run -> return (void . run)
    parMapM_
        connCount
        (go outputVar runInBase)
        (Map.toList toFetchAll)

    liftIO $ readTVarIO outputVar
  where
    go :: (MonadIO m,Functor m,MonadThrow m,MonadLogger m,MonadReader env m,HasHttpManager env)
       => TVar (Map PackageIdentifier (Path Abs Dir))
       -> (m () -> IO ())
       -> (PackageIdentifier, ToFetch)
       -> m ()
    go outputVar runInBase (ident, toFetch) = do
        req <- parseUrl $ T.unpack $ tfUrl toFetch
        let destpath = tfTarball toFetch

        let toHashCheck bs = HashCheck SHA512 (CheckHexDigestByteString bs)
        let downloadReq = DownloadRequest
                { drRequest = req
                , drHashChecks = map toHashCheck $ maybeToList (tfSHA512 toFetch)
                , drLengthCheck = fromIntegral <$> tfSize toFetch
                , drRetryPolicy = drRetryPolicyDefault
                }
        let progressSink _ =
                liftIO $ runInBase $ $logInfo $ packageIdentifierText ident <> ": download"
        _ <- verifiedDownload downloadReq destpath progressSink

        let fp = toFilePath destpath

        F.forM_ (tfDestDir toFetch) $ \destDir -> do
            let dest = toFilePath $ parent destDir
                innerDest = toFilePath destDir

            liftIO $ ensureDir (parent destDir)

            liftIO $ withBinaryFile fp ReadMode $ \h -> do
                -- Avoid using L.readFile, which is more likely to leak
                -- resources
                lbs <- L.hGetContents h
                let entries = fmap (either wrap wrap)
                            $ Tar.checkTarbomb identStr
                            $ Tar.read $ decompress lbs
                    wrap :: Exception e => e -> FetchException
                    wrap = Couldn'tReadPackageTarball fp . toException
                    identStr = packageIdentifierString ident

                    getPerms :: Tar.Entry -> (FilePath, Tar.Permissions)
                    getPerms e = (dest FP.</> Tar.fromTarPath (Tar.entryTarPath e),
                                  Tar.entryPermissions e)

                    filePerms :: [(FilePath, Tar.Permissions)]
                    filePerms = catMaybes $ Tar.foldEntries (\e -> (:) (Just $ getPerms e))
                                                            [] (const []) entries
                Tar.unpack dest entries
                -- Reset file permissions as they were in the tarball
                mapM_ (\(fp', perm) -> setFileMode
                    (FP.dropTrailingPathSeparator fp')
                    perm) filePerms

                case mdistDir of
                    Nothing -> return ()
                    -- See: https://github.com/fpco/stack/issues/157
                    Just distDir -> do
                        let inner = dest FP.</> identStr
                            oldDist = inner FP.</> "dist"
                            newDist = inner FP.</> toFilePath distDir
                        exists <- D.doesDirectoryExist oldDist
                        when exists $ do
                            -- Previously used takeDirectory, but that got confused
                            -- by trailing slashes, see:
                            -- https://github.com/commercialhaskell/stack/issues/216
                            --
                            -- Instead, use Path which is a bit more resilient
                            ensureDir . parent =<< parseAbsDir newDist
                            D.renameDirectory oldDist newDist

                let cabalFP =
                        innerDest FP.</>
                        packageNameString (packageIdentifierName ident)
                        <.> "cabal"
                S.writeFile cabalFP $ tfCabal toFetch

                atomically $ modifyTVar outputVar $ Map.insert ident destDir

parMapM_ :: (F.Foldable f,MonadIO m,MonadBaseControl IO m)
         => Int
         -> (a -> m ())
         -> f a
         -> m ()
parMapM_ (max 1 -> 1) f xs = F.mapM_ f xs
parMapM_ cnt f xs0 = do
    var <- liftIO (newTVarIO $ F.toList xs0)

    -- See comment on similar line in Stack.Build
    runInBase <- liftBaseWith $ \run -> return (void . run)

    let worker = fix $ \loop -> join $ atomically $ do
            xs <- readTVar var
            case xs of
                [] -> return $ return ()
                x:xs' -> do
                    writeTVar var xs'
                    return $ do
                        runInBase $ f x
                        loop
        workers 1 = Concurrently worker
        workers i = Concurrently worker *> workers (i - 1)
    liftIO $ runConcurrently $ workers cnt

damerauLevenshtein :: String -> String -> Int
damerauLevenshtein = ED.restrictedDamerauLevenshteinDistance ED.defaultEditCosts

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

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