{- This file is part of Vervis.
 -
 - Written in 2016 by fr33domlover <fr33domlover@riseup.net>.
 -
 - ♡ Copying is an act of love. Please copy, reuse and share.
 -
 - The author(s) have dedicated all copyright and related and neighboring
 - rights to this software to the public domain worldwide. This software is
 - distributed without any warranty.
 -
 - You should have received a copy of the CC0 Public Domain Dedication along
 - with this software. If not, see
 - <http://creativecommons.org/publicdomain/zero/1.0/>.
 -}

module Vervis.Git
    ( readSourceView
    , readChangesView
    )
where

import Prelude

import Data.Foldable (find)
import Data.Git
import Data.Git.Graph
import Data.Git.Harder
import Data.Git.Ref (toHex)
import Data.Git.Storage (getObject_)
import Data.Git.Storage.Object (Object (..))
import Data.Git.Types (GitTime (..))
import Data.Graph.Inductive.Graph (noNodes)
import Data.Graph.Inductive.Query.Topsort
import Data.Set (Set)
import Data.String (fromString)
import Data.Text (Text)
import Data.Text.Encoding (encodeUtf8)
import System.Hourglass (timeCurrent)
import Time.Types (Elapsed (..))

import qualified Data.ByteString.Lazy as BL (ByteString)
import qualified Data.DList as D (DList, empty, snoc, toList)
import qualified Data.Set as S (member, mapMonotonic)
import qualified Data.Text as T (pack, unpack)
import qualified Data.Text.Encoding as TE (decodeUtf8With)
import qualified Data.Text.Encoding.Error as TE (lenientDecode)

import Data.ByteString.Char8.Local (takeLine)
import Data.EventTime.Local
import Data.Git.Local
import Vervis.Changes
import Vervis.Foundation (Widget)
import Vervis.Readme
import Vervis.SourceTree

matchReadme :: (ModePerm, ObjId, Text, EntObjType) -> Bool
matchReadme (_, _, name, EntObjBlob) = isReadme name
matchReadme _                        = False

-- | Find a README file in a directory. Return the filename and the file
-- content.
findReadme :: Git -> TreeRows -> IO (Maybe (Text, BL.ByteString))
findReadme git rows =
    case find matchReadme rows of
        Nothing                         -> return Nothing
        Just (_perm, oid, name, _etype) -> do
            obj <- getObject_ git (unObjId oid) True
            return $ case obj of
                ObjBlob b -> Just (name, blobGetContent b)
                _         -> Nothing

matchType :: EntObjType -> EntryType
matchType EntObjBlob = TypeBlob
matchType EntObjTree = TypeTree

rowToEntry :: (ModePerm, ObjId, Text, EntObjType) -> DirEntry
rowToEntry (_, _, name, etype) = DirEntry (matchType etype) name

loadSourceView
    :: Git
    -> Text
    -> [Text]
    -> IO (Set RefName, Set RefName, Maybe (SourceView BL.ByteString))
loadSourceView git refT dir = do
    branches <- branchList git
    tags <- tagList git
    let refS = T.unpack refT
        refN = RefName refS
    msv <- if refN `S.member` branches || refN `S.member` tags
        then do
            tipOid <- resolveName git refS
            mtree <- resolveTreeish git $ unObjId tipOid
            case mtree of
                Nothing   -> return Nothing
                Just tree -> do
                    let dir' = map (entName . encodeUtf8) dir
                    view <- viewPath git tree dir'
                    Just <$> case view of
                        RootView rows -> do
                            mreadme <- findReadme git rows
                            let ents = map rowToEntry rows
                            return $ SourceDir $
                                DirectoryView Nothing ents mreadme
                        TreeView name _ rows -> do
                            mreadme <- findReadme git rows
                            let ents = map rowToEntry rows
                            return $ SourceDir $
                                DirectoryView (Just name) ents mreadme
                        BlobView name _ body ->
                            return $ SourceFile $ FileView name body
        else return Nothing
    return (branches, tags, msv)

readSourceView
    :: FilePath
    -- ^ Repository path
    -> Text
    -- ^ Name of branch or tag
    -> [Text]
    -- ^ Path in the source tree pointing to a file or directory
    -> IO (Set Text, Set Text, Maybe (SourceView Widget))
    -- ^ Branches, tags, view of the selected item
readSourceView path ref dir = do
    (bs, ts, msv) <-
        withRepo (fromString path) $ \ git -> loadSourceView git ref dir
    let toTexts = S.mapMonotonic $ T.pack . refNameRaw
    return (toTexts bs, toTexts ts, renderSources dir <$> msv)

instance ResultList D.DList where
    emptyList = D.empty
    appendItem = flip D.snoc

readChangesView
    :: FilePath
    -- ^ Repository path
    -> Text
    -- ^ Name of branch or tag
    -> IO (Set Text, Set Text, Maybe [LogEntry])
    -- ^ Branches, tags, view of selected ref's change log
readChangesView path ref = withRepo (fromString path) $ \ git -> do
    let toTexts = S.mapMonotonic $ T.pack . refNameRaw
    branches <- toTexts <$> branchList git
    tags <- toTexts <$> tagList git
    ml <- if ref `S.member` branches || ref `S.member` tags
        then do
            oid <- resolveName git $ T.unpack ref
            graph <- loadCommitGraphPT git [oid]
            let mnodes = topsortUnmixOrder graph (NodeStack [noNodes graph])
                nodes = case mnodes of
                    Nothing -> error "commit graph contains a cycle"
                    Just ns -> ns
                pairs = D.toList $ fmap (nodeLabel graph) nodes
                toText = TE.decodeUtf8With TE.lenientDecode
            Elapsed now <- timeCurrent
            let mkrow oid commit = LogEntry
                    { leAuthor  = toText $ personName $ commitAuthor commit
                    , leHash    = toText $ toHex $ unObjId oid
                    , leMessage = toText $ takeLine $ commitMessage commit
                    , leTime    =
                        intervalToEventTime $
                        FriendlyConvert $
                        now - t
                    }
                    where
                    Elapsed t = gitTimeUTC $ personTime $ commitAuthor commit
            return $ Just $ map (uncurry mkrow) pairs
        else return Nothing
    return (branches, tags, ml)