{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE RecordWildCards #-}
{-# LANGUAGE TupleSections #-}

module Internal.Statement
  ( readImport
  )
where

import Data.Csv
import Internal.Database.Model
import Internal.Types
import Internal.Utils
import RIO
import qualified RIO.ByteString.Lazy as BL
import RIO.FilePath
import qualified RIO.List as L
import qualified RIO.Map as M
import qualified RIO.Text as T
import RIO.Time
import qualified RIO.Vector as V

-- TODO this probably won't scale well (pipes?)

readImport :: MonadUnliftIO m => Import -> MappingT m (EitherErr [BalTx])
readImport Import {..} =
  matchRecords impMatches . L.sort . concat
    <$> mapM (readImport_ impSkipLines impDelim impTxOpts) impPaths

readImport_
  :: MonadUnliftIO m
  => Natural
  -> Word
  -> TxOpts
  -> FilePath
  -> MappingT m [TxRecord]
readImport_ n delim tns p = do
  dir <- asks kmConfigDir
  bs <- liftIO $ BL.readFile $ dir </> p
  case decodeByNameWithP (parseTxRecord p tns) opts $ skip bs of
    Left m -> liftIO $ putStrLn m >> return []
    Right (_, v) -> return $ catMaybes $ V.toList v
  where
    opts = defaultDecodeOptions {decDelimiter = fromIntegral delim}
    skip = BL.intercalate "\n" . L.drop (fromIntegral n) . BL.split 10

-- TODO handle this better, this maybe thing is a hack to skip lines with
-- blank dates but will likely want to make this more flexible
parseTxRecord :: FilePath -> TxOpts -> NamedRecord -> Parser (Maybe TxRecord)
parseTxRecord p TxOpts {..} r = do
  d <- r .: T.encodeUtf8 toDate
  if d == ""
    then return Nothing
    else do
      a <- parseRational toAmountFmt =<< r .: T.encodeUtf8 toAmount
      e <- r .: T.encodeUtf8 toDesc
      os <- M.fromList <$> mapM (\n -> (n,) <$> r .: T.encodeUtf8 n) toOther
      d' <- parseTimeM True defaultTimeLocale (T.unpack toDateFmt) d
      return $ Just $ TxRecord d' a e os p

matchRecords :: [Match] -> [TxRecord] -> EitherErr [BalTx]
matchRecords ms rs = do
  (matched, unmatched, notfound) <- matchAll (matchPriorities ms) rs
  -- TODO record number of times each match hits for debugging
  matched_ <- mapM balanceTx matched
  case (matched_, unmatched, notfound) of
    (xs, [], []) -> Right xs
    (_, us, ns) -> Left $ StatementError us ns

matchPriorities :: [Match] -> [MatchGroup]
matchPriorities =
  fmap matchToGroup
    . L.groupBy (\a b -> mPriority a == mPriority b)
    . L.sortOn (Down . mPriority)

matchToGroup :: [Match] -> MatchGroup
matchToGroup ms =
  uncurry MatchGroup $
    first (L.sortOn mDate) $
      L.partition (isJust . mDate) ms

-- TDOO could use a better struct to flatten the maybe date subtype
data MatchGroup = MatchGroup
  { mgDate :: [Match]
  , mgNoDate :: [Match]
  }
  deriving (Show)

data Zipped a = Zipped ![a] ![a]

data Unzipped a = Unzipped ![a] ![a] ![a]

initZipper :: [a] -> Zipped a
initZipper = Zipped []

resetZipper :: Zipped a -> Zipped a
resetZipper = initZipper . recoverZipper

recoverZipper :: Zipped a -> [a]
recoverZipper (Zipped as bs) = reverse as ++ bs

zipperSlice :: (a -> b -> Ordering) -> b -> Zipped a -> Either (Zipped a) (Unzipped a)
zipperSlice f x = go
  where
    go z@(Zipped _ []) = Left z
    go z@(Zipped bs (a : as)) = case f a x of
      GT -> go $ Zipped (a : bs) as
      EQ -> Right $ goEq (Unzipped bs [a] as)
      LT -> Left z
    goEq z@(Unzipped _ _ []) = z
    goEq z@(Unzipped bs cs (a : as)) = case f a x of
      GT -> goEq $ Unzipped (a : bs) cs as
      EQ -> goEq $ Unzipped bs (a : cs) as
      LT -> z

zipperMatch :: Unzipped Match -> TxRecord -> EitherErr (Zipped Match, MatchRes RawTx)
zipperMatch (Unzipped bs cs as) x = go [] cs
  where
    go _ [] = Right (Zipped bs $ cs ++ as, MatchFail)
    go prev (m : ms) = do
      res <- matches m x
      case res of
        MatchFail -> go (m : prev) ms
        skipOrPass ->
          let ps = reverse prev
              ms' = maybe ms (: ms) (matchDec m)
           in Right (Zipped bs $ ps ++ ms' ++ as, skipOrPass)

zipperMatch' :: Zipped Match -> TxRecord -> EitherErr (Zipped Match, MatchRes RawTx)
zipperMatch' z x = go z
  where
    go (Zipped bs (a : as)) = do
      res <- matches a x
      case res of
        MatchFail -> go (Zipped (a : bs) as)
        skipOrPass -> Right (Zipped (maybe bs (: bs) $ matchDec a) as, skipOrPass)
    go z' = Right (z', MatchFail)

matchDec :: Match -> Maybe Match
matchDec m@Match {mTimes = t} =
  if t' == Just 0 then Nothing else Just $ m {mTimes = t'}
  where
    t' = fmap pred t

matchAll :: [MatchGroup] -> [TxRecord] -> EitherErr ([RawTx], [TxRecord], [Match])
matchAll = go ([], [])
  where
    go (matched, unused) gs rs = case (gs, rs) of
      (_, []) -> return (matched, [], unused)
      ([], _) -> return (matched, rs, unused)
      (g : gs', _) -> do
        (ts, unmatched, us) <- matchGroup g rs
        go (ts ++ matched, us ++ unused) gs' unmatched

matchGroup :: MatchGroup -> [TxRecord] -> EitherErr ([RawTx], [TxRecord], [Match])
matchGroup MatchGroup {mgDate = ds, mgNoDate = ns} rs = do
  (md, rest, ud) <- matchDates ds rs
  (mn, unmatched, un) <- matchNonDates ns rest
  return (md ++ mn, unmatched, filter ((/= Nothing) . mTimes) $ ud ++ un)

matchDates :: [Match] -> [TxRecord] -> EitherErr ([RawTx], [TxRecord], [Match])
matchDates ms = go ([], [], initZipper ms)
  where
    go (matched, unmatched, z) [] =
      Right
        ( catMaybes matched
        , reverse unmatched
        , recoverZipper z
        )
    go (matched, unmatched, z) (r : rs) = case zipperSlice findDate r z of
      Left zipped -> go (matched, r : unmatched, zipped) rs
      Right unzipped -> do
        (z', res) <- zipperMatch unzipped r
        let (m, u) = case res of
              MatchPass p -> (Just p : matched, unmatched)
              MatchSkip -> (Nothing : matched, unmatched)
              MatchFail -> (matched, r : unmatched)
        go (m, u, z') rs
    findDate m r = maybe EQ (`compareDate` trDate r) $ mDate m

matchNonDates :: [Match] -> [TxRecord] -> EitherErr ([RawTx], [TxRecord], [Match])
matchNonDates ms = go ([], [], initZipper ms)
  where
    go (matched, unmatched, z) [] =
      Right
        ( catMaybes matched
        , reverse unmatched
        , recoverZipper z
        )
    go (matched, unmatched, z) (r : rs) = do
      (z', res) <- zipperMatch' z r
      let (m, u) = case res of
            MatchPass p -> (Just p : matched, unmatched)
            MatchSkip -> (Nothing : matched, unmatched)
            MatchFail -> (matched, r : unmatched)
       in go (m, u, resetZipper z') rs

balanceTx :: RawTx -> EitherErr BalTx
balanceTx t@Tx {txSplits = ss} = do
  bs <- balanceSplits ss
  return $ t {txSplits = bs}

balanceSplits :: [RawSplit] -> EitherErr [BalSplit]
balanceSplits ss =
  fmap concat
    <$> mapM (uncurry bal)
    $ groupByKey
    $ fmap (\s -> (sCurrency s, s)) ss
  where
    hasValue s@(Split {sValue = Just v}) = Right s {sValue = v}
    hasValue s = Left s
    bal cur rss
      | length rss < 2 = Left $ BalanceError TooFewSplits cur
      | otherwise = case partitionEithers $ fmap hasValue rss of
          ([noVal], val) -> Right $ noVal {sValue = foldr (\s x -> x - sValue s) 0 val} : val
          ([], val) -> Right val
          _ -> Left $ BalanceError NotOneBlank cur

groupByKey :: Ord k => [(k, v)] -> [(k, [v])]
groupByKey = M.toList . M.fromListWith (++) . fmap (second (: []))