{-# LANGUAGE GADTs #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE RecordWildCards #-}
{-# LANGUAGE NoImplicitPrelude #-}

module Internal.Insert
  ( insertStatements
  , insertBudget
  )
where

import Data.Hashable
import Database.Persist.Class
import Database.Persist.Sql hiding (Single, Statement)
import Internal.Database.Model
import Internal.Statement
import Internal.Types hiding (sign)
import Internal.Utils
import RIO hiding (to)
import qualified RIO.Text as T
import RIO.Time

--------------------------------------------------------------------------------
-- intervals

expandDatePat :: Bounds -> DatePat -> EitherErrs [Day]
expandDatePat b (Cron cp) = expandCronPat b cp
expandDatePat i (Mod mp) = Right $ expandModPat mp i

expandModPat :: ModPat -> Bounds -> [Day]
expandModPat ModPat {mpStart = s, mpBy = b, mpUnit = u, mpRepeats = r} bs =
  takeWhile (<= upper) $
    (`addFun` start) . (* b')
      <$> maybe id (take . fromIntegral) r [0 ..]
  where
    (lower, upper) = expandBounds bs
    start = maybe lower fromGregorian' s
    b' = fromIntegral b
    addFun = case u of
      Day -> addDays
      Week -> addDays . (* 7)
      Month -> addGregorianMonthsClip
      Year -> addGregorianYearsClip

expandCronPat :: Bounds -> CronPat -> EitherErrs [Day]
expandCronPat b CronPat {..} = concatEither3 yRes mRes dRes $ \ys ms ds ->
  filter validWeekday $
    mapMaybe (uncurry3 toDay) $
      takeWhile (\((y, _), m, d) -> (y, m, d) <= (yb1, mb1, db1)) $
        dropWhile (\((y, _), m, d) -> (y, m, d) < (yb0, mb0, db0)) $
          [(y, m, d) | y <- (\y -> (y, isLeapYear y)) <$> ys, m <- ms, d <- ds]
  where
    yRes = case cronYear of
      Nothing -> return [yb0 .. yb1]
      Just pat -> do
        ys <- expandMDYPat (fromIntegral yb1) pat
        return $ dropWhile (< yb0) $ fromIntegral <$> ys
    mRes = expandMD 12 cronMonth
    dRes = expandMD 31 cronDay
    (s, e) = expandBounds b
    (yb0, mb0, db0) = toGregorian s
    (yb1, mb1, db1) = toGregorian $ addDays (-1) e
    expandMD lim = fmap (fromIntegral <$>) . maybe (return [1 .. lim]) (expandMDYPat lim)
    expandW (OnDay x) = [fromEnum x]
    expandW (OnDays xs) = fromEnum <$> xs
    ws = maybe [] expandW cronWeekly
    validWeekday = if null ws then const True else \day -> dayToWeekday day `elem` ws
    toDay (y, leap) m d
      | m == 2 && (not leap && d > 28 || leap && d > 29) = Nothing
      | m `elem` [4, 6, 9, 11] && d > 30 = Nothing
      | otherwise = Just $ fromGregorian y m d

expandMDYPat :: Natural -> MDYPat -> EitherErr [Natural]
expandMDYPat _ (Single x) = Right [x]
expandMDYPat _ (Multi xs) = Right xs
expandMDYPat lim (Repeat RepeatPat {rpStart = s, rpBy = b, rpRepeats = r})
  | b < 1 = Left $ PatternError s b r ZeroLength
  | otherwise = do
      k <- limit r
      return $ takeWhile (<= k) [s + i * b | i <- [0 ..]]
  where
    limit Nothing = Right lim
    limit (Just n)
      -- this guard not only produces the error for the user but also protects
      -- from an underflow below it
      | n < 1 = Left $ PatternError s b r ZeroRepeats
      | otherwise = Right $ min (s + b * (n - 1)) lim

dayToWeekday :: Day -> Int
dayToWeekday (ModifiedJulianDay d) = mod (fromIntegral d + 2) 7

withDates
  :: MonadUnliftIO m
  => DatePat
  -> (Day -> MappingT m a)
  -> MappingT m (EitherErrs [a])
withDates dp f = do
  bounds <- asks kmBudgetInterval
  let days = expandDatePat bounds dp
  mapM (mapM f) days

--------------------------------------------------------------------------------
-- budget

insertBudget :: MonadUnliftIO m => Budget -> MappingT m [InsertError]
insertBudget Budget {income = is, transfers = es} = do
  es1 <- mapM insertIncome is
  es2 <- mapM insertTransfer es
  return $ concat $ es1 ++ es2

-- TODO this hashes twice (not that it really matters)
whenHash
  :: (Hashable a, MonadUnliftIO m)
  => ConfigType
  -> a
  -> b
  -> (Key CommitR -> MappingT m b)
  -> MappingT m b
whenHash t o def f = do
  let h = hash o
  hs <- asks kmNewCommits
  if h `elem` hs then f =<< lift (insert $ CommitR h t) else return def

-- TODO allow currency conversions here
data BudgetSplit b = BudgetSplit
  { bsAcnt :: !AcntID
  , bsBucket :: !(Maybe b)
  }

data BudgetMeta = BudgetMeta
  { bmCommit :: !(Key CommitR)
  , bmWhen :: !Day
  , bmCur :: !CurID
  }

data BudgetTx = BudgetTx
  { btMeta :: !BudgetMeta
  , btFrom :: !(BudgetSplit IncomeBucket)
  , btTo :: !(BudgetSplit ExpenseBucket)
  , btValue :: !Rational
  , btName :: !T.Text
  }

insertIncome :: MonadUnliftIO m => Income -> MappingT m [InsertError]
insertIncome i@Income {..} =
  whenHash CTIncome i [] $ \c ->
    unlessLeft (balanceIncome i) $ \balance -> do
      res <- withDates incWhen $ \day -> do
        let meta = BudgetMeta c day incCurrency
        let fromAllos b = concatMap (fromAllo meta incFrom (Just b))
        let pre = fromAllos PreTax incPretax
        let tax = fmap (fromTax meta incFrom) incTaxes
        let post = fromAllos PostTax incPosttax
        let bal =
              BudgetTx
                { btMeta = meta
                , btFrom = BudgetSplit incFrom $ Just PostTax
                , btTo = BudgetSplit incToBal Nothing
                , btValue = balance
                , btName = "balance after deductions"
                }
        fmap concat $ mapM insertBudgetTx $ bal : (pre ++ tax ++ post)
      unlessLefts res $ return . concat

fromAllo
  :: BudgetMeta
  -> AcntID
  -> Maybe IncomeBucket
  -> Allocation
  -> [BudgetTx]
fromAllo meta from ib Allocation {..} = fmap (toBT alloPath) alloAmts
  where
    toBT to (Amount desc v) =
      BudgetTx
        { btFrom = BudgetSplit from ib
        , btTo = BudgetSplit to $ Just alloBucket
        , btValue = dec2Rat v
        , btName = desc
        , btMeta = meta
        }

fromTax :: BudgetMeta -> AcntID -> Tax -> BudgetTx
fromTax meta from Tax {taxAcnt = to, taxValue = v} =
  BudgetTx
    { btFrom = BudgetSplit from (Just IntraTax)
    , btTo = BudgetSplit to (Just Fixed)
    , btValue = dec2Rat v
    , btName = ""
    , btMeta = meta
    }

balanceIncome :: Income -> EitherErr Rational
balanceIncome
  Income
    { incGross = g
    , incWhen = dp
    , incPretax = pre
    , incTaxes = tax
    , incPosttax = post
    }
    | bal < 0 = Left $ IncomeError dp
    | otherwise = Right bal
    where
      bal = dec2Rat g - sum (sumAllocation <$> pre ++ post) - sumTaxes tax

sumAllocation :: Allocation -> Rational
sumAllocation = sum . fmap (dec2Rat . amtValue) . alloAmts

sumTaxes :: [Tax] -> Rational
sumTaxes = sum . fmap (dec2Rat . taxValue)

insertTransfer :: MonadUnliftIO m => Transfer -> MappingT m [InsertError]
insertTransfer t@Transfer {..} =
  fmap concat $ whenHash CTExpense t [] $ \key -> do
    forM transAmounts $ \(TimeAmount amt pat) -> do
      res <- withDates pat $ \day -> insertBudgetTx $ budgetTx amt day key
      unlessLefts res $ return . concat
  where
    meta d c = BudgetMeta {bmWhen = d, bmCur = transCurrency, bmCommit = c}
    budgetTx (Amount desc v) d c =
      BudgetTx
        { btMeta = meta d c
        , btFrom = BudgetSplit transFrom Nothing
        , btTo = BudgetSplit transTo Nothing
        , btValue = dec2Rat v
        , btName = desc
        }

insertBudgetTx :: MonadUnliftIO m => BudgetTx -> MappingT m [InsertError]
insertBudgetTx BudgetTx {..} = do
  res <- splitPair (bsAcnt btFrom) (bsAcnt btTo) (bmCur btMeta) btValue
  unlessLefts_ res $ \(sFrom, sTo) -> lift $ do
    k <- insert $ TransactionR (bmCommit btMeta) (bmWhen btMeta) btName
    skFrom <- insertSplit k sFrom
    bFrom <- insert $ BudgetLabelR skFrom btName
    forM_ (bsBucket btFrom) $ \b ->
      insert_ $ IncomeBucketR bFrom b
    skTo <- insertSplit k sTo
    bTo <- insert $ BudgetLabelR skTo btName
    forM_ (bsBucket btTo) $ \b ->
      insert_ $ ExpenseBucketR bTo b

splitPair
  :: MonadUnliftIO m
  => AcntID
  -> AcntID
  -> CurID
  -> Rational
  -> MappingT m (EitherErrs (KeySplit, KeySplit))
splitPair from to cur val = do
  s1 <- split from (-val)
  s2 <- split to val
  return $ concatEithers2 s1 s2 (,)
  where
    split a v =
      resolveSplit $
        Split
          { sAcnt = a
          , sValue = v
          , sComment = ""
          , sCurrency = cur
          }

--------------------------------------------------------------------------------
-- statements

insertStatements :: MonadUnliftIO m => Config -> MappingT m [InsertError]
insertStatements conf = concat <$> mapM insertStatement (statements conf)

insertStatement :: MonadUnliftIO m => Statement -> MappingT m [InsertError]
insertStatement (StmtManual m) = insertManual m
insertStatement (StmtImport i) = insertImport i

insertManual :: MonadUnliftIO m => Manual -> MappingT m [InsertError]
insertManual
  m@Manual
    { manualDate = dp
    , manualFrom = from
    , manualTo = to
    , manualValue = v
    , manualCurrency = u
    , manualDesc = e
    } = do
    whenHash CTManual m [] $ \c -> do
      bounds <- asks kmStatementInterval
      -- let days = expandDatePat bounds dp
      let dayRes = expandDatePat bounds dp
      unlessLefts dayRes $ \days -> do
        txRes <- mapM tx days
        unlessLefts_ (concatEithersL txRes) $ lift . mapM_ (insertTx c)
    where
      tx day = txPair day from to u (dec2Rat v) e

insertImport :: MonadUnliftIO m => Import -> MappingT m [InsertError]
insertImport i = whenHash CTImport i [] $ \c -> do
  -- TODO this isn't efficient, the whole file will be read and maybe no
  -- transactions will be desired
  recoverIO (readImport i) $ \r -> unlessLefts r $ \bs -> do
    bounds <- expandBounds <$> asks kmStatementInterval
    res <- mapM resolveTx $ filter (inBounds bounds . txDate) bs
    unlessLefts_ (concatEithersL res) $ lift . mapM_ (insertTx c)
  where
    recoverIO x rest = do
      res <- tryIO x
      case res of
        Right r -> rest r
        -- If file is not found (or something else happens) then collect the
        -- error try the remaining imports
        Left e -> return [InsertIOError $ showT e]

--------------------------------------------------------------------------------
-- low-level transaction stuff

txPair
  :: MonadUnliftIO m
  => Day
  -> AcntID
  -> AcntID
  -> CurID
  -> Rational
  -> T.Text
  -> MappingT m (EitherErrs KeyTx)
txPair day from to cur val desc = resolveTx tx
  where
    split a v = Split {sAcnt = a, sValue = v, sComment = "", sCurrency = cur}
    tx =
      Tx
        { txDescr = desc
        , txDate = day
        , txTags = []
        , txSplits = [split from (-val), split to val]
        }

resolveTx :: MonadUnliftIO m => BalTx -> MappingT m (EitherErrs KeyTx)
resolveTx t@Tx {txSplits = ss} = do
  res <- concatEithersL <$> mapM resolveSplit ss
  return $ fmap (\kss -> t {txSplits = kss}) res

resolveSplit :: MonadUnliftIO m => BalSplit -> MappingT m (EitherErrs KeySplit)
resolveSplit s@Split {sAcnt = p, sCurrency = c, sValue = v} = do
  aid <- lookupAccountKey p
  cid <- lookupCurrency c
  sign <- lookupAccountSign p
  -- TODO correct sign here?
  -- TODO lenses would be nice here
  return $ concatEither3 aid cid sign $ \aid_ cid_ sign_ ->
    s
      { sAcnt = aid_
      , sCurrency = cid_
      , sValue = v * fromIntegral (sign2Int sign_)
      }

insertTx :: MonadUnliftIO m => Key CommitR -> KeyTx -> SqlPersistT m ()
insertTx c Tx {txDate = d, txDescr = e, txSplits = ss} = do
  k <- insert $ TransactionR c d e
  mapM_ (insertSplit k) ss

insertSplit :: MonadUnliftIO m => Key TransactionR -> KeySplit -> SqlPersistT m (Key SplitR)
insertSplit t Split {sAcnt = aid, sCurrency = cid, sValue = v, sComment = c} = do
  insert $ SplitR t cid aid c v

lookupAccount :: MonadUnliftIO m => AcntID -> MappingT m (EitherErr (Key AccountR, AcntSign))
lookupAccount p = lookupErr (DBKey AcntField) p <$> asks kmAccount

lookupAccountKey :: MonadUnliftIO m => AcntID -> MappingT m (EitherErr (Key AccountR))
lookupAccountKey = fmap (fmap fst) . lookupAccount

lookupAccountSign :: MonadUnliftIO m => AcntID -> MappingT m (EitherErr AcntSign)
lookupAccountSign = fmap (fmap snd) . lookupAccount

lookupCurrency :: MonadUnliftIO m => T.Text -> MappingT m (EitherErr (Key CurrencyR))
lookupCurrency c = lookupErr (DBKey CurField) c <$> asks kmCurrency