module Internal.Utils
  ( compareDate
  , expandDatePat
  , askDays
  , fromWeekday
  , inDaySpan
  , fmtRational
  , matches
  , fromGregorian'
  , resolveDaySpan
  , resolveDaySpan_
  , intersectDaySpan
  , liftInner
  , liftExceptT
  , liftExcept
  , liftIOExcept
  , liftIOExceptT
  , combineError
  , combineError_
  , combineError3
  , combineErrors
  , mapErrors
  , combineErrorM
  , combineErrorM3
  , combineErrorIO2
  , combineErrorIO3
  , combineErrorIOM2
  , combineErrorIOM3
  , collectErrorsIO
  , mapErrorsIO
  , parseRational
  , showError
  , unlessLeft_
  , unlessLefts_
  , unlessLeft
  , unlessLefts
  , acntPath2Text
  , showT
  , lookupErr
  , gregorians
  , uncurry3
  , fstOf3
  , sndOf3
  , thdOf3
  , xGregToDay
  , compileMatch
  , compileOptions
  , dateMatches
  , valMatches
  , roundPrecision
  , roundPrecisionCur
  , lookupAccountKey
  , lookupAccountSign
  , lookupAccountType
  , lookupCurrencyKey
  , lookupCurrencyPrec
  , lookupTag
  , mapAdd_
  )
where

import Control.Monad.Error.Class
import Control.Monad.Except
import Control.Monad.Reader
import Data.Time.Format.ISO8601
import GHC.Real
import Internal.Types.Main
import RIO
import qualified RIO.List as L
import qualified RIO.Map as M
import qualified RIO.NonEmpty as NE
import qualified RIO.Text as T
import RIO.Time
import Text.Regex.TDFA
import Text.Regex.TDFA.Text

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

expandDatePat :: DaySpan -> DatePat -> InsertExcept [Day]
expandDatePat b (Cron cp) = expandCronPat b cp
expandDatePat i (Mod mp) = return $ expandModPat mp i

expandModPat :: ModPat -> DaySpan -> [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) = fromDaySpan bs
    start = maybe lower fromGregorian' s
    b' = fromIntegral b
    addFun = case u of
      Day -> addDays
      Week -> addDays . (* 7)
      Month -> addGregorianMonthsClip
      Year -> addGregorianYearsClip

expandCronPat :: DaySpan -> CronPat -> InsertExcept [Day]
expandCronPat b CronPat {cpYear, cpMonth, cpDay, cpWeekly} =
  combineError3 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 cpYear of
      Nothing -> return [yb0 .. yb1]
      Just pat -> do
        ys <- expandMDYPat (fromIntegral yb0) (fromIntegral yb1) pat
        return $ dropWhile (< yb0) $ fromIntegral <$> ys
    mRes = expandMD 12 cpMonth
    dRes = expandMD 31 cpDay
    (s, e) = fromDaySpan b
    (yb0, mb0, db0) = toGregorian s
    (yb1, mb1, db1) = toGregorian $ addDays (-1) e
    expandMD lim =
      fmap (fromIntegral <$>)
        . maybe (return [1 .. lim]) (expandMDYPat 1 lim)
    expandW (OnDay x) = [fromEnum x]
    expandW (OnDays xs) = fromEnum <$> xs
    ws = maybe [] expandW cpWeekly
    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 -> Natural -> MDYPat -> InsertExcept [Natural]
expandMDYPat lower upper (Single x) = return [x | lower <= x && x <= upper]
expandMDYPat lower upper (Multi xs) = return $ dropWhile (<= lower) $ takeWhile (<= upper) xs
expandMDYPat lower upper (After x) = return [max lower x .. upper]
expandMDYPat lower upper (Before x) = return [lower .. min upper x]
expandMDYPat lower upper (Between x y) = return [max lower x .. min upper y]
expandMDYPat lower upper (Repeat RepeatPat {rpStart = s, rpBy = b, rpRepeats = r})
  | b < 1 = throwError $ InsertException [PatternError s b r ZeroLength]
  | otherwise = do
      k <- limit r
      return $ dropWhile (<= lower) $ takeWhile (<= k) [s + i * b | i <- [0 ..]]
  where
    limit Nothing = return upper
    limit (Just n)
      -- this guard not only produces the error for the user but also protects
      -- from an underflow below it
      | n < 1 = throwError $ InsertException [PatternError s b r ZeroRepeats]
      | otherwise = return $ min (s + b * (n - 1)) upper

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

askDays
  :: (MonadFinance m, MonadInsertError m)
  => DatePat
  -> Maybe Interval
  -> m [Day]
askDays dp i = do
  globalSpan <- askDBState kmBudgetInterval
  case i of
    Just i' -> do
      localSpan <- liftExcept $ resolveDaySpan i'
      maybe (return []) expand $ intersectDaySpan globalSpan localSpan
    Nothing -> expand globalSpan
  where
    expand = liftExcept . (`expandDatePat` dp)

--------------------------------------------------------------------------------
-- dates

-- | Lame weekday converter since day of weeks aren't in dhall (yet)
fromWeekday :: Weekday -> DayOfWeek
fromWeekday Mon = Monday
fromWeekday Tue = Tuesday
fromWeekday Wed = Wednesday
fromWeekday Thu = Thursday
fromWeekday Fri = Friday
fromWeekday Sat = Saturday
fromWeekday Sun = Sunday

-- | find the next date
-- this is meant to go in a very tight loop and be very fast (hence no
-- complex date functions, most of which heavily use 'mod' and friends)
nextXGreg :: XGregorian -> XGregorian
nextXGreg XGregorian {xgYear = y, xgMonth = m, xgDay = d, xgDayOfWeek = w}
  | m == 12 && d == 31 = XGregorian (y + 1) 1 1 w_
  | (m == 2 && (not leap && d == 28 || (leap && d == 29)))
      || (m `elem` [4, 6, 9, 11] && d == 30)
      || (d == 31) =
      XGregorian y (m + 1) 1 w_
  | otherwise = XGregorian y m (d + 1) w_
  where
    -- don't use DayOfWeek from Data.Time since this uses mod (which uses a
    -- division opcode) and thus will be slower than just checking for equality
    -- and adding
    w_ = if w == 6 then 0 else w + 1
    leap = isLeapYear $ fromIntegral y

gregorians :: Day -> [XGregorian]
gregorians x = L.iterate nextXGreg $ XGregorian (fromIntegral y) m d w
  where
    (y, m, d) = toGregorian x
    w = fromEnum $ dayOfWeek x

xGregToDay :: XGregorian -> Day
xGregToDay XGregorian {xgYear = y, xgMonth = m, xgDay = d} = fromGregorian (fromIntegral y) m d

gregTup :: Gregorian -> (Integer, Int, Int)
gregTup Gregorian {gYear, gMonth, gDay} =
  ( fromIntegral gYear
  , fromIntegral gMonth
  , fromIntegral gDay
  )

gregMTup :: GregorianM -> (Integer, Int)
gregMTup GregorianM {gmYear, gmMonth} =
  ( fromIntegral gmYear
  , fromIntegral gmMonth
  )

data YMD_ = Y_ !Integer | YM_ !Integer !Int | YMD_ !Integer !Int !Int

fromYMDMatcher :: YMDMatcher -> YMD_
fromYMDMatcher m = case m of
  Y y -> Y_ $ fromIntegral y
  YM g -> uncurry YM_ $ gregMTup g
  YMD g -> uncurry3 YMD_ $ gregTup g

compareDate :: DateMatcher -> Day -> Ordering
compareDate (On md) x =
  case fromYMDMatcher md of
    Y_ y' -> compare y y'
    YM_ y' m' -> compare (y, m) (y', m')
    YMD_ y' m' d' -> compare (y, m, d) (y', m', d')
  where
    (y, m, d) = toGregorian x
compareDate (In md offset) x = do
  case fromYMDMatcher md of
    Y_ y' -> compareRange y' y
    YM_ y' m' -> compareRange (toMonth y' m') $ toMonth y m
    YMD_ y' m' d' ->
      let s = toModifiedJulianDay $ fromGregorian y' m' d'
       in compareRange s $ toModifiedJulianDay x
  where
    (y, m, _) = toGregorian x
    compareRange start z
      | z < start = LT
      | otherwise = if (start + fromIntegral offset - 1) < z then GT else EQ
    toMonth year month = (year * 12) + fromIntegral month

fromGregorian' :: Gregorian -> Day
fromGregorian' = uncurry3 fromGregorian . gregTup

inDaySpan :: DaySpan -> Day -> Bool
inDaySpan bs = withinDays (fromDaySpan bs)

withinDays :: (Day, Day) -> Day -> Bool
withinDays (d0, d1) x = d0 <= x && x < d1

resolveDaySpan :: Interval -> InsertExcept DaySpan
resolveDaySpan i@Interval {intStart = s} =
  resolveDaySpan_ (s {gYear = gYear s + 50}) i

intersectDaySpan :: DaySpan -> DaySpan -> Maybe DaySpan
intersectDaySpan a b =
  if b' > a' then Nothing else Just $ toDaySpan (a', b')
  where
    (a0, a1) = fromDaySpan a
    (b0, b1) = fromDaySpan b
    a' = max a0 a1
    b' = min b0 b1

resolveDaySpan_ :: Gregorian -> Interval -> InsertExcept DaySpan
resolveDaySpan_ def Interval {intStart = s, intEnd = e} =
  case fromGregorian' <$> e of
    Nothing -> return $ toDaySpan_ $ fromGregorian' def
    Just e_
      | s_ < e_ -> return $ toDaySpan_ e_
      | otherwise -> throwError $ InsertException [DaySpanError s e]
  where
    s_ = fromGregorian' s
    toDaySpan_ end = toDaySpan (s_, end)

fromDaySpan :: DaySpan -> (Day, Day)
fromDaySpan (d, n) = (d, addDays (fromIntegral n + 1) d)

-- ASSUME a < b
toDaySpan :: (Day, Day) -> DaySpan
toDaySpan (a, b) = (a, fromIntegral $ diffDays b a - 1)

--------------------------------------------------------------------------------
-- matching

matches :: MatchRe -> TxRecord -> InsertExceptT CurrencyM (MatchRes DeferredTx)
matches
  StatementParser {spTx, spOther, spVal, spDate, spDesc}
  r@TxRecord {trDate, trAmount, trDesc, trOther} = do
    res <- liftInner $
      combineError3 val other desc $
        \x y z -> x && y && z && date
    if res
      then maybe (return MatchSkip) convert spTx
      else return MatchFail
    where
      val = valMatches spVal trAmount
      date = maybe True (`dateMatches` trDate) spDate
      other = foldM (\a o -> (a &&) <$> otherMatches trOther o) True spOther
      desc = maybe (return True) (matchMaybe trDesc . snd) spDesc
      convert tg = MatchPass <$> toTx tg r

toTx :: TxGetter -> TxRecord -> InsertExceptT CurrencyM DeferredTx
toTx
  TxGetter {tgFromAcnt, tgToAcnt, tgCurrency, tgFromEntries, tgToEntries, tgOtherEntries}
  r@TxRecord {trAmount, trDate, trDesc} = do
    combineError3 acntRes curRes subRes $ \(fa, ta) (cur, fe, te) ss -> do
      let fromEntry =
            Entry
              { eAcnt = fa
              , eValue = ()
              , eComment = "" -- TODO actually fill this in
              , eTags = [] -- TODO what goes here?
              }
          toEntry =
            Entry
              { eAcnt = ta
              , eValue = ()
              , eComment = ""
              , eTags = []
              }
       in Tx
            { dtxDate = trDate
            , dtxDescr = trDesc
            , dtxEntries =
                EntrySet
                  { desTotalValue = trAmount
                  , desCurrency = cur
                  , desFromEntry0 = fromEntry
                  , desFromEntries = fe
                  , desToEntries = te
                  , desToEntryBal = toEntry
                  }
                  : ss
            }
    where
      resolveAcnt_ = liftInner . resolveAcnt r
      acntRes =
        combineError
          (resolveAcnt_ tgFromAcnt)
          (resolveAcnt_ tgToAcnt)
          (,)
      curRes = do
        cur <- liftInner $ resolveCurrency r tgCurrency
        let feRes = mapErrors (resolveEntry cur r) tgFromEntries
        let teRes = mapErrors (resolveEntry cur r) tgToEntries
        combineError feRes teRes (cur,,)
      subRes = mapErrors (resolveSubGetter r) tgOtherEntries

resolveSubGetter
  :: TxRecord
  -> TxSubGetter
  -> InsertExceptT CurrencyM DeferredEntrySet
resolveSubGetter
  r
  TxSubGetter
    { tsgFromAcnt
    , tsgToAcnt
    , tsgValue
    , tsgCurrency
    , tsgFromEntries
    , tsgToEntries
    } = combineErrorM acntRes curRes $ \(fa, ta) (cur, fe, te) ->
    do
      m <- ask
      -- TODO laaaaame...
      (Deferred _ val) <- liftInner $ mapM (roundPrecisionCur cur m) =<< resolveValue r tsgValue
      let fromEntry =
            Entry
              { eAcnt = fa
              , eValue = ()
              , eComment = "" -- TODO actually fill this in
              , eTags = [] -- TODO what goes here?
              }
      let toEntry =
            Entry
              { eAcnt = ta
              , eValue = ()
              , eComment = ""
              , eTags = []
              }
      return
        EntrySet
          { desTotalValue = val
          , desCurrency = cur
          , desFromEntry0 = fromEntry
          , desFromEntries = fe
          , desToEntries = te
          , desToEntryBal = toEntry
          }
    where
      resolveAcnt_ = liftInner . resolveAcnt r
      acntRes =
        combineError
          (resolveAcnt_ tsgFromAcnt)
          (resolveAcnt_ tsgToAcnt)
          (,)
      curRes = do
        cur <- liftInner $ resolveCurrency r tsgCurrency
        let feRes = mapErrors (resolveEntry cur r) tsgFromEntries
        let teRes = mapErrors (resolveEntry cur r) tsgToEntries
        combineError feRes teRes (cur,,)

valMatches :: ValMatcher -> Rational -> InsertExcept Bool
valMatches ValMatcher {vmDen, vmSign, vmNum, vmPrec} x
  | Just d_ <- vmDen, d_ >= p = throwError $ InsertException [MatchValPrecisionError d_ p]
  | otherwise =
      return $
        checkMaybe (s ==) vmSign
          && checkMaybe (n ==) vmNum
          && checkMaybe ((d * fromIntegral p ==) . fromIntegral) vmDen
  where
    (n, d) = properFraction $ abs x
    p = 10 ^ vmPrec
    s = signum x >= 0
    checkMaybe = maybe True

dateMatches :: DateMatcher -> Day -> Bool
dateMatches md = (EQ ==) . compareDate md

otherMatches :: M.Map T.Text T.Text -> FieldMatcherRe -> InsertExcept Bool
otherMatches dict m = case m of
  Val (Field n mv) -> valMatches mv =<< (readRational =<< lookup_ MatchNumeric n)
  Desc (Field n (_, md)) -> (`matchMaybe` md) =<< lookup_ MatchText n
  where
    lookup_ t n = lookupErr (MatchField t) n dict

-- TODO this should be more general?
resolveEntry
  :: CurID
  -> TxRecord
  -> EntryGetter
  -> InsertExceptT CurrencyM (Entry AcntID (Deferred Rational) TagID)
resolveEntry cur r s@Entry {eAcnt, eValue} = do
  m <- ask
  liftInner $ combineErrorM acntRes valRes $ \a v -> do
    v' <- mapM (roundPrecisionCur cur m) v
    return $ s {eAcnt = a, eValue = v'}
  where
    acntRes = resolveAcnt r eAcnt
    valRes = resolveValue r eValue

-- curRes = resolveCurrency r eCurrency

-- -- TODO wet code (kinda, not sure if it's worth combining with above)
-- resolveToEntry :: TxRecord -> EntryGetter -> InsertExceptT CurrencyM RawEntry
-- resolveToEntry r s@Entry {eAcnt, eValue, eCurrency} = do
--   m <- ask
--   liftInner $ combineErrorM3 acntRes curRes valRes $ \a c v -> do
--     v' <- mapM (roundPrecisionCur c m) v
--     return $ s {eAcnt = a, eValue = maybe Derive (ConstD False) v', eCurrency = c}
--   where
--     acntRes = resolveAcnt r eAcnt
--     curRes = resolveCurrency r eCurrency
--     valRes = mapM (resolveToValue r) eValue

liftInner :: Monad m => ExceptT e Identity a -> ExceptT e m a
liftInner = mapExceptT (return . runIdentity)

liftExceptT :: MonadError e m => ExceptT e m a -> m a
liftExceptT x = runExceptT x >>= either throwError return

liftExcept :: MonadError e m => Except e a -> m a
liftExcept = either throwError return . runExcept

-- tryError :: MonadError e m => m a -> m (Either e a)
-- tryError action = (Right <$> action) `catchError` (pure . Left)

liftIOExceptT :: MonadIO m => InsertExceptT m a -> m a
liftIOExceptT = fromEither <=< runExceptT

liftIOExcept :: MonadIO m => InsertExcept a -> m a
liftIOExcept = fromEither . runExcept

combineError :: MonadError InsertException m => m a -> m b -> (a -> b -> c) -> m c
combineError a b f = combineErrorM a b (\x y -> pure $ f x y)

combineError_ :: MonadError InsertException m => m a -> m b -> m ()
combineError_ a b = do
  _ <- catchError a $ \e ->
    throwError =<< catchError (e <$ b) (return . (e <>))
  _ <- b
  return ()

combineErrorM :: MonadError InsertException m => m a -> m b -> (a -> b -> m c) -> m c
combineErrorM a b f = do
  a' <- catchError a $ \e ->
    throwError =<< catchError (e <$ b) (return . (e <>))
  f a' =<< b

combineError3 :: MonadError InsertException m => m a -> m b -> m c -> (a -> b -> c -> d) -> m d
combineError3 a b c f =
  combineError (combineError a b (,)) c $ \(x, y) z -> f x y z

combineErrorM3 :: MonadError InsertException m => m a -> m b -> m c -> (a -> b -> c -> m d) -> m d
combineErrorM3 a b c f = do
  combineErrorM (combineErrorM a b (curry return)) c $ \(x, y) z -> f x y z

mapErrors
  :: (Traversable t, MonadError InsertException m)
  => (a -> m b)
  -> t a
  -> m (t b)
-- First, record number of each action. Then try each action. On first failure,
-- note it's position in the sequence, skip ahead to the untried actions,
-- collect failures and add to the first failure.
mapErrors f xs = mapM go $ enumTraversable xs
  where
    go (n, x) = catchError (f x) $ \e -> do
      es <- fmap catMaybes $ mapM (err . f) $ drop (n + 1) $ toList xs
      throwError $ foldr (<>) e es
    err x = catchError (Nothing <$ x) (pure . Just)

combineErrors :: (Traversable t, MonadError InsertException m) => t (m a) -> m (t a)
combineErrors = mapErrors id

enumTraversable :: (Num n, Traversable t) => t a -> t (n, a)
enumTraversable = snd . L.mapAccumL go 0
  where
    go n x = (n + 1, (n, x))

combineErrorIO2 :: MonadUnliftIO m => m a -> m b -> (a -> b -> c) -> m c
combineErrorIO2 a b f = combineErrorIOM2 a b (\x y -> pure $ f x y)

combineErrorIO3 :: MonadUnliftIO m => m a -> m b -> m c -> (a -> b -> c -> d) -> m d
combineErrorIO3 a b c f = combineErrorIOM3 a b c (\x y z -> pure $ f x y z)

combineErrorIOM2 :: MonadUnliftIO m => m a -> m b -> (a -> b -> m c) -> m c
combineErrorIOM2 a b f = do
  a' <- catch a $ \(InsertException es) ->
    (throwIO . InsertException)
      =<< catch (es <$ b) (\(InsertException es') -> return (es' ++ es))
  f a' =<< b

combineErrorIOM3 :: MonadUnliftIO m => m a -> m b -> m c -> (a -> b -> c -> m d) -> m d
combineErrorIOM3 a b c f =
  combineErrorIOM2 (combineErrorIOM2 a b (curry return)) c $ \(x, y) z -> f x y z

mapErrorsIO :: (Traversable t, MonadUnliftIO m) => (a -> m b) -> t a -> m (t b)
mapErrorsIO f xs = mapM go $ enumTraversable xs
  where
    go (n, x) = catch (f x) $ \(InsertException e) -> do
      es <- fmap catMaybes $ mapM (err . f) $ drop (n + 1) $ toList xs
      throwIO $ InsertException $ foldr (<>) e es
    err x = catch (Nothing <$ x) $ \(InsertException es) -> pure $ Just es

collectErrorsIO :: (Traversable t, MonadUnliftIO m) => t (m a) -> m (t a)
collectErrorsIO = mapErrorsIO id

resolveValue :: TxRecord -> EntryNumGetter -> InsertExcept (Deferred Double)
resolveValue TxRecord {trOther, trAmount} s = case s of
  (LookupN t) -> Deferred False <$> (readDouble =<< lookupErr EntryValField t trOther)
  (ConstN c) -> return $ Deferred False c
  AmountN m -> return $ Deferred False $ (* m) $ fromRational trAmount
  BalanceN x -> return $ Deferred True x

-- -- TODO not DRY
-- resolveToValue :: TxRecord -> ToEntryNumGetter -> InsertExcept Double
-- resolveToValue TxRecord {trOther, trAmount} s = case s of
--   (TLookupN t) -> readDouble =<< lookupErr EntryValField t trOther
--   (TConstN c) -> return c
--   TAmountN m -> return $ (* m) $ fromRational trAmount

resolveAcnt :: TxRecord -> EntryAcnt -> InsertExcept T.Text
resolveAcnt = resolveEntryField AcntField

resolveCurrency :: TxRecord -> EntryCur -> InsertExcept T.Text
resolveCurrency = resolveEntryField CurField

resolveEntryField :: EntryIDType -> TxRecord -> EntryAcnt -> InsertExcept T.Text
resolveEntryField t TxRecord {trOther = o} s = case s of
  ConstT p -> return p
  LookupT f -> lookup_ f o
  MapT (Field f m) -> do
    k <- lookup_ f o
    lookup_ k m
  Map2T (Field (f1, f2) m) -> do
    (k1, k2) <- combineError (lookup_ f1 o) (lookup_ f2 o) (,)
    lookup_ (k1, k2) m
  where
    lookup_ :: (Ord k, Show k) => k -> M.Map k v -> InsertExcept v
    lookup_ = lookupErr (EntryIDField t)

lookupErr :: (Ord k, Show k) => LookupSuberr -> k -> M.Map k v -> InsertExcept v
lookupErr what k m = case M.lookup k m of
  Just x -> return x
  _ -> throwError $ InsertException [LookupError what $ showT k]

parseRational :: MonadFail m => (T.Text, Regex) -> T.Text -> m Rational
parseRational (pat, re) s = case matchGroupsMaybe s re of
  [sign, x, ""] -> uncurry (*) <$> readWhole sign x
  [sign, x, y] -> do
    d <- readT "decimal" y
    let p = 10 ^ T.length y
    (k, w) <- readWhole sign x
    return $ k * (w + d % p)
  _ -> msg "malformed decimal"
  where
    readT what t = case readMaybe $ T.unpack t of
      Just d -> return $ fromInteger d
      _ -> msg $ T.unwords ["could not parse", what, singleQuote t]
    msg :: MonadFail m => T.Text -> m a
    msg m =
      fail $
        T.unpack $
          T.unwords [m, "-", keyVals [("pattern", pat), ("query", s)]]
    readSign x
      | x == "-" = return (-1)
      | x == "+" || x == "" = return 1
      | otherwise = msg $ T.append "invalid sign: " x
    readWhole sign x = do
      w <- readT "whole number" x
      k <- readSign sign
      return (k, w)

readDouble :: T.Text -> InsertExcept Double
readDouble s = case readMaybe $ T.unpack s of
  Just x -> return x
  Nothing -> throwError $ InsertException [ConversionError s]

readRational :: T.Text -> InsertExcept Rational
readRational s = case T.split (== '.') s of
  [x] -> maybe err (return . fromInteger) $ readT x
  [x, y] -> case (readT x, readT y) of
    (Just x', Just y') ->
      let p = 10 ^ T.length y
          k = if x' >= 0 then 1 else -1
       in return $ fromInteger x' + k * y' % p
    _ -> err
  _ -> err
  where
    readT = readMaybe . T.unpack
    err = throwError $ InsertException [ConversionError s]

-- TODO smells like a lens
-- mapTxSplits :: (a -> b) -> Tx a -> Tx b
-- mapTxSplits f t@Tx {txSplits = ss} = t {txSplits = fmap f ss}

fmtRational :: Natural -> Rational -> T.Text
fmtRational precision x = T.concat [s, txt n', ".", pad 2 "0" $ txt d']
  where
    s = if x >= 0 then "" else "-"
    x'@(n :% d) = abs x
    p = 10 ^ precision
    n' = div n d
    d' = (\(a :% b) -> div a b) ((x' - fromIntegral n') * p)
    txt = T.pack . show
    pad i c z = T.append (T.replicate (i - T.length z) c) z

roundPrecision :: Natural -> Double -> Rational
roundPrecision n = (% p) . round . (* fromIntegral p) . toRational
  where
    p = 10 ^ n

roundPrecisionCur :: CurID -> CurrencyMap -> Double -> InsertExcept Rational
roundPrecisionCur c m x =
  case M.lookup c m of
    Just (_, n) -> return $ roundPrecision n x
    Nothing -> throwError $ InsertException [undefined]

acntPath2Text :: AcntPath -> T.Text
acntPath2Text (AcntPath t cs) = T.intercalate "/" (atName t : cs)

--------------------------------------------------------------------------------
-- error display

showError :: InsertError -> [T.Text]
showError other = case other of
  (StatementError ts ms) -> (showTx <$> ts) ++ (showMatch <$> ms)
  (DaySpanError a b) ->
    [T.unwords ["Could not create bounds from", showGregorian_ a, "and", showGreg b]]
    where
      showGreg (Just g) = showGregorian_ g
      showGreg Nothing = "Inf"
  (AccountError a ts) ->
    [ T.unwords
        [ "account type of key"
        , singleQuote a
        , "is not one of:"
        , ts_
        ]
    ]
    where
      ts_ = T.intercalate ", " $ NE.toList $ fmap atName ts
  (PatternError s b r p) -> [T.unwords [msg, "in pattern: ", pat]]
    where
      pat =
        keyVals $
          [ (k, v)
          | (k, Just v) <-
              [ ("start", Just $ showT s)
              , ("by", Just $ showT b)
              , ("repeats", showT <$> r)
              ]
          ]
      msg = case p of
        ZeroLength -> "Zero repeat length"
        ZeroRepeats -> "Zero repeats"
  (RegexError re) -> [T.append "could not make regex from pattern: " re]
  (ConversionError x) -> [T.append "Could not convert to rational number: " x]
  (InsertIOError msg) -> [T.append "IO Error: " msg]
  (ParseError msg) -> [T.append "Parse Error: " msg]
  (MatchValPrecisionError d p) ->
    [T.unwords ["Match denominator", showT d, "must be less than", showT p]]
  (LookupError t f) ->
    [T.unwords ["Could not find field", f, "when resolving", what]]
    where
      what = case t of
        EntryIDField st -> T.unwords ["entry", idName st, "ID"]
        EntryValField -> "entry value"
        MatchField mt -> T.unwords [matchName mt, "match"]
        DBKey st -> T.unwords ["database", idName st, "ID key"]
      -- TODO this should be its own function
      idName AcntField = "account"
      idName CurField = "currency"
      idName TagField = "tag"
      matchName MatchNumeric = "numeric"
      matchName MatchText = "text"
  (IncomeError day name balance) ->
    [ T.unwords
        [ "Income allocations for budget"
        , singleQuote name
        , "exceed total on day"
        , showT day
        , "where balance is"
        , showT (fromRational balance :: Double)
        ]
    ]
  (PeriodError start next) ->
    [ T.unwords
        [ "First pay period on "
        , singleQuote $ showT start
        , "must start before first income payment on "
        , singleQuote $ showT next
        ]
    ]

showGregorian_ :: Gregorian -> T.Text
showGregorian_ Gregorian {gYear, gMonth, gDay} = T.intercalate "-" $ showT <$> [gYear, gMonth, gDay]

showTx :: TxRecord -> T.Text
showTx TxRecord {trDate = d, trAmount = v, trDesc = e, trFile = f} =
  T.append "Unmatched transaction: " $
    keyVals
      [ ("path", T.pack f)
      , ("date", T.pack $ iso8601Show d)
      , ("value", showT (fromRational v :: Float))
      , ("description", doubleQuote e)
      ]

showMatch :: MatchRe -> T.Text
showMatch StatementParser {spDate, spVal, spDesc, spOther, spTimes, spPriority} =
  T.append "Unused match: " $ keyVals [(x, y) | (x, Just y) <- kvs]
  where
    kvs =
      [ ("date", showDateMatcher <$> spDate)
      , ("val", showValMatcher spVal)
      , ("desc", fst <$> spDesc)
      , ("other", others)
      , ("counter", Just $ maybe "Inf" showT spTimes)
      , ("priority", Just $ showT spPriority)
      ]
    others = case spOther of
      [] -> Nothing
      xs -> Just $ singleQuote $ T.concat $ showMatchOther <$> xs

-- | Convert match date to text
-- Single date matches will just show the single date, and ranged matches will
-- show an interval like [YY-MM-DD, YY-MM-DD)
showDateMatcher :: DateMatcher -> T.Text
showDateMatcher md = case md of
  (On x) -> showYMDMatcher x
  (In start n) -> T.concat ["[", showYMDMatcher start, " ", showYMD_ end, ")"]
    where
      -- TODO not DRY (this shifting thing happens during the comparison
      -- function (kinda)
      end = case fromYMDMatcher start of
        Y_ y -> Y_ $ y + fromIntegral n
        YM_ y m ->
          let (y_, m_) = divMod (m + fromIntegral n - 1) 12
           in YM_ (y + fromIntegral y_) (m + m_ + 1)
        YMD_ y m d ->
          uncurry3 YMD_ $
            toGregorian $
              addDays (fromIntegral n) $
                fromGregorian y m d

-- | convert YMD match to text
showYMDMatcher :: YMDMatcher -> T.Text
showYMDMatcher = showYMD_ . fromYMDMatcher

showYMD_ :: YMD_ -> T.Text
showYMD_ md =
  T.intercalate "-" $ L.take 3 (fmap showT digits ++ L.repeat "*")
  where
    digits = case md of
      Y_ y -> [fromIntegral y]
      YM_ y m -> [fromIntegral y, m]
      YMD_ y m d -> [fromIntegral y, m, d]

showValMatcher :: ValMatcher -> Maybe T.Text
showValMatcher ValMatcher {vmSign = Nothing, vmNum = Nothing, vmDen = Nothing} = Nothing
showValMatcher ValMatcher {vmNum, vmDen, vmSign, vmPrec} =
  Just $ singleQuote $ keyVals [(k, v) | (k, Just v) <- kvs]
  where
    kvs =
      [ ("sign", (\s -> if s then "+" else "-") <$> vmSign)
      , ("numerator", showT <$> vmNum)
      , ("denominator", showT <$> vmDen)
      , ("precision", Just $ showT vmPrec)
      ]

showMatchOther :: FieldMatcherRe -> T.Text
showMatchOther (Desc (Field f (re, _))) =
  T.unwords ["desc field", singleQuote f, "with re", singleQuote re]
showMatchOther (Val (Field f mv)) =
  T.unwords
    [ "val field"
    , singleQuote f
    , "with match value"
    , singleQuote $ fromMaybe "*" $ showValMatcher mv
    ]

singleQuote :: T.Text -> T.Text
singleQuote t = T.concat ["'", t, "'"]

doubleQuote :: T.Text -> T.Text
doubleQuote t = T.concat ["'", t, "'"]

keyVal :: T.Text -> T.Text -> T.Text
keyVal a b = T.concat [a, "=", b]

keyVals :: [(T.Text, T.Text)] -> T.Text
keyVals = T.intercalate "; " . fmap (uncurry keyVal)

showT :: Show a => a -> T.Text
showT = T.pack . show

--------------------------------------------------------------------------------
-- pure error processing

-- concatEither2 :: Either x a -> Either x b -> (a -> b -> c) -> Either [x] c
-- concatEither2 a b fun = case (a, b) of
--   (Right a_, Right b_) -> Right $ fun a_ b_
--   _ -> Left $ catMaybes [leftToMaybe a, leftToMaybe b]

-- concatEither2M :: Monad m => Either x a -> Either x b -> (a -> b -> m c) -> m (Either [x] c)
-- concatEither2M a b fun = case (a, b) of
--   (Right a_, Right b_) -> Right <$> fun a_ b_
--   _ -> return $ Left $ catMaybes [leftToMaybe a, leftToMaybe b]

-- concatEither3 :: Either x a -> Either x b -> Either x c -> (a -> b -> c -> d) -> Either [x] d
-- concatEither3 a b c fun = case (a, b, c) of
--   (Right a_, Right b_, Right c_) -> Right $ fun a_ b_ c_
--   _ -> Left $ catMaybes [leftToMaybe a, leftToMaybe b, leftToMaybe c]

-- concatEithers2 :: Either [x] a -> Either [x] b -> (a -> b -> c) -> Either [x] c
-- concatEithers2 a b = merge . concatEither2 a b

-- concatEithers2M
--   :: Monad m
--   => Either [x] a
--   -> Either [x] b
--   -> (a -> b -> m c)
--   -> m (Either [x] c)
-- concatEithers2M a b = fmap merge . concatEither2M a b

-- concatEithers3
--   :: Either [x] a
--   -> Either [x] b
--   -> Either [x] c
--   -> (a -> b -> c -> d)
--   -> Either [x] d
-- concatEithers3 a b c = merge . concatEither3 a b c

-- concatEitherL :: [Either x a] -> Either [x] [a]
-- concatEitherL as = case partitionEithers as of
--   ([], bs) -> Right bs
--   (es, _) -> Left es

-- concatEithersL :: [Either [x] a] -> Either [x] [a]
-- concatEithersL = merge . concatEitherL

-- leftToMaybe :: Either a b -> Maybe a
-- leftToMaybe (Left a) = Just a
-- leftToMaybe _ = Nothing

unlessLeft :: (Monad m, MonadPlus n) => Either a b -> (b -> m (n a)) -> m (n a)
unlessLeft (Left es) _ = return (return es)
unlessLeft (Right rs) f = f rs

unlessLefts :: (Monad m) => Either (n a) b -> (b -> m (n a)) -> m (n a)
unlessLefts (Left es) _ = return es
unlessLefts (Right rs) f = f rs

unlessLeft_ :: (Monad m, MonadPlus n) => Either a b -> (b -> m ()) -> m (n a)
unlessLeft_ e f = unlessLeft e (\x -> void (f x) >> return mzero)

unlessLefts_ :: (Monad m, MonadPlus n) => Either (n a) b -> (b -> m ()) -> m (n a)
unlessLefts_ e f = unlessLefts e (\x -> void (f x) >> return mzero)

-- plural :: Either a b -> Either [a] b
-- plural = first (: [])

-- merge :: Either [[a]] b -> Either [a] b
-- merge = first concat

--------------------------------------------------------------------------------
-- random functions

-- when bifunctor fails...
-- thrice :: (a -> d) -> (b -> e) -> (c -> f) -> (a, b, c) -> (d, e, f)
-- thrice f1 f2 f3 (x, y, z) = (f1 x, f2 y, f3 z)

-- groupKey :: Ord c => (a -> c) -> [(a, b)] -> [(a, [b])]
-- groupKey f = fmap go . NE.groupAllWith (f . fst)
--   where
--     go xs@((c, _) :| _) = (c, NE.toList $ fmap snd xs)

mapAdd_ :: (Ord k, Num v) => k -> v -> M.Map k v -> M.Map k v
mapAdd_ k v = M.alter (maybe (Just v) (Just . (+ v))) k

uncurry3 :: (a -> b -> c -> d) -> (a, b, c) -> d
uncurry3 f (a, b, c) = f a b c

fstOf3 :: (a, b, c) -> a
fstOf3 (a, _, _) = a

sndOf3 :: (a, b, c) -> b
sndOf3 (_, b, _) = b

thdOf3 :: (a, b, c) -> c
thdOf3 (_, _, c) = c

-- lpad :: a -> Int -> [a] -> [a]
-- lpad c n s = replicate (n - length s) c ++ s

-- rpad :: a -> Int -> [a] -> [a]
-- rpad c n s = s ++ replicate (n - length s) c

-- lpadT :: Char -> Int -> T.Text -> T.Text
-- lpadT c n s = T.append (T.replicate (n - T.length s) (T.singleton c)) s

-- TODO this regular expression appears to be compiled each time, which is
-- super slow
-- NOTE: see https://github.com/haskell-hvr/regex-tdfa/issues/9 - performance
-- is likely not going to be optimal for text
-- matchMaybe :: T.Text -> T.Text -> EitherErr Bool
-- matchMaybe q pat = case compres of
--   Right re -> case execute re q of
--     Right res -> Right $ isJust res
--     Left _ -> Left $ RegexError "this should not happen"
--   Left _ -> Left $ RegexError pat
--   where
--     -- these options barely do anything in terms of performance
--     compres = compile (blankCompOpt {newSyntax = True}) (blankExecOpt {captureGroups = False}) pat

compileOptions :: TxOpts T.Text -> InsertExcept TxOptsRe
compileOptions o@TxOpts {toAmountFmt = pat} = do
  re <- compileRegex True pat
  return $ o {toAmountFmt = re}

compileMatch :: StatementParser T.Text -> InsertExcept MatchRe
compileMatch m@StatementParser {spDesc, spOther} = do
  combineError dres ores $ \d os -> m {spDesc = d, spOther = os}
  where
    go = compileRegex False
    dres = mapM go spDesc
    ores = combineErrors $ fmap (mapM go) spOther

compileRegex :: Bool -> T.Text -> InsertExcept (Text, Regex)
compileRegex groups pat = case res of
  Right re -> return (pat, re)
  Left _ -> throwError $ InsertException [RegexError pat]
  where
    res =
      compile
        (blankCompOpt {newSyntax = True})
        (blankExecOpt {captureGroups = groups})
        pat

matchMaybe :: T.Text -> Regex -> InsertExcept Bool
matchMaybe q re = case execute re q of
  Right res -> return $ isJust res
  Left _ -> throwError $ InsertException [RegexError "this should not happen"]

matchGroupsMaybe :: T.Text -> Regex -> [T.Text]
matchGroupsMaybe q re = case regexec re q of
  Right Nothing -> []
  Right (Just (_, _, _, xs)) -> xs
  -- this should never fail as regexec always returns Right
  Left _ -> []

lookupAccount :: (MonadInsertError m, MonadFinance m) => AcntID -> m (AccountRId, AcntSign, AcntType)
lookupAccount = lookupFinance AcntField kmAccount

lookupAccountKey :: (MonadInsertError m, MonadFinance m) => AcntID -> m AccountRId
lookupAccountKey = fmap fstOf3 . lookupAccount

lookupAccountSign :: (MonadInsertError m, MonadFinance m) => AcntID -> m AcntSign
lookupAccountSign = fmap sndOf3 . lookupAccount

lookupAccountType :: (MonadInsertError m, MonadFinance m) => AcntID -> m AcntType
lookupAccountType = fmap thdOf3 . lookupAccount

lookupCurrency :: (MonadInsertError m, MonadFinance m) => T.Text -> m (CurrencyRId, Natural)
lookupCurrency = lookupFinance CurField kmCurrency

lookupCurrencyKey :: (MonadInsertError m, MonadFinance m) => AcntID -> m CurrencyRId
lookupCurrencyKey = fmap fst . lookupCurrency

lookupCurrencyPrec :: (MonadInsertError m, MonadFinance m) => AcntID -> m Natural
lookupCurrencyPrec = fmap snd . lookupCurrency

lookupTag :: (MonadInsertError m, MonadFinance m) => TagID -> m TagRId
lookupTag = lookupFinance TagField kmTag

lookupFinance
  :: (MonadInsertError m, MonadFinance m)
  => EntryIDType
  -> (DBState -> M.Map T.Text a)
  -> T.Text
  -> m a
lookupFinance t f c = (liftExcept . lookupErr (DBKey t) c) =<< askDBState f