--- * doc
-- Lines beginning "--- *" are collapsible orgstruct nodes. Emacs users,
-- (add-hook 'haskell-mode-hook
--   (lambda () (set-variable 'orgstruct-heading-prefix-regexp "--- " t))
--   'orgstruct-mode)
-- and press TAB on nodes to expand/collapse.

{-|

Some common parsers and helpers used by several readers.
Some of these might belong in Hledger.Read.JournalReader or Hledger.Read.

-}

--- * module
{-# LANGUAGE CPP, BangPatterns, DeriveDataTypeable, RecordWildCards, NamedFieldPuns, NoMonoLocalBinds, ScopedTypeVariables, FlexibleContexts, TupleSections, OverloadedStrings #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE LambdaCase #-}
{-# LANGUAGE PackageImports #-}

module Hledger.Read.Common (
  Reader (..),
  InputOpts (..),
  definputopts,
  rawOptsToInputOpts,

  -- * parsing utilities
  runTextParser,
  rtp,
  runJournalParser,
  rjp,
  runErroringJournalParser,
  rejp,
  genericSourcePos,
  journalSourcePos,
  parseAndFinaliseJournal,
  parseAndFinaliseJournal',
  finaliseJournal,
  setYear,
  getYear,
  setDefaultCommodityAndStyle,
  getDefaultCommodityAndStyle,
  getDefaultAmountStyle,
  getAmountStyle,
  addDeclaredAccountType,
  pushParentAccount,
  popParentAccount,
  getParentAccount,
  addAccountAlias,
  getAccountAliases,
  clearAccountAliases,
  journalAddFile,

  -- * parsers
  -- ** transaction bits
  statusp,
  codep,
  descriptionp,

  -- ** dates
  datep,
  datetimep,
  secondarydatep,

  -- ** account names
  modifiedaccountnamep,
  accountnamep,

  -- ** amounts
  spaceandamountormissingp,
  amountp,
  amountp',
  mamountp',
  commoditysymbolp,
  priceamountp,
  balanceassertionp,
  fixedlotpricep,
  numberp,
  fromRawNumber,
  rawnumberp,

  -- ** comments
  multilinecommentp,
  emptyorcommentlinep,

  followingcommentp,
  transactioncommentp,
  postingcommentp,

  -- ** bracketed dates
  bracketeddatetagsp,

  -- ** misc
  singlespacedtextp,
  singlespacedtextsatisfyingp,
  singlespacep,

  -- * tests
  tests_Common,
)
where
--- * imports
import qualified "base-compat-batteries" Control.Monad.Fail.Compat as Fail (fail)
import Control.Monad.Except (ExceptT(..), runExceptT, throwError)
import Control.Monad.State.Strict hiding (fail)
import Data.Bifunctor (bimap, second)
import Data.Char
import Data.Data
import Data.Decimal (DecimalRaw (Decimal), Decimal)
import Data.Default
import Data.Functor.Identity
import "base-compat-batteries" Data.List.Compat
import Data.List.NonEmpty (NonEmpty(..))
import Data.Maybe
import qualified Data.Map as M
import qualified Data.Semigroup as Sem
import Data.Text (Text)
import qualified Data.Text as T
import Data.Time.Calendar
import Data.Time.LocalTime
import System.Time (getClockTime)
import Text.Megaparsec
import Text.Megaparsec.Char
import Text.Megaparsec.Char.Lexer (decimal)
import Text.Megaparsec.Custom

import Hledger.Data
import Hledger.Utils

-- $setup
-- >>> :set -XOverloadedStrings

-- | A hledger journal reader is a triple of storage format name, a
-- detector of that format, and a parser from that format to Journal.
data Reader = Reader {

     -- The canonical name of the format handled by this reader
     rFormat   :: StorageFormat

     -- The file extensions recognised as containing this format
    ,rExtensions :: [String]

     -- A text parser for this format, accepting input options, file
     -- path for error messages and file contents, producing an exception-raising IO
     -- action that returns a journal or error message.
    ,rParser   :: InputOpts -> FilePath -> Text -> ExceptT String IO Journal

     -- Experimental readers are never tried automatically.
    ,rExperimental :: Bool
    }

instance Show Reader where show r = rFormat r ++ " reader"

-- $setup

-- | Various options to use when reading journal files.
-- Similar to CliOptions.inputflags, simplifies the journal-reading functions.
data InputOpts = InputOpts {
     -- files_             :: [FilePath]
     mformat_           :: Maybe StorageFormat  -- ^ a file/storage format to try, unless overridden
                                                --   by a filename prefix. Nothing means try all.
    ,mrules_file_       :: Maybe FilePath       -- ^ a conversion rules file to use (when reading CSV)
    ,separator_         :: Char                 -- ^ the separator to use (when reading CSV)
    ,aliases_           :: [String]             -- ^ account name aliases to apply
    ,anon_              :: Bool                 -- ^ do light anonymisation/obfuscation of the data
    ,ignore_assertions_ :: Bool                 -- ^ don't check balance assertions
    ,new_               :: Bool                 -- ^ read only new transactions since this file was last read
    ,new_save_          :: Bool                 -- ^ save latest new transactions state for next time
    ,pivot_             :: String               -- ^ use the given field's value as the account name
    ,auto_              :: Bool                 -- ^ generate automatic postings when journal is parsed
 } deriving (Show, Data) --, Typeable)

instance Default InputOpts where def = definputopts

definputopts :: InputOpts
definputopts = InputOpts def def ',' def def def def True def def

rawOptsToInputOpts :: RawOpts -> InputOpts
rawOptsToInputOpts rawopts = InputOpts{
   -- files_             = listofstringopt "file" rawopts
   mformat_           = Nothing
  ,mrules_file_       = maybestringopt "rules-file" rawopts
  ,separator_         = fromMaybe ',' (maybecharopt "separator" rawopts)
  ,aliases_           = listofstringopt "alias" rawopts
  ,anon_              = boolopt "anon" rawopts
  ,ignore_assertions_ = boolopt "ignore-assertions" rawopts
  ,new_               = boolopt "new" rawopts
  ,new_save_          = True
  ,pivot_             = stringopt "pivot" rawopts
  ,auto_              = boolopt "auto" rawopts
  }

--- * parsing utilities

-- | Run a text parser in the identity monad. See also: parseWithState.
runTextParser, rtp
  :: TextParser Identity a -> Text -> Either (ParseErrorBundle Text CustomErr) a
runTextParser p t =  runParser p "" t
rtp = runTextParser

-- | Run a journal parser in some monad. See also: parseWithState.
runJournalParser, rjp
  :: Monad m
  => JournalParser m a -> Text -> m (Either (ParseErrorBundle Text CustomErr) a)
runJournalParser p t = runParserT (evalStateT p mempty) "" t
rjp = runJournalParser

-- | Run an erroring journal parser in some monad. See also: parseWithState.
runErroringJournalParser, rejp
  :: Monad m
  => ErroringJournalParser m a
  -> Text
  -> m (Either FinalParseError (Either (ParseErrorBundle Text CustomErr) a))
runErroringJournalParser p t =
  runExceptT $ runParserT (evalStateT p mempty) "" t
rejp = runErroringJournalParser

genericSourcePos :: SourcePos -> GenericSourcePos
genericSourcePos p = GenericSourcePos (sourceName p) (fromIntegral . unPos $ sourceLine p) (fromIntegral . unPos $ sourceColumn p)

-- | Construct a generic start & end line parse position from start and end megaparsec SourcePos's.
journalSourcePos :: SourcePos -> SourcePos -> GenericSourcePos
journalSourcePos p p' = JournalSourcePos (sourceName p) (fromIntegral . unPos $ sourceLine p, fromIntegral $ line')
    where line'
            | (unPos $ sourceColumn p') == 1 = unPos (sourceLine p') - 1
            | otherwise = unPos $ sourceLine p' -- might be at end of file withat last new-line


-- | Given a megaparsec ParsedJournal parser, input options, file
-- path and file content: parse and finalise a Journal, or give an error.
parseAndFinaliseJournal :: ErroringJournalParser IO ParsedJournal -> InputOpts
                           -> FilePath -> Text -> ExceptT String IO Journal
parseAndFinaliseJournal parser iopts f txt = do
  y <- liftIO getCurrentYear
  let initJournal = nulljournal{ jparsedefaultyear = Just y, jincludefilestack = [f] }
  eep <- liftIO $ runExceptT $ runParserT (evalStateT parser initJournal) f txt
  -- TODO: urgh.. clean this up somehow
  case eep of
    Left finalParseError -> throwError $ finalErrorBundlePretty $ attachSource f txt finalParseError
    Right ep -> case ep of
                  Left e   -> throwError $ customErrorBundlePretty e
                  Right pj -> finaliseJournal iopts f txt pj

-- | Like parseAndFinaliseJournal but takes a (non-Erroring) JournalParser.
-- Used for timeclock/timedot.
-- TODO: get rid of this, use parseAndFinaliseJournal instead
parseAndFinaliseJournal' :: JournalParser IO ParsedJournal -> InputOpts
                           -> FilePath -> Text -> ExceptT String IO Journal
parseAndFinaliseJournal' parser iopts f txt = do
  y <- liftIO getCurrentYear
  let initJournal = nulljournal
        { jparsedefaultyear = Just y
        , jincludefilestack = [f] }
  ep <- liftIO $ runParserT (evalStateT parser initJournal) f txt
  -- see notes above
  case ep of
    Left e   -> throwError $ customErrorBundlePretty e
    Right pj -> finaliseJournal iopts f txt pj

-- | Post-process a Journal that has just been parsed or generated, in this order:
--
-- - apply canonical amount styles,
--
-- - save misc info and reverse transactions into their original parse order,
--
-- - evaluate balance assignments and balance each transaction,
--
-- - apply transaction modifiers (auto postings) if enabled,
--
-- - check balance assertions if enabled.
--
finaliseJournal :: InputOpts -> FilePath -> Text -> Journal -> ExceptT String IO Journal
finaliseJournal iopts f txt pj = do
  t <- liftIO getClockTime
  -- Infer and apply canonical styles for each commodity (or fail).
  -- TODO: since #903's refactoring for hledger 1.12,
  -- journalApplyCommodityStyles here is seeing the
  -- transactions before they get reversesd to normal order.
  case journalApplyCommodityStyles pj of
    Left e    -> throwError e
    Right pj' -> 
      -- Finalise the parsed journal.
      let fj =
            if auto_ iopts && (not . null . jtxnmodifiers) pj
            then
              -- When automatic postings are active, we finalise twice:
              -- once before and once after. However, if we are running it
              -- twice, we don't check assertions the first time (they might
              -- be false pending modifiers) and we don't reorder the second
              -- time. If we are only running once, we reorder and follow
              -- the options for checking assertions.
              --
              -- first pass, doing most of the work
              (
               (journalModifyTransactions <$>) $  -- add auto postings after balancing ? #893b fails
               journalBalanceTransactions False $ -- balance transactions without checking assertions
               -- journalModifyTransactions <$>   -- add auto postings before balancing ? probably #893a, #928, #938 fail
               journalReverse $
               journalSetLastReadTime t $
               journalAddFile (f, txt) $
               pj')
              -- balance transactions a second time, now just checking balance assertions
              >>= (\j ->
                 journalBalanceTransactions (not $ ignore_assertions_ iopts) $
                 j)

            else
              -- automatic postings are not active
              journalBalanceTransactions (not $ ignore_assertions_ iopts) $
              journalReverse $
              journalSetLastReadTime t $
              journalAddFile (f, txt) $
              pj'
      in
        case fj of
          Left e  -> throwError e
          Right j -> return j

setYear :: Year -> JournalParser m ()
setYear y = modify' (\j -> j{jparsedefaultyear=Just y})

getYear :: JournalParser m (Maybe Year)
getYear = fmap jparsedefaultyear get

setDefaultCommodityAndStyle :: (CommoditySymbol,AmountStyle) -> JournalParser m ()
setDefaultCommodityAndStyle cs = modify' (\j -> j{jparsedefaultcommodity=Just cs})

getDefaultCommodityAndStyle :: JournalParser m (Maybe (CommoditySymbol,AmountStyle))
getDefaultCommodityAndStyle = jparsedefaultcommodity `fmap` get

-- | Get amount style associated with default currency.
--
-- Returns 'AmountStyle' used to defined by a latest default commodity directive
-- prior to current position within this file or its parents.
getDefaultAmountStyle :: JournalParser m (Maybe AmountStyle)
getDefaultAmountStyle = fmap snd <$> getDefaultCommodityAndStyle

-- | Lookup currency-specific amount style.
--
-- Returns 'AmountStyle' used in commodity directive within current journal
-- prior to current position or in its parents files.
getAmountStyle :: CommoditySymbol -> JournalParser m (Maybe AmountStyle)
getAmountStyle commodity = do
    specificStyle <-  maybe Nothing cformat . M.lookup commodity . jcommodities <$> get
    defaultStyle <- fmap snd <$> getDefaultCommodityAndStyle
    let effectiveStyle = listToMaybe $ catMaybes [specificStyle, defaultStyle]
    return effectiveStyle

addDeclaredAccountType :: AccountName -> AccountType -> JournalParser m ()
addDeclaredAccountType acct atype =
  modify' (\j -> j{jdeclaredaccounttypes = M.insertWith (++) atype [acct] (jdeclaredaccounttypes j)})

pushParentAccount :: AccountName -> JournalParser m ()
pushParentAccount acct = modify' (\j -> j{jparseparentaccounts = acct : jparseparentaccounts j})

popParentAccount :: JournalParser m ()
popParentAccount = do
  j <- get
  case jparseparentaccounts j of
    []       -> unexpected (Tokens ('E' :| "nd of apply account block with no beginning"))
    (_:rest) -> put j{jparseparentaccounts=rest}

getParentAccount :: JournalParser m AccountName
getParentAccount = fmap (concatAccountNames . reverse . jparseparentaccounts) get

addAccountAlias :: MonadState Journal m => AccountAlias -> m ()
addAccountAlias a = modify' (\(j@Journal{..}) -> j{jparsealiases=a:jparsealiases})

getAccountAliases :: MonadState Journal m => m [AccountAlias]
getAccountAliases = fmap jparsealiases get

clearAccountAliases :: MonadState Journal m => m ()
clearAccountAliases = modify' (\(j@Journal{..}) -> j{jparsealiases=[]})

-- getTransactionCount :: MonadState Journal m =>  m Integer
-- getTransactionCount = fmap jparsetransactioncount get
--
-- setTransactionCount :: MonadState Journal m => Integer -> m ()
-- setTransactionCount i = modify' (\j -> j{jparsetransactioncount=i})
--
-- -- | Increment the transaction index by one and return the new value.
-- incrementTransactionCount :: MonadState Journal m => m Integer
-- incrementTransactionCount = do
--   modify' (\j -> j{jparsetransactioncount=jparsetransactioncount j + 1})
--   getTransactionCount

journalAddFile :: (FilePath,Text) -> Journal -> Journal
journalAddFile f j@Journal{jfiles=fs} = j{jfiles=fs++[f]}
  -- append, unlike the other fields, even though we do a final reverse,
  -- to compensate for additional reversal due to including/monoid-concatting

--- * parsers

--- ** transaction bits

statusp :: TextParser m Status
statusp =
  choice'
    [ skipMany spacenonewline >> char '*' >> return Cleared
    , skipMany spacenonewline >> char '!' >> return Pending
    , return Unmarked
    ]

codep :: TextParser m Text
codep = option "" $ do
  try $ do
    skipSome spacenonewline
    char '('
  code <- takeWhileP Nothing $ \c -> c /= ')' && c /= '\n'
  char ')' <?> "closing bracket ')' for transaction code"
  pure code

descriptionp :: TextParser m Text
descriptionp = takeWhileP Nothing (not . semicolonOrNewline)
  where semicolonOrNewline c = c == ';' || c == '\n'

--- ** dates

-- | Parse a date in YYYY/MM/DD format.
-- Hyphen (-) and period (.) are also allowed as separators.
-- The year may be omitted if a default year has been set.
-- Leading zeroes may be omitted.
datep :: JournalParser m Day
datep = do
  mYear <- getYear
  lift $ datep' mYear

datep' :: Maybe Year -> TextParser m Day
datep' mYear = do
  startOffset <- getOffset
  d1 <- decimal <?> "year or month"
  sep <- satisfy isDateSepChar <?> "date separator"
  d2 <- decimal <?> "month or day"
  fullDate startOffset d1 sep d2 <|> partialDate startOffset mYear d1 sep d2
  <?> "full or partial date"

  where

  fullDate :: Int -> Integer -> Char -> Int -> TextParser m Day
  fullDate startOffset year sep1 month = do
    sep2 <- satisfy isDateSepChar <?> "date separator"
    day <- decimal <?> "day"
    endOffset <- getOffset
    let dateStr = show year ++ [sep1] ++ show month ++ [sep2] ++ show day

    when (sep1 /= sep2) $ customFailure $ parseErrorAtRegion startOffset endOffset $
      "invalid date (mixing date separators is not allowed): " ++ dateStr

    case fromGregorianValid year month day of
      Nothing -> customFailure $ parseErrorAtRegion startOffset endOffset $
                   "well-formed but invalid date: " ++ dateStr
      Just date -> pure $! date

  partialDate
    :: Int -> Maybe Year -> Integer -> Char -> Int -> TextParser m Day
  partialDate startOffset mYear month sep day = do
    endOffset <- getOffset
    case mYear of
      Just year ->
        case fromGregorianValid year (fromIntegral month) day of
          Nothing -> customFailure $ parseErrorAtRegion startOffset endOffset $
                      "well-formed but invalid date: " ++ dateStr
          Just date -> pure $! date
        where dateStr = show year ++ [sep] ++ show month ++ [sep] ++ show day

      Nothing -> customFailure $ parseErrorAtRegion startOffset endOffset $
        "partial date "++dateStr++" found, but the current year is unknown"
        where dateStr = show month ++ [sep] ++ show day

{-# INLINABLE datep' #-}

-- | Parse a date and time in YYYY/MM/DD HH:MM[:SS][+-ZZZZ] format.
-- Hyphen (-) and period (.) are also allowed as date separators.
-- The year may be omitted if a default year has been set.
-- Seconds are optional.
-- The timezone is optional and ignored (the time is always interpreted as a local time).
-- Leading zeroes may be omitted (except in a timezone).
datetimep :: JournalParser m LocalTime
datetimep = do
  mYear <- getYear
  lift $ datetimep' mYear

datetimep' :: Maybe Year -> TextParser m LocalTime
datetimep' mYear = do
  day <- datep' mYear
  skipSome spacenonewline
  time <- timeOfDay
  optional timeZone -- ignoring time zones
  pure $ LocalTime day time

  where
    timeOfDay :: TextParser m TimeOfDay
    timeOfDay = do
      off1 <- getOffset
      h' <- twoDigitDecimal <?> "hour"
      off2 <- getOffset
      unless (h' >= 0 && h' <= 23) $ customFailure $
        parseErrorAtRegion off1 off2 "invalid time (bad hour)"

      char ':' <?> "':' (hour-minute separator)"
      off3 <- getOffset
      m' <- twoDigitDecimal <?> "minute"
      off4 <- getOffset
      unless (m' >= 0 && m' <= 59) $ customFailure $
        parseErrorAtRegion off3 off4 "invalid time (bad minute)"

      s' <- option 0 $ do
        char ':' <?> "':' (minute-second separator)"
        off5 <- getOffset
        s' <- twoDigitDecimal <?> "second"
        off6 <- getOffset
        unless (s' >= 0 && s' <= 59) $ customFailure $
          parseErrorAtRegion off5 off6 "invalid time (bad second)"
          -- we do not support leap seconds
        pure s'

      pure $ TimeOfDay h' m' (fromIntegral s')

    twoDigitDecimal :: TextParser m Int
    twoDigitDecimal = do
      d1 <- digitToInt <$> digitChar
      d2 <- digitToInt <$> (digitChar <?> "a second digit")
      pure $ d1*10 + d2

    timeZone :: TextParser m String
    timeZone = do
      plusminus <- satisfy $ \c -> c == '-' || c == '+'
      fourDigits <- count 4 (digitChar <?> "a digit (for a time zone)")
      pure $ plusminus:fourDigits

secondarydatep :: Day -> TextParser m Day
secondarydatep primaryDate = char '=' *> datep' (Just primaryYear)
  where primaryYear = first3 $ toGregorian primaryDate

--- ** account names

-- | Parse an account name (plus one following space if present),
-- then apply any parent account prefix and/or account aliases currently in effect,
-- in that order. (Ie first add the parent account prefix, then rewrite with aliases).
modifiedaccountnamep :: JournalParser m AccountName
modifiedaccountnamep = do
  parent <- getParentAccount
  aliases <- getAccountAliases
  a <- lift accountnamep
  return $!
    accountNameApplyAliases aliases $
     -- XXX accountNameApplyAliasesMemo ? doesn't seem to make a difference (retest that function)
    joinAccountNames parent
    a

-- | Parse an account name, plus one following space if present.
-- Account names have one or more parts separated by the account separator character,
-- and are terminated by two or more spaces (or end of input).
-- Each part is at least one character long, may have single spaces inside it,
-- and starts with a non-whitespace.
-- Note, this means "{account}", "%^!" and ";comment" are all accepted
-- (parent parsers usually prevent/consume the last).
-- It should have required parts to start with an alphanumeric;
-- for now it remains as-is for backwards compatibility.
accountnamep :: TextParser m AccountName
accountnamep = singlespacedtextp


-- | Parse any text beginning with a non-whitespace character, until a
-- double space or the end of input.
singlespacedtextp :: TextParser m T.Text
singlespacedtextp = singlespacedtextsatisfyingp (const True)

-- | Similar to 'singlespacedtextp', except that the text must only contain
-- characters satisfying the given predicate.
singlespacedtextsatisfyingp :: (Char -> Bool) -> TextParser m T.Text
singlespacedtextsatisfyingp pred = do
  firstPart <- partp
  otherParts <- many $ try $ singlespacep *> partp
  pure $! T.unwords $ firstPart : otherParts
  where
    partp = takeWhile1P Nothing (\c -> pred c && not (isSpace c))

-- | Parse one non-newline whitespace character that is not followed by another one.
singlespacep :: TextParser m ()
singlespacep = void spacenonewline *> notFollowedBy spacenonewline

--- ** amounts

-- | Parse whitespace then an amount, with an optional left or right
-- currency symbol and optional price, or return the special
-- "missing" marker amount.
spaceandamountormissingp :: JournalParser m MixedAmount
spaceandamountormissingp =
  option missingmixedamt $ try $ do
    lift $ skipSome spacenonewline
    Mixed . (:[]) <$> amountp

-- | Parse a single-commodity amount, with optional symbol on the left or
-- right, optional unit or total price, and optional (ignored)
-- ledger-style balance assertion or fixed lot price declaration.
amountp :: JournalParser m Amount
amountp = label "amount" $ do
  amount <- amountwithoutpricep
  lift $ skipMany spacenonewline
  mprice <- priceamountp
  pure $ amount { aprice = mprice }

amountwithoutpricep :: JournalParser m Amount
amountwithoutpricep = do
  (mult, sign) <- lift $ (,) <$> multiplierp <*> signp
  leftsymbolamountp mult sign <|> rightornosymbolamountp mult sign

  where

  leftsymbolamountp :: Bool -> (Decimal -> Decimal) -> JournalParser m Amount
  leftsymbolamountp mult sign = label "amount" $ do
    c <- lift commoditysymbolp
    suggestedStyle <- getAmountStyle c
    commodityspaced <- lift $ skipMany' spacenonewline
    sign2 <- lift $ signp
    offBeforeNum <- getOffset
    ambiguousRawNum <- lift rawnumberp
    mExponent <- lift $ optional $ try exponentp
    offAfterNum <- getOffset
    let numRegion = (offBeforeNum, offAfterNum)
    (q,prec,mdec,mgrps) <- lift $ interpretNumber numRegion suggestedStyle ambiguousRawNum mExponent
    let s = amountstyle{ascommodityside=L, ascommodityspaced=commodityspaced, asprecision=prec, asdecimalpoint=mdec, asdigitgroups=mgrps}
    return $ nullamt{acommodity=c, aquantity=sign (sign2 q), aismultiplier=mult, astyle=s, aprice=Nothing}

  rightornosymbolamountp :: Bool -> (Decimal -> Decimal) -> JournalParser m Amount
  rightornosymbolamountp mult sign = label "amount" $ do
    offBeforeNum <- getOffset
    ambiguousRawNum <- lift rawnumberp
    mExponent <- lift $ optional $ try exponentp
    offAfterNum <- getOffset
    let numRegion = (offBeforeNum, offAfterNum)
    mSpaceAndCommodity <- lift $ optional $ try $ (,) <$> skipMany' spacenonewline <*> commoditysymbolp
    case mSpaceAndCommodity of
      -- right symbol amount
      Just (commodityspaced, c) -> do
        suggestedStyle <- getAmountStyle c
        (q,prec,mdec,mgrps) <- lift $ interpretNumber numRegion suggestedStyle ambiguousRawNum mExponent
        let s = amountstyle{ascommodityside=R, ascommodityspaced=commodityspaced, asprecision=prec, asdecimalpoint=mdec, asdigitgroups=mgrps}
        return $ nullamt{acommodity=c, aquantity=sign q, aismultiplier=mult, astyle=s, aprice=Nothing}
      -- no symbol amount
      Nothing -> do
        suggestedStyle <- getDefaultAmountStyle
        (q,prec,mdec,mgrps) <- lift $ interpretNumber numRegion suggestedStyle ambiguousRawNum mExponent
        -- if a default commodity has been set, apply it and its style to this amount
        -- (unless it's a multiplier in an automated posting)
        defcs <- getDefaultCommodityAndStyle
        let (c,s) = case (mult, defcs) of
              (False, Just (defc,defs)) -> (defc, defs{asprecision=max (asprecision defs) prec})
              _ -> ("", amountstyle{asprecision=prec, asdecimalpoint=mdec, asdigitgroups=mgrps})
        return $ nullamt{acommodity=c, aquantity=sign q, aismultiplier=mult, astyle=s, aprice=Nothing}

  -- For reducing code duplication. Doesn't parse anything. Has the type
  -- of a parser only in order to throw parse errors (for convenience).
  interpretNumber
    :: (Int, Int) -- offsets
    -> Maybe AmountStyle
    -> Either AmbiguousNumber RawNumber
    -> Maybe Int
    -> TextParser m (Quantity, Int, Maybe Char, Maybe DigitGroupStyle)
  interpretNumber posRegion suggestedStyle ambiguousNum mExp =
    let rawNum = either (disambiguateNumber suggestedStyle) id ambiguousNum
    in  case fromRawNumber rawNum mExp of
          Left errMsg -> customFailure $
                           uncurry parseErrorAtRegion posRegion errMsg
          Right res -> pure res

-- | Parse an amount from a string, or get an error.
amountp' :: String -> Amount
amountp' s =
  case runParser (evalStateT (amountp <* eof) mempty) "" (T.pack s) of
    Right amt -> amt
    Left err  -> error' $ show err -- XXX should throwError

-- | Parse a mixed amount from a string, or get an error.
mamountp' :: String -> MixedAmount
mamountp' = Mixed . (:[]) . amountp'

signp :: Num a => TextParser m (a -> a)
signp = char '-' *> pure negate <|> char '+' *> pure id <|> pure id

multiplierp :: TextParser m Bool
multiplierp = option False $ char '*' *> pure True

-- | This is like skipMany but it returns True if at least one element
-- was skipped. This is helpful if you’re just using many to check if
-- the resulting list is empty or not.
skipMany' :: MonadPlus m => m a -> m Bool
skipMany' p = go False
  where
    go !isNull = do
      more <- option False (True <$ p)
      if more
        then go True
        else pure isNull

commoditysymbolp :: TextParser m CommoditySymbol
commoditysymbolp =
  quotedcommoditysymbolp <|> simplecommoditysymbolp <?> "commodity symbol"

quotedcommoditysymbolp :: TextParser m CommoditySymbol
quotedcommoditysymbolp =
  between (char '"') (char '"') $ takeWhile1P Nothing f
  where f c = c /= ';' && c /= '\n' && c /= '\"'

simplecommoditysymbolp :: TextParser m CommoditySymbol
simplecommoditysymbolp = takeWhile1P Nothing (not . isNonsimpleCommodityChar)

priceamountp :: JournalParser m (Maybe AmountPrice)
priceamountp = option Nothing $ do
  char '@'
  priceConstructor <- char '@' *> pure TotalPrice <|> pure UnitPrice

  lift (skipMany spacenonewline)
  priceAmount <- amountwithoutpricep <?> "unpriced amount (specifying a price)"

  pure $ Just $ priceConstructor priceAmount

balanceassertionp :: JournalParser m BalanceAssertion
balanceassertionp = do
  sourcepos <- genericSourcePos <$> lift getSourcePos
  char '='
  istotal <- fmap isJust $ optional $ try $ char '='
  isinclusive <- fmap isJust $ optional $ try $ char '*'
  lift (skipMany spacenonewline)
  -- this amount can have a price; balance assertions ignore it,
  -- but balance assignments will use it
  a <- amountp <?> "amount (for a balance assertion or assignment)"
  return BalanceAssertion
    { baamount    = a
    , batotal     = istotal
    , bainclusive = isinclusive
    , baposition  = sourcepos
    }

-- Parse a Ledger-style fixed lot price: {=PRICE}
-- https://www.ledger-cli.org/3.0/doc/ledger3.html#Fixing-Lot-Prices .
-- Currently we ignore these (hledger's @ PRICE is equivalent),
-- and we don't parse a Ledger-style {PRICE} (equivalent to Ledger's @ PRICE).
fixedlotpricep :: JournalParser m (Maybe Amount)
fixedlotpricep = optional $ do
  try $ do
    lift (skipMany spacenonewline)
    char '{'
  lift (skipMany spacenonewline)
  char '='
  lift (skipMany spacenonewline)
  a <- amountwithoutpricep <?> "unpriced amount (for an ignored ledger-style fixed lot price)"
  lift (skipMany spacenonewline)
  char '}'
  return a

-- | Parse a string representation of a number for its value and display
-- attributes.
--
-- Some international number formats are accepted, eg either period or comma
-- may be used for the decimal point, and the other of these may be used for
-- separating digit groups in the integer part. See
-- http://en.wikipedia.org/wiki/Decimal_separator for more examples.
--
-- This returns: the parsed numeric value, the precision (number of digits
-- seen following the decimal point), the decimal point character used if any,
-- and the digit group style if any.
--
numberp :: Maybe AmountStyle -> TextParser m (Quantity, Int, Maybe Char, Maybe DigitGroupStyle)
numberp suggestedStyle = label "number" $ do
    -- a number is an optional sign followed by a sequence of digits possibly
    -- interspersed with periods, commas, or both
    -- dbgparse 0 "numberp"
    sign <- signp
    rawNum <- either (disambiguateNumber suggestedStyle) id <$> rawnumberp
    mExp <- optional $ try $ exponentp
    dbg8 "numberp suggestedStyle" suggestedStyle `seq` return ()
    case dbg8 "numberp quantity,precision,mdecimalpoint,mgrps"
           $ fromRawNumber rawNum mExp of
      Left errMsg -> Fail.fail errMsg
      Right (q, p, d, g) -> pure (sign q, p, d, g)

exponentp :: TextParser m Int
exponentp = char' 'e' *> signp <*> decimal <?> "exponent"

-- | Interpret a raw number as a decimal number.
--
-- Returns:
-- - the decimal number
-- - the precision (number of digits after the decimal point)
-- - the decimal point character, if any
-- - the digit group style, if any (digit group character and sizes of digit groups)
fromRawNumber
  :: RawNumber
  -> Maybe Int
  -> Either String
            (Quantity, Int, Maybe Char, Maybe DigitGroupStyle)
fromRawNumber raw mExp = case raw of

  NoSeparators digitGrp mDecimals ->
    let mDecPt = fmap fst mDecimals
        decimalGrp = maybe mempty snd mDecimals

        (quantity, precision) =
          maybe id applyExp mExp $ toQuantity digitGrp decimalGrp

    in  Right (quantity, precision, mDecPt, Nothing)

  WithSeparators digitSep digitGrps mDecimals -> case mExp of
    Nothing ->
      let mDecPt = fmap fst mDecimals
          decimalGrp = maybe mempty snd mDecimals
          digitGroupStyle = DigitGroups digitSep (groupSizes digitGrps)

          (quantity, precision) = toQuantity (mconcat digitGrps) decimalGrp

      in  Right (quantity, precision, mDecPt, Just digitGroupStyle)
    Just _ -> Left
      "invalid number: mixing digit separators with exponents is not allowed"

  where
    -- Outputs digit group sizes from least significant to most significant
    groupSizes :: [DigitGrp] -> [Int]
    groupSizes digitGrps = reverse $ case map digitGroupLength digitGrps of
      (a:b:cs) | a < b -> b:cs
      gs               -> gs

    toQuantity :: DigitGrp -> DigitGrp -> (Quantity, Int)
    toQuantity preDecimalGrp postDecimalGrp = (quantity, precision)
      where
        quantity = Decimal (fromIntegral precision)
                           (digitGroupNumber $ preDecimalGrp <> postDecimalGrp)
        precision = digitGroupLength postDecimalGrp

    applyExp :: Int -> (Decimal, Int) -> (Decimal, Int)
    applyExp exponent (quantity, precision) =
      (quantity * 10^^exponent, max 0 (precision - exponent))


disambiguateNumber :: Maybe AmountStyle -> AmbiguousNumber -> RawNumber
disambiguateNumber suggestedStyle (AmbiguousNumber grp1 sep grp2) =
  -- If present, use the suggested style to disambiguate;
  -- otherwise, assume that the separator is a decimal point where possible.
  if isDecimalPointChar sep &&
     maybe True (sep `isValidDecimalBy`) suggestedStyle
  then NoSeparators grp1 (Just (sep, grp2))
  else WithSeparators sep [grp1, grp2] Nothing
  where
    isValidDecimalBy :: Char -> AmountStyle -> Bool
    isValidDecimalBy c = \case
      AmountStyle{asdecimalpoint = Just d} -> d == c
      AmountStyle{asdigitgroups = Just (DigitGroups g _)} -> g /= c
      AmountStyle{asprecision = 0} -> False
      _ -> True

-- | Parse and interpret the structure of a number without external hints.
-- Numbers are digit strings, possibly separated into digit groups by one
-- of two types of separators. (1) Numbers may optionally have a decimal
-- mark, which may be either a period or comma. (2) Numbers may
-- optionally contain digit group marks, which must all be either a
-- period, a comma, or a space.
--
-- It is our task to deduce the characters used as decimal mark and
-- digit group mark, based on the allowed syntax. For instance, we
-- make use of the fact that a decimal mark can occur at most once and
-- must be to the right of all digit group marks.
--
-- >>> parseTest rawnumberp "1,234,567.89"
-- Right (WithSeparators ',' ["1","234","567"] (Just ('.',"89")))
-- >>> parseTest rawnumberp "1,000"
-- Left (AmbiguousNumber "1" ',' "000")
-- >>> parseTest rawnumberp "1 000"
-- Right (WithSeparators ' ' ["1","000"] Nothing)
--
rawnumberp :: TextParser m (Either AmbiguousNumber RawNumber)
rawnumberp = label "number" $ do
  rawNumber <- fmap Right leadingDecimalPt <|> leadingDigits

  -- Guard against mistyped numbers
  mExtraDecimalSep <- optional $ lookAhead $ satisfy isDecimalPointChar
  when (isJust mExtraDecimalSep) $
    Fail.fail "invalid number (invalid use of separator)"

  mExtraFragment <- optional $ lookAhead $ try $
    char ' ' *> getOffset <* digitChar
  case mExtraFragment of
    Just off -> customFailure $
                  parseErrorAt off "invalid number (excessive trailing digits)"
    Nothing -> pure ()

  return $ dbg8 "rawnumberp" rawNumber
  where

  leadingDecimalPt :: TextParser m RawNumber
  leadingDecimalPt = do
    decPt <- satisfy isDecimalPointChar
    decGrp <- digitgroupp
    pure $ NoSeparators mempty (Just (decPt, decGrp))

  leadingDigits :: TextParser m (Either AmbiguousNumber RawNumber)
  leadingDigits = do
    grp1 <- digitgroupp
    withSeparators grp1 <|> fmap Right (trailingDecimalPt grp1)
                        <|> pure (Right $ NoSeparators grp1 Nothing)

  withSeparators :: DigitGrp -> TextParser m (Either AmbiguousNumber RawNumber)
  withSeparators grp1 = do
    (sep, grp2) <- try $ (,) <$> satisfy isDigitSeparatorChar <*> digitgroupp
    grps <- many $ try $ char sep *> digitgroupp

    let digitGroups = grp1 : grp2 : grps
    fmap Right (withDecimalPt sep digitGroups)
      <|> pure (withoutDecimalPt grp1 sep grp2 grps)

  withDecimalPt :: Char -> [DigitGrp] -> TextParser m RawNumber
  withDecimalPt digitSep digitGroups = do
    decPt <- satisfy $ \c -> isDecimalPointChar c && c /= digitSep
    decDigitGrp <- option mempty digitgroupp

    pure $ WithSeparators digitSep digitGroups (Just (decPt, decDigitGrp))

  withoutDecimalPt
    :: DigitGrp
    -> Char
    -> DigitGrp
    -> [DigitGrp]
    -> Either AmbiguousNumber RawNumber
  withoutDecimalPt grp1 sep grp2 grps
    | null grps && isDecimalPointChar sep =
        Left $ AmbiguousNumber grp1 sep grp2
    | otherwise = Right $ WithSeparators sep (grp1:grp2:grps) Nothing

  trailingDecimalPt :: DigitGrp -> TextParser m RawNumber
  trailingDecimalPt grp1 = do
    decPt <- satisfy isDecimalPointChar
    pure $ NoSeparators grp1 (Just (decPt, mempty))


isDecimalPointChar :: Char -> Bool
isDecimalPointChar c = c == '.' || c == ','

isDigitSeparatorChar :: Char -> Bool
isDigitSeparatorChar c = isDecimalPointChar c || c == ' '

-- | Some kinds of number literal we might parse.
data RawNumber
  = NoSeparators   DigitGrp (Maybe (Char, DigitGrp))
    -- ^ A number with no digit group marks (eg 100),
    --   or with a leading or trailing comma or period
    --   which (apparently) we interpret as a decimal mark (like 100. or .100)
  | WithSeparators Char [DigitGrp] (Maybe (Char, DigitGrp))
    -- ^ A number with identifiable digit group marks
    --   (eg 1,000,000 or 1,000.50 or 1 000)
  deriving (Show, Eq)

-- | Another kind of number literal: this one contains either a digit
-- group separator or a decimal mark, we're not sure which (eg 1,000 or 100.50).
data AmbiguousNumber = AmbiguousNumber DigitGrp Char DigitGrp
  deriving (Show, Eq)

-- | Description of a single digit group in a number literal.
-- "Thousands" is one well known digit grouping, but there are others.
data DigitGrp = DigitGrp {
  digitGroupLength :: !Int,    -- ^ The number of digits in this group.
  digitGroupNumber :: !Integer -- ^ The natural number formed by this group's digits.
} deriving (Eq)

-- | A custom show instance, showing digit groups as the parser saw them.
instance Show DigitGrp where
  show (DigitGrp len num)
    | len > 0 = "\"" ++ padding ++ numStr ++ "\""
    | otherwise = "\"\""
    where numStr = show num
          padding = replicate (len - length numStr) '0'

instance Sem.Semigroup DigitGrp where
  DigitGrp l1 n1 <> DigitGrp l2 n2 = DigitGrp (l1 + l2) (n1 * 10^l2 + n2)

instance Monoid DigitGrp where
  mempty = DigitGrp 0 0
  mappend = (Sem.<>)

digitgroupp :: TextParser m DigitGrp
digitgroupp = label "digits"
            $ makeGroup <$> takeWhile1P (Just "digit") isDigit
  where
    makeGroup = uncurry DigitGrp . foldl' step (0, 0) . T.unpack
    step (!l, !a) c = (l+1, a*10 + fromIntegral (digitToInt c))

--- ** comments

multilinecommentp :: TextParser m ()
multilinecommentp = startComment *> anyLine `skipManyTill` endComment
  where
    startComment = string "comment" *> trailingSpaces
    endComment = eof <|> string "end comment" *> trailingSpaces

    trailingSpaces = skipMany spacenonewline <* newline
    anyLine = void $ takeWhileP Nothing (\c -> c /= '\n') *> newline

{-# INLINABLE multilinecommentp #-}

emptyorcommentlinep :: TextParser m ()
emptyorcommentlinep = do
  skipMany spacenonewline
  skiplinecommentp <|> void newline
  where
    -- A line (file-level) comment can start with a semicolon, hash, or star
    -- (allowing org nodes).
    skiplinecommentp :: TextParser m ()
    skiplinecommentp = do
      satisfy $ \c -> c == ';' || c == '#' || c == '*'
      void $ takeWhileP Nothing (\c -> c /= '\n')
      optional newline
      pure ()

{-# INLINABLE emptyorcommentlinep #-}

-- A parser combinator for parsing (possibly multiline) comments
-- following journal items.
--
-- Several journal items may be followed by comments, which begin with
-- semicolons and extend to the end of the line. Such comments may span
-- multiple lines, but comment lines below the journal item must be
-- preceded by leading whitespace.
--
-- This parser combinator accepts a parser that consumes all input up
-- until the next newline. This parser should extract the "content" from
-- comments. The resulting parser returns this content plus the raw text
-- of the comment itself.
--
-- See followingcommentp for tests.
--
followingcommentp' :: (Monoid a, Show a) => TextParser m a -> TextParser m (Text, a)
followingcommentp' contentp = do
  skipMany spacenonewline
  -- there can be 0 or 1 sameLine
  sameLine <- try headerp *> ((:[]) <$> match' contentp) <|> pure []
  _ <- eolof
  -- there can be 0 or more nextLines
  nextLines <- many $
    try (skipSome spacenonewline *> headerp) *> match' contentp <* eolof
  let
    -- if there's just a next-line comment, insert an empty same-line comment
    -- so the next-line comment doesn't get rendered as a same-line comment.
    sameLine' | null sameLine && not (null nextLines) = [("",mempty)]
              | otherwise = sameLine
    (texts, contents) = unzip $ sameLine' ++ nextLines
    strippedCommentText = T.unlines $ map T.strip texts
    commentContent = mconcat contents
  pure (strippedCommentText, commentContent)

  where
    headerp = char ';' *> skipMany spacenonewline

{-# INLINABLE followingcommentp' #-}

-- | Parse the text of a (possibly multiline) comment following a journal item.
--
-- >>> rtp followingcommentp ""   -- no comment
-- Right ""
-- >>> rtp followingcommentp ";"    -- just a (empty) same-line comment. newline is added
-- Right "\n"
-- >>> rtp followingcommentp ";  \n"
-- Right "\n"
-- >>> rtp followingcommentp ";\n ;\n"  -- a same-line and a next-line comment
-- Right "\n\n"
-- >>> rtp followingcommentp "\n ;\n"  -- just a next-line comment. Insert an empty same-line comment so the next-line comment doesn't become a same-line comment.
-- Right "\n\n"
--
followingcommentp :: TextParser m Text
followingcommentp =
  fst <$> followingcommentp' (void $ takeWhileP Nothing (/= '\n'))
{-# INLINABLE followingcommentp #-}


-- | Parse a transaction comment and extract its tags.
--
-- The first line of a transaction may be followed by comments, which
-- begin with semicolons and extend to the end of the line. Transaction
-- comments may span multiple lines, but comment lines below the
-- transaction must be preceded by leading whitespace.
--
-- 2000/1/1 ; a transaction comment starting on the same line ...
--   ; extending to the next line
--   account1  $1
--   account2
--
-- Tags are name-value pairs.
--
-- >>> let getTags (_,tags) = tags
-- >>> let parseTags = fmap getTags . rtp transactioncommentp
--
-- >>> parseTags "; name1: val1, name2:all this is value2"
-- Right [("name1","val1"),("name2","all this is value2")]
--
-- A tag's name must be immediately followed by a colon, without
-- separating whitespace. The corresponding value consists of all the text
-- following the colon up until the next colon or newline, stripped of
-- leading and trailing whitespace.
--
transactioncommentp :: TextParser m (Text, [Tag])
transactioncommentp = followingcommentp' commenttagsp
{-# INLINABLE transactioncommentp #-}

commenttagsp :: TextParser m [Tag]
commenttagsp = do
  tagName <- fmap (last . T.split isSpace)
            $ takeWhileP Nothing (\c -> c /= ':' && c /= '\n')
  atColon tagName <|> pure [] -- if not ':', then either '\n' or EOF

  where
    atColon :: Text -> TextParser m [Tag]
    atColon name = char ':' *> do
      if T.null name
        then commenttagsp
        else do
          skipMany spacenonewline
          val <- tagValue
          let tag = (name, val)
          (tag:) <$> commenttagsp

    tagValue :: TextParser m Text
    tagValue = do
      val <- T.strip <$> takeWhileP Nothing (\c -> c /= ',' && c /= '\n')
      _ <- optional $ char ','
      pure val

{-# INLINABLE commenttagsp #-}


-- | Parse a posting comment and extract its tags and dates.
--
-- Postings may be followed by comments, which begin with semicolons and
-- extend to the end of the line. Posting comments may span multiple
-- lines, but comment lines below the posting must be preceded by
-- leading whitespace.
--
-- 2000/1/1
--   account1  $1 ; a posting comment starting on the same line ...
--   ; extending to the next line
--
--   account2
--   ; a posting comment beginning on the next line
--
-- Tags are name-value pairs.
--
-- >>> let getTags (_,tags,_,_) = tags
-- >>> let parseTags = fmap getTags . rtp (postingcommentp Nothing)
--
-- >>> parseTags "; name1: val1, name2:all this is value2"
-- Right [("name1","val1"),("name2","all this is value2")]
--
-- A tag's name must be immediately followed by a colon, without
-- separating whitespace. The corresponding value consists of all the text
-- following the colon up until the next colon or newline, stripped of
-- leading and trailing whitespace.
--
-- Posting dates may be expressed with "date"/"date2" tags or with
-- bracketed date syntax. Posting dates will inherit their year from the
-- transaction date if the year is not specified. We throw parse errors on
-- invalid dates.
--
-- >>> let getDates (_,_,d1,d2) = (d1, d2)
-- >>> let parseDates = fmap getDates . rtp (postingcommentp (Just 2000))
--
-- >>> parseDates "; date: 1/2, date2: 1999/12/31"
-- Right (Just 2000-01-02,Just 1999-12-31)
-- >>> parseDates "; [1/2=1999/12/31]"
-- Right (Just 2000-01-02,Just 1999-12-31)
--
-- Example: tags, date tags, and bracketed dates
-- >>> rtp (postingcommentp (Just 2000)) "; a:b, date:3/4, [=5/6]"
-- Right ("a:b, date:3/4, [=5/6]\n",[("a","b"),("date","3/4")],Just 2000-03-04,Just 2000-05-06)
--
-- Example: extraction of dates from date tags ignores trailing text
-- >>> rtp (postingcommentp (Just 2000)) "; date:3/4=5/6"
-- Right ("date:3/4=5/6\n",[("date","3/4=5/6")],Just 2000-03-04,Nothing)
--
postingcommentp
  :: Maybe Year -> TextParser m (Text, [Tag], Maybe Day, Maybe Day)
postingcommentp mYear = do
  (commentText, (tags, dateTags)) <-
    followingcommentp' (commenttagsanddatesp mYear)
  let mdate  = fmap snd $ find ((=="date") .fst) dateTags
      mdate2 = fmap snd $ find ((=="date2").fst) dateTags
  pure (commentText, tags, mdate, mdate2)
{-# INLINABLE postingcommentp #-}


commenttagsanddatesp
  :: Maybe Year -> TextParser m ([Tag], [DateTag])
commenttagsanddatesp mYear = do
  (txt, dateTags) <- match $ readUpTo ':'
  -- next char is either ':' or '\n' (or EOF)
  let tagName = last (T.split isSpace txt)
  (fmap.second) (dateTags++) (atColon tagName) <|> pure ([], dateTags) -- if not ':', then either '\n' or EOF

  where
    readUpTo :: Char -> TextParser m [DateTag]
    readUpTo end = do
      void $ takeWhileP Nothing (\c -> c /= end && c /= '\n' && c /= '[')
      -- if not '[' then ':' or '\n' or EOF
      atBracket (readUpTo end) <|> pure []

    atBracket :: TextParser m [DateTag] -> TextParser m [DateTag]
    atBracket cont = do
      -- Uses the fact that bracketed date-tags cannot contain newlines
      dateTags <- option [] $ lookAhead (bracketeddatetagsp mYear)
      _ <- char '['
      dateTags' <- cont
      pure $ dateTags ++ dateTags'

    atColon :: Text -> TextParser m ([Tag], [DateTag])
    atColon name = char ':' *> do
      skipMany spacenonewline
      (tags, dateTags) <- case name of
        ""      -> pure ([], [])
        "date"  -> dateValue name
        "date2" -> dateValue name
        _       -> tagValue name
      _ <- optional $ char ','
      bimap (tags++) (dateTags++) <$> commenttagsanddatesp mYear

    dateValue :: Text -> TextParser m ([Tag], [DateTag])
    dateValue name = do
      (txt, (date, dateTags)) <- match' $ do
        date <- datep' mYear
        dateTags <- readUpTo ','
        pure (date, dateTags)
      let val = T.strip txt
      pure $ ( [(name, val)]
             , (name, date) : dateTags )

    tagValue :: Text -> TextParser m ([Tag], [DateTag])
    tagValue name = do
      (txt, dateTags) <- match' $ readUpTo ','
      let val = T.strip txt
      pure $ ( [(name, val)]
             , dateTags )

{-# INLINABLE commenttagsanddatesp #-}


--- ** bracketed dates

-- | Parse Ledger-style bracketed posting dates ([DATE=DATE2]), as
-- "date" and/or "date2" tags. Anything that looks like an attempt at
-- this (a square-bracketed sequence of 0123456789/-.= containing at
-- least one digit and one date separator) is also parsed, and will
-- throw an appropriate error.
--
-- The dates are parsed in full here so that errors are reported in
-- the right position. A missing year in DATE can be inferred if a
-- default date is provided. A missing year in DATE2 will be inferred
-- from DATE.
--
-- >>> either (Left . customErrorBundlePretty) Right $ rtp (bracketeddatetagsp Nothing) "[2016/1/2=3/4]"
-- Right [("date",2016-01-02),("date2",2016-03-04)]
--
-- >>> either (Left . customErrorBundlePretty) Right $ rtp (bracketeddatetagsp Nothing) "[1]"
-- Left ...not a bracketed date...
--
-- >>> either (Left . customErrorBundlePretty) Right $ rtp (bracketeddatetagsp Nothing) "[2016/1/32]"
-- Left ...1:2:...well-formed but invalid date: 2016/1/32...
--
-- >>> either (Left . customErrorBundlePretty) Right $ rtp (bracketeddatetagsp Nothing) "[1/31]"
-- Left ...1:2:...partial date 1/31 found, but the current year is unknown...
--
-- >>> either (Left . customErrorBundlePretty) Right $ rtp (bracketeddatetagsp Nothing) "[0123456789/-.=/-.=]"
-- Left ...1:13:...expecting month or day...
--
bracketeddatetagsp
  :: Maybe Year -> TextParser m [(TagName, Day)]
bracketeddatetagsp mYear1 = do
  -- dbgparse 0 "bracketeddatetagsp"
  try $ do
    s <- lookAhead
       $ between (char '[') (char ']')
       $ takeWhile1P Nothing isBracketedDateChar
    unless (T.any isDigit s && T.any isDateSepChar s) $
      Fail.fail "not a bracketed date"
  -- Looks sufficiently like a bracketed date to commit to parsing a date

  between (char '[') (char ']') $ do
    md1 <- optional $ datep' mYear1

    let mYear2 = fmap readYear md1 <|> mYear1
    md2 <- optional $ char '=' *> datep' mYear2

    pure $ catMaybes [("date",) <$> md1, ("date2",) <$> md2]

  where
    readYear = first3 . toGregorian
    isBracketedDateChar c = isDigit c || isDateSepChar c || c == '='

{-# INLINABLE bracketeddatetagsp #-}


--- ** helper parsers

-- A version of `match` that is strict in the returned text
match' :: TextParser m a -> TextParser m (Text, a)
match' p = do
  (!txt, p) <- match p
  pure (txt, p)

--- * tests

tests_Common = tests "Common" [

   tests "amountp" [
    test "basic"                  $ assertParseEq amountp "$47.18"     (usd 47.18)
   ,test "ends with decimal mark" $ assertParseEq amountp "$1."        (usd 1  `withPrecision` 0)
   ,test "unit price"             $ assertParseEq amountp "$10 @ €0.5"
      -- not precise enough:
      -- (usd 10 `withPrecision` 0 `at` (eur 0.5 `withPrecision` 1)) -- `withStyle` asdecimalpoint=Just '.'
      amount{
         acommodity="$"
        ,aquantity=10 -- need to test internal precision with roundTo ? I think not
        ,astyle=amountstyle{asprecision=0, asdecimalpoint=Nothing}
        ,aprice=Just $ UnitPrice $
          amount{
             acommodity="€"
            ,aquantity=0.5
            ,astyle=amountstyle{asprecision=1, asdecimalpoint=Just '.'}
            }
        }
   ,test "total price"            $ assertParseEq amountp "$10 @@ €5"
      amount{
         acommodity="$"
        ,aquantity=10
        ,astyle=amountstyle{asprecision=0, asdecimalpoint=Nothing}
        ,aprice=Just $ TotalPrice $
          amount{
             acommodity="€"
            ,aquantity=5
            ,astyle=amountstyle{asprecision=0, asdecimalpoint=Nothing}
            }
        }
    ]

  ,let p = lift (numberp Nothing) :: JournalParser IO (Quantity, Int, Maybe Char, Maybe DigitGroupStyle) in
   test "numberp" $ do
     assertParseEq p "0"          (0, 0, Nothing, Nothing)
     assertParseEq p "1"          (1, 0, Nothing, Nothing)
     assertParseEq p "1.1"        (1.1, 1, Just '.', Nothing)
     assertParseEq p "1,000.1"    (1000.1, 1, Just '.', Just $ DigitGroups ',' [3])
     assertParseEq p "1.00.000,1" (100000.1, 1, Just ',', Just $ DigitGroups '.' [3,2])
     assertParseEq p "1,000,000"  (1000000, 0, Nothing, Just $ DigitGroups ',' [3,3])  -- could be simplified to [3]
     assertParseEq p "1."         (1, 0, Just '.', Nothing)
     assertParseEq p "1,"         (1, 0, Just ',', Nothing)
     assertParseEq p ".1"         (0.1, 1, Just '.', Nothing)
     assertParseEq p ",1"         (0.1, 1, Just ',', Nothing)
     assertParseError p "" ""
     assertParseError p "1,000.000,1" ""
     assertParseError p "1.000,000.1" ""
     assertParseError p "1,000.000.1" ""
     assertParseError p "1,,1" ""
     assertParseError p "1..1" ""
     assertParseError p ".1," ""
     assertParseError p ",1." ""

  ,tests "spaceandamountormissingp" [
     test "space and amount" $ assertParseEq spaceandamountormissingp " $47.18" (Mixed [usd 47.18])
    ,test "empty string" $ assertParseEq spaceandamountormissingp "" missingmixedamt
    -- ,test "just space" $ assertParseEq spaceandamountormissingp " " missingmixedamt  -- XXX should it ?
    -- ,test "just amount" $ assertParseError spaceandamountormissingp "$47.18" ""  -- succeeds, consuming nothing
    ]

  ]