{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE TypeOperators #-}

module Hledger.Utils.Parse (
  SimpleStringParser,
  SimpleTextParser,
  TextParser,

  -- * SourcePos
  SourcePos(..),
  mkPos,
  unPos,
  initialPos,
  sourcePosPretty,
  sourcePosPairPretty,

  choice',
  choiceInState,
  surroundedBy,
  parsewith,
  runTextParser,
  rtp,
  parsewithString,
  parseWithState,
  parseWithState',
  fromparse,
  parseerror,
  showDateParseError,
  nonspace,
  isNewline,
  isNonNewlineSpace,
  restofline,
  eolof,

  spacenonewline,
  skipNonNewlineSpaces,
  skipNonNewlineSpaces1,
  skipNonNewlineSpaces',

  -- ** Trace the state of hledger parsers
  dbgparse,
  traceOrLogParse,

  -- * re-exports
  HledgerParseErrors,
  HledgerParseErrorData,
  customErrorBundlePretty,
)
where

import Control.Monad (when)
import qualified Data.Text as T
import Safe (tailErr)
import Text.Megaparsec
import Text.Printf
import Control.Monad.State.Strict (StateT, evalStateT)
import Data.Char
import Data.Functor (void)
import Data.Functor.Identity (Identity(..))
import Data.List
import Data.Text (Text)
import Text.Megaparsec.Char
import Text.Megaparsec.Custom
import Hledger.Utils.Debug (debugLevel, traceOrLog)

-- | A parser of string to some type.
type SimpleStringParser a = Parsec HledgerParseErrorData String a

-- | A parser of strict text to some type.
type SimpleTextParser = Parsec HledgerParseErrorData Text  -- XXX an "a" argument breaks the CsvRulesParser declaration somehow

-- | A parser of text that runs in some monad.
type TextParser m a = ParsecT HledgerParseErrorData Text m a

-- class (Stream s, MonadPlus m) => MonadParsec e s m 
-- dbgparse :: (MonadPlus m, MonadParsec e String m) => Int -> String -> m ()

-- | Trace to stderr or log to debug log the provided label (if non-null)
-- and current parser state (position and next input),
-- if the global debug level is at or above the specified level.
-- Uses unsafePerformIO.
dbgparse :: Int -> String -> TextParser m ()
dbgparse level msg = when (level <= debugLevel) $ traceOrLogParse msg

-- | Trace to stderr or log to debug log the provided label (if non-null)
-- and current parser state (position and next input).
-- See also: Hledger.Utils.Debug, megaparsec's dbg.
-- Uses unsafePerformIO.
-- XXX Can be hard to make this evaluate.
traceOrLogParse :: String -> TextParser m ()
traceOrLogParse msg = do
  pos <- getSourcePos
  next <- (T.take peeklength) `fmap` getInput
  let (l,c) = (sourceLine pos, sourceColumn pos)
      s  = printf "at line %2d col %2d: %s" (unPos l) (unPos c) (show next) :: String
      s' = printf ("%-"++show (peeklength+30)++"s") s ++ " " ++ msg
  traceOrLog s' $ return ()
  where
    peeklength = 30

-- | Render a pair of source positions in human-readable form, only displaying the range of lines.
sourcePosPairPretty :: (SourcePos, SourcePos) -> String
sourcePosPairPretty (SourcePos fp l1 _, SourcePos _ l2 c2) =
    fp ++ ":" ++ show (unPos l1) ++ "-" ++ show l2'
  where
    l2' = if unPos c2 == 1 then unPos l2 - 1 else unPos l2  -- might be at end of file with a final new line

-- | Backtracking choice, use this when alternatives share a prefix.
-- Consumes no input if all choices fail.
choice' :: [TextParser m a] -> TextParser m a
choice' = choice . map try

-- | Backtracking choice, use this when alternatives share a prefix.
-- Consumes no input if all choices fail.
choiceInState :: [StateT s (ParsecT HledgerParseErrorData Text m) a] -> StateT s (ParsecT HledgerParseErrorData Text m) a
choiceInState = choice . map try

surroundedBy :: Applicative m => m openclose -> m a -> m a
surroundedBy p = between p p

parsewith :: Parsec e Text a -> Text -> Either (ParseErrorBundle Text e) a
parsewith p = runParser p ""

-- | Run a text parser in the identity monad. See also: parseWithState.
runTextParser, rtp
  :: TextParser Identity a -> Text -> Either HledgerParseErrors a
runTextParser = parsewith
rtp = runTextParser

parsewithString
  :: Parsec e String a -> String -> Either (ParseErrorBundle String e) a
parsewithString p = runParser p ""

-- | Run a stateful parser with some initial state on a text.
-- See also: runTextParser, runJournalParser.
parseWithState
  :: Monad m
  => st
  -> StateT st (ParsecT HledgerParseErrorData Text m) a
  -> Text
  -> m (Either HledgerParseErrors a)
parseWithState ctx p = runParserT (evalStateT p ctx) ""

parseWithState'
  :: (Stream s)
  => st
  -> StateT st (ParsecT e s Identity) a
  -> s
  -> (Either (ParseErrorBundle s e) a)
parseWithState' ctx p = runParser (evalStateT p ctx) ""

fromparse
  :: (Show t, Show (Token t), Show e) => Either (ParseErrorBundle t e) a -> a
fromparse = either parseerror id

parseerror :: (Show t, Show (Token t), Show e) => ParseErrorBundle t e -> a
parseerror e = errorWithoutStackTrace $ showParseError e  -- PARTIAL:

showParseError
  :: (Show t, Show (Token t), Show e)
  => ParseErrorBundle t e -> String
showParseError e = "parse error at " ++ show e

showDateParseError
  :: (Show t, Show (Token t), Show e) => ParseErrorBundle t e -> String
showDateParseError e = printf "date parse error (%s)" (intercalate ", " $ tailErr $ lines $ show e)  -- PARTIAL tailError won't be null because showing a parse error

isNewline :: Char -> Bool 
isNewline '\n' = True
isNewline _    = False

nonspace :: TextParser m Char
nonspace = satisfy (not . isSpace)

isNonNewlineSpace :: Char -> Bool
isNonNewlineSpace c = not (isNewline c) && isSpace c

spacenonewline :: (Stream s, Char ~ Token s) => ParsecT HledgerParseErrorData s m Char
spacenonewline = satisfy isNonNewlineSpace
{-# INLINABLE spacenonewline #-}

restofline :: TextParser m String
restofline = anySingle `manyTill` eolof

-- Skip many non-newline spaces.
skipNonNewlineSpaces :: (Stream s, Token s ~ Char) => ParsecT HledgerParseErrorData s m ()
skipNonNewlineSpaces = void $ takeWhileP Nothing isNonNewlineSpace
{-# INLINABLE skipNonNewlineSpaces #-}

-- Skip many non-newline spaces, failing if there are none.
skipNonNewlineSpaces1 :: (Stream s, Token s ~ Char) => ParsecT HledgerParseErrorData s m ()
skipNonNewlineSpaces1 = void $ takeWhile1P Nothing isNonNewlineSpace
{-# INLINABLE skipNonNewlineSpaces1 #-}

-- Skip many non-newline spaces, returning True if any have been skipped.
skipNonNewlineSpaces' :: (Stream s, Token s ~ Char) => ParsecT HledgerParseErrorData s m Bool
skipNonNewlineSpaces' = True <$ skipNonNewlineSpaces1 <|> pure False
{-# INLINABLE skipNonNewlineSpaces' #-}

eolof :: TextParser m ()
eolof = void newline <|> eof