{-# LANGUAGE ImportQualifiedPost #-}
{-# LANGUAGE NamedFieldPuns #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE TypeApplications #-}

module Text.FDF (FDF (FDF, body), Field (Field, name, value, kids),
                 mapWithKey, mapFieldWithKey,
                 foldMapWithKey, foldMapFieldWithKey,
                 traverseWithKey, traverseFieldWithKey,
                 parse, serialize) where

import Control.Applicative ((<*), (<*>), (<|>), many, some, optional)
import Data.Bifunctor (bimap)
import Data.ByteString (ByteString)
import Data.Char (isSpace)
import Data.Monoid.Instances.ByteString.UTF8 (ByteStringUTF8 (ByteStringUTF8))
import Data.Monoid.Textual (toString, toText)
import Data.Text (Text)
import Data.Text qualified as Text
import Data.Text.Encoding (encodeUtf8)
import Rank2 qualified
import Text.Grampa
import Text.Grampa.Combinators
import Text.Parser.Combinators (manyTill)
import Text.Grampa.PEG.Backtrack qualified as PEG

type Parser = PEG.Parser (Rank2.Only FDF)

data FDF = FDF {
  header :: ByteString,
  body :: Field,
  trailer :: ByteString}
  deriving (Show)

data Field = Field {
  name :: Text,
  value :: Maybe Text,
  kids :: [Field]}
  deriving (Show)

mapWithKey :: ([Text] -> Text -> Text) -> FDF -> FDF
mapWithKey f x@FDF{body} = x{body = mapFieldWithKey f body}

mapFieldWithKey :: ([Text] -> Text -> Text) -> Field -> Field
mapFieldWithKey f x@Field{name, value, kids} =
  x{value = f [name] <$> value,
    kids = mapFieldWithKey (f . (name:)) <$> kids}

foldMapWithKey :: Monoid a => ([Text] -> Text -> a) -> FDF -> a
foldMapWithKey f x@FDF{body} = foldMapFieldWithKey f body

foldMapFieldWithKey :: Monoid a => ([Text] -> Text -> a) -> Field -> a
foldMapFieldWithKey f x@Field{name, value, kids} =
  foldMap (f [name]) value <> foldMap (foldMapFieldWithKey $ f . (name:)) kids

traverseWithKey :: Applicative f => ([Text] -> Text -> f Text) -> FDF -> f FDF
traverseWithKey f x@FDF{body} = (\body'-> x{body = body'}) <$> traverseFieldWithKey f body

traverseFieldWithKey :: Applicative f => ([Text] -> Text -> f Text) -> Field -> f Field
traverseFieldWithKey f x@Field{name, value, kids} =
  Field name <$> traverse (f [name]) value <*> traverse (traverseFieldWithKey $ f . (name:)) kids

serialize :: FDF -> ByteString
serialize FDF{header, body, trailer} =
  "%FDF-1.2\n"
  <> header
  <> "<<\n"
  <> "/FDF\n"
  <> "<<\n"
  <> "/Fields [\n"
  <> encodeUtf8 (serializeField body) <> "\n"
  <> "]\n"
  <> ">>\n"
  <> ">>\n"
  <> trailer
  <> "%%EOF\n"

serializeField :: Field -> Text
serializeField Field{name, value, kids} =
  "<<\n"
  <> "/T (" <> name <> ")\n"
  <> foldMap (\v-> "/V (" <> v <> ")\n") value
  <> (if null kids then "" else "/Kids [\n" <> Text.intercalate "\n" (serializeField <$> kids) <> "]\n")
  <> ">>"

parse :: ByteString -> Either String FDF
parse input =
  bimap (\failure-> toString (const "<?>") $ failureDescription s failure 4) id $ simply parseComplete parser s
  where s = ByteStringUTF8 input

parser :: Parser ByteStringUTF8 FDF
parser = FDF
  <$ (string "%FDF-1.2" <* lineEnd <?> "first line")
  <*> extract ((takeWhile1 (`notElem` ["\r", "\n"]) <?> "bytes")
               <> lineEnd <> (mconcat <$> manyTill line begin) <?> "header")
  <* (string "/FDF" <* takeCharsWhile (== ' ') <* lineEnd <?> "end header")
  <* begin
  <* (string "/Fields [" <* takeCharsWhile (== ' ') <* lineEnd <?> "fields")
  <*> field
  <* (string "]" <* takeCharsWhile (== ' ') <* lineEnd <?> "end the fields")
  <* (end <?> "end the body")
  <*> extract ((end <?> "end the object")
               <> string "endobj" <> lineEnd
               <> takeCharsWhile isSpace
               <> string "trailer" <> lineEnd
               <> (mconcat <$> manyTill line (string "%%EOF" <?> "last line"))
               <?> "trailer")
  <* optional lineEnd

field :: Parser ByteStringUTF8 Field
field = Field <$ begin
  <*> strictText (string "/T (" *> takeCharsWhile (`notElem` [')', '\r', '\n']) <* string ")" <* lineEnd <?> "name")
  <*> optional (strictText $ admit (string "/V (" *> commit (takeCharsWhile (`notElem` [')', '\r', '\n']) <* string ")" <* lineEnd)
                                    <|> string "/V /" *> commit (takeCharsWhile (`notElem` ['\r', '\n']) <* lineEnd)
                                    <?> "value"))
  <*> admit (string "/Kids [" *> commit (lineEnd *> takeSome field <* string "]" <* lineEnd <?> "kids")
             <|> commit mempty)
  <* end

begin :: Parser ByteStringUTF8 ByteStringUTF8
begin = string "<<" *> lineEnd <?> "<<"

end :: Parser ByteStringUTF8 ByteStringUTF8
end = string ">>" *> takeCharsWhile (== ' ') *> moptional lineEnd <?> ">>"

line :: Parser ByteStringUTF8 ByteStringUTF8
line = takeCharsWhile (`notElem` ['\r', '\n']) <> lineEnd <?> "line"

lineEnd :: Parser ByteStringUTF8 ByteStringUTF8
lineEnd = string "\r\n" <|> string "\r" <|> string "\n"

strictText :: Parser ByteStringUTF8 ByteStringUTF8 -> Parser ByteStringUTF8 Text
strictText = fmap $ toText (error . ("Invalid UTF-8 sequence: " ++) . show)

extract :: Parser ByteStringUTF8 ByteStringUTF8 -> Parser ByteStringUTF8 ByteString
extract = fmap $ \(ByteStringUTF8 bs) -> bs