{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE NamedFieldPuns #-}
{-# LANGUAGE FlexibleInstances #-}
module PDF.Object (
      Dictionary
    , DirectObject(..)
    , Flow(..)
    , IndexedObjects
    , IndirectObjCoordinates(..)
    , InputStructure(..)
    , Name(..)
    , Number(..)
    , Object(..)
    , Occurrence(..)
    , StringObject(..)
    , Structure(..)
    , XRefEntry(..)
    , XRefSection
    , array
    , blank
    , dictionary
    , directObject
    , eofMarker
    , integer
    , line
    , magicNumber
    , name
    , number
    , outputBody
    , regular
    , stringObject
    , structure
    , toByteString
  ) where

import Control.Applicative ((<|>), many)
import Data.Attoparsec.ByteString.Char8 (choice, count, option, sepBy)
import Data.ByteString (ByteString)
import qualified Data.ByteString as BS (concat)
import qualified Data.ByteString.Char8 as Char8 (
    cons, length, pack, singleton, snoc, unpack
  )
import Data.ByteString.Char8.Util (B16Int(..), b16ToBytes, unescape)
import Data.Map (Map, (!))
import qualified Data.Map as Map (
    delete, empty, fromList, lookup, minViewWithKey, toList, union
  )
import qualified Data.Set as Set (fromList, member)
import qualified PDF.EOL as EOL (charset, parser)
import qualified PDF.Output as Output (line, string)
import PDF.Output (
      OBuilder, ObjectId(..), Offset(..), Output(..), Resource(..)
    , byteString, getObjectId, getOffset, join, newLine, saveOffset
  )
import PDF.Parser (MonadParser(..), Parser, (<?>), octDigit, oneOf)
import Text.Printf (printf)

line :: MonadParser m => String -> m ()
line l = (string (Char8.pack l) *> blank *> return ()) <?> printf "line «%s»" l

magicNumber :: ByteString
magicNumber = "%PDF-"

eofMarker :: ByteString
eofMarker = "%%EOF"

whiteSpaceCharset :: String
whiteSpaceCharset = "\0\t\12 "

blank :: MonadParser m => m ()
blank = takeAll (`elem` (EOL.charset ++ whiteSpaceCharset)) *> pure ()

delimiterCharset :: String
delimiterCharset = "()<>[]{}/%"

regular :: Char -> Bool
regular = not . (`elem` (EOL.charset ++ whiteSpaceCharset ++ delimiterCharset))

integer :: MonadParser m => m Int
integer = decNumber <* blank <?> "decimal integer"

-------------------------------------
--          OBJECTS
-------------------------------------

type IndexedObjects = Map ObjectId Object

--
-- Boolean
--
boolean :: MonadParser m => m Bool
boolean =
  (string "true" *> return True) <|> (string "false" *> return False) <?> "boolean"

--
-- Number
--
newtype Number = Number Double deriving (Eq, Show)

instance Output Number where
  output (Number f) = Output.string $
    case properFraction f of
      (n, 0) -> printf "%d" (n :: Int)
      _ -> printf "%f" f

number :: MonadParser m => m Number
number = Number <$> (sign <*> value) <?> "number"
  where
    sign = (string "-" *> return negate) <|> option id (char '+' >> return id)
    value = floatNumber <|> (char '.' *> afterPoint)
    afterPoint = read . ("0." ++) . Char8.unpack <$> takeAll (`Set.member` digits)
    digits = Set.fromList ['0' .. '9']

--
-- StringObject
--
data StringObject = Literal ByteString | Hexadecimal B16Int deriving (Eq, Show)

instance Output StringObject where
  output (Literal s) = Output.string (printf "(%s)" (Char8.unpack s))
  output (Hexadecimal (B16Int n)) = Output.string (printf "<%s>" (Char8.unpack n))

stringObject :: MonadParser m => m StringObject
stringObject =
    Literal <$> (char '(' *> (BS.concat <$> literalString) <* char ')')
  <|> Hexadecimal . roundBytes <$> (char '<' *> hexNumber <* char '>')
  <?> "string object (literal or hexadecimal)"
  where
    literalString = many literalStringBlock
    literalStringBlock = takeAll1 normalChar <|> matchingParenthesis <|> escapedChar
    normalChar = not . (`elem` ("\\()" :: String))
    matchingParenthesis =
      mappend <$> (Char8.cons <$> char '(' <*> literalStringBlock) <*> string ")"
    escapedChar =
      Char8.cons <$> char '\\' <*> (Char8.singleton <$> oneOf "nrtbf()\\\n" <|> octalCode)
    octalCode = choice $ (\n -> Char8.pack <$> count n octDigit) <$> [1..3]
    roundBytes (B16Int bs)
      | Char8.length bs `mod` 2 == 1 = B16Int (bs `Char8.snoc` '0')
      | otherwise = B16Int bs

toByteString :: StringObject -> ByteString
toByteString (Hexadecimal h) = b16ToBytes h
toByteString (Literal s) = unescape s

--
-- Name
--
newtype Name = Name String deriving (Eq, Ord, Show)

instance Output Name where
  output (Name n) = Output.string ('/':n)

name :: MonadParser m => m Name
name = Name . Char8.unpack <$> (char '/' *> takeAll regular) <?> "name"

--
-- Array
--
array :: MonadParser m => m [DirectObject]
array =
  char '[' *> blank *> directObject `sepBy` blank <* blank <* char ']' <?> "array"

--
-- Dictionary
--
type Dictionary = Map Name DirectObject

instance Output Dictionary where
  output aDictionary =
    "<<" `mappend` keyValues `mappend` ">>"
    where
      keyValues = join " " $ outputKeyVal <$> Map.toList aDictionary
      outputKeyVal :: (Name, DirectObject) -> OBuilder
      outputKeyVal (key, val) = mconcat [output key, " ", output val]

dictionary :: MonadParser m => m Dictionary
dictionary =
  string "<<" *> blank *> keyValPairs <* string ">>" <?> "dictionary"
  where
    keyVal = (,) <$> name <* blank <*> directObject
    keyValPairs = Map.fromList <$> keyVal `sepBy` blank <* blank

--
-- Null
--
nullObject :: MonadParser m => m ()
nullObject = string "null" *> return () <?> "null object"

--
-- Reference
--
data IndirectObjCoordinates = IndirectObjCoordinates {
      objectId :: ObjectId
    , versionNumber :: Int
  } deriving Show

reference :: MonadParser m => m IndirectObjCoordinates
reference = IndirectObjCoordinates
  <$> (fmap ObjectId integer) <*> integer <* char 'R' <?> "reference to an object"

--
-- DirectObject
--
data DirectObject =
    Boolean Bool
  | NumberObject Number
  | StringObject StringObject
  | NameObject Name
  | Array [DirectObject]
  | Dictionary Dictionary
  | Null
  | Reference IndirectObjCoordinates
  deriving Show

instance Output DirectObject where
  output (Boolean b) = output b
  output (NumberObject n) = output n
  output (StringObject s) = output s
  output (NameObject n) = output n
  output (Array a) = mconcat ["[", join " " a, "]"]
  output (Dictionary d) = output d
  output (Null) = "null"
  output (Reference (IndirectObjCoordinates {objectId, versionNumber})) =
    Output.string (printf "%d %d R" (getObjectId objectId) versionNumber)

directObject :: MonadParser m => m DirectObject
directObject = (peek >>= dispatch) <?> "direct object"
  where
    dispatch 't' = Boolean <$> boolean
    dispatch 'f' = Boolean <$> boolean
    dispatch '(' = StringObject <$> stringObject
    dispatch '<' = StringObject <$> stringObject <|> Dictionary <$> dictionary
    dispatch '/' = NameObject <$> name
    dispatch '[' = Array <$> array
    dispatch 'n' = nullObject *> return Null
    dispatch _ =
        Reference <$> reference {- defined before Number because Number is a prefix of it -}
      <|> NumberObject <$> number

--
-- Object
--
data Object =
    Direct DirectObject
  | Stream {
        header :: Dictionary
      , streamContent :: ByteString
    }
  deriving Show

instance Output Object where
  output (Direct d) = output d
  output (Stream {header, streamContent}) = mconcat [
        output header, newLine
      , Output.line "stream"
      , byteString streamContent
      , "endstream"
    ]

--
-- Occurrence
--
data Occurrence = Comment String | Indirect IndirectObjCoordinates deriving Show

outputOccurrence :: IndexedObjects -> Occurrence -> OBuilder
outputOccurrence _ (Comment c) = Output.line c
outputOccurrence objects (Indirect (IndirectObjCoordinates {objectId, versionNumber})) =
  saveOffset (Object objectId) >> mconcat [
        Output.line (printf "%d %d obj" (getObjectId objectId) versionNumber)
      , output (objects ! objectId), newLine
      , Output.line "endobj"
    ]

outputBody :: ([Occurrence], IndexedObjects) -> OBuilder
outputBody (occurrences, objects) =
  output (outputOccurrence objects <$> occurrences) <* saveOffset StartXRef

-------------------------------------
--          XREF TABLE
-------------------------------------

--
-- XRefEntry
--
data XRefEntry = InUse {
      offset :: Offset
    , generation :: Int
  } | Free {
      nextFree :: ObjectId
    , generation :: Int
  } deriving Show

instance Output XRefEntry where
  output (InUse {offset, generation}) =
      Output.line (printf "%010d %05d n " (getOffset offset) generation)
  output (Free {nextFree, generation}) =
      Output.line (printf "%010d %05d f " (getObjectId nextFree) generation)

entry :: Parser u XRefEntry
entry = do
  (big, small) <- (,) <$> integer <*> integer
  (inUse big small <|> free big small <?> "XRef entry") <* blank
  where
    inUse :: Int -> Int -> Parser u XRefEntry
    inUse big generation =
      char 'n' *> return (InUse {offset = Offset big, generation})
    free :: Int -> Int -> Parser u XRefEntry
    free big generation =
      char 'f' *> return (Free {nextFree = ObjectId big, generation})

--
-- XRefSubSection
--
data XRefSubSection = XRefSubSection {
      firstObjectId :: ObjectId
    , entries :: [XRefEntry]
  } deriving Show

instance Output XRefSubSection where
  output (XRefSubSection {firstObjectId, entries}) =
      Output.line (printf "%d %d" (getObjectId firstObjectId) (length entries))
    `mappend` output entries

xRefSubSection :: Parser u XRefSubSection
xRefSubSection = do
  (firstId, entriesNumber) <- (,) <$> integer <*> integer <?> "XRef subsection"
  entries <- count entriesNumber entry
  return $ XRefSubSection {firstObjectId = ObjectId firstId, entries}

type XRefSection = Map ObjectId XRefEntry

instance Output XRefSection where
  output = output . sections
    where
      sections tmp =
        case Map.minViewWithKey tmp of
          Nothing -> []
          Just ((objectId@(ObjectId value), firstEntry), rest) ->
            let (subSection, sndRest) = section objectId [firstEntry] (value + 1) rest in
            subSection : sections sndRest
      section firstObjectId stack nextValue tmp =
        let nextId = ObjectId nextValue in
        case Map.lookup nextId tmp of
          Nothing -> (XRefSubSection {firstObjectId, entries = reverse stack}, tmp)
          Just nextEntry ->
            section firstObjectId (nextEntry:stack) (nextValue + 1) (Map.delete nextId tmp)


xRefSection :: Parser u XRefSection
xRefSection = foldr addSubsection Map.empty <$>
  (line "xref" *> xRefSubSection `sepBy` many EOL.parser)
  where
    addSubsection (XRefSubSection {firstObjectId, entries}) =
      Map.union . Map.fromList $ zip ([firstObjectId..]) entries

--
-- Structure
--
data InputStructure = InputStructure {
      startOffset :: Int
    , inputStructure :: Structure
  }

data Structure = Structure {
      xRef :: XRefSection
    , trailer :: Dictionary
  } deriving Show

structure :: Parser u Structure
structure =
    Structure
  <$> xRefSection
  <*> (string "trailer" *> blank *> dictionary <* EOL.parser)

--
-- Flow
--
data Flow = Flow {
      occurrencesStack :: [Occurrence]
    , tmpObjects :: IndexedObjects
  } deriving Show