{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE NamedFieldPuns #-}
{-# LANGUAGE FlexibleInstances #-}
module PDF.Object (
      Content(..)
    , Dictionary
    , DirectObject(..)
    , Flow(..)
    , IndexedObjects
    , IndirectObjCoordinates(..)
    , InputStructure(..)
    , Name(..)
    , Number(..)
    , Object(..)
    , Occurrence(..)
    , StringObject(..)
    , Structure(..)
    , XRefEntry(..)
    , XRefSection
    , array
    , blank
    , dictionary
    , directObject
    , eofMarker
    , integer
    , line
    , magicNumber
    , name
    , number
    , 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, pack, singleton, unpack)
import Data.ByteString.Char8.Util (B16Int(..), b16ToBytes, unescape)
import Data.Map (Map, (!), mapWithKey)
import qualified Data.Map as Map (
    delete, empty, fromList, lookup, minViewWithKey, toList, union
  )
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, getOffsets, 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 :: (Read a, Num a, MonadParser m) => m a
integer = read . Char8.unpack <$> 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 . read . Char8.unpack <$>
  (mappend <$> sign <*> (integerPart <|> Char8.cons '0' <$> floatPart))
  <?> "number"
  where
    sign = string "-" <|> option "" (char '+' >> return "")
    integerPart = mappend <$> decNumber <*> option "" floatPart
    floatPart = Char8.cons <$> char '.' <*> (option "0" $ decNumber)

--
-- 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 <$> (char '<' *> hexNumber <* char '>')
  <?> "string object (literal or hexadecimal)"
  where
    literalString = many literalStringBlock
    literalStringBlock = takeAll1 normalChar <|> matchingParenthesis <|> escapedChar
    normalChar = not . (`elem` ("\\()" :: String))
    matchingParenthesis =
      mappend <$> (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]

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"
    ]

-------------------------------------
--          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)

updateXrefs :: XRefSection -> Map Resource Offset -> (XRefSection, Offset)
updateXrefs xRef offsets = (mapWithKey updateEntry xRef, offsets ! StartXRef)
  where
    updateEntry objectId e@(InUse {}) = e {offset = offsets ! (Object objectId)}
    updateEntry _ e = e

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

--
-- Content
--
data Content = Content {
      occurrences :: [Occurrence]
    , objects :: IndexedObjects
    , docStructure :: Structure
  } deriving Show

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

instance Output Content where
  output (Content {occurrences, objects, docStructure}) =
    fmap (updateXrefs xRef) <$> getOffsets (outputBody (occurrences, objects))
    >>= \(body, (xref, startXRef)) -> mconcat [
          body
        , Output.line "xref"
        , output xref
        , Output.line "trailer"
        , output trailer, newLine
        , Output.line "startxref"
        , Output.line (printf "%d" (getOffset startXRef))
        , byteString eofMarker
      ]
    where
      Structure {xRef, trailer} = docStructure