{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE NamedFieldPuns #-}
{-# LANGUAGE FlexibleInstances #-}
module PDF.Object (
      Content(..)
    , DirectObject(..)
    , IndirectObjCoordinates(..)
    , Object(..)
    , Occurrence(..)
    , Parser
    , XRefEntry(..)
    , XRefSection
    , XRefSubSection(..)
    , blank
    , content
    , dictionary
    , directObject
    , eofMarker
    , integer
    , line
    , magicNumber
  ) where

import Data.ByteString.Lazy.Char8 (ByteString)
import Data.Int (Int64)
import Data.Map (Map, (!))
import qualified Data.Map as Map (empty, elems, fromList, toList)
import qualified PDF.EOL as EOL (charset, parser)
import qualified PDF.Output as Output (string)
import PDF.Output (OBuilder, Output(..), byteString, join, newLine, nextLine)
import Text.Parsec
import Text.Printf (printf)

type Parser u = Parsec ByteString u

type Dictionary = Map String DirectObject

instance Output (Map String DirectObject) where
  output dict =
    "<<" `mappend` keyValues `mappend` ">>"
    where
      keyValues = join " " $ outputKeyVal <$> Map.toList dict
      outputKeyVal (key, val) =
        Output.string (printf "/%s " key) `mappend` output val

data StringObj = Literal String | Hexadecimal String deriving Show

instance Output StringObj where
  output (Literal s) = Output.string (printf "(%s)" s)
  output (Hexadecimal s) = Output.string (printf "<%s>" s)

data DirectObject =
    Boolean Bool
  | Number Float
  | String StringObj
  | Name String
  | Array [DirectObject]
  | Dictionary Dictionary
  | Null
  | Reference IndirectObjCoordinates
  deriving Show

outputFloat :: Float -> OBuilder
outputFloat f = Output.string $
  case properFraction f of
    (n, 0) -> printf "%d" (n :: Int)
    _ -> printf "%f" f

instance Output DirectObject where
  output (Boolean b) = output b
  output (Number n) = outputFloat n
  output (String s) = output s
  output (Name n) = "/" `mappend` Output.string n
  output (Array a) = "[" `mappend` join " " a `mappend` "]"
  output (Dictionary d) = output d
  output (Null) = "null"
  output (Reference (IndirectObjCoordinates {objectId, versionNumber})) =
    Output.string (printf "%d %d R" objectId versionNumber)

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

instance Output Object where
  output (Direct d) = output d
  output (Stream {header, streamContent}) =
      output header
    `nextLine` "stream"
    `nextLine` byteString streamContent
    `mappend` "endstream"

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

data Occurrence = Comment String | Indirect IndirectObjCoordinates deriving Show

outputOccurrence :: Map Int Object -> Occurrence -> OBuilder
outputOccurrence _ (Comment c) =
  Output.string (printf "%%%s" c) `mappend` newLine
outputOccurrence objects (Indirect (IndirectObjCoordinates {objectId, versionNumber})) =
    Output.string (printf "%d %d obj" objectId versionNumber)
  `nextLine` output (objects ! objectId)
  `nextLine` "endobj" `mappend` newLine

data XRefEntry = InUse {
      offset :: Int64
    , generation :: Int
  } | Free {
      nextFree :: Int64
    , generation :: Int
  } deriving Show

instance Output XRefEntry where
  output (InUse {offset, generation}) =
      Output.string (printf "%010d %05d n " offset generation) `mappend` newLine
  output (Free {nextFree, generation}) =
      Output.string (printf "%010d %05d f " nextFree generation) `mappend` newLine

data XRefSubSection = XRefSubSection {
      firstObjectId :: Int
    , entriesNumber :: Int
    , entries :: Map Int XRefEntry
  } deriving Show

instance Output XRefSubSection where
  output (XRefSubSection {firstObjectId, entriesNumber, entries}) =
      Output.string (printf "%d %d" firstObjectId entriesNumber)
    `nextLine` output (Map.elems entries)

type XRefSection = [XRefSubSection]

data Content = Content {
      startOffset :: Int64
    , body :: [Occurrence]
    , objects :: Map Int Object
    , xrefSection :: XRefSection
    , trailer :: Dictionary
    , startXrefPosition :: Int64
  } deriving Show

instance Output Content where
  output (Content {body, objects, trailer, xrefSection, startXrefPosition}) =
      output (outputOccurrence objects <$> body)
    `mappend` output xrefSection
    `mappend` "trailer"
    `nextLine` output trailer
    `nextLine` "startxref"
    `nextLine` Output.string (printf "%d" startXrefPosition)
    `nextLine` byteString eofMarker

line :: String -> Parser u ()
line l = string l *> EOL.parser *> return ()

magicNumber :: String
magicNumber = "%PDF-"

eofMarker :: ByteString
eofMarker = "%%EOF"

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

whiteSpace :: Parser u ()
whiteSpace = oneOf whiteSpaceCharset *> return () <|> EOL.parser *> return ()

blank :: Parser u ()
blank = skipMany whiteSpace

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

regular :: Parser u Char
regular = noneOf $ EOL.charset ++ whiteSpaceCharset ++ delimiterCharset

integer :: (Read a, Num a) => Parser u a
integer = read <$> many1 digit <* whiteSpace

directObject :: Parser u DirectObject
directObject =
    Boolean <$> try boolean
  <|> Reference <$> try reference {- defined before Number because Number is a prefix of it -}
  <|> Number <$> try number
  <|> String <$> try stringObj
  <|> Name <$> try name
  <|> Array <$> try array
  <|> Dictionary <$> try dictionary
  <|> const Null <$> try nullObject

boolean :: Parser u Bool
boolean = (string "true" *> return True) <|> (string "false" *> return False)

number :: Parser u Float
number = read <$> (mappend <$> sign <*> (integerPart <|> ('0':) <$> floatPart))
  where
    sign = string "-" <|> option "" (char '+' >> return "")
    integerPart = mappend <$> many1 digit <*> option "" floatPart
    floatPart = (:) <$> char '.' <*> (option "0" $ many1 digit)

stringObj :: Parser u StringObj
stringObj =
    Literal <$> (char '(' *> (concat <$> many literalStringBlock) <* char ')')
  <|> Hexadecimal <$> (char '<' *> many hexDigit <* char '>')
  where
    literalStringBlock = many1 (noneOf "\\()") <|> matchingParenthesis <|> escapedChar
    matchingParenthesis =
      (++) <$> ((:) <$> char '(' <*> literalStringBlock) <*> string ")"
    escapedChar = (:) <$> char '\\' <*> ((:[]) <$> oneOf "nrtbf()\\" <|> octalCode)
    octalCode = choice $ (\n -> count n octDigit) <$> [1..3]

name :: Parser u String
name = char '/' *> many regular

array :: Parser u [DirectObject]
array = char '[' *> blank *> directObject `endBy` blank <* char ']'

dictionary :: Parser u Dictionary
dictionary =
  try (string "<<" *> blank *> keyValPairs <* string ">>")
  where
    keyVal = (,) <$> name <* blank <*> directObject
    keyValPairs = Map.fromList <$> keyVal `endBy` blank

nullObject :: Parser u ()
nullObject = string "null" *> return ()

reference :: Parser u IndirectObjCoordinates
reference = IndirectObjCoordinates <$> integer <*> integer <* char 'R'

entry :: Parser u XRefEntry
entry = do
  (big, small) <- (,) <$> integer <*> integer
  (inUse big small <|> free big small) <* blank
  where
    inUse :: Int64 -> Int -> Parser u XRefEntry
    inUse offset generation = char 'n' *> return (InUse {offset, generation})
    free :: Int64 -> Int -> Parser u XRefEntry
    free nextFree generation = char 'f' *> return (Free {nextFree, generation})

xrefSubSection :: Parser u XRefSubSection
xrefSubSection = do
  (firstObjectId, entriesNumber) <- (,) <$> integer <*> integer
  entries <- Map.fromList . zip [firstObjectId..] <$> count entriesNumber entry
  return $ XRefSubSection {firstObjectId, entriesNumber, entries}

content :: Parser u Content
content =
    Content 0 [] Map.empty
  <$> (line "xref" *> xrefSubSection `sepBy` EOL.parser)
  <*> (line "trailer" *> dictionary <* EOL.parser)
  <*> (line "startxref" *> integer)