-----------------------------------------------------------------------------
-- |
-- Module      :  Data.Json.Builder
-- Copyright   :  (c) 2011 Leon P Smith
-- License     :  BSD3
--
-- Maintainer  :  Leon P Smith <leon@melding-monads.com>
--
-- Data structure agnostic JSON serialization
--
-----------------------------------------------------------------------------

{-# LANGUAGE BangPatterns        #-}
{-# LANGUAGE ViewPatterns        #-}
{-# LANGUAGE OverloadedStrings   #-}
{-# LANGUAGE FlexibleInstances   #-}
{-# LANGUAGE IncoherentInstances #-}

module Data.Json.Builder
     ( Value(toJson)
     , Json
     , toBuilder
     , toJsonByteString
     , toJsonLazyByteString
     , Array
     , element
     , Object
     , row
     , JsString(escape)
     , Escaped
     ) where

import           Prelude hiding ((++))

import           Blaze.ByteString.Builder as Blaze
                   ( Write
                   , Builder
                   , copyByteString
                   , fromByteString
                   , fromLazyByteString
                   , writeByteString
                   , fromWrite
                   , fromWriteList
                   , writeWord8
                   , toByteString
                   , toLazyByteString    )
import           Blaze.ByteString.Builder.Char.Utf8
                   ( fromChar, writeChar, fromText, fromLazyText )
import           Blaze.Text (float, double, integral)

import           Data.Bits ( Bits((.&.), shiftR) )
import qualified Data.Map               as Map
import           Data.Monoid ( Monoid (mempty, mappend, mconcat) )
import           Data.Int    ( Int8, Int16, Int32, Int64)
import           Data.Word   ( Word, Word8, Word16, Word32, Word64 )

import qualified Data.Char              as Char

import qualified Data.ByteString        as BS
import qualified Data.ByteString.Lazy   as BL
import qualified Data.ByteString.UTF8   as BU
import qualified Data.ByteString.Lazy.UTF8 as BLU
import           Data.ByteString.Internal ( c2w )

import qualified Data.Text              as T
import qualified Data.Text.Lazy         as TL

import qualified Data.HashMap.Lazy      as HashMap

import           Data.Json.Builder.Internal

(++) :: Monoid a => a -> a -> a
(++) = mappend
infixr 5 ++

toBuilder :: Value a => a -> Builder
toBuilder x = case toJson x of
                Json y -> y
{-# SPECIALIZE toBuilder :: Json -> Builder #-}
{-# INLINE toBuilder #-}

toJsonByteString     :: Value a => a -> BS.ByteString
toJsonByteString     = toByteString     . toBuilder

toJsonLazyByteString :: Value a => a -> BL.ByteString
toJsonLazyByteString = toLazyByteString . toBuilder

-- |  The 'row' function constructs a json object consisting of exactly
-- one field.  These objects can be concatinated using 'mappend'.
row :: (JsString k, Value a) => k -> a -> Object
row   k a = Object (Comma (toBuilder k ++ fromChar ':' ++ toBuilder a))

-- |  The 'element' function constructs a json array consisting of exactly
-- one value.  These arrays can be concatinated using 'mappend'.
element :: Value a => a -> Array
element a = Array  (Comma (toBuilder a))

-- Primitive instances for json-builder

-- | renders as @null@
instance Value () where
  toJson _ = Json (copyByteString "null")

instance Value Int     where
  toJson = Json . integral

instance Value Int8    where
  toJson = Json . integral

instance Value Int16   where
  toJson = Json . integral

instance Value Int32   where
  toJson = Json . integral

instance Value Int64   where
  toJson = Json . integral

instance Value Integer where
  toJson = Json . integral

instance Value Word    where
  toJson = Json . integral

instance Value Word8   where
  toJson = Json . integral

instance Value Word16  where
  toJson = Json . integral

instance Value Word32  where
  toJson = Json . integral

instance Value Word64  where
  toJson = Json . integral

instance Value Double where
  toJson = Json . double

instance Value Float where
  toJson = Json . float

-- | renders as @true@ or @false@

instance Value Bool where
  toJson True  = Json (copyByteString "true")
  toJson False = Json (copyByteString "false")

-- | must be UTF-8 encoded

instance JsString BS.ByteString where
  escape x = Escaped (loop x)
    where
      loop (BU.break quoteNeeded -> (a,b))
        = fromByteString a ++
            case BU.decode b of
              Nothing     ->  mempty
              Just (c,n)  ->  quoteChar c ++ loop (BS.drop n b)

instance Value BS.ByteString where
  toJson = toJson . escape

-- | must be UTF-8 encoded

instance JsString BL.ByteString where
  escape x = Escaped (loop x)
    where
      loop (BLU.break quoteNeeded -> (a,b))
        = fromLazyByteString a ++
            case BLU.decode b of
              Nothing     ->  mempty
              Just (c,n)  ->  quoteChar c ++ loop (BL.drop n b)

instance Value BL.ByteString where
  toJson = toJson . escape

instance JsString T.Text where
  escape x = Escaped (loop x)
    where
      loop (T.break quoteNeeded -> (a,b))
        = fromText a ++
            case T.uncons b of
              Nothing      ->  mempty
              Just (c,b')  ->  quoteChar c ++ loop b'

instance Value T.Text where
  toJson = toJson . escape

instance JsString TL.Text where
  escape x = Escaped (loop x)
    where
      loop (TL.break quoteNeeded -> (a,b))
        = fromLazyText a ++
            case TL.uncons b of
              Nothing      ->  mempty
              Just (c,b')  ->  quoteChar c ++ loop b'

instance Value TL.Text where
  toJson = toJson . escape

instance JsString [Char] where
  escape str = Escaped (fromWriteList writeEscapedChar str)
    where
      writeEscapedChar c | quoteNeeded c = quoteCharW c
                         | otherwise     = writeChar  c

instance Value [Char] where
  toJson = toJson . escape

-- | renders as an 'Array'
instance Value a => Value [a] where
  toJson = toJson . mconcat . map element

-- | renders as an 'Object'
instance (JsString k, Value a) => Value (Map.Map k a) where
  toJson = toJson . Map.foldrWithKey     (\k a b -> row k a ++ b) mempty

-- | renders as an 'Object'
instance (JsString k, Value a) => Value (HashMap.HashMap k a) where
  toJson = toJson . HashMap.foldrWithKey (\k a b -> row k a ++ b) mempty

------------------------------------------------------------------------------

quoteNeeded :: Char -> Bool
quoteNeeded c = c == '\\' || c == '"' || Char.ord c < 0x20
{-# INLINE quoteNeeded #-}

quoteChar :: Char -> Builder
quoteChar c = case c of
                 '\\'  ->  copyByteString "\\\\"
                 '"'   ->  copyByteString "\\\""
                 '\b'  ->  copyByteString "\\b"
                 '\f'  ->  copyByteString "\\f"
                 '\n'  ->  copyByteString "\\n"
                 '\r'  ->  copyByteString "\\r"
                 '\t'  ->  copyByteString "\\t"
                 _     ->  fromWrite (hexEscape c)

quoteCharW :: Char -> Write
quoteCharW c = case c of
                 '\\'  ->  writeByteString "\\\\"
                 '"'   ->  writeByteString "\\\""
                 '\b'  ->  writeByteString "\\b"
                 '\f'  ->  writeByteString "\\f"
                 '\n'  ->  writeByteString "\\n"
                 '\r'  ->  writeByteString "\\r"
                 '\t'  ->  writeByteString "\\t"
                 _     ->  hexEscape c

hexEscape  :: Char -> Write
hexEscape  (c2w -> c)
  = writeByteString "\\u00"
    ++ writeWord8 (char ((c `shiftR` 4) .&. 0xF))
    ++ writeWord8 (char ( c             .&. 0xF))

char :: Word8 -> Word8
char i | i < 10    = i + 48
       | otherwise = i + 87
{-# INLINE char #-}