{-# LANGUAGE OverloadedStrings #-}
module Graphics.Text.Font.Choose.FontSet where

import Graphics.Text.Font.Choose.Pattern
import Graphics.Text.Font.Choose.Result (throwFalse, throwNull)

import Foreign.Ptr (Ptr, castPtr, nullPtr)
import Foreign.Storable (pokeElemOff, sizeOf)
import Foreign.Marshal.Alloc (allocaBytes)
import Foreign.Marshal.Array (peekArray)
import Control.Monad (forM)
import Control.Exception (bracket)

-- For CSS bindings
import Stylist.Parse (StyleSheet(..), parseProperties)
import Data.CSS.Syntax.Tokens (Token(..), serialize)
import Data.Text (unpack, Text)
import Graphics.Text.Font.Choose.Range (iRange)
import Graphics.Text.Font.Choose.CharSet (parseCharSet)
import Data.List (intercalate)

-- | An `FontSet` contains a list of `Pattern`s.
-- Internally fontconfig uses this data structure to hold sets of fonts.
-- Externally, fontconfig returns the results of listing fonts in this format.
type FontSet = [Pattern]

------
--- Low-level
------
data FontSet'
type FontSet_ = Ptr FontSet'

withNewFontSet :: (FontSet_ -> IO a) -> IO a
withNewFontSet = bracket fcFontSetCreate fcFontSetDestroy
foreign import ccall "FcFontSetCreate" fcFontSetCreate :: IO FontSet_
foreign import ccall "FcFontSetDestroy" fcFontSetDestroy :: FontSet_ -> IO ()

withFontSet :: FontSet -> (FontSet_ -> IO a) -> IO a
withFontSet fonts cb = withNewFontSet $ \fonts' -> do
    forM fonts $ \font -> do
        font' <- patternAsPointer font
        throwFalse <$> fcFontSetAdd fonts' font'
    cb fonts'
foreign import ccall "FcFontSetAdd" fcFontSetAdd :: FontSet_ -> Pattern_ -> IO Bool

withFontSets :: [FontSet] -> (Ptr FontSet_ -> Int -> IO a) -> IO a
withFontSets fontss cb = let n = length fontss in
    allocaBytes (sizeOf (undefined :: FontSet_) * n) $ \fontss' ->
        withFontSets' fontss 0 fontss' $ cb fontss' n
withFontSets' :: [FontSet] -> Int -> Ptr FontSet_ -> IO a -> IO a
withFontSets' [] _ _ cb = cb
withFontSets' (fonts:fontss) i fontss' cb = withFontSet fonts $ \fonts' -> do
    pokeElemOff fontss' i fonts'
    withFontSets' fontss (succ i) fontss' cb

thawFontSet :: FontSet_ -> IO FontSet
thawFontSet fonts' = do
    -- Very hacky, but these debug statements must be in here to avoid segfaults.
    -- FIXME: Is there an alternative?
    print "a"
    n <- get_fontSet_nfont fonts'
    print "b"
    if n == 0 then return []
    else do
        print "c"
        ret <- forM [0..pred n] (thawPattern_ . get_fontSet_font fonts')
        print "d"
        return ret
foreign import ccall "get_fontSet_nfont" get_fontSet_nfont :: FontSet_ -> IO Int
foreign import ccall "get_fontSet_font" get_fontSet_font :: FontSet_ -> Int -> IO Pattern_

thawFontSet_ :: IO FontSet_ -> IO FontSet
thawFontSet_ cb = bracket (throwNull <$> cb) fcFontSetDestroy thawFontSet

------
--- CSS Bindings
------

-- | `StyleSheet` wrapper to parse @font-face rules.
data FontFaceParser a = FontFaceParser { cssFonts :: FontSet, cssInner :: a}

parseFontFaceSrc (Function "local":Ident name:RightParen:Comma:rest) =
    ("local:" ++ unpack name):parseFontFaceSrc rest
parseFontFaceSrc (Function "local":String name:RightParen:Comma:rest) =
    ("local:" ++ unpack name):parseFontFaceSrc rest
parseFontFaceSrc (Function "local":Ident name:RightParen:[]) = ["local:" ++ unpack name]
parseFontFaceSrc (Function "local":String name:RightParen:[]) = ["local:" ++ unpack name]

parseFontFaceSrc (Url link:toks)
    | Comma:rest <- skipMeta toks = unpack link:parseFontFaceSrc rest
    | [] <- skipMeta toks = [unpack link]
    | otherwise = [""] -- Error indicator!
  where
    skipMeta (Function "format":Ident _:RightParen:rest) = skipMeta rest
    skipMeta (Function "format":String _:RightParen:rest) = skipMeta rest
    skipMeta (Function "tech":Ident _:RightParen:rest) = skipMeta rest
    skipMeta (Function "tech":String _:RightParen:rest) = skipMeta rest
    skipMeta toks = toks

parseFontFaceSrc _ = [""]

properties2font :: [(Text, [Token])] -> Pattern
properties2font (("font-family", [String font]):props) =
    setValue "family" Strong (unpack font) $ properties2font props
properties2font (("font-family", [Ident font]):props) =
    setValue "family" Strong (unpack font) $ properties2font props

properties2font (("font-stretch", [tok]):props) | Just x <- parseFontStretch tok =
    setValue "width" Strong x $ properties2font props
properties2font (("font-stretch", [start, end]):props)
    | Just x <- parseFontStretch start, Just y <- parseFontStretch end =
        setValue "width" Strong (x `iRange` y) $ properties2font props

properties2font (("font-weight", [tok]):props) | Just x <- parseFontWeight tok =
    setValue "width" Strong x $ properties2font props
properties2font (("font-weight", [start, end]):props)
    | Just x <- parseFontStretch start, Just y <- parseFontStretch end =
        setValue "weight" Strong (x `iRange` y) $ properties2font props

properties2font (("font-feature-settings", toks):props)
    | (features, True, []) <- parseFontFeatures toks =
        setValue "fontfeatures" Strong (intercalate "," $ map fst features) $
            properties2font props

properties2font (("font-variation-settings", toks):props)
    | (_, True, []) <- parseFontVars toks =
        setValue "variable" Strong True $ properties2font props

properties2font (("unicode-range", toks):props)
    | Just chars <- parseCharSet $ unpack $ serialize toks =
        setValue "charset" Strong chars $ properties2font props

-- Ignoring metadata & trusting in FreeType's broad support for fonts.
properties2font (("src", toks):props)
    | fonts@(_:_) <- parseFontFaceSrc toks, "" `notElem` fonts =
        setValue "web-src" Strong (intercalate "\t" fonts) $ properties2font props

properties2font (_:props) = properties2font props
properties2font [] = []

instance StyleSheet a => StyleSheet (FontFaceParser a) where
    setPriorities v (FontFaceParser x self) = FontFaceParser x $ setPriorities v self
    addRule (FontFaceParser x self) rule = FontFaceParser x $ addRule self rule

    addAtRule (FontFaceParser fonts self) "font-face" toks =
        let ((props, _), toks') = parseProperties toks
        in (FontFaceParser (properties2font props:fonts) self, toks')
    addAtRule (FontFaceParser x self) key toks =
        let (a, b) = addAtRule self key toks in (FontFaceParser x a, b)