{-# LANGUAGE OverloadedStrings #-}
-- These following language extensions are to aid a dependency injection into
-- inline styling.
{-# LANGUAGE TypeSynonymInstances, FlexibleInstances, FlexibleContexts #-}
-- | Parses & desugars CSS properties to general CatTrap datastructures.
module Graphics.Layout.CSS(CSSBox(..), BoxSizing(..), Display(..),
        finalizeCSS, finalizeCSS') where

import qualified Data.Text as Txt
import Stylist (PropertyParser(..))
import Stylist.Tree (StyleTree(..))
import Data.Text.ParagraphLayout.Rich (paragraphLineHeight, constructParagraph,
        defaultParagraphOptions, defaultBoxOptions,
        LineHeight(..), InnerNode(..), Box(..), RootNode(..))

import Graphics.Layout.Box as B
import Graphics.Layout
import Graphics.Layout.CSS.Length
import Graphics.Layout.CSS.Font
import Graphics.Layout.Grid.CSS
import Graphics.Layout.Inline.CSS

import Data.Char (isSpace)
import Graphics.Layout.CSS.Parse

instance (PropertyParser x, Zero m, Zero n) => Default (UserData m n x) where
    def = ((placeholderFont, 0), zero, temp)

-- | Desugar parsed CSS into more generic layout parameters.
finalizeCSS :: PropertyParser x => Font' -> Font' -> StyleTree (CSSBox x) ->
        LayoutItem Length Length x
finalizeCSS root parent StyleTree { style = self'@CSSBox { display = None } } =
    LayoutFlow (inner self') lengthBox []
finalizeCSS root parent self@StyleTree {
    style = self'@CSSBox { display = Grid, inner = val }, children = childs
  } = LayoutFlow val (finalizeBox self' font_) [
        finalizeGrid (gridStyles self') font_ (map cellStyles $ map style childs)
            (finalizeChilds root font_ self' childs)]
  where
    font_ = pattern2font (font self') (font' self') parent root
finalizeCSS root parent self@StyleTree {
        style = self'@CSSBox { display = Table, captionBelow = False }, children = childs
    } = LayoutFlow (inner self') (finalizeBox self' font_)
        ([finalizeCSS root font_ child { style = child' { display = Block } }
            | child@StyleTree { style = child'@CSSBox { display = TableCaption } } <- childs] ++
        [finalizeTable root font_ (inner self') childs])
  where
    font_ = pattern2font (font self') (font' self') parent root
finalizeCSS root parent self@StyleTree {
        style = self'@CSSBox { display = Table, captionBelow = True }, children = childs
    } = LayoutFlow (inner self') (finalizeBox self' font_)
        (finalizeTable root font_ temp childs:
        [finalizeCSS root font_ child { style = child' { display = Block } }
            | child@StyleTree { style = child'@CSSBox { display = TableCaption } } <- childs])
  where
    font_ = pattern2font (font self') (font' self') parent root
finalizeCSS root parent self@StyleTree {
    style = self'@CSSBox { inner = val }, children = childs
  } = LayoutFlow val (finalizeBox self' font_) (finalizeChilds root font_ self' childs)
  where
    font_ = pattern2font (font self') (font' self') parent root
finalizeCSS' sysfont self@StyleTree { style = self' } =
    finalizeCSS (pattern2font (font self') (font' self') sysfont sysfont) sysfont self

-- | Desugar a sequence of child nodes, taking care to capture runs of inlines.
finalizeChilds :: PropertyParser x => Font' -> Font' -> CSSBox x ->
        [StyleTree (CSSBox x)] -> [LayoutItem Length Length x]
finalizeChilds root parent style' (StyleTree { style = CSSBox { display = None } }:childs) =
    finalizeChilds root parent style' childs
finalizeChilds root parent style' childs@(child:childs')
    | isInlineTree childs, Just self <- finalizeParagraph (flattenTree0 childs) =
        [LayoutInline (inherit $ inner style') self paging]
    | (inlines@(_:_), blocks) <- spanInlines childs,
        Just self <- finalizeParagraph (flattenTree0 inlines) =
            LayoutInline (inherit $ inner style') self paging :
                finalizeChilds root parent style' blocks
    | (StyleTree { style = CSSBox { display = Inline } }:childs') <- childs =
        finalizeChilds root parent style' childs' -- Inline's all whitespace...
    | otherwise = finalizeCSS root parent child : finalizeChilds root parent style' childs'
  where
    paging = pageOptions $ style child
    isInlineTree = all isInlineTree0
    isInlineTree0 StyleTree { style = CSSBox { display = Inline }, children = childs } =
        isInlineTree childs
    isInlineTree0 _ = False
    spanInlines childs = case span isInlineTree0 childs of
        (inlines, (StyleTree {
            style = CSSBox { display = Inline }, children = tail
          }:blocks)) -> let (inlines', blocks') = spanInlines tail
            in (inlines ++ inlines', blocks' ++ blocks)
        ret -> ret
    flattenTree0 childs
        | iStyle@(CSSInline _ _ bidi) <- inlineStyles style',
            bidi `elem` [BdOverride, BdIsolateOverride] = RootBox $ Box
                (applyBidi iStyle $ map (flattenTree parent) $ enumerate childs)
                $ flip applyFontInline parent $ txtOpts style'
        | otherwise = RootBox $ Box (map (flattenTree parent) $ enumerate childs)
            $ flip applyFontInline parent $ txtOpts style'
    flattenTree p (i, StyleTree { children = child@(_:_), style = self }) =
        buildInline f i self $ map (flattenTree f) $ enumerate child
      where f = pattern2font (font self) (font' self) p root
    flattenTree f (i,StyleTree {style=self@CSSBox {inlineStyles=CSSInline txt _ _}})
        = buildInline f i self [TextSequence ((f,0),zero,inherit $ inner self) txt]
    buildInline f i self childs =
        InlineBox ((f, i), finalizeBox self f, inner self)
                (Box childs' $ flip applyFontInline f $ txtOpts self)
                defaultBoxOptions -- Fill in during layout.
      where childs' = applyBidi (inlineStyles self) childs
    finalizeParagraph (RootBox (Box [TextSequence _ txt] _))
        | Txt.all isSpace txt = Nothing -- Discard isolated whitespace.
    finalizeParagraph tree =
        Just $ constructParagraph "" tree "" defaultParagraphOptions {
            paragraphLineHeight = Absolute $ toEnum $ fromEnum
                    (lineheight parent * hbUnit)
          }
    enumerate = zip $ enumFrom 0
finalizeChilds _ _ _ [] = []

-- | Desugar most units, possibly in reference to given font.
finalizeBox self@CSSBox { cssBox = box } font_ =
    mapY' (flip finalizeLength font_) $ mapX' (flip finalizeLength font_) box

-- | (Unused, incomplete) Desugar a styletree of table elements to a grid layout.
finalizeTable root parent val childs = LayoutFlow val lengthBox [] -- Placeholder!
{- finalizeTable root parent val childs = LayoutGrid val grid $ zip cells' childs'
  where -- FIXME? How to handle non-table items in <table>?
    grid = Grid {
        rows = take width $ repeat ("", (0,"auto")),
        rowBounds = [],
        subgridRows = 0,
        columns = take height $ repeat ("", (0,"auto")),
        colBounds = [],
        subgridCols = 0,
        gap = Size (0,"px") (0,"px"), -- FIXME where to get this from?
        containerSize = Size Auto Auto, -- Proper size is set on parent.
        containerMin = Size Auto Auto,
        containerMax = Size Auto Auto
    }
    cells' = adjustWidths cells
    
    (cells, width, height) = lowerCells childs
    lowerCells (StyleTree self@CSSBox { display = TableRow } cells:rest) =
        (row:rows, max rowwidth width', succ height)
      where
        (row, rowwidth) = lowerRow cells 0 -- FIXME: How to dodge colspans?
        (rows, width', height') = lowerCells rest
    lowerCells (StyleTree self@CSSBox { display = TableHeaderGroup } childs ) =
        -}