{-# LANGUAGE OverloadedStrings #-}
module SVG (svg, fillStyleName) where

import Data.Text (Text, pack)
import qualified Data.Text as T
import Data.List (intersperse)
import Data.Monoid ((<>), mconcat)
import Numeric (showHex)
import Text.FShow.RealFloat (fshow, Double7(D7))

import Graphics (Graphics(Graphics), Point, Size, Angle, FontSize, Anchor(..), StrokeWidth, Opacity, RGB(..), PatternID, colour, patternIx)
import qualified Graphics as G
import Pattern (patterns)

svg :: Graphics
svg =
  Graphics
  { G.text     = text
  , G.rect     = rect
  , G.line     = line
  , G.polygon  = polygon
  , G.pattern  = pattern
  , G.visual   = visual
  , G.document = document
  }

text :: Maybe Angle -> Anchor -> FontSize -> Point -> [Text] -> [Text]
text r a s (x,y) inner =
  let coords = case r of
        Nothing -> ["x='", showF x, "' y='", showF y, "'"]
        Just ra -> ["transform='translate(" , showF x, "," , showF y, ") rotate(", showF ra, ")'"]
      showAnchor Start = "start"
      showAnchor Middle = "middle"
      showAnchor End = "end"
  in  ["<text stroke='none' "] ++ coords ++ [" font-size='", showF s, "' text-anchor='", showAnchor a, "'>"] ++ map escape inner ++ ["</text>\n"]

escape :: Text -> Text
escape = T.concatMap escapeChar
  where
    escapeChar '<' = "&lt;"
    escapeChar '>' = "&gt;"
    escapeChar '&' = "&amp;"
    escapeChar c   = T.singleton c

rect :: Point -> Size -> [Text]
rect (x,y) (w,h) = ["<rect x='", showF x, "' y='", showF y, "' width='" , showF w , "' height='" , showF h , "' />\n"]

line :: Point -> Point -> [Text]
line (x1,y1) (x2,y2) = ["<line x1='" , showF x1, "' x2='", showF x2, "' y1='", showF y1, "' y2='", showF y2, "' />\n"]

pattern :: Text -> (PatternID, [Text])
pattern t = ("url(#" <> pid <> ")",
  [ "<pattern id='", pid, "' x='0' y='0' width='16' height='16' patternUnits='userSpaceOnUse'>\n"
  , "  <path fill='none' stroke-width='2' stroke='" , s, "' line-cap='round' d='"] ++ intersperse " " (map p ps) ++ ["' />\n"
  , "</pattern>\n"])
  where
    pid = mconcat ["P", pack (show ix), "p", T.tail s]
    s = showRGB rgb
    p ((x0, y0), (x1, y1)) = pack $ "M " ++ show x0 ++ "," ++ show y0 ++ " L " ++ show x1 ++ "," ++ show y1
    rgb = colour t
    ix = patternIx t
    ps = patterns !! ix

visual :: Maybe (Either PatternID RGB) -> Maybe Opacity -> Maybe RGB -> Maybe StrokeWidth -> [Text] -> [Text]
visual mfill mfillo mstroke mstrokew inner =
  let fill = maybe [] (\f -> [" fill='", either id showRGB f, "'"]) mfill
      fillo = maybe [] (\o -> [" fill-opacity='", showF o, "'"]) mfillo
      stroke = maybe [] (\s -> [" stroke='", showRGB s, "'"]) mstroke
      strokew = maybe [] (\w -> [" stroke-width='", showF w, "'"]) mstrokew
  in ["<g"] ++ fill ++ fillo ++ stroke ++ strokew ++ [">\n"] ++ inner ++ ["</g>\n"]

document :: Size -> [Text] -> [Text] -> [Text]
document (w,h) defs inner =
  [ "<?xml version='1.0' encoding='UTF-8' ?>\n"
  , "<svg xmlns='http://www.w3.org/2000/svg' version='1.0'"
  , " width='", showF w, "' height='", showF h, "'>\n"
  ] ++ ["<defs>\n"] ++ defs ++ ["</defs>\n"] ++ inner ++ ["</svg>\n"]

polygon :: [Point] -> [Text]
polygon ps = ["<path d='"] ++ path ps ++ ["' />"]

path :: [(Double,Double)] -> [Text]
path [] = error "SVG.path: empty"
path (p0:ps) =
  let lineTo p = [ " L " ] ++ showP p
  in  [ "M " ] ++ showP p0 ++ concatMap lineTo (ps ++ [p0]) ++ [ " Z" ]

showRGB :: RGB -> Text
showRGB (RGB r g b) =
  let toInt x = let y = floor (256 * x) in 0 `max` y `min` 255 :: Int
      hex2 i = (if i < 16 then ('0':) else id) (showHex i "")
  in  pack $ '#' : concatMap (hex2 . toInt) [r,g,b]

showP :: Point -> [Text]
showP (x,y) = [showF x, ",", showF y]

showF :: Double -> Text
showF x = pack $ fshow (D7 x)

fillStyleName :: Either PatternID RGB -> Text
fillStyleName (Left c) = T.drop 5 (T.init c)
fillStyleName (Right c) = T.singleton 'C' <> T.tail (showRGB c)