module Piece (
  Piece(..),
  PieceColor(..),
  PieceType(..),
  letterToPiece,
  loadPieces,
) where

import Data.Array

import Graphics.Rendering.Cairo.SVG

data Piece = Piece PieceColor PieceType
  deriving (Eq, Ord, Ix, Bounded, Show)

data PieceType = Pawn | Knight | Bishop | Rook | Queen | King
  deriving (Eq, Ord, Ix, Enum, Bounded, Show)

data PieceColor = White | Black
  deriving (Eq, Ord, Ix, Enum, Bounded, Show)

{-
instance Enum Piece where
  toEnum i =
    Piece (toEnum (i `div` (fromEnum (maxBound :: PieceType) + 1)))
          (toEnum (i `mod` (fromEnum (maxBound :: PieceType) + 1)))
  fromEnum (Piece c t) =
    fromEnum c * (fromEnum (maxBound :: PieceType) + 1) + fromEnum t
  enumFrom p = enumFromTo p maxBound
-}

letterToPiece :: Char -> Piece
letterToPiece 'P' = Piece White Pawn
letterToPiece 'N' = Piece White Knight
letterToPiece 'B' = Piece White Bishop
letterToPiece 'R' = Piece White Rook
letterToPiece 'Q' = Piece White Queen
letterToPiece 'K' = Piece White King
letterToPiece 'p' = Piece Black Pawn
letterToPiece 'n' = Piece Black Knight
letterToPiece 'b' = Piece Black Bishop
letterToPiece 'r' = Piece Black Rook
letterToPiece 'q' = Piece Black Queen
letterToPiece 'k' = Piece Black King
letterToPiece _   = error "wrong piece identification"

piecesBase :: String
piecesBase = "pieces/default/"

pieceToFile :: Piece -> FilePath
pieceToFile (Piece White t) = concat [piecesBase, 'w' : typeToFile t, ".svg"]
pieceToFile (Piece Black t) = concat [piecesBase, 'b' : typeToFile t, ".svg"]

typeToFile :: PieceType -> FilePath
typeToFile Pawn   = "p"
typeToFile Knight = "n"
typeToFile Bishop = "b"
typeToFile Rook   = "r"
typeToFile Queen  = "q"
typeToFile King   = "k"

loadPieces :: IO (Array Piece SVG)
loadPieces = do
  let allPieces = [ Piece c t | c <- [White ..], t <- [Pawn ..] ]
  allSVGs <- mapM (svgNewFromFile . pieceToFile) allPieces
  return $ array (minBound,maxBound) (zip allPieces allSVGs)