{-# OPTIONS_HADDOCK ignore-exports #-}

module Parser.Meshparser where

import Algebra.Vector(PT)
import Control.Applicative
import Data.Attoparsec.ByteString.Char8
import Data.Either
import qualified Data.ByteString.Char8 as B
import Diagrams.TwoD.Types


-- |Convert a text String with multiple vertices and faces into
-- a list of vertices, ordered by the faces specification.
meshFaceVertices :: B.ByteString -> [[PT]]
meshFaceVertices str = fmap (fmap (\y -> meshVertices str !! (y - 1)))
                            (meshFaces str)


-- |Convert a text String with multiple vertices into
-- an array of float tuples.
meshVertices :: B.ByteString -- ^ the string to convert
          -> [PT]         -- ^ the resulting vertice table
meshVertices
  = fmap p2
    . rights
    . fmap (parseOnly parseVertice)
    . B.lines


-- |Creates a Parser that accepts a single vertice, such as 'v 1.0 2.0'.
parseVertice :: Parser (Double, Double)
parseVertice =
  (,)
    <$> (char 'v' *> many' space *> double)
    <*> (many' space *> double)


parseFace :: (Integral a) => Parser [a]
parseFace = char 'f' *> many1' (many' space *> decimal)


meshFaces :: B.ByteString -> [[Int]]
meshFaces
  = rights
    . fmap (parseOnly parseFace)
    . B.lines