{-# LANGUAGE ForeignFunctionInterface #-}

-- File.chs

-- hgeometric: A geometric library with bindings to GPC.
-- File.chs is part of hgeometric.

-- Copyright (C) 2007 Marco Túlio Gontijo e Silva
-- Copyright (C) 2007 Rafael Cunha de Almeida

-- hgeometric is free software; you can redistribute it and/or modify
-- it under the terms of the GNU General Public License as published by
-- the Free Software Foundation; either version 2 of the License, or
-- (at your option) any later version.

-- hgeometric is distributed in the hope that it will be useful,
-- but WITHOUT ANY WARRANTY; without even the implied warranty of
-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-- GNU General Public License for more details.

-- You should have received a copy of the GNU General Public License
-- along with hgeometric; if not, write to the Free Software
-- Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

-- | Support for reading and writing a 'Polygon' in a file.
module Algebra.Geometric.Polygon.File (readPolygon, writePolygon) where

#include <stdio.h>
#include "gpc.h"

import Foreign
import Foreign.C

import Algebra.Geometric.Polygon

{#context prefix = "gpc"#}

{#pointer *polygon as CPolygon -> Polygon#}

-- | Reads a file into a 'Polygon'. If the file isn't accessible, then
-- 'Nothing' is returned.
readPolygon :: FilePath -> Bool -> IO (Maybe Polygon)
readPolygon fileName hole =
    alloca $
    \cResult ->
    do
    cFileName <- newCString fileName
    mode <- newCString "r"

    file <- {#call unsafe fopen#} cFileName mode

    let free_ = free cFileName >> free mode

    if file == nullPtr
        then free_ >> return Nothing
        else
        do
        {#call unsafe read_polygon#} file (fromBool hole) cResult
        {#call unsafe fclose#} file

        result <- peek cResult

        free_
        {#call unsafe free_polygon#} cResult

        return $ Just result

-- | If the 'Polygon' was successfully written, then this function returns
-- 'True', and 'False' otherwise.
writePolygon :: String -> Bool -> Polygon -> IO Bool
writePolygon fileName hole polygon =
    alloca $
    \cPolygon ->
    do
    poke cPolygon polygon

    cFileName <- newCString fileName
    mode <- newCString "w"

    file <- {#call unsafe fopen#} cFileName mode

    let free_ = free cFileName >> free mode

    if file == nullPtr
        then free_ >> return False
        else
        {#call unsafe write_polygon#} file (fromBool hole) cPolygon >>
        {#call unsafe fclose#} file >>

        free_ >> {#call unsafe free_polygon#} cPolygon >>

        return True