/*
 *   libee         ASCII-Art library
 *   Copyright (c) 2002, 2003 Sam Hocevar <sam@zoy.org>
 *                 All Rights Reserved
 *
 *   $Id$
 *
 *   This program 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.
 *
 *   This program 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 this program; if not, write to the Free Software
 *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include "config.h"

#include <inttypes.h>
#include <stdlib.h>

#include "ee.h"

static uint8_t clip_bits(int, int);
static void draw_solid_line(int, int, int, int, char);

void ee_draw_line(int x1, int y1, int x2, int y2, char c)
{
    uint8_t bits1, bits2;

    bits1 = clip_bits(x1, y1);
    bits2 = clip_bits(x2, y2);

    if(bits1 & bits2)
        return;

    if(bits1 == 0)
    {
        if(bits2 == 0)
            draw_solid_line(x1, y1, x2, y2, c);
        else
            ee_draw_line(x2, y2, x1, y1, c);

        return;
    }

    if(bits1 & (1<<0))
    {
        y1 = y2 - (x2-0) * (y2-y1) / (x2-x1);
        x1 = 0;
    }
    else if( bits1 & (1<<1) )
    {
        int xmax = ee_get_width() - 1;
        y1 = y2 - (x2-xmax) * (y2-y1) / (x2-x1);
        x1 = xmax;
    }
    else if( bits1 & (1<<2) )
    {
        x1 = x2 - (y2-0) * (x2-x1) / (y2-y1);
        y1 = 0;
    }
    else if( bits1 & (1<<3) )
    {
        int ymax = ee_get_height() - 1;
        x1 = x2 - (y2-ymax) * (x2-x1) / (y2-y1);
        y1 = ymax;
    }

    ee_draw_line(x1, y1, x2, y2, c);
}

static void draw_solid_line(int x1, int y1, int x2, int y2, char c)
{
    int dx = abs(x2-x1);
    int dy = abs(y2-y1);

    int xinc, yinc;

    xinc = (x1 > x2) ? -1 : 1;
    yinc = (y1 > y2) ? -1 : 1;

    if(dx >= dy)
    {
        int dpr = dy << 1;
        int dpru = dpr - (dx << 1);
        int delta = dpr - dx;

        for(; dx>=0; dx--)
        {
            ee_goto(x1, y1);
            ee_putchar(c);
            if(delta > 0)
            {
                x1 += xinc;
                y1 += yinc;
                delta += dpru;
            }
            else
            {
                x1 += xinc;
                delta += dpr;
            }
        }
    }
    else
    {
        int dpr = dx << 1;
        int dpru = dpr - (dy << 1);
        int delta = dpr - dy;

        for(; dy >= 0; dy--)
        {
            ee_goto(x1, y1);
            ee_putchar(c);
            if(delta > 0)
            {
                x1 += xinc;
                y1 += yinc;
                delta += dpru;
            }
            else
            {
                y1 += yinc;
                delta += dpr;
            }
        }
    }
}

static uint8_t clip_bits(int x, int y)
{
    uint8_t b = 0;

    if(x < 0)
        b |= (1<<0);
    else if(x >= ee_get_width())
        b |= (1<<1);

    if(y < 0)
        b |= (1<<2);
    else if(y >= ee_get_height())
        b |= (1<<3);

    return b;
}