/***************************************************************************

  vidhrdw.c

  Functions to emulate the video hardware of the machine.

***************************************************************************/

#include "driver.h"

UINT8 *ironhors_scroll;
static int palettebank, charbank, spriterambank;

static tilemap *bg_tilemap;

/***************************************************************************

  Convert the color PROMs into a more useable format.

  Iron Horse has three 256x4 palette PROMs (one per gun) and two 256x4
  lookup table PROMs (one for characters, one for sprites).
  I don't know for sure how the palette PROMs are connected to the RGB
  output, but it's probably the usual:

  bit 3 -- 220 ohm resistor  -- RED/GREEN/BLUE
        -- 470 ohm resistor  -- RED/GREEN/BLUE
        -- 1  kohm resistor  -- RED/GREEN/BLUE
  bit 0 -- 2.2kohm resistor  -- RED/GREEN/BLUE

***************************************************************************/
PALETTE_INIT( ironhors )
{
	int i;
	#define TOTAL_COLORS(gfxn) (Machine->gfx[gfxn]->total_colors * Machine->gfx[gfxn]->color_granularity)
	#define COLOR(gfxn,offs) (colortable[Machine->drv->gfxdecodeinfo[gfxn].color_codes_start + offs])


	for (i = 0;i < Machine->drv->total_colors;i++)
	{
		int bit0,bit1,bit2,bit3,r,g,b;


		bit0 = (color_prom[0] >> 0) & 0x01;
		bit1 = (color_prom[0] >> 1) & 0x01;
		bit2 = (color_prom[0] >> 2) & 0x01;
		bit3 = (color_prom[0] >> 3) & 0x01;
		r = 0x0e * bit0 + 0x1f * bit1 + 0x43 * bit2 + 0x8f * bit3;
		bit0 = (color_prom[Machine->drv->total_colors] >> 0) & 0x01;
		bit1 = (color_prom[Machine->drv->total_colors] >> 1) & 0x01;
		bit2 = (color_prom[Machine->drv->total_colors] >> 2) & 0x01;
		bit3 = (color_prom[Machine->drv->total_colors] >> 3) & 0x01;
		g = 0x0e * bit0 + 0x1f * bit1 + 0x43 * bit2 + 0x8f * bit3;
		bit0 = (color_prom[2*Machine->drv->total_colors] >> 0) & 0x01;
		bit1 = (color_prom[2*Machine->drv->total_colors] >> 1) & 0x01;
		bit2 = (color_prom[2*Machine->drv->total_colors] >> 2) & 0x01;
		bit3 = (color_prom[2*Machine->drv->total_colors] >> 3) & 0x01;
		b = 0x0e * bit0 + 0x1f * bit1 + 0x43 * bit2 + 0x8f * bit3;

		palette_set_color(i,r,g,b);
		color_prom++;
	}

	color_prom += 2*Machine->drv->total_colors;
	/* color_prom now points to the beginning of the character lookup table */


	/* there are eight 32 colors palette banks; sprites use colors 0-15 and */
	/* characters 16-31 of each bank. */
	for (i = 0;i < TOTAL_COLORS(0)/8;i++)
	{
		int j;


		for (j = 0;j < 8;j++)
			COLOR(0,i + j * TOTAL_COLORS(0)/8) = (*color_prom & 0x0f) + 32 * j + 16;

		color_prom++;
	}

	for (i = 0;i < TOTAL_COLORS(1)/8;i++)
	{
		int j;


		for (j = 0;j < 8;j++)
			COLOR(1,i + j * TOTAL_COLORS(1)/8) = (*color_prom & 0x0f) + 32 * j;

		color_prom++;
	}
}

WRITE8_HANDLER( ironhors_videoram_w )
{
	if (videoram[offset] != data)
	{
		videoram[offset] = data;
		tilemap_mark_tile_dirty(bg_tilemap, offset);
	}
}

WRITE8_HANDLER( ironhors_colorram_w )
{
	if (colorram[offset] != data)
	{
		colorram[offset] = data;
		tilemap_mark_tile_dirty(bg_tilemap, offset);
	}
}

WRITE8_HANDLER( ironhors_charbank_w )
{
	if (charbank != (data & 0x03))
	{
		charbank = data & 0x03;
		tilemap_mark_all_tiles_dirty(ALL_TILEMAPS);
	}

	spriterambank = data & 0x08;

	/* other bits unknown */
}

WRITE8_HANDLER( ironhors_palettebank_w )
{
	if (palettebank != (data & 0x07))
	{
		palettebank = data & 0x07;
		tilemap_mark_all_tiles_dirty(ALL_TILEMAPS);
	}

	coin_counter_w(0, data & 0x10);
	coin_counter_w(1, data & 0x20);

	/* bit 6 unknown - set after game over */

	if (data & 0x88) ui_popup("ironhors_palettebank_w %02x",data);
}

WRITE8_HANDLER( ironhors_flipscreen_w )
{
	if (flip_screen != (~data & 0x08))
	{
		flip_screen_set(~data & 0x08);
		tilemap_mark_all_tiles_dirty(ALL_TILEMAPS);
	}

	/* other bits are used too, but unknown */
}

static void get_bg_tile_info(int tile_index)
{
	int code = videoram[tile_index] + ((colorram[tile_index] & 0x40) << 2) +
		((colorram[tile_index] & 0x20) << 4) + (charbank << 10);
	int color = (colorram[tile_index] & 0x0f) + 16 * palettebank;
	int flags = ((colorram[tile_index] & 0x10) ? TILE_FLIPX : 0) |
		((colorram[tile_index] & 0x20) ? TILE_FLIPY : 0);

	SET_TILE_INFO(0, code, color, flags)
}

VIDEO_START( ironhors )
{
	bg_tilemap = tilemap_create(get_bg_tile_info, tilemap_scan_rows,
		TILEMAP_OPAQUE, 8, 8, 32, 32);

	if ( !bg_tilemap )
		return 1;

	tilemap_set_scroll_rows(bg_tilemap, 32);

	return 0;
}

static void ironhors_draw_sprites( mame_bitmap *bitmap )
{
	int offs;
	UINT8 *sr;

	if (spriterambank != 0)
		sr = spriteram;
	else
		sr = spriteram_2;

	for (offs = 0;offs < spriteram_size;offs += 5)
	{
		int sx = sr[offs+3];
		int sy = sr[offs+2];
		int flipx = sr[offs+4] & 0x20;
		int flipy = sr[offs+4] & 0x40;
		int code = (sr[offs] << 2) + ((sr[offs+1] & 0x03) << 10) + ((sr[offs+1] & 0x0c) >> 2);
		int color = ((sr[offs+1] & 0xf0)>>4) + 16 * palettebank;
	//  int mod = flip_screen ? -8 : 8;

		if (flip_screen)
		{
			sx = 240 - sx;
			sy = 240 - sy;
			flipx = !flipx;
			flipy = !flipy;
		}

		switch (sr[offs+4] & 0x0c)
		{
			case 0x00:	/* 16x16 */
				drawgfx(bitmap,Machine->gfx[1],
						code/4,
						color,
						flipx,flipy,
						sx,sy,
						&Machine->visible_area[0],TRANSPARENCY_PEN,0);
				break;

			case 0x04:	/* 16x8 */
				{
					if (flip_screen) sy += 8; // this fixes the train wheels' position

					drawgfx(bitmap,Machine->gfx[2],
							code & ~1,
							color,
							flipx,flipy,
							flipx?sx+8:sx,sy,
							&Machine->visible_area[0],TRANSPARENCY_PEN,0);
					drawgfx(bitmap,Machine->gfx[2],
							code | 1,
							color,
							flipx,flipy,
							flipx?sx:sx+8,sy,
							&Machine->visible_area[0],TRANSPARENCY_PEN,0);
				}
				break;

			case 0x08:	/* 8x16 */
				{
					drawgfx(bitmap,Machine->gfx[2],
							code & ~2,
							color,
							flipx,flipy,
							sx,flipy?sy+8:sy,
							&Machine->visible_area[0],TRANSPARENCY_PEN,0);
					drawgfx(bitmap,Machine->gfx[2],
							code | 2,
							color,
							flipx,flipy,
							sx,flipy?sy:sy+8,
							&Machine->visible_area[0],TRANSPARENCY_PEN,0);
				}
				break;

			case 0x0c:	/* 8x8 */
				{
					drawgfx(bitmap,Machine->gfx[2],
							code,
							color,
							flipx,flipy,
							sx,sy,
							&Machine->visible_area[0],TRANSPARENCY_PEN,0);
				}
				break;
		}
	}
}

VIDEO_UPDATE( ironhors )
{
	int row;

	for (row = 0; row < 32; row++)
		tilemap_set_scrollx(bg_tilemap, row, ironhors_scroll[row]);

	tilemap_draw(bitmap, &Machine->visible_area[0], bg_tilemap, 0, 0);
	ironhors_draw_sprites(bitmap);
	return 0;
}
