#include "driver.h"

unsigned char *blktiger_txvideoram;

#define BGRAM_BANK_SIZE 0x1000
#define BGRAM_BANKS 4

static UINT32 blktiger_scroll_bank;
static UINT8 *scroll_ram;
static UINT8 screen_layout;
static UINT8 chon,objon,bgon;

static tilemap *tx_tilemap,*bg_tilemap8x4,*bg_tilemap4x8;


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

  Callbacks for the TileMap code

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

static UINT32 bg8x4_scan(UINT32 col,UINT32 row,UINT32 num_cols,UINT32 num_rows)
{
	/* logical (col,row) -> memory offset */
	return (col & 0x0f) + ((row & 0x0f) << 4) + ((col & 0x70) << 4) + ((row & 0x30) << 7);
}

static UINT32 bg4x8_scan(UINT32 col,UINT32 row,UINT32 num_cols,UINT32 num_rows)
{
	/* logical (col,row) -> memory offset */
	return (col & 0x0f) + ((row & 0x0f) << 4) + ((col & 0x30) << 4) + ((row & 0x70) << 6);
}

static void get_bg_tile_info(int tile_index)
{
	/* the tile priority table is a guess compiled by looking at the game. It
       was not derived from a PROM so it could be wrong. */
	static int split_table[16] =
	{
		3,0,2,2,	/* the fourth could be 1 instead of 2 */
		0,1,0,0,
		0,0,0,0,
		0,0,0,0
	};
	unsigned char attr = scroll_ram[2*tile_index + 1];
	int color = (attr & 0x78) >> 3;
	SET_TILE_INFO(
			1,
			scroll_ram[2*tile_index] + ((attr & 0x07) << 8),
			color,
			TILE_SPLIT(split_table[color]) | ((attr & 0x80) ? TILE_FLIPX : 0))
}

static void get_tx_tile_info(int tile_index)
{
	unsigned char attr = blktiger_txvideoram[tile_index + 0x400];
	SET_TILE_INFO(
			0,
			blktiger_txvideoram[tile_index] + ((attr & 0xe0) << 3),
			attr & 0x1f,
			0)
}


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

  Start the video hardware emulation.

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

VIDEO_START( blktiger )
{
	scroll_ram = auto_malloc(BGRAM_BANK_SIZE * BGRAM_BANKS);

	tx_tilemap =    tilemap_create(get_tx_tile_info,tilemap_scan_rows,TILEMAP_TRANSPARENT,8,8,32,32);
	bg_tilemap8x4 = tilemap_create(get_bg_tile_info,bg8x4_scan,       TILEMAP_SPLIT,   16,16,128,64);
	bg_tilemap4x8 = tilemap_create(get_bg_tile_info,bg4x8_scan,       TILEMAP_SPLIT,   16,16,64,128);

	tilemap_set_transparent_pen(tx_tilemap,3);

	tilemap_set_transmask(bg_tilemap8x4,0,0xffff,0x8000);	/* split type 0 is totally transparent in front half */
	tilemap_set_transmask(bg_tilemap8x4,1,0xfff0,0x800f);	/* split type 1 has pens 4-15 transparent in front half */
	tilemap_set_transmask(bg_tilemap8x4,2,0xff00,0x80ff);	/* split type 1 has pens 8-15 transparent in front half */
	tilemap_set_transmask(bg_tilemap8x4,3,0xf000,0x8fff);	/* split type 1 has pens 12-15 transparent in front half */
	tilemap_set_transmask(bg_tilemap4x8,0,0xffff,0x8000);
	tilemap_set_transmask(bg_tilemap4x8,1,0xfff0,0x800f);
	tilemap_set_transmask(bg_tilemap4x8,2,0xff00,0x80ff);
	tilemap_set_transmask(bg_tilemap4x8,3,0xf000,0x8fff);

	state_save_register_global(blktiger_scroll_bank);
	state_save_register_global(screen_layout);
	state_save_register_global(chon);
	state_save_register_global(objon);
	state_save_register_global(bgon);
	state_save_register_global_pointer(scroll_ram, BGRAM_BANK_SIZE * BGRAM_BANKS);

	return 0;
}



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

  Memory handlers

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

WRITE8_HANDLER( blktiger_txvideoram_w )
{
	if (blktiger_txvideoram[offset] != data)
	{
		blktiger_txvideoram[offset] = data;
		tilemap_mark_tile_dirty(tx_tilemap,offset & 0x3ff);
	}
}

READ8_HANDLER( blktiger_bgvideoram_r )
{
	return scroll_ram[offset + blktiger_scroll_bank];
}

WRITE8_HANDLER( blktiger_bgvideoram_w )
{
	offset += blktiger_scroll_bank;

	if (scroll_ram[offset] != data)
	{
		scroll_ram[offset] = data;
		tilemap_mark_tile_dirty(bg_tilemap8x4,offset/2);
		tilemap_mark_tile_dirty(bg_tilemap4x8,offset/2);
	}
}

WRITE8_HANDLER( blktiger_bgvideoram_bank_w )
{
	blktiger_scroll_bank = (data % BGRAM_BANKS) * BGRAM_BANK_SIZE;
}


WRITE8_HANDLER( blktiger_scrolly_w )
{
	static unsigned char scroll[2];
	int scrolly;

	scroll[offset] = data;
	scrolly = scroll[0] | (scroll[1] << 8);
	tilemap_set_scrolly(bg_tilemap8x4,0,scrolly);
	tilemap_set_scrolly(bg_tilemap4x8,0,scrolly);
}

WRITE8_HANDLER( blktiger_scrollx_w )
{
	static unsigned char scroll[2];
	int scrollx;

	scroll[offset] = data;
	scrollx = scroll[0] | (scroll[1] << 8);
	tilemap_set_scrollx(bg_tilemap8x4,0,scrollx);
	tilemap_set_scrollx(bg_tilemap4x8,0,scrollx);
}


WRITE8_HANDLER( blktiger_video_control_w )
{
	/* bits 0 and 1 are coin counters */
	coin_counter_w(0,data & 1);
	coin_counter_w(1,data & 2);

	/* bit 5 resets the sound CPU */
	cpunum_set_input_line(1, INPUT_LINE_RESET, (data & 0x20) ? ASSERT_LINE : CLEAR_LINE);

	/* bit 6 flips screen */
	flip_screen_set(data & 0x40);

	/* bit 7 enables characters? Just a guess */
	chon = ~data & 0x80;
}

WRITE8_HANDLER( blktiger_video_enable_w )
{
	/* not sure which is which, but I think that bit 1 and 2 enable background and sprites */
	/* bit 1 enables bg ? */
	bgon = ~data & 0x02;

	/* bit 2 enables sprites ? */
	objon = ~data & 0x04;
}

WRITE8_HANDLER( blktiger_screen_layout_w )
{
	screen_layout = data;
	tilemap_set_enable(bg_tilemap8x4, screen_layout);
	tilemap_set_enable(bg_tilemap4x8,!screen_layout);
}



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

  Display refresh

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

static void draw_sprites(mame_bitmap *bitmap, const rectangle *cliprect)
{
	int offs;

	/* Draw the sprites. */
	for (offs = spriteram_size - 4;offs >= 0;offs -= 4)
	{
		int attr = buffered_spriteram[offs+1];
		int sx = buffered_spriteram[offs + 3] - ((attr & 0x10) << 4);
		int sy = buffered_spriteram[offs + 2];
		int code = buffered_spriteram[offs] | ((attr & 0xe0) << 3);
		int color = attr & 0x07;
		int flipx = attr & 0x08;

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

		drawgfx(bitmap,Machine->gfx[2],
				code,
				color,
				flipx,flip_screen,
				sx,sy,
				cliprect,TRANSPARENCY_PEN,15);
	}
}

VIDEO_UPDATE( blktiger )
{
	fillbitmap(bitmap,machine->pens[1023],cliprect);

	if (bgon)
		tilemap_draw(bitmap,cliprect,screen_layout ? bg_tilemap8x4 : bg_tilemap4x8,TILEMAP_BACK,0);

	if (objon)
		draw_sprites(bitmap,cliprect);

	if (bgon)
		tilemap_draw(bitmap,cliprect,screen_layout ? bg_tilemap8x4 : bg_tilemap4x8,TILEMAP_FRONT,0);

	if (chon)
		tilemap_draw(bitmap,cliprect,tx_tilemap,0,0);
	return 0;
}

VIDEO_EOF( blktiger )
{
	buffer_spriteram_w(0,0);
}
