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

  Target Hits Video Hardware

  Functions to emulate the video hardware of the machine

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

#include "emu.h"
#include "includes/targeth.h"


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

    Callbacks for the TileMap code

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

/*
    Tile format
    -----------

    Screen 0 & 1: (64*32, 16x16 tiles)

    Word | Bit(s)            | Description
    -----+-FEDCBA98-76543210-+--------------------------
      0  | --xxxxxx xxxxxxxx | code
      0  | xx------ -------- | not used?
      1  | -------- ---xxxxx | color (uses 1st half of the palette)
      1  | -------- --x----- | flip y
      1  | -------- -x------ | flip x
      1  | xxxxxxxx x------- | not used?
*/

static TILE_GET_INFO( get_tile_info_targeth_screen0 )
{
	targeth_state *state = machine.driver_data<targeth_state>();
	int data = state->m_videoram[tile_index << 1];
	int data2 = state->m_videoram[(tile_index << 1) + 1];
	int code = data & 0x3fff;

	SET_TILE_INFO(0, code, data2 & 0x1f, TILE_FLIPXY((data2 >> 5) & 0x03));
}

static TILE_GET_INFO( get_tile_info_targeth_screen1 )
{
	targeth_state *state = machine.driver_data<targeth_state>();
	int data = state->m_videoram[(0x2000/2) + (tile_index << 1)];
	int data2 = state->m_videoram[(0x2000/2) + (tile_index << 1) + 1];
	int code = data & 0x3fff;

	SET_TILE_INFO(0, code, data2 & 0x1f, TILE_FLIPXY((data2 >> 5) & 0x03));
}

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

    Memory Handlers

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

WRITE16_HANDLER( targeth_vram_w )
{
	targeth_state *state = space->machine().driver_data<targeth_state>();
	state->m_videoram[offset] = data;
	tilemap_mark_tile_dirty(state->m_pant[(offset & 0x1fff) >> 12], ((offset << 1) & 0x1fff) >> 2);
}


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

    Start/Stop the video hardware emulation.

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

VIDEO_START( targeth )
{
	targeth_state *state = machine.driver_data<targeth_state>();
	state->m_pant[0] = tilemap_create(machine, get_tile_info_targeth_screen0,tilemap_scan_rows,16,16,64,32);
	state->m_pant[1] = tilemap_create(machine, get_tile_info_targeth_screen1,tilemap_scan_rows,16,16,64,32);

	tilemap_set_transparent_pen(state->m_pant[0],0);
}


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

    Sprites

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

/*
    Sprite Format
    -------------

    Word | Bit(s)            | Description
    -----+-FEDCBA98-76543210-+--------------------------
      0  | -------- xxxxxxxx | y position
      0  | --xxxxxx -------- | not used?
      0  | -x------ -------- | flipx
      0  | x------- -------- | flipy
      1  | xxxxxxxx xxxxxxxx | not used?
      2  | ------xx xxxxxxxx | x position
      2  | -xxxxx-- -------- | sprite color (uses 2nd half of the palette)
      3  | --xxxxxx xxxxxxxx | sprite code
      3  | xx------ -------- | not used?
*/

static void draw_sprites(running_machine &machine, bitmap_t *bitmap, const rectangle *cliprect)
{
	targeth_state *state = machine.driver_data<targeth_state>();
	int i;
	const gfx_element *gfx = machine.gfx[0];

	for (i = 3; i < (0x1000 - 6)/2; i += 4){
		int sx = state->m_spriteram[i+2] & 0x03ff;
		int sy = (240 - (state->m_spriteram[i] & 0x00ff)) & 0x00ff;
		int number = state->m_spriteram[i+3] & 0x3fff;
		int color = (state->m_spriteram[i+2] & 0x7c00) >> 10;
		int attr = (state->m_spriteram[i] & 0xfe00) >> 9;

		int xflip = attr & 0x20;
		int yflip = attr & 0x40;

		drawgfx_transpen(bitmap,cliprect,gfx,number,
				0x20 + color,xflip,yflip,
				sx - 0x0f,sy,0);
	}
}

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

    Display Refresh

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

SCREEN_UPDATE( targeth )
{
	targeth_state *state = screen->machine().driver_data<targeth_state>();
	/* set scroll registers */
	tilemap_set_scrolly(state->m_pant[0], 0, state->m_vregs[0]);
	tilemap_set_scrollx(state->m_pant[0], 0, state->m_vregs[1] + 0x04);
	tilemap_set_scrolly(state->m_pant[1], 0, state->m_vregs[2]);
	tilemap_set_scrollx(state->m_pant[1], 0, state->m_vregs[3]);

	tilemap_draw(bitmap,cliprect,state->m_pant[1],0,0);
	tilemap_draw(bitmap,cliprect,state->m_pant[0],0,0);
	draw_sprites(screen->machine(), bitmap,cliprect);

	return 0;
}
