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

Atari Wolf Pack (prototype) video emulation

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

#include "driver.h"

int wolfpack_collision;

UINT8* wolfpack_alpha_num_ram;

static unsigned current_index;

static UINT8 wolfpack_video_invert;
static UINT8 wolfpack_ship_reflect;
static UINT8 wolfpack_pt_pos_select;
static UINT8 wolfpack_pt_horz;
static UINT8 wolfpack_pt_pic;
static UINT8 wolfpack_ship_h;
static UINT8 wolfpack_torpedo_pic;
static UINT8 wolfpack_ship_size;
static UINT8 wolfpack_ship_h_precess;
static UINT8 wolfpack_ship_pic;
static UINT8 wolfpack_torpedo_h;
static UINT8 wolfpack_torpedo_v;

static UINT8* LFSR;

static struct mame_bitmap* helper;


WRITE8_HANDLER( wolfpack_ship_size_w )
{
	UINT8 color;

	color = 0x48;

	if (data & 0x10) color += 0x13;
	if (data & 0x20) color += 0x22;
	if (data & 0x40) color += 0x3A;
	if (data & 0x80) color += 0x48;

	palette_set_color(3,
		color,
		color,
		color);

	palette_set_color(7,
		color < 0xb8 ? color + 0x48 : 0xff,
		color < 0xb8 ? color + 0x48 : 0xff,
		color < 0xb8 ? color + 0x48 : 0xff);

	wolfpack_ship_size = data >> 2;
}


WRITE8_HANDLER( wolfpack_video_invert_w )
{
	wolfpack_video_invert = data & 1;
}
WRITE8_HANDLER( wolfpack_ship_reflect_w )
{
	wolfpack_ship_reflect = data & 1;
}
WRITE8_HANDLER( wolfpack_pt_pos_select_w )
{
	wolfpack_pt_pos_select = data & 1;
}
WRITE8_HANDLER( wolfpack_pt_horz_w )
{
	wolfpack_pt_horz = data;
}
WRITE8_HANDLER( wolfpack_pt_pic_w )
{
	wolfpack_pt_pic = data & 0x3f;
}
WRITE8_HANDLER( wolfpack_ship_h_w )
{
	wolfpack_ship_h = data;
}
WRITE8_HANDLER( wolfpack_torpedo_pic_w )
{
	wolfpack_torpedo_pic = data;
}
WRITE8_HANDLER( wolfpack_ship_h_precess_w )
{
	wolfpack_ship_h_precess = data & 0x3f;
}
WRITE8_HANDLER( wolfpack_ship_pic_w )
{
	wolfpack_ship_pic = data & 0x0f;
}
WRITE8_HANDLER( wolfpack_torpedo_h_w )
{
	wolfpack_torpedo_h = data;
}
WRITE8_HANDLER( wolfpack_torpedo_v_w )
{
	wolfpack_torpedo_v = data;
}


VIDEO_START( wolfpack )
{
	UINT16 val = 0;

	int i;

	if ((LFSR = auto_malloc(0x8000)) == NULL)
	{
		return 1;
	}

	if ((helper = auto_bitmap_alloc(Machine->drv->screen_width, Machine->drv->screen_height)) == NULL)
	{
		return 1;
	}

	for (i = 0; i < 0x8000; i++)
	{
		int bit =
			(val >> 0x0) ^
			(val >> 0xE) ^ 1;

		val = (val << 1) | (bit & 1);

		LFSR[i] = (val & 0xc00) == 0xc00;
	}

	current_index = 0x80;

	return 0;
}


static void draw_ship(struct mame_bitmap* bitmap, const struct rectangle* cliprect)
{
	static const UINT32 scaler[] =
	{
		0x00000, 0x00500, 0x00A00, 0x01000,
		0x01000, 0x01200, 0x01500, 0x01800,
		0x01800, 0x01D00, 0x02200, 0x02800,
		0x02800, 0x02800, 0x02800, 0x02800,
		0x02800, 0x03000, 0x03800, 0x04000,
		0x04000, 0x04500, 0x04A00, 0x05000,
		0x05000, 0x05500, 0x05A00, 0x06000,
		0x06000, 0x06A00, 0x07500, 0x08000,
		0x08000, 0x08A00, 0x09500, 0x0A000,
		0x0A000, 0x0B000, 0x0C000, 0x0D000,
		0x0D000, 0x0E000, 0x0F000, 0x10000,
		0x10000, 0x11A00, 0x13500, 0x15000,
		0x15000, 0x17500, 0x19A00, 0x1C000,
		0x1C000, 0x1EA00, 0x21500, 0x24000,
		0x24000, 0x26A00, 0x29500, 0x2C000,
		0x2C000, 0x2FA00, 0x33500, 0x37000
	};

	int chop = (scaler[wolfpack_ship_size] * wolfpack_ship_h_precess) >> 16;

	drawgfxzoom(bitmap, Machine->gfx[1],
		wolfpack_ship_pic,
		0,
		wolfpack_ship_reflect, 0,
		2 * (wolfpack_ship_h - chop),
		128,
		cliprect,
		TRANSPARENCY_PEN, 0,
		2 * scaler[wolfpack_ship_size], scaler[wolfpack_ship_size]);
}


static void draw_torpedo(struct mame_bitmap* bitmap, const struct rectangle* cliprect)
{
	int count = 0;

	int x;
	int y;

	drawgfx(bitmap, Machine->gfx[3],
		wolfpack_torpedo_pic,
		0,
		0, 0,
		2 * (244 - wolfpack_torpedo_h),
		224 - wolfpack_torpedo_v,
		cliprect,
		TRANSPARENCY_PEN, 0);

	for (y = 16; y < 224 - wolfpack_torpedo_v; y++)
	{
		int x1;
		int x2;

		if (y % 16 == 1)
		{
			count = (count - 1) & 7;
		}

		x1 = 248 - wolfpack_torpedo_h - count;
		x2 = 248 - wolfpack_torpedo_h + count;

		for (x = 2 * x1; x < 2 * x2; x++)
		{
			if (LFSR[(current_index + 0x300 * y + x) % 0x8000])
			{
				plot_pixel(bitmap, x, y, 1);
			}
		}
	}
}


static void draw_pt(struct mame_bitmap* bitmap, const struct rectangle* cliprect)
{
	struct rectangle rect = *cliprect;

	if (!(wolfpack_pt_pic & 0x20))
	{
		rect.min_x = 256;
	}
	if (!(wolfpack_pt_pic & 0x10))
	{
		rect.max_x = 255;
	}

	drawgfx(bitmap, Machine->gfx[2],
		wolfpack_pt_pic,
		0,
		0, 0,
		2 * wolfpack_pt_horz,
		wolfpack_pt_pos_select ? 0x70 : 0xA0,
		&rect,
		TRANSPARENCY_PEN, 0);

	drawgfx(bitmap, Machine->gfx[2],
		wolfpack_pt_pic,
		0,
		0, 0,
		2 * wolfpack_pt_horz - 512,
		wolfpack_pt_pos_select ? 0x70 : 0xA0,
		&rect,
		TRANSPARENCY_PEN, 0);
}


static void draw_water(struct mame_bitmap* bitmap, const struct rectangle* cliprect)
{
	struct rectangle rect = *cliprect;

	int x;
	int y;

	if (rect.max_y > 127)
	{
		rect.max_y = 127;
	}

	for (y = rect.min_y; y <= rect.max_y; y++)
	{
		UINT16* p = bitmap->line[y];

		for (x = rect.min_x; x <= rect.max_x; x++)
		{
			p[x] |= 4;
		}
	}
}


VIDEO_UPDATE( wolfpack )
{
	int i;
	int j;

	fillbitmap(bitmap, wolfpack_video_invert, cliprect);

	for (i = 0; i < 8; i++)
	{
		for (j = 0; j < 32; j++)
		{
			int code = wolfpack_alpha_num_ram[32 * i + j];

			drawgfx(bitmap, Machine->gfx[0],
				code,
				wolfpack_video_invert,
				0, 0,
				16 * j,
				192 + 8 * i,
				cliprect,
				TRANSPARENCY_NONE, 0);
		}
	}

	draw_pt(bitmap, cliprect);
	draw_ship(bitmap, cliprect);
	draw_torpedo(bitmap, cliprect);
	draw_water(bitmap, cliprect);
}


VIDEO_EOF( wolfpack )
{
	struct rectangle rect;

	int x;
	int y;

	rect.min_x = 0;
	rect.min_y = 0;
	rect.max_x = helper->width - 1;
	rect.max_y = helper->height - 1;

	fillbitmap(helper, 0, &rect);

	draw_ship(helper, &rect);

	for (y = 128; y < 224 - wolfpack_torpedo_v; y++)
	{
		int x1 = 248 - wolfpack_torpedo_h - 1;
		int x2 = 248 - wolfpack_torpedo_h + 1;

		for (x = 2 * x1; x < 2 * x2; x++)
		{
			if (x < 0 || x >= helper->width)
				continue;
			if (y < 0 || y >= helper->height)
				continue;

			if (read_pixel(helper, x, y))
			{
				wolfpack_collision = 1;
			}
		}
	}

	current_index += 0x300 * 262;
}
