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

Video Hardware for MAGMAX.

Driver by Takahiro Nogi (nogi@kt.rim.or.jp) 1999/11/05 -
Additional tweaking by Jarek Burczynski

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

#include "driver.h"

UINT16 *magmax_scroll_x;
UINT16 *magmax_scroll_y;
UINT16 *magmax_vreg;
static int flipscreen = 0;

static UINT32 *prom_tab;


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

  Convert the color PROMs into a more useable format.

  Mag Max has three 256x4 palette PROMs (one per gun), connected to the
  RGB output this way:

  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( magmax )
{
	int i;

	/* allocate the colortable */
	machine->colortable = colortable_alloc(machine, 0x100);

	/* create a lookup table for the palette */
	for (i = 0; i < 0x100; i++)
	{
		int r = pal4bit(color_prom[i + 0x000]);
		int g = pal4bit(color_prom[i + 0x100]);
		int b = pal4bit(color_prom[i + 0x200]);

		colortable_palette_set_color(machine->colortable, i, MAKE_RGB(r, g, b));
	}

	/* color_prom now points to the beginning of the lookup table */
	color_prom += 0x300;

	/* characters use colors 0-0x0f */
	for (i = 0; i < 0x10; i++)
		colortable_entry_set_value(machine->colortable, i, i);

	/*sprites use colors 0x10-0x1f, color 0x1f being transparent*/
	for (i = 0x10; i < 0x110; i++)
	{
		UINT8 ctabentry = (color_prom[i - 0x10] & 0x0f) | 0x10;
		colortable_entry_set_value(machine->colortable, i, ctabentry);
	}

	/* background uses all colors (no lookup table) */
	for (i = 0x110; i < 0x210; i++)
		colortable_entry_set_value(machine->colortable, i, i - 0x110);

}

VIDEO_START( magmax )
{
	int i,v;
	UINT8 * prom14D = memory_region(machine, "user2");

	/* Set up save state */
	state_save_register_global(machine, flipscreen);

	prom_tab = auto_alloc_array(machine, UINT32, 256);

	/* Allocate temporary bitmap */
 	tmpbitmap = video_screen_auto_bitmap_alloc(machine->primary_screen);

	for (i=0; i<256; i++)
	{
		v = (prom14D[i] << 4) + prom14D[i + 0x100];
		prom_tab[i] = ((v&0x1f)<<8) | ((v&0x10)<<10) | ((v&0xe0)>>1); /*convert data into more useful format*/
	}
}



VIDEO_UPDATE( magmax )
{
	int offs;

	/* bit 2 flip screen */
	flipscreen = *magmax_vreg & 0x04;

	/* copy the background graphics */
	if (*magmax_vreg & 0x40)		/* background disable */
		bitmap_fill(bitmap, cliprect, 0);
	else
	{
		int v;
		UINT8 * rom18B = memory_region(screen->machine, "user1");
		UINT32 scroll_h = (*magmax_scroll_x) & 0x3fff;
		UINT32 scroll_v = (*magmax_scroll_y) & 0xff;

		/*clear background-over-sprites bitmap*/
		bitmap_fill(tmpbitmap, NULL, 0);

		for (v = 2*8; v < 30*8; v++) /*only for visible area*/
		{
			int h;
			UINT16 line_data[256];

			UINT32 map_v_scr_100 =   (scroll_v + v) & 0x100;
			UINT32 rom18D_addr   =  ((scroll_v + v) & 0xf8)     + (map_v_scr_100<<5);
			UINT32 rom15F_addr   = (((scroll_v + v) & 0x07)<<2) + (map_v_scr_100<<5);
			UINT32 map_v_scr_1fe_6 =((scroll_v + v) & 0x1fe)<<6;

			pen_t pen_base = 0x110 + 0x20 + (map_v_scr_100>>1);

			for (h = 0; h < 0x100; h++)
			{
				UINT32 graph_data;
				UINT32 graph_color;
				UINT32 LS283;
				UINT32 prom_data;

				LS283 =	scroll_h + h;

				if (!map_v_scr_100)
				{
					if (h & 0x80)
						LS283 =	LS283 + (rom18B[ map_v_scr_1fe_6 + (h ^ 0xff) ] ^ 0xff);
					else
						LS283 =	LS283 + rom18B[ map_v_scr_1fe_6 + h ] + 0xff01;
				}

				prom_data = prom_tab[ (LS283 >> 6) & 0xff ];

				rom18D_addr &= 0x20f8;
				rom18D_addr += (prom_data & 0x1f00) + ((LS283 & 0x38) >>3);

				rom15F_addr &= 0x201c;
				rom15F_addr += (rom18B[0x4000 + rom18D_addr ]<<5) + ((LS283 & 0x6)>>1);
				rom15F_addr += (prom_data & 0x4000);

				graph_color = (prom_data & 0x0070);

				graph_data = rom18B[0x8000 + rom15F_addr];
				if ((LS283 & 1))
					graph_data >>= 4;
				graph_data &= 0x0f;

				line_data[h] = pen_base + graph_color + graph_data;

				/*priority: background over sprites*/
				if (map_v_scr_100 && ((graph_data & 0x0c)==0x0c))
					*BITMAP_ADDR16(tmpbitmap, v, h) = line_data[h];
			}

			if (flipscreen)
			{
				int i;
				UINT16 line_data_flip_x[256];
				for (i=0; i<256; i++)
					line_data_flip_x[i] = line_data[255-i];
				draw_scanline16(bitmap, 0, 255-v, 256, line_data_flip_x, NULL);
			}
			else
				draw_scanline16(bitmap, 0, v, 256, line_data, NULL);
		}
	}

	/* draw the sprites */
	for (offs = 0; offs < spriteram_size/2; offs += 4)
	{
		int sx, sy;

		sy = spriteram16[offs] & 0xff;

		if (sy)
		{
			int code = spriteram16[offs + 1] & 0xff;
			int attr = spriteram16[offs + 2] & 0xff;
			int color = (attr & 0xf0) >> 4;
			int flipx = attr & 0x04;
			int flipy = attr & 0x08;

			sx = (spriteram16[offs + 3] & 0xff) - 0x80 + 0x100 * (attr & 0x01);
			sy = 239 - sy;

			if (flipscreen)
			{
				sx = 255-16 - sx;
				sy = 239 - sy;
				flipx = !flipx;
				flipy = !flipy;
			}

			if (code & 0x80)	/* sprite bankswitch */
				code += (*magmax_vreg & 0x30) * 0x8;

			drawgfx_transmask(bitmap, cliprect, screen->machine->gfx[1],
					code,
					color,
					flipx, flipy,
					sx, sy,
					colortable_get_transpen_mask(screen->machine->colortable, screen->machine->gfx[1], color, 0x1f));
		}
	}

	if (!(*magmax_vreg & 0x40))		/* background disable */
		copybitmap_trans(bitmap, tmpbitmap, flipscreen,flipscreen,0,0, cliprect, 0);

	/* draw the foreground characters */
	for (offs = 32*32-1; offs >= 0; offs -= 1)
	{
		//int page = (*magmax_vreg>>3) & 0x1;
		int code;

		code = videoram16[offs /*+ page*/] & 0xff;
		if (code)
		{
			int sx = (offs % 32);
			int sy = (offs / 32);

			if (flipscreen)
			{
				sx = 31 - sx;
				sy = 31 - sy;
			}

			drawgfx_transpen(bitmap, cliprect, screen->machine->gfx[0],
					code,
					0,
					flipscreen, flipscreen,
					8 * sx, 8 * sy, 0x0f);
		}
	}
	return 0;
}
