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

	breakthru:vidhrdw.c

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

#include "driver.h"
#include "vidhrdw/generic.h"


unsigned char *brkthru_scroll;
unsigned char *brkthru_videoram;
size_t brkthru_videoram_size;
static int bgscroll;
static int bgbasecolor;
static int flipscreen;



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

  Convert the color PROMs into a more useable format.

  Break Thru has one 256x8 and one 256x4 palette PROMs.
  I don't know for sure how the palette PROMs are connected to the RGB
  output, but it's probably the usual:

  bit 7 -- 220 ohm resistor  -- GREEN
        -- 470 ohm resistor  -- GREEN
        -- 1  kohm resistor  -- GREEN
        -- 2.2kohm resistor  -- GREEN
        -- 220 ohm resistor  -- RED
        -- 470 ohm resistor  -- RED
        -- 1  kohm resistor  -- RED
  bit 0 -- 2.2kohm resistor  -- RED

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

***************************************************************************/
PALETTE_INIT( brkthru )
{
	int i;


	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[0] >> 4) & 0x01;
		bit1 = (color_prom[0] >> 5) & 0x01;
		bit2 = (color_prom[0] >> 6) & 0x01;
		bit3 = (color_prom[0] >> 7) & 0x01;
		g = 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;
		b = 0x0e * bit0 + 0x1f * bit1 + 0x43 * bit2 + 0x8f * bit3;

		palette_set_color(i,r,g,b);

		color_prom++;
	}
}



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

  Start the video hardware emulation.

***************************************************************************/
VIDEO_START( brkthru )
{
	if ((dirtybuffer = auto_malloc(videoram_size)) == 0)
		return 1;
	memset(dirtybuffer,1,videoram_size);

	/* the background area is twice as wide as the screen */
	if ((tmpbitmap = auto_bitmap_alloc(2*Machine->drv->screen_width,Machine->drv->screen_height)) == 0)
		return 1;

	return 0;
}



WRITE_HANDLER( brkthru_1800_w )
{
	if (offset == 0)	/* low 8 bits of scroll */
		bgscroll = (bgscroll & 0x100) | data;
	else if (offset == 1)
	{
		int bankaddress;
		unsigned char *RAM = memory_region(REGION_CPU1);


		/* bit 0-2 = ROM bank select */
		bankaddress = 0x10000 + (data & 0x07) * 0x2000;
		cpu_setbank(1,&RAM[bankaddress]);

		/* bit 3-5 = background tiles color code */
		if (((data & 0x38) >> 2) != bgbasecolor)
		{
			bgbasecolor = (data & 0x38) >> 2;
			memset(dirtybuffer,1,videoram_size);
		}

		/* bit 6 = screen flip */
		if (flipscreen != (data & 0x40))
		{
			flipscreen = data & 0x40;
			memset(dirtybuffer,1,videoram_size);
		}

		/* bit 7 = high bit of scroll */
		bgscroll = (bgscroll & 0xff) | ((data & 0x80) << 1);
	}
}



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

  Draw the game screen in the given mame_bitmap.
  Do NOT call osd_update_display() from this function, it will be called by
  the main emulation engine.

***************************************************************************/
VIDEO_UPDATE( brkthru )
{
	int offs;


	/* for every character in the Video RAM, check if it has been modified */
	/* since last time and update it accordingly. */
	for (offs = videoram_size - 2;offs >= 0;offs -= 2)
	{
		if (dirtybuffer[offs] || dirtybuffer[offs+1])
		{
			int sx,sy,code;


			dirtybuffer[offs] = dirtybuffer[offs+1] = 0;

			sx = (offs/2) / 16;
			sy = (offs/2) % 16;
			if (flipscreen)
			{
				sx = 31 - sx;
				sy = 15 - sy;
			}

			code = videoram[offs] + 256 * (videoram[offs+1] & 3);
			drawgfx(tmpbitmap,Machine->gfx[1 + (code >> 7)],
					code & 0x7f,
					bgbasecolor + ((videoram[offs+1] & 0x04) >> 2),
					flipscreen,flipscreen,
					16*sx,16*sy,
					0,TRANSPARENCY_NONE,0);
		}
	}


	/* copy the background graphics */
	{
		int scroll;


		if (flipscreen) scroll = 256 + bgscroll;
		else scroll = -bgscroll;
		copyscrollbitmap(bitmap,tmpbitmap,1,&scroll,0,0,&Machine->visible_area,TRANSPARENCY_NONE,0);
	}


	/* Draw the sprites. Note that it is important to draw them exactly in this */
	/* order, to have the correct priorities. */
	for (offs = 0;offs < spriteram_size; offs += 4)
	{
		if (spriteram[offs] & 0x01)	/* enable */
		{
			int sx,sy,code,color;


			/* the meaning of bit 3 of [offs] is unknown */

			sx = 240 - spriteram[offs+3];
			if (sx < -7) sx += 256;
			sy = 240 - spriteram[offs+2];
			code = spriteram[offs+1] + 128 * (spriteram[offs] & 0x06);
			color = (spriteram[offs] & 0xe0) >> 5;
			if (flipscreen)
			{
				sx = 240 - sx;
				sy = 240 - sy;
			}

			if (spriteram[offs] & 0x10)	/* double height */
			{
				drawgfx(bitmap,Machine->gfx[9],
						code & ~1,
						color,
						flipscreen,flipscreen,
						sx,flipscreen? sy + 16 : sy - 16,
						&Machine->visible_area,TRANSPARENCY_PEN,0);
				drawgfx(bitmap,Machine->gfx[9],
						code | 1,
						color,
						flipscreen,flipscreen,
						sx,sy,
						&Machine->visible_area,TRANSPARENCY_PEN,0);

				/* redraw with wraparound */
				drawgfx(bitmap,Machine->gfx[9],
						code & ~1,
						color,
						flipscreen,flipscreen,
						sx,(flipscreen? sy + 16 : sy - 16) + 256,
						&Machine->visible_area,TRANSPARENCY_PEN,0);
				drawgfx(bitmap,Machine->gfx[9],
						code | 1,
						color,
						flipscreen,flipscreen,
						sx,sy + 256,
						&Machine->visible_area,TRANSPARENCY_PEN,0);
			}
			else
			{
				drawgfx(bitmap,Machine->gfx[9],
						code,
						color,
						flipscreen,flipscreen,
						sx,sy,
						&Machine->visible_area,TRANSPARENCY_PEN,0);

				/* redraw with wraparound */
				drawgfx(bitmap,Machine->gfx[9],
						code,
						color,
						flipscreen,flipscreen,
						sx,sy + 256,
						&Machine->visible_area,TRANSPARENCY_PEN,0);
			}
		}
	}


	/* draw the frontmost playfield. They are characters, but draw them as sprites */
	for (offs = brkthru_videoram_size - 1;offs >= 0;offs--)
	{
		int sx,sy;


		sx = offs % 32;
		sy = offs / 32;
		if (flipscreen)
		{
			sx = 31 - sx;
			sy = 31 - sy;
		}

		drawgfx(bitmap,Machine->gfx[0],
				brkthru_videoram[offs],
				0,
				flipscreen,flipscreen,
				8*sx,8*sy,
				&Machine->visible_area,TRANSPARENCY_PEN,0);
	}
}
