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

  vidhrdw.c

  Functions to emulate the video hardware of the machine.

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

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



unsigned char *c1942_backgroundram;
int c1942_backgroundram_size;
unsigned char *c1942_scroll;
unsigned char *c1942_palette_bank;
static unsigned char *dirtybuffer2;
static struct osd_bitmap *tmpbitmap2;



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

  Convert the color PROMs into a more useable format.

  1942 has a three 256x4 palette PROMs (one per gun) and three 256x4 lookup
  table PROMs (one for characters, one for sprites, one for background tiles).
  The palette PROMs are 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

***************************************************************************/
void c1942_vh_convert_color_prom(unsigned char *palette, unsigned char *colortable,const unsigned char *color_prom)
{
	int i;


	for (i = 0;i < 256;i++)
	{
		int bit0,bit1,bit2,bit3;


		bit0 = (color_prom[i] >> 0) & 0x01;
		bit1 = (color_prom[i] >> 1) & 0x01;
		bit2 = (color_prom[i] >> 2) & 0x01;
		bit3 = (color_prom[i] >> 3) & 0x01;
		palette[3*i] = 0x0e * bit0 + 0x1f * bit1 + 0x43 * bit2 + 0x8f * bit3;
		bit0 = (color_prom[i+256] >> 0) & 0x01;
		bit1 = (color_prom[i+256] >> 1) & 0x01;
		bit2 = (color_prom[i+256] >> 2) & 0x01;
		bit3 = (color_prom[i+256] >> 3) & 0x01;
		palette[3*i + 1] = 0x0e * bit0 + 0x1f * bit1 + 0x43 * bit2 + 0x8f * bit3;
		bit0 = (color_prom[i+256*2] >> 0) & 0x01;
		bit1 = (color_prom[i+256*2] >> 1) & 0x01;
		bit2 = (color_prom[i+256*2] >> 2) & 0x01;
		bit3 = (color_prom[i+256*2] >> 3) & 0x01;
		palette[3*i + 2] = 0x0e * bit0 + 0x1f * bit1 + 0x43 * bit2 + 0x8f * bit3;
	}

	/* characters use colors 128-143 */
	for (i = 0;i < 64*4;i++)
		colortable[i] = color_prom[i + 256*3] + 128;

	/* sprites use colors 64-79 */
	for (i = 64*4;i < 64*4+16*16;i++)
		colortable[i] = color_prom[i + 256*3] + 64;

	/* background tiles use colors 0-63 in four banks */
	for (i = 64*4+16*16;i < 64*4+16*16+32*8;i++)
	{
		colortable[i] = color_prom[i + 256*3];
		colortable[i+32*8] = color_prom[i + 256*3] + 16;
		colortable[i+2*32*8] = color_prom[i + 256*3] + 32;
		colortable[i+3*32*8] = color_prom[i + 256*3] + 48;
	}
}



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

  Start the video hardware emulation.

***************************************************************************/
int c1942_vh_start(void)
{
	if (generic_vh_start() != 0)
		return 1;

	if ((dirtybuffer2 = malloc(c1942_backgroundram_size)) == 0)
	{
		generic_vh_stop();
		return 1;
	}
	memset(dirtybuffer2,0,c1942_backgroundram_size);

	/* the background area is twice as tall as the screen */
	if ((tmpbitmap2 = osd_create_bitmap(Machine->drv->screen_width,2*Machine->drv->screen_height)) == 0)
	{
		free(dirtybuffer2);
		generic_vh_stop();
		return 1;
	}

	return 0;
}



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

  Stop the video hardware emulation.

***************************************************************************/
void c1942_vh_stop(void)
{
	osd_free_bitmap(tmpbitmap2);
	free(dirtybuffer2);
	generic_vh_stop();
}



void c1942_background_w(int offset,int data)
{
	if (c1942_backgroundram[offset] != data)
	{
		dirtybuffer2[offset] = 1;

		c1942_backgroundram[offset] = data;
	}
}



void c1942_palette_bank_w(int offset,int data)
{
	if (*c1942_palette_bank != data)
	{
		memset(dirtybuffer2,1,c1942_backgroundram_size);
		*c1942_palette_bank = data;
	}
}



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

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

***************************************************************************/
void c1942_vh_screenrefresh(struct osd_bitmap *bitmap)
{
	int offs,sx,sy;


	for (sy = 0;sy < 32;sy++)
	{
		for (sx = 0;sx < 16;sx++)
		{
			offs = 32 * (31 - sy) + sx;

			if (dirtybuffer2[offs] != 0 || dirtybuffer2[offs + 16] != 0)
			{
				dirtybuffer2[offs] = dirtybuffer2[offs + 16] = 0;

				drawgfx(tmpbitmap2,Machine->gfx[(c1942_backgroundram[offs + 16] & 0x80) ? 2 : 1],
						c1942_backgroundram[offs],
						(c1942_backgroundram[offs + 16] & 0x1f) + 32 * *c1942_palette_bank,
						c1942_backgroundram[offs + 16] & 0x40,(c1942_backgroundram[offs + 16] & 0x20),
						16 * sx,16 * sy,
						0,TRANSPARENCY_NONE,0);
			}
		}
	}


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


		scroll = c1942_scroll[0] + 256 * c1942_scroll[1] - 256;

		copyscrollbitmap(bitmap,tmpbitmap2,0,0,1,&scroll,&Machine->drv->visible_area,TRANSPARENCY_NONE,0);
	}


	/* Draw the sprites. */
	for (offs = spriteram_size - 4;offs >= 0;offs -= 4)
	{
		int bank,i,code,col,sx,sy;


		bank = 3;
		if (spriteram[offs] & 0x80) bank++;
		if (spriteram[offs + 1] & 0x20) bank += 2;

		code = spriteram[offs] & 0x7f;
		col = spriteram[offs + 1] & 0x0f;
		sx = spriteram[offs + 2];
		sy = 240 - spriteram[offs + 3] + 0x10 * (spriteram[offs + 1] & 0x10);

		i = (spriteram[offs + 1] & 0xc0) >> 6;
		if (i == 2) i = 3;

		do
		{
			drawgfx(bitmap,Machine->gfx[bank],
					code + i,col,
					0, 0,
					sx + 16 * i,sy,
					&Machine->drv->visible_area,TRANSPARENCY_PEN,15);

			i--;
		} while (i >= 0);
	}


	/* draw the frontmost playfield. They are characters, but draw them as sprites */
	for (offs = videoram_size - 1;offs >= 0;offs--)
	{
		if (videoram[offs] != 0x30)	/* don't draw spaces */
		{
			int sx,sy;


			sx = 8 * (offs / 32);
			sy = 8 * (31 - offs % 32);

			drawgfx(bitmap,Machine->gfx[0],
					videoram[offs] + 2 * (colorram[offs] & 0x80),
					colorram[offs] & 0x3f,
					0,0,sx,sy,
					&Machine->drv->visible_area,TRANSPARENCY_PEN,0);
		}
	}
}