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

  vidhrdw.c

  Functions to emulate the video hardware of the machine.

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

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



unsigned char *gberet_videoram,*gberet_colorram;
unsigned char *gberet_spritebank;
unsigned char *gberet_scrollram;
static struct tilemap *bg_tilemap;
static int interruptenable;
static int flipscreen;
static int sprites_type;


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

  Convert the color PROMs into a more useable format.

  Green Beret has a 32 bytes palette PROM and two 256 bytes color lookup table
  PROMs (one for sprites, one for characters).
  The palette PROM is connected to the RGB output, this way:

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

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

void gberet_vh_convert_color_prom(unsigned char *palette, unsigned short *colortable,const unsigned char *color_prom)
{
	int i;
	#define TOTAL_COLORS(gfxn) (Machine->gfx[gfxn]->total_colors * Machine->gfx[gfxn]->color_granularity)
	#define COLOR(gfxn,offs) (colortable[Machine->drv->gfxdecodeinfo[gfxn].color_codes_start + offs])


	for (i = 0;i < Machine->drv->total_colors;i++)
	{
		int bit0,bit1,bit2;


		bit0 = (*color_prom >> 0) & 0x01;
		bit1 = (*color_prom >> 1) & 0x01;
		bit2 = (*color_prom >> 2) & 0x01;
		*(palette++) = 0x21 * bit0 + 0x47 * bit1 + 0x97 * bit2;
		bit0 = (*color_prom >> 3) & 0x01;
		bit1 = (*color_prom >> 4) & 0x01;
		bit2 = (*color_prom >> 5) & 0x01;
		*(palette++) = 0x21 * bit0 + 0x47 * bit1 + 0x97 * bit2;
		bit0 = 0;
		bit1 = (*color_prom >> 6) & 0x01;
		bit2 = (*color_prom >> 7) & 0x01;
		*(palette++) = 0x21 * bit0 + 0x47 * bit1 + 0x97 * bit2;

		color_prom++;
	}

	for (i = 0;i < TOTAL_COLORS(1);i++)
	{
		if (*color_prom & 0x0f) COLOR(1,i) = *color_prom & 0x0f;
		else COLOR(1,i) = 0;
		color_prom++;
	}
	for (i = 0;i < TOTAL_COLORS(0);i++)
	{
		COLOR(0,i) = (*(color_prom++) & 0x0f) + 0x10;
	}
}



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

  Callbacks for the TileMap code

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

static void get_tile_info(int tile_index)
{
	unsigned char attr = gberet_colorram[tile_index];
	SET_TILE_INFO(0,gberet_videoram[tile_index] + ((attr & 0x40) << 2),attr & 0x0f)
	tile_info.flags = TILE_FLIPYX((attr & 0x30) >> 4) | TILE_SPLIT((attr & 0x80) >> 7);
}



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

  Start the video hardware emulation.

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

int gberet_vh_start(void)
{
	bg_tilemap = tilemap_create(get_tile_info,tilemap_scan_rows,TILEMAP_SPLIT,8,8,64,32);

	if (!bg_tilemap)
		return 0;

	bg_tilemap->transmask[0] = 0x0001; /* split type 0 has pen 1 transparent in front half */
	bg_tilemap->transmask[1] = 0xffff; /* split type 1 is totally transparent in front half */
	tilemap_set_scroll_rows(bg_tilemap,32);

	return 0;
}

void init_gberet(void)
{
	sprites_type = 0;
}

void init_gberetb(void)
{
	sprites_type = 1;
}



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

  Memory handlers

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

WRITE_HANDLER( gberet_videoram_w )
{
	if (gberet_videoram[offset] != data)
	{
		gberet_videoram[offset] = data;
		tilemap_mark_tile_dirty(bg_tilemap,offset);
	}
}

WRITE_HANDLER( gberet_colorram_w )
{
	if (gberet_colorram[offset] != data)
	{
		gberet_colorram[offset] = data;
		tilemap_mark_tile_dirty(bg_tilemap,offset);
	}
}

WRITE_HANDLER( gberet_e044_w )
{
	/* bit 0 enables interrupts */
	interruptenable = data & 1;

	/* bit 3 flips screen */
	flipscreen = data & 0x08;
	tilemap_set_flip(ALL_TILEMAPS,flipscreen ? (TILEMAP_FLIPY | TILEMAP_FLIPX) : 0);

	/* don't know about the other bits */
}

WRITE_HANDLER( gberet_scroll_w )
{
	int scroll;

	gberet_scrollram[offset] = data;

	scroll = gberet_scrollram[offset & 0x1f] | (gberet_scrollram[offset | 0x20] << 8);
	tilemap_set_scrollx(bg_tilemap,offset & 0x1f,scroll);
}

WRITE_HANDLER( gberetb_scroll_w )
{
	if (offset) data |= 0x100;

	for (offset = 6;offset < 29;offset++)
		tilemap_set_scrollx(bg_tilemap,offset,data + 64-8);
}


int gberet_interrupt(void)
{
	if (cpu_getiloops() == 0) return interrupt();
	else if (cpu_getiloops() % 2)
	{
		if (interruptenable) return nmi_interrupt();
	}

	return ignore_interrupt();
}



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

  Display refresh

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

static void draw_sprites0(struct osd_bitmap *bitmap)
{
	int offs;
	unsigned char *sr;

	if (*gberet_spritebank & 0x08)
		sr = spriteram_2;
	else sr = spriteram;

	for (offs = 0;offs < spriteram_size;offs += 4)
	{
		if (sr[offs+3])
		{
			int sx,sy,flipx,flipy;


			sx = sr[offs+2] - 2*(sr[offs+1] & 0x80);
			sy = sr[offs+3];
			if (sprites_type) sy = 240 - sy;
			flipx = sr[offs+1] & 0x10;
			flipy = sr[offs+1] & 0x20;

			if (flipscreen)
			{
				sx = 240 - sx;
				sy = 240 - sy;
				flipx = !flipx;
				flipy = !flipy;
			}

			drawgfx(bitmap,Machine->gfx[1],
					sr[offs+0] + ((sr[offs+1] & 0x40) << 2),
					sr[offs+1] & 0x0f,
					flipx,flipy,
					sx,sy,
					&Machine->visible_area,TRANSPARENCY_COLOR,0);
		}
	}
}

static void draw_sprites1(struct osd_bitmap *bitmap)
{
	int offs;
	unsigned char *sr;

	sr = spriteram;

	for (offs = spriteram_size - 4;offs >= 0;offs -= 4)
	{
		if (sr[offs+1])
		{
			int sx,sy,flipx,flipy;


			sx = sr[offs+2] - 2*(sr[offs+3] & 0x80);
			sy = sr[offs+1];
			if (sprites_type) sy = 240 - sy;
			flipx = sr[offs+3] & 0x10;
			flipy = sr[offs+3] & 0x20;

			if (flipscreen)
			{
				sx = 240 - sx;
				sy = 240 - sy;
				flipx = !flipx;
				flipy = !flipy;
			}

			drawgfx(bitmap,Machine->gfx[1],
					sr[offs+0] + ((sr[offs+3] & 0x40) << 2),
					sr[offs+3] & 0x0f,
					flipx,flipy,
					sx,sy,
					&Machine->visible_area,TRANSPARENCY_COLOR,0);
		}
	}
}


void gberet_vh_screenrefresh(struct osd_bitmap *bitmap,int full_refresh)
{
	tilemap_update(ALL_TILEMAPS);

	tilemap_render(ALL_TILEMAPS);

	tilemap_draw(bitmap,bg_tilemap,TILEMAP_BACK);
	if (sprites_type == 0) draw_sprites0(bitmap);	/* original */
	else draw_sprites1(bitmap);	/* bootleg */
	tilemap_draw(bitmap,bg_tilemap,TILEMAP_FRONT);
}