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

  vidhrdw.c

  Functions to emulate the video hardware of the machine.

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

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

UINT8 *bankp_videoram2;
UINT8 *bankp_colorram2;

static int scroll_x;
static int priority;

static struct tilemap *bg_tilemap, *fg_tilemap;

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

  Convert the color PROMs into a more useable format.

  Bank Panic has a 32x8 palette PROM (I'm not sure whether the second 16
  bytes are used - they contain the same colors as the first 16 with only
  one different) and two 256x4 lookup table PROMs (one for charset #1, one
  for charset #2 - only the first 128 nibbles seem to be used).

  I don't know for sure how the palette PROM is connected to the RGB output,
  but it's probably the usual:

  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

***************************************************************************/
PALETTE_INIT( bankp )
{
	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,r,g,b;


		/* red component */
		bit0 = (*color_prom >> 0) & 0x01;
		bit1 = (*color_prom >> 1) & 0x01;
		bit2 = (*color_prom >> 2) & 0x01;
		r = 0x21 * bit0 + 0x47 * bit1 + 0x97 * bit2;
		/* green component */
		bit0 = (*color_prom >> 3) & 0x01;
		bit1 = (*color_prom >> 4) & 0x01;
		bit2 = (*color_prom >> 5) & 0x01;
		g = 0x21 * bit0 + 0x47 * bit1 + 0x97 * bit2;
		/* blue component */
		bit0 = 0;
		bit1 = (*color_prom >> 6) & 0x01;
		bit2 = (*color_prom >> 7) & 0x01;
		b = 0x21 * bit0 + 0x47 * bit1 + 0x97 * bit2;

		palette_set_color(i,r,g,b);

		color_prom++;
	}

	/* color_prom now points to the beginning of the lookup table */

	/* charset #1 lookup table */
	for (i = 0;i < TOTAL_COLORS(0);i++)
		COLOR(0,i) = *(color_prom++) & 0x0f;

	color_prom += 128;	/* skip the bottom half of the PROM - seems to be not used */

	/* charset #2 lookup table */
	for (i = 0;i < TOTAL_COLORS(1);i++)
		COLOR(1,i) = *(color_prom++) & 0x0f;

	/* the bottom half of the PROM seems to be not used */
}

WRITE_HANDLER( bankp_scroll_w )
{
	scroll_x = data;
}

WRITE_HANDLER( bankp_videoram_w )
{
	if (videoram[offset] != data)
	{
		videoram[offset] = data;
		tilemap_mark_tile_dirty(fg_tilemap, offset);
	}
}

WRITE_HANDLER( bankp_colorram_w )
{
	if (colorram[offset] != data)
	{
		colorram[offset] = data;
		tilemap_mark_tile_dirty(fg_tilemap, offset);
	}
}

WRITE_HANDLER( bankp_videoram2_w )
{
	if (bankp_videoram2[offset] != data)
	{
		bankp_videoram2[offset] = data;
		tilemap_mark_tile_dirty(bg_tilemap, offset);
	}
}

WRITE_HANDLER( bankp_colorram2_w )
{
	if (bankp_colorram2[offset] != data)
	{
		bankp_colorram2[offset] = data;
		tilemap_mark_tile_dirty(bg_tilemap, offset);
	}
}

WRITE_HANDLER( bankp_out_w )
{
	/* bits 0-1 are playfield priority */
	/* TODO: understand how this works */
	priority = data & 0x03;

	/* bits 2-3 unknown (2 is used) */

	/* bit 4 controls NMI */
	interrupt_enable_w(0,(data & 0x10)>>4);

	/* bit 5 controls screen flip */
	if (flip_screen != (data & 0x20))
	{
		flip_screen_set(data & 0x20);
		tilemap_mark_all_tiles_dirty(ALL_TILEMAPS);
	}

	/* bits 6-7 unknown */
}

static void get_bg_tile_info(int tile_index)
{
	int code = bankp_videoram2[tile_index] + 256 * (bankp_colorram2[tile_index] & 0x07);
	int color = bankp_colorram2[tile_index] >> 4;
	int flags = (bankp_colorram2[tile_index] & 0x08) ? TILE_FLIPX : 0;

	SET_TILE_INFO(1, code, color, flags)
}

static void get_fg_tile_info(int tile_index)
{
	int code = videoram[tile_index] + 256 * ((colorram[tile_index] & 3) >> 0);
	int color = colorram[tile_index] >> 3;
	int flags = (colorram[tile_index] & 0x04) ? TILE_FLIPX : 0;

	SET_TILE_INFO(0, code, color, flags)
}

VIDEO_START( bankp )
{
	bg_tilemap = tilemap_create(get_bg_tile_info, tilemap_scan_rows, 
		TILEMAP_TRANSPARENT_COLOR, 8, 8, 32, 32);

	if ( !bg_tilemap )
		return 1;

	fg_tilemap = tilemap_create(get_fg_tile_info, tilemap_scan_rows, 
		TILEMAP_TRANSPARENT_COLOR, 8, 8, 32, 32);

	if ( !fg_tilemap )
		return 1;

	tilemap_set_transparent_pen(bg_tilemap, 0);
	tilemap_set_transparent_pen(fg_tilemap, 0);

	return 0;
}

VIDEO_UPDATE( bankp )
{
	/* The tilemap has to be shifted to the left in flip screen mode
		because the visible tilemap data is not centered in video memory */

	if (flip_screen)
	{
		tilemap_set_scrollx(fg_tilemap, 0, -scroll_x - 16);
		tilemap_set_scrollx(bg_tilemap, 0, -16);
	} 
	else
	{
		tilemap_set_scrollx(fg_tilemap, 0, scroll_x);
		tilemap_set_scrollx(bg_tilemap, 0, 0);
	}	

	switch (priority)
	{
	case 0:
		tilemap_draw(bitmap, &Machine->visible_area, bg_tilemap, TILEMAP_IGNORE_TRANSPARENCY, 0); /* just a guess*/
		break;
	case 1:
		tilemap_draw(bitmap, &Machine->visible_area, bg_tilemap, TILEMAP_IGNORE_TRANSPARENCY, 0);
		tilemap_draw(bitmap, &Machine->visible_area, fg_tilemap, 0, 0);
		break;
	case 2:
		tilemap_draw(bitmap, &Machine->visible_area, fg_tilemap, TILEMAP_IGNORE_TRANSPARENCY, 0);
		tilemap_draw(bitmap, &Machine->visible_area, bg_tilemap, 0, 0);
		break;
	case 3:
		tilemap_draw(bitmap, &Machine->visible_area, fg_tilemap, TILEMAP_IGNORE_TRANSPARENCY, 0); /* just a guess*/
		break;
	}
}
