/*
 * 86Box	A hypervisor and IBM PC system emulator that specializes in
 *		running old operating systems and software designed for IBM
 *		PC systems and compatibles from 1981 through fairly recent
 *		system designs based on the PCI bus.
 *
 *		This file is part of the 86Box distribution.
 *
 *		Hercules emulation.
 *
 *
 *
 * Authors:	Sarah Walker, <http://pcem-emulator.co.uk/>
 *		Miran Grca, <mgrca8@gmail.com>
 *
 *		Copyright 2008-2019 Sarah Walker.
 *		Copyright 2016-2019 Miran Grca.
 */
#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <wchar.h>
#include <86box/86box.h>
#include "cpu.h"
#include <86box/mem.h>
#include <86box/rom.h>
#include <86box/io.h>
#include <86box/timer.h>
#include <86box/lpt.h>
#include <86box/pit.h>
#include <86box/device.h>
#include <86box/video.h>


typedef struct {
    mem_mapping_t	mapping;

    uint8_t	crtc[32], charbuffer[4096];
    int		crtcreg;

    uint8_t	ctrl,
		ctrl2,
		stat;

    uint64_t	dispontime,
		dispofftime;
    pc_timer_t	timer;

    int		firstline,
		lastline;

    int		linepos,
		displine;
    int		vc,
		sc;
    uint16_t	ma,
		maback;
    int		con, coff,
		cursoron;
    int		dispon,
		blink;
    int	vsynctime;
    int		vadj;

    int		lp_ff;

    int		cols[256][2][2];

    uint8_t	*vram;
} hercules_t;

static video_timings_t timing_hercules = {VIDEO_ISA, 8, 16, 32,   8, 16, 32};


static void
recalc_timings(hercules_t *dev)
{
    double disptime;
    double _dispontime, _dispofftime;

    disptime = dev->crtc[0] + 1;
    _dispontime  = dev->crtc[1];
    _dispofftime = disptime - _dispontime;
    _dispontime  *= HERCCONST;
    _dispofftime *= HERCCONST;

    dev->dispontime  = (uint64_t)(_dispontime);
    dev->dispofftime = (uint64_t)(_dispofftime);
}


static uint8_t crtcmask[32] = 
{
	0xff, 0xff, 0xff, 0xff, 0x7f, 0x1f, 0x7f, 0x7f, 0xf3, 0x1f, 0x7f, 0x1f, 0x3f, 0xff, 0x3f, 0xff,
	0xff, 0xff, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
};

static void
hercules_out(uint16_t addr, uint8_t val, void *priv)
{
    hercules_t *dev = (hercules_t *)priv;
    uint8_t old;

    switch (addr) {
	case 0x03b0:
	case 0x03b2:
	case 0x03b4:
	case 0x03b6:
		dev->crtcreg = val & 31;
		break;

	case 0x03b1:
	case 0x03b3:
	case 0x03b5:
	case 0x03b7:
		old = dev->crtc[dev->crtcreg];
		dev->crtc[dev->crtcreg] = val & crtcmask[dev->crtcreg];

		/*
		 * Fix for Generic Turbo XT BIOS, which
		 * sets up cursor registers wrong.
		 */
		if (dev->crtc[10] == 6 && dev->crtc[11] == 7) {
			dev->crtc[10] = 0xb;
			dev->crtc[11] = 0xc;
		}

		if (old != val) {
			if ((dev->crtcreg < 0xe) || (dev->crtcreg > 0x10)) {
				fullchange = changeframecount;
				recalc_timings(dev);
			}
		}
		break;

	case 0x03b8:
		old = dev->ctrl;

		/* Prevent setting of bits if they are disabled in CTRL2. */
		if ((old & 0x02) && !(val & 0x02))
			dev->ctrl &= 0xfd;
		else if ((val & 0x02) && (dev->ctrl2 & 0x01))
			dev->ctrl |= 0x02;

		if ((old & 0x80) && !(val & 0x80))
			dev->ctrl &= 0x7f;
		else if ((val & 0x80) && (dev->ctrl2 & 0x02))
			dev->ctrl |= 0x80;

		dev->ctrl = (dev->ctrl & 0x82) | (val & 0x7d);

		if (old ^ val)
			recalc_timings(dev);
		break;

	case 0x03b9:
	case 0x03bb:
		dev->lp_ff = !(addr & 0x0002);
		break;

	case 0x03bf:
		old = dev->ctrl2;
		dev->ctrl2 = val;
		/* According to the Programmer's guide to the Hercules graphics cars
		   by David B. Doty from 1988, the CTRL2 modes (bits 1,0) are as follow:
		   - 00: DIAG: Text mode only, only page 0 accessible;
		   - 01: HALF: Graphics mode allowed, only page 0 accessible;
		   - 11: FULL: Graphics mode allowed, both pages accessible. */
		if (val & 0x01)
			mem_mapping_set_exec(&dev->mapping, dev->vram);
		else
			mem_mapping_set_exec(&dev->mapping, NULL);
		if (val & 0x02)
			mem_mapping_set_addr(&dev->mapping, 0xb0000, 0x10000);
		else
			mem_mapping_set_addr(&dev->mapping, 0xb0000, 0x08000);
		if (old ^ val)
			recalc_timings(dev);
		break;

	default:
		break;
    }
}


static uint8_t
hercules_in(uint16_t addr, void *priv)
{
    hercules_t *dev = (hercules_t *)priv;
    uint8_t ret = 0xff;

    switch (addr) {
	case 0x03b0:
	case 0x03b2:
	case 0x03b4:
	case 0x03b6:
		ret = dev->crtcreg;
		break;

	case 0x03b1:
	case 0x03b3:
	case 0x03b5:
	case 0x03b7:
		if (dev->crtcreg == 0x0c)
			ret = (dev->ma >> 8) & 0x3f;
		else if (dev->crtcreg == 0x0d)
			ret = dev->ma & 0xff;
		else
			ret = dev->crtc[dev->crtcreg];
		break;

	case 0x03ba:
		ret = 0x70;	/* Hercules ident */
		ret |= (dev->lp_ff ? 2 : 0);
		ret |= (dev->stat & 0x01);
		if (dev->stat & 0x08)
			ret |= 0x80;
		if ((ret & 0x81) == 0x80)
			ret |= 0x08;
		break;

	default:
		break;
    }

    return(ret);
}


static void
hercules_waitstates(void *p)
{
    int ws_array[16] = {3, 4, 5, 6, 7, 8, 4, 5, 6, 7, 8, 4, 5, 6, 7, 8};
    int ws;

    ws = ws_array[cycles & 0xf];
    cycles -= ws;
}


static void
hercules_write(uint32_t addr, uint8_t val, void *priv)
{
    hercules_t *dev = (hercules_t *)priv;

    if (dev->ctrl2 & 0x01)
	addr &= 0xffff;
    else
	addr &= 0x0fff;

    dev->vram[addr] = val;

    hercules_waitstates(dev);
}


static uint8_t
hercules_read(uint32_t addr, void *priv)
{
    hercules_t *dev = (hercules_t *)priv;
    uint8_t ret = 0xff;

    if (dev->ctrl2 & 0x01)
	addr &= 0xffff;
    else
	addr &= 0x0fff;

    hercules_waitstates(dev);

    ret = dev->vram[addr];

    return ret;
}


static void
hercules_render_overscan_left(hercules_t *dev)
{
    int i;
    uint32_t width;

    if (dev->ctrl & 0x02)
	width = (((uint32_t) dev->crtc[1]) << 4);
    else
	width = (((uint32_t) dev->crtc[1]) * 9);

    if ((dev->displine + 14) < 0)
	return;

    if (width == 0)
	return;

    for (i = 0; i < 8; i++)
	buffer32->line[dev->displine + 14][i] = 0x00000000;
}


static void
hercules_render_overscan_right(hercules_t *dev)
{
    int i;
    uint32_t width;

    if (dev->ctrl & 0x02)
	width = (((uint32_t) dev->crtc[1]) << 4);
    else
	width = (((uint32_t) dev->crtc[1]) * 9);

    if ((dev->displine + 14) < 0)
	return;

    if (width == 0)
	return;

    for (i = 0; i < 8; i++)
	buffer32->line[dev->displine + 14][8 + width + i] = 0x00000000;
}


static void
hercules_poll(void *priv)
{
    hercules_t *dev = (hercules_t *)priv;
    uint8_t chr, attr;
    uint16_t ca, dat;
    uint16_t pa;
    int oldsc, blink;
    int x, xx, y, yy, c, oldvc;
    int drawcursor;
    uint32_t *p;

    ca = (dev->crtc[15] | (dev->crtc[14] << 8)) & 0x3fff;

    if (! dev->linepos) {
	timer_advance_u64(&dev->timer, dev->dispofftime);
	dev->stat |= 1;
	dev->linepos = 1;
	oldsc = dev->sc;

	if ((dev->crtc[8] & 3) == 3) 
		dev->sc = (dev->sc << 1) & 7;

	if (dev->dispon) {
		if (dev->displine < dev->firstline) {
			dev->firstline = dev->displine;
			video_wait_for_buffer();
		}
		dev->lastline = dev->displine;

		hercules_render_overscan_left(dev);

		if (dev->ctrl & 0x02) {
			ca = (dev->sc & 3) * 0x2000;
			if (dev->ctrl & 0x80)
				ca += 0x8000;

			for (x = 0; x < dev->crtc[1]; x++) {
				if (dev->ctrl & 8)
					dat = (dev->vram[((dev->ma << 1) & 0x1fff) + ca] << 8) | dev->vram[((dev->ma << 1) & 0x1fff) + ca + 1];
				else
					dat = 0;
				dev->ma++;
				for (c = 0; c < 16; c++)
					buffer32->line[dev->displine + 14][(x << 4) + c + 8] = (dat & (32768 >> c)) ? 7 : 0;
				for (c = 0; c < 16; c += 8)
					video_blend((x << 4) + c + 8, dev->displine + 14);
			}
		} else {
			for (x = 0; x < dev->crtc[1]; x++) {
				if (dev->ctrl & 8) {
					/* Undocumented behavior: page 1 in text mode means characters are read
					   from page 1 and attributes from page 0. */
					chr  = dev->charbuffer[x << 1];
					attr = dev->charbuffer[(x << 1) + 1];
				} else
					chr = attr = 0;
				drawcursor = ((dev->ma == ca) && dev->con && dev->cursoron);
				blink = ((dev->blink & 16) && (dev->ctrl & 0x20) && (attr & 0x80) && !drawcursor);

				if (dev->sc == 12 && ((attr & 7) == 1)) {
					for (c = 0; c < 9; c++)
						buffer32->line[dev->displine + 14][(x * 9) + c + 8] = dev->cols[attr][blink][1];
				} else {
					for (c = 0; c < 8; c++)
						buffer32->line[dev->displine + 14][(x * 9) + c + 8] = dev->cols[attr][blink][(fontdatm[chr][dev->sc] & (1 << (c ^ 7))) ? 1 : 0];

					if ((chr & ~0x1f) == 0xc0)
						buffer32->line[dev->displine + 14][(x * 9) + 8 + 8] = dev->cols[attr][blink][fontdatm[chr][dev->sc] & 1];
					else
						buffer32->line[dev->displine + 14][(x * 9) + 8 + 8] = dev->cols[attr][blink][0];
				}
				if (dev->ctrl2 & 0x01)
					dev->ma = (dev->ma + 1) & 0x3fff;
				else
					dev->ma = (dev->ma + 1) & 0x7ff;

				if (drawcursor) {
					for (c = 0; c < 9; c++)
						buffer32->line[dev->displine + 14][(x * 9) + c + 8] ^= dev->cols[attr][0][1];
				}
			}
		}

		hercules_render_overscan_right(dev);
	}
	dev->sc = oldsc;

	if (dev->vc == dev->crtc[7] && !dev->sc)
		dev->stat |= 8;
	dev->displine++;
	if (dev->displine >= 500) 
		dev->displine = 0;
    } else {
	timer_advance_u64(&dev->timer, dev->dispontime);

	if (dev->dispon)
		dev->stat &= ~1;

	dev->linepos = 0;
	if (dev->vsynctime) {
		dev->vsynctime--;
		if (! dev->vsynctime)
				dev->stat &= ~8;
	}

	if (dev->sc == (dev->crtc[11] & 31) ||
	    ((dev->crtc[8] & 3)==3 && dev->sc == ((dev->crtc[11] & 31) >> 1))) {
		dev->con = 0; 
		dev->coff = 1; 
	}

	if (dev->vadj) {
		dev->sc++;
		dev->sc &= 31;
		dev->ma = dev->maback;
		dev->vadj--;
		if (! dev->vadj) {
			dev->dispon = 1;
			dev->ma = dev->maback = (dev->crtc[13] | (dev->crtc[12] << 8)) & 0x3fff;
			dev->sc = 0;
		}
	} else if (((dev->crtc[8] & 3) != 3 && dev->sc == dev->crtc[9]) || ((dev->crtc[8] & 3) == 3 && dev->sc == (dev->crtc[9] >> 1))) {
		dev->maback = dev->ma;
		dev->sc = 0;
		oldvc = dev->vc;
		dev->vc++;
		dev->vc &= 127;

		if (dev->vc == dev->crtc[6]) 
			dev->dispon = 0;

		if (oldvc == dev->crtc[4]) {
			dev->vc = 0;
			dev->vadj = dev->crtc[5];
			if (! dev->vadj) {
				dev->dispon = 1;
				dev->ma = dev->maback = (dev->crtc[13] | (dev->crtc[12] << 8)) & 0x3fff;
			}
			switch (dev->crtc[10] & 0x60) {
				case 0x20:
					dev->cursoron = 0;
					break;
				case 0x60:
					dev->cursoron = dev->blink & 0x10;
					break;
				default:
					dev->cursoron = dev->blink & 0x08;
					break;
			}
		}

		if (dev->vc == dev->crtc[7]) {
			dev->dispon = 0;
			dev->displine = 0;
			if ((dev->crtc[8] & 3) == 3)
				dev->vsynctime = ((int32_t)dev->crtc[4] * ((dev->crtc[9] >> 1) + 1)) + dev->crtc[5] - dev->crtc[7] + 1;
			else
				dev->vsynctime = ((int32_t)dev->crtc[4] * (dev->crtc[9] + 1)) + dev->crtc[5] - dev->crtc[7] + 1;
			if (dev->crtc[7]) {
				if (dev->ctrl & 0x02)
					x = dev->crtc[1] << 4;
				else
					x = dev->crtc[1] * 9;

				dev->lastline++;
				y = (dev->lastline - dev->firstline);

				if ((dev->ctrl & 8) && x && y && ((x != xsize) || (y != ysize) || video_force_resize_get())) {
					xsize = x;
					ysize = y;
					if (xsize < 64) xsize = enable_overscan ? 640 : 656;
					if (ysize < 32) ysize = 200;

					set_screen_size(xsize + (enable_overscan ? 16 : 0), ysize + (enable_overscan ? 28 : 0));

					if (video_force_resize_get())
						video_force_resize_set(0);
				}

				if ((x >= 160) && ((y + 1) >= 120)) {
					/* Draw (overscan_size) lines of overscan on top and bottom. */
					for (yy = 0; yy < 14; yy++) {
						p = &(buffer32->line[(dev->firstline + yy) & 0x7ff][0]);

						for (xx = 0; xx < (x + 16); xx++)
							p[xx] = 0x00000000;
					}

					for (yy = 0; yy < 14; yy++) {
						p = &(buffer32->line[(dev->firstline + 14 + y + yy) & 0x7ff][0]);

						for (xx = 0; xx < (x + 16); xx++)
							p[xx] = 0x00000000;
					}
				}

				if (enable_overscan)
					video_blit_memtoscreen_8(0, dev->firstline, 0, ysize + 28, xsize + 16, ysize + 28);
				else
					video_blit_memtoscreen_8(8, dev->firstline + 14, 0, ysize + 14, xsize, ysize);
				frames++;
				// if ((dev->ctrl & 2) && (dev->ctrl2 & 1)) {
				if (dev->ctrl & 0x02) {
					video_res_x = dev->crtc[1] * 16;
					video_res_y = dev->crtc[6] * 4;
					video_bpp = 1;
				} else {
					video_res_x = dev->crtc[1];
					video_res_y = dev->crtc[6];
					video_bpp = 0;
				}
			}
			dev->firstline = 1000;
			dev->lastline = 0;
			dev->blink++;
		}
	} else {
		dev->sc++;
		dev->sc &= 31;
		dev->ma = dev->maback;
	}

	if ((dev->sc == (dev->crtc[10] & 31) ||
	    ((dev->crtc[8] & 3)==3 && dev->sc == ((dev->crtc[10] & 31) >> 1))))
		dev->con = 1;
	if (dev->dispon && !(dev->ctrl & 0x02)) {
		for (x = 0; x < (dev->crtc[1] << 1); x++) {
    			pa = (dev->ctrl & 0x80) ? ((x & 1) ? 0x0000 : 0x8000) : 0x0000;
			dev->charbuffer[x] = dev->vram[(((dev->ma << 1) + x) & 0x3fff) + pa];
		}
	}
    }
}


static void *
hercules_init(const device_t *info)
{
    hercules_t *dev;
    int c;

    dev = (hercules_t *)malloc(sizeof(hercules_t));
    memset(dev, 0x00, sizeof(hercules_t));

    overscan_x = 16;
    overscan_y = 28;

    dev->vram = (uint8_t *)malloc(0x10000);

    timer_add(&dev->timer, hercules_poll, dev, 1);

    mem_mapping_add(&dev->mapping, 0xb0000, 0x08000,
		    hercules_read,NULL,NULL, hercules_write,NULL,NULL,
		    NULL /*dev->vram*/, MEM_MAPPING_EXTERNAL, dev);

    io_sethandler(0x03b0, 16,
		  hercules_in,NULL,NULL, hercules_out,NULL,NULL, dev);

    for (c = 0; c < 256; c++) {
	dev->cols[c][0][0] = dev->cols[c][1][0] = dev->cols[c][1][1] = 16;

	if (c & 0x08)
		dev->cols[c][0][1] = 15 + 16;
	  else
		dev->cols[c][0][1] =  7 + 16;
    }
    dev->cols[0x70][0][1] = 16;
    dev->cols[0x70][0][0] = dev->cols[0x70][1][0] =
		dev->cols[0x70][1][1] = 16 + 15;
    dev->cols[0xF0][0][1] = 16;
    dev->cols[0xF0][0][0] = dev->cols[0xF0][1][0] =
		dev->cols[0xF0][1][1] = 16 + 15;
    dev->cols[0x78][0][1] = 16 + 7;
    dev->cols[0x78][0][0] = dev->cols[0x78][1][0] =
		dev->cols[0x78][1][1] = 16 + 15;
    dev->cols[0xF8][0][1] = 16 + 7;
    dev->cols[0xF8][0][0] = dev->cols[0xF8][1][0] =
		dev->cols[0xF8][1][1] = 16 + 15;
    dev->cols[0x00][0][1] = dev->cols[0x00][1][1] = 16;
    dev->cols[0x08][0][1] = dev->cols[0x08][1][1] = 16;
    dev->cols[0x80][0][1] = dev->cols[0x80][1][1] = 16;
    dev->cols[0x88][0][1] = dev->cols[0x88][1][1] = 16;

    overscan_x = overscan_y = 0;

    cga_palette = device_get_config_int("rgb_type") << 1;
    if (cga_palette > 6)
	cga_palette = 0;
    cgapal_rebuild();

    herc_blend = device_get_config_int("blend");

    video_inform(VIDEO_FLAG_TYPE_MDA, &timing_hercules);

    /* Force the LPT3 port to be enabled. */
    lpt3_init(0x3BC);

    return(dev);
}


static void
hercules_close(void *priv)
{
    hercules_t *dev = (hercules_t *)priv;

    if (!dev)
	return;

    if (dev->vram)
	free(dev->vram);

    free(dev);
}


static void
speed_changed(void *priv)
{
    hercules_t *dev = (hercules_t *)priv;
	
    recalc_timings(dev);
}


static const device_config_t hercules_config[] = {
    {
	"rgb_type", "Display type", CONFIG_SELECTION, "", 0, "", { 0 },
	{
		{
			"Default", 0
		},
		{
			"Green", 1
		},
		{
			"Amber", 2
		},
		{
			"Gray", 3
		},
		{
			""
		}
	}
    },
    {
	"blend", "Blend", CONFIG_BINARY, "", 1
    },
    {
	"", "", -1
    }
};

const device_t hercules_device = {
    "Hercules",
    DEVICE_ISA,
    0,
    hercules_init, hercules_close, NULL,
    { NULL },
    speed_changed,
    NULL,
    hercules_config
};