/*
 * fbvncserver.c
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; either version 2, or (at your option) any
 * later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * Taken from the original fbvncserver for the iPAQ and Zaurus.
 * 	http://fbvncserver.sourceforge.net/
 *
 * Modified by Jim Huang <jserv.tw@gmail.com>
 * 	- Simplified and sizing down
 * 	- Performance tweaks
 *
 * NOTE: depends libvncserver.
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <unistd.h>
#include <sys/mman.h>
#include <sys/ioctl.h>

#include <sys/stat.h>
#include <sys/sysmacros.h>             /* For makedev() */

#include <fcntl.h>
#include <linux/fb.h>

#include <assert.h>
#include <errno.h>

/* libvncserver */
#include "rfb/rfb.h"
#include "rfb/keysym.h"

/* framebuffer */
#define FB_DEVICE "/dev/fb0"
static struct fb_var_screeninfo scrinfo;
static int fbfd = -1;
static unsigned short int *fbmmap = MAP_FAILED;
static unsigned short int *vncbuf;
static unsigned short int *fbbuf;

#define VNC_PORT 5900
static rfbScreenInfoPtr vncscr;

/* part of the frame differerencing algorithm. */
static struct varblock_t {
	int min_i;
	int min_j;
	int max_i;
	int max_j;
	int r_offset;
	int g_offset;
	int b_offset;
	int rfb_xres;
	int rfb_maxy;
} varblock;

/* event handler callback */
static void keyevent(rfbBool down, rfbKeySym key, rfbClientPtr cl);
static void ptrevent(int buttonMask, int x, int y, rfbClientPtr cl);

static void init_fb(void)
{
	size_t pixels;
	size_t bytespp;

	if ((fbfd = open(FB_DEVICE, O_RDONLY)) == -1) {
		perror("open");
		exit(EXIT_FAILURE);
	}

	if (ioctl(fbfd, FBIOGET_VSCREENINFO, &scrinfo) != 0) {
		perror("ioctl");
		exit(EXIT_FAILURE);
	}

	pixels = scrinfo.xres * scrinfo.yres;
	bytespp = scrinfo.bits_per_pixel / 8;

	fprintf(stderr, "xres=%d, yres=%d, "
			"xresv=%d, yresv=%d, "
			"xoffs=%d, yoffs=%d, "
			"bpp=%d\n", 
	  (int)scrinfo.xres, (int)scrinfo.yres,
	  (int)scrinfo.xres_virtual, (int)scrinfo.yres_virtual,
	  (int)scrinfo.xoffset, (int)scrinfo.yoffset,
	  (int)scrinfo.bits_per_pixel);

	fbmmap = mmap(NULL, pixels * bytespp, PROT_READ, MAP_SHARED, fbfd, 0);

	if (fbmmap == MAP_FAILED) {
		perror("mmap");
		exit(EXIT_FAILURE);
	}
}

static void cleanup_fb(void)
{
	/* TODO */
}

static void init_fb_server(int argc, char **argv)
{
	printf("Initializing server...\n");

	/* Allocate the VNC server buffer to be managed (not manipulated) by 
	 * libvncserver. */
	vncbuf = calloc(scrinfo.xres * scrinfo.yres, scrinfo.bits_per_pixel / 2);
	assert(vncbuf != NULL);

	/* Allocate the comparison buffer for detecting drawing updates from frame
	 * to frame. */
	fbbuf = calloc(scrinfo.xres * scrinfo.yres, scrinfo.bits_per_pixel / 2);
	assert(fbbuf != NULL);

	/* FIXME: This assumes scrinfo.bits_per_pixel is 16. */
	vncscr = rfbGetScreen(&argc, argv, scrinfo.xres, scrinfo.yres, 5, 2, 2);
	assert(vncscr != NULL);

	vncscr->desktopName = "AG101";
	vncscr->frameBuffer = (char *)vncbuf;
	vncscr->alwaysShared = TRUE;
	vncscr->httpDir = NULL;
	vncscr->port = VNC_PORT;

	vncscr->kbdAddEvent = keyevent;
	vncscr->ptrAddEvent = ptrevent;

	rfbInitServer(vncscr);

	/* Mark as dirty since we haven't sent any updates at all yet. */
	rfbMarkRectAsModified(vncscr, 0, 0, scrinfo.xres, scrinfo.yres);

	/* No idea. */
	varblock.r_offset = scrinfo.red.offset + scrinfo.red.length - 5;
	varblock.g_offset = scrinfo.green.offset + scrinfo.green.length - 5;
	varblock.b_offset = scrinfo.blue.offset + scrinfo.blue.length - 5;
	varblock.rfb_xres = scrinfo.yres;
	varblock.rfb_maxy = scrinfo.xres - 1;
}

static void keyevent(rfbBool down, rfbKeySym key, rfbClientPtr cl)
{
	/* XXX */
}

static void ptrevent(int buttonMask, int x, int y, rfbClientPtr cl)
{
	/* XXX */
}

#define PIXEL_FB_TO_RFB(p,r,g,b) \
	((p >> r) & 0x1f001f) | \
	(((p >> g) & 0x1f001f) << 5) | \
	(((p >> b) & 0x1f001f) << 10)

static void update_screen(void)
{
	unsigned int *f, *c, *r;
	int x, y;

	varblock.min_i = varblock.min_j = 9999;
	varblock.max_i = varblock.max_j = -1;

	f = (unsigned int *)fbmmap;        /* -> framebuffer         */
	c = (unsigned int *)fbbuf;         /* -> compare framebuffer */
	r = (unsigned int *)vncbuf;        /* -> remote framebuffer  */

	for (y = 0; y < scrinfo.yres; y++) {
		/* Compare every 2 pixels at a time, assuming that changes are
		 * likely in pairs. */
		for (x = 0; x < scrinfo.xres; x += 2) {
			unsigned int pixel = *f;

			if (pixel != *c) {
				*c = pixel;

				/* XXX: Undo the checkered pattern to test the
				 * efficiency gain using hextile encoding. */
				if (pixel == 0x18e320e4 || pixel == 0x20e418e3)
					pixel = 0x18e318e3;

				*r = PIXEL_FB_TO_RFB(pixel,
				                     varblock.r_offset,
						     varblock.g_offset,
						     varblock.b_offset);

				if (x < varblock.min_i)
					varblock.min_i = x;
				else {
					if (x > varblock.max_i)
						varblock.max_i = x;

					if (y > varblock.max_j)
						varblock.max_j = y;
					else if (y < varblock.min_j)
						varblock.min_j = y;
				}
			}

			f++, c++;
			r++;
		}
	}

	if (varblock.min_i < 9999) {
		if (varblock.max_i < 0)
			varblock.max_i = varblock.min_i;

		if (varblock.max_j < 0)
			varblock.max_j = varblock.min_j;

		fprintf(stderr, "Dirty page: %dx%d+%d+%d...\n",
		  (varblock.max_i + 2) - varblock.min_i,
		  (varblock.max_j + 1) - varblock.min_j,
		  varblock.min_i, varblock.min_j);

		rfbMarkRectAsModified(vncscr, varblock.min_i, varblock.min_j,
		  varblock.max_i + 2, varblock.max_j + 1);

		rfbProcessEvents(vncscr, 10000);
	}
}

int main(int argc, char **argv)
{
	printf("Initializing framebuffer device " FB_DEVICE "...\n");
	init_fb();

	printf("Initializing Framebuffer VNC server:\n");
	printf("	width:  %d\n", (int)scrinfo.xres);
	printf("	height: %d\n", (int)scrinfo.yres);
	printf("	bpp:    %d\n", (int)scrinfo.bits_per_pixel);
	printf("	port:   %d\n", (int)VNC_PORT);
	init_fb_server(argc, argv);

	/* Implement our own event loop to detect changes in the framebuffer. */
	while (1) {
		while (vncscr->clientHead == NULL)
			rfbProcessEvents(vncscr, 100000);

		rfbProcessEvents(vncscr, 100000);
		update_screen();
	}

	printf("Cleaning up...\n");
	cleanup_fb();
	return 0;
}