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

#include <unistd.h>
#include <sys/stat.h>
#include <fcntl.h>

#define WBUF_SIZE 32

static int fifo_fd;

#define VGASIM_CMD_INIT  0x01
#define VGASIM_CMD_RESET 0x02
#define VGASIM_CMD_TICK  0x03

int vgasim_init(int screen_h, int screen_w, int screen_bpp) {
  int ret;
  ssize_t  bytes_written, bytes_written_total;
  ssize_t  pkt_size;
  char     wbuf[WBUF_SIZE];
  uint16_t *wbuf_ptr;
  printf("dpi: vgasim_init: %d x %d x %d\n", screen_h, screen_w, screen_bpp);

  ret = open("/tmp/vgasim", O_WRONLY | O_NONBLOCK);
  if (ret == -1) {
    printf("dpi: vgasim_init: failed (%d)\n", errno);
    return 1;
  }

  fifo_fd = ret;

  wbuf_ptr = (uint16_t*)wbuf;

  *wbuf_ptr++ = VGASIM_CMD_INIT;
  *wbuf_ptr++ = (uint16_t)screen_h;
  *wbuf_ptr++ = (uint16_t)screen_w;
  *wbuf_ptr++ = (uint16_t)screen_bpp;

  pkt_size = 4 * sizeof(uint16_t);

  bytes_written_total = 0;
  do {
    bytes_written = write(fifo_fd, wbuf + bytes_written_total, pkt_size - bytes_written_total);
    if (bytes_written < 0) {
      printf("dpi: vgasim_init: write error (%d): %s\n", errno, strerror(errno));
      return 2;
    }
    bytes_written_total += bytes_written;
  } while (bytes_written_total < pkt_size);

  return 0;
}

int vgasim_reset() {
  int ret;
  ssize_t  bytes_written, bytes_written_total;
  ssize_t  pkt_size;
  char     wbuf[WBUF_SIZE];
  uint16_t *wbuf_ptr;

  printf("dpi: vgasim_reset\n");

  wbuf_ptr = (uint16_t*)wbuf;
  *wbuf_ptr++ = VGASIM_CMD_RESET;
  pkt_size = sizeof(uint16_t);

  bytes_written_total = 0;
  do {
    bytes_written = write(fifo_fd, wbuf + bytes_written_total, pkt_size - bytes_written_total);
    if (bytes_written < 0) {
      printf("dpi: vgasim_init: write error (%d): %s\n", errno, strerror(errno));
      return 2;
    }
    bytes_written_total += bytes_written;
  } while (bytes_written_total < pkt_size);

  return 0;
}

int vgasim_tick(int r, int g, int b, int hsync, int vsync) {
  int ret;
  ssize_t  bytes_written, bytes_written_total;
  ssize_t  pkt_size;
  char     wbuf[WBUF_SIZE];
  uint16_t *wbuf_ptr16;
  uint8_t *wbuf_ptr8;

  //printf("dpi: vgasim_tick: %X, %X, %X (%s%s)\n", r, g, b, hsync ? "h" : "", vsync ? "v" : "");

  wbuf_ptr16 = (uint16_t*)wbuf;
  *wbuf_ptr16++ = VGASIM_CMD_TICK;
  wbuf_ptr8 = (uint8_t*)wbuf_ptr16;
  *wbuf_ptr8++ = (uint8_t)r;
  *wbuf_ptr8++ = (uint8_t)g;
  *wbuf_ptr8++ = (uint8_t)b;
  *wbuf_ptr8++ = (uint8_t)((vsync ? 0x02 : 0x00) | (hsync ? 0x01 : 0x00));
  pkt_size = sizeof(uint16_t) + 4 * sizeof(uint8_t);

  bytes_written_total = 0;
  do {
    bytes_written = write(fifo_fd, wbuf + bytes_written_total, pkt_size - bytes_written_total);
    if (bytes_written < 0) {
      printf("dpi: vgasim_init: write error (%d): %s\n", errno, strerror(errno));
      return 2;
    }
    bytes_written_total += bytes_written;
  } while (bytes_written_total < pkt_size);

  return 0;
}