#include <stdint.h>
#include <stdbool.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <string.h>
#include "lodepng.h"
#include "gb.h"

#define SKIP_FRAMES 1200
#define NUM_FRAMES 60
// #define SKIP_STEPS 1000000
#define NUM_STEPS 300000
#define UNUSED(a) ((void) (a))

static uint32_t
file_size(
  const char * const path
) {
  struct stat st;

  if (stat(path, &st)) {
    perror("stat():");
    exit(EXIT_FAILURE);
  }

  return st.st_size;
}

static const uint8_t *
load(
  const char * const path,
  uint32_t * const r_file_size
) {
  const uint32_t rom_size = file_size(path);
  uint8_t *rom_data = malloc(rom_size);
  if (!rom_data) {
    perror("malloc():");
    exit(EXIT_FAILURE);
  }

  FILE *fh = fopen(path, "rb");
  if (!fh) {
    perror("fopen():");
    exit(EXIT_FAILURE);
  }

  if (!fread(rom_data, rom_size, 1, fh)) {
    perror("fread():");
    exit(EXIT_FAILURE);
  }

  fclose(fh);

  if (r_file_size) {
    *r_file_size = (uint32_t) rom_size;
  }
  
  return rom_data;
}

// buffer for rendered frames
static uint8_t frames[NUM_FRAMES * GB_FB_SIZE];

static void
on_set_rom_bank(
  const gb_t * const ctx,
  const uint16_t bank
) {
  printf("set rom bank: bank = %u, PC = %04x\n", bank, ctx->cpu.rs[5]);
}

static void
on_set_ram_bank(
  const gb_t * const ctx,
  const uint16_t bank
) {
  printf("set ram bank: bank = %u, PC = %04x\n", bank, ctx->cpu.rs[5]);
}

static void
on_vblank(
  const gb_t * const ctx
) {
  printf("vblank: PC = %04x\n", ctx->cpu.rs[5]);
}

static void
on_hblank(
  const gb_t * const ctx
) {
  printf("hblank: PC = %04x\n", ctx->cpu.rs[5]);
}

static void
on_timer(
  const gb_t * const ctx
) {
  printf("timer: PC = %04x\n", ctx->cpu.rs[5]);
}

/* 
 * static void
 * on_gpu_step(
 *   const gb_t * const ctx
 * ) {
 *   printf("gpu step: gpu clock = 0x%04x\n", ctx->gpu.clock);
 * }
 */ 

static void
on_gpu_set_mode(
  const gb_t * const ctx,
  const uint8_t mode
) {
  UNUSED(ctx);
  printf("gpu mode: %u, line = %u\n", mode, ctx->gpu.line);
}

static void
on_set_cpu_state(
  const gb_t * const ctx,
  const gb_cpu_state_t state
) {
  printf("cpu state: PC = %04x, state = %d\n", ctx->cpu.rs[5], state);
}

static void
on_rst(
  const gb_t * const ctx,
  const uint16_t addr
) {
  UNUSED(ctx);
  printf("rst: addr = %04x\n", addr);
}

/* 
 * static void
 * on_mmu_rb(
 *   const gb_t * const ctx,
 *   const uint16_t addr,
 *   const uint8_t val
 * ) {
 *   UNUSED(ctx);
 *   printf("mmu_rb: addr = 0x%04X, val = 0x%02X\n", addr, val);
 * }
 */ 

/* 
 * static void
 * on_mmu_wb(
 *   const gb_t * const ctx,
 *   const uint16_t addr,
 *   const uint8_t val
 * ) {
 *   UNUSED(ctx);
 *   printf("mmu_wb: addr = 0x%04X, val = 0x%02X\n", addr, val);
 * }
 */ 

static void
on_oam_wb(
  const gb_t * const ctx,
  const uint16_t addr,
  const uint8_t val
) {
  UNUSED(ctx);
  printf("oam_wb: addr = 0x%04X, val = 0x%02X\n", addr, val);
}

static const gb_config_t
EXECUTE_CONFIG = {
  .on_set_rom_bank  = on_set_rom_bank,
  .on_set_ram_bank  = on_set_ram_bank,
  .on_vblank        = on_vblank,
  .on_hblank        = on_hblank,
  .on_timer         = on_timer,
  // .on_gpu_step      = on_gpu_step,
  .on_gpu_set_mode  = on_gpu_set_mode,
  .on_set_cpu_state = on_set_cpu_state,
  .on_rst           = on_rst,
  // .on_mmu_rb        = on_mmu_rb,
  // .on_mmu_wb        = on_mmu_wb,
  .on_oam_wb        = on_oam_wb,
};

static void
test_render_frames(
  const char * const png_path,
  const char * const rom_path
) {
  // load rom data
  uint32_t rom_size = 0;
  const uint8_t *rom_data = load(rom_path, &rom_size);
  fprintf(stderr, "loaded \"%s\" (%u bytes)\n", rom_path, rom_size);

  // init context
  gb_t ctx;
  gb_init(&ctx, NULL, rom_data, rom_size);
  fprintf(stderr, "gb context initialized\n");

  for (size_t i = 0; i < SKIP_FRAMES; i++) {
    // render frame
    gb_frame(&ctx);
  }

  // render frames
  for (size_t i = 0; i < NUM_FRAMES; i++) {
    // render frame
    gb_frame(&ctx);

    // copy frame to buffer
    memcpy(frames + GB_FB_SIZE * i, gb_get_frame(&ctx), GB_FB_SIZE);
  }

  // save png
  if (lodepng_encode24_file(png_path, frames, 160, 144 * NUM_FRAMES)) {
    fprintf(stderr, "lode_png_encode24_file() failed\n");
    exit(EXIT_FAILURE);
  }
  fprintf(stderr, "%d frames rendered\n", NUM_FRAMES);

  // free rom data
  free((void*) rom_data);
}

const char * const RWS[] = {
  "AF",
  "BC",
  "DE",
  "HL",
  "SP",
  "PC",
  NULL
};

static void
gb_dump_context(
  gb_t * const ctx
) {
  for (int i = 0; RWS[i]; i++) {
    printf("%s:%04X ", RWS[i], ctx->cpu.rs[i]);
  }

  char buf[128];
  size_t buf_len = sizeof(buf);
  if (gb_disasm(ctx, buf, &buf_len)) {
    printf("%s\n", buf);
  } else {
    printf("\n");
  }
}

static void
test_execute_steps(
  const char * const rom_path
) {
  // load rom data
  uint32_t rom_size = 0;
  const uint8_t *rom_data = load(rom_path, &rom_size);
  fprintf(stderr, "loaded \"%s\" (%u bytes)\n", rom_path, rom_size);

  // init context
  gb_t ctx;
  gb_init(&ctx, &EXECUTE_CONFIG, rom_data, rom_size);
  fprintf(stderr, "gb context initialized\n");

#ifdef SKIP_STEPS
  for (size_t i = 0; i < SKIP_STEPS; i++) {
    // step cpu
    gb_step(&ctx);
  }
#endif /* SKIP_STEPS */

  // run cpu
  for (size_t i = 0; i < NUM_STEPS; i++) {
    // print context
    gb_dump_context(&ctx);

    // step cpu
    gb_step(&ctx);
  }

  // free rom data
  free((void*) rom_data);
}

static const uint8_t
TEST_IMAGE[] = {
  0xFF, 0x00, 0x00,   0x00, 0xFF, 0x00,   0x00, 0x00, 0xFF,
  0x00, 0xFF, 0x00,   0x00, 0x00, 0xFF,   0xFF, 0x00, 0x00,
  0x00, 0x00, 0xFF,   0xFF, 0x00, 0x00,   0x00, 0xFF, 0x00,
};

static void
test_write_image(
  const char * const img_path
) {
  // save png
  if (lodepng_encode24_file(img_path, TEST_IMAGE, 3, 3)) {
    fprintf(stderr, "lode_png_encode24_file() failed\n");
    exit(EXIT_FAILURE);
  }
  fprintf(stderr, "saved image as \"%s\"\n", img_path);
}

int main(int argc, char *argv[]) {
  // render 600 frames
  for (int i = 2; i < argc; i++) {
    if (argv[1][0] == 'f') {
      test_render_frames("out.png", argv[i]);
    } else if (argv[1][0] == 'e') {
      test_execute_steps(argv[i]);
    } else if (argv[1][0] == 'i') {
      test_write_image(argv[i]);
    } else {
      fprintf(stderr, "unknown test: %s\n", argv[i]);
      exit(EXIT_FAILURE);
    }
  }

  // return success
  return 0;
}