#include <errno.h>
#include "nebulae.h"

#ifdef _POSIX_SOURCE
#include <unistd.h>
#include <sys/types.h>
#include <fcntl.h>
#endif

#include "lephisto.h"
#include "log.h"
#include "lfile.h"
#include "perlin.h"

/* -- CUSTOM NEBULAE FORMAT. --
 * Header (16 byte string).
 * Dimesnions (4 byte w and 4 byte h).
 * Body (1 byte per pixel).
 */

#define NEBU_FORMAT_HEADER    16  /* Size of header. */
#define NEBU_VERSION          "1" /* Will be used for version checking. */

#define NEBULAE_Z             32  /* Z plane. */
#define NEBULAE_PATH          "gen/nebu_%02d.nebu"

/* The nebulae textures. */
static GLuint nebu_textures[NEBULAE_Z];
static int nebu_w, nebu_h, nebu_pw, nebu_ph;

static int nebu_checkCompat(const char* file);
static void saveNebulae(float* map, const uint32_t w, const uint32_t h,
    const char* file);
static unsigned char* loadNebulae(const char* file, int* w, int* h);

void nebu_init(void) {
  int i;
  char nebu_file[PATH_MAX];
  unsigned char* nebu_padded;
  int w, h;
  unsigned char* nebu_data;

  /* Set expected sizes. */
  nebu_w = SCREEN_W;
  nebu_h = SCREEN_H;
  nebu_pw = gl_pot(nebu_w);
  nebu_ph = gl_pot(nebu_h);

  /* Load each, checking for compatibility and padding. */
  nebu_padded = malloc(nebu_pw * nebu_ph);
  glGenTextures(NEBULAE_Z, nebu_textures);
  for(i = 0; i < NEBULAE_Z; i++) {
    snprintf(nebu_file, PATH_MAX, NEBULAE_PATH, i);

    if(nebu_checkCompat(nebu_file)) { /* Incompatable. */
      LOG("No nebulae found, generating (this may take a while).");

      /* So we generate and reload. */
      free(nebu_padded);
      nebu_generate(nebu_w, nebu_h);
      nebu_init();
      return;
    }

    /* Load the file. */
    nebu_data = loadNebulae(nebu_file, &w, &h);
    memcpy(nebu_padded, nebu_data, w*h);

    /* Load the textures. */
    glBindTexture(GL_TEXTURE_2D, nebu_textures[i]);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_ALPHA8, nebu_pw, nebu_ph,
        0, GL_ALPHA, GL_UNSIGNED_BYTE, nebu_padded);
    gl_checkErr();

    free(nebu_data); /* No longer need the data. */
  }
  free(nebu_padded);
}

/* Clean up the nebu subsystem. */
void nebu_exit(void) {
  glDeleteTextures(NEBULAE_Z, nebu_textures);
}

/* Force generation of new nebulae. */
void nebu_generate(const int w, const int h) {
  int i;
  float* nebu;
  char nebu_file[PATH_MAX];

  /* Generate all the nebulae. */
  nebu = noise_genNebulaeMap(w, h, NEBULAE_Z, 15.);
  lfile_dirMakeExist("gen");

  /* Save each nebulae as an image. */
  for(i = 0; i < NEBULAE_Z; i++) {
    snprintf(nebu_file, PATH_MAX, NEBULAE_PATH, i);
    saveNebulae(&nebu[i*w*h], w, h, nebu_file);
  }

  /* Cleanup. */
  free(nebu);
}

/* Check the validity of a nebulae. 0 on success. */
static int nebu_checkCompat(const char* file) {
  if(lfile_fileExists(file) == 0) /* First check to see if file exists. */
    return -1;
  return 0;
}

/* Save a nebulae. */
static void saveNebulae(float* map, const uint32_t w, const uint32_t h,
    const char* file) {
  
  int x, y;
  char* buf;
  unsigned char c;
  int cur;
  ssize_t size;
  char file_path[PATH_MAX];

  size = w*h + 16 + 4;
  buf = malloc(size);

  /* Write the header. */
  memset(buf, '0', 16);
  snprintf(buf, NEBU_FORMAT_HEADER, "LEPHISTO NEBU v" NEBU_VERSION);
  cur = 16;
  memcpy(&buf[cur], &w, 4);
  memcpy(&buf[cur], &h, 4);
  cur += 8;

  /* The Body. */
  for(y = 0; y < (int)h; y++)
    for(x = 0; x < (int)w; x++) {
      c = (unsigned char) 255.*map[y*w + x];
      memcpy(&buf[cur++], &c, 1);
    }

  /* Write to a file. */
  snprintf(file_path, PATH_MAX, "%s%s", lfile_basePath(), file);
#ifdef _POSIX_SOURCE
  int fd;
  fd = open(file_path, O_WRONLY | O_CREAT | O_TRUNC,
      S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);

  if(fd < 0) {
    ERR("Unable to open file %s: %s", file, strerror(errno));
    return;
  }
  if(write(fd, buf, size) != size) {
    ERR("Error writing nebulae to %s: %s", file, strerror(errno));
    return;
  }
  close(fd);
#else
#error "Needs implementation."
#endif
}

/* Load the nebulae from file. */
static unsigned char* loadNebulae(const char* file, int* w, int* h) {
  unsigned char* buf;
  char header[16];
  uint32_t tw, th;
  ssize_t len;
  char file_path[PATH_MAX];

#ifdef _POSIX_SOURCE
#define READ(b, l) \
  len = read(fd, b, l); \
  if(len < l) {\
    WARN("Read too few bytes from %s: %s", file, strerror(errno)); \
    return NULL; \
  }

  int fd;
  snprintf(file_path, PATH_MAX, "%s%s", lfile_basePath(), file);
  fd = open(file, O_RDONLY);
  if(fd < 0) {
    ERR("Unable to open file %s: %s", file_path, strerror(errno));
    return NULL;
  }
  READ(header, 16);
  READ(&tw, 4);
  READ(&th, 4);
  buf = malloc(tw*th);
  READ(buf, tw*th);
#else
#error "Needs implementation."
#endif
  (*w) = (int)tw;
  (*h) = (int)th;

  return buf;
}