// x-run: ~/scripts/runc.sh % -Wall -Wextra -std=c99 -pedantic -lm --- ~/images/boykisser.png cpi-images/boykisser.cpi
#define STB_IMAGE_IMPLEMENTATION
#include <stb/stb_image.h>
#define STB_IMAGE_RESIZE_IMPLEMENTATION
#include <stb/stb_image_resize2.h>
#include <argp.h>
#include <stdio.h>
#include <getopt.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include <strings.h>
#include <stdbool.h>

#define MAX_COLOR_DIFFERENCE 768

struct arguments {
  bool text_mode;
  int width, height;
  enum cpi_version {
    CPI_VERSION_AUTO,
    CPI_VERSION_0,
    CPI_VERSION_1,
    CPI_VERSION_2,
  } cpi_version;
  enum placement {
    PLACEMENT_CENTER,
    PLACEMENT_COVER,
    PLACEMENT_TILE,
    PLACEMENT_FULL,
    PLACEMENT_EXTEND,
    PLACEMENT_FILL
  } placement;
  char *input_path;
  char *output_path;
} args = {
  .text_mode = false,
  .width = 4 * 8 - 1,
  .height = 3 * 6 - 2,
  .cpi_version = CPI_VERSION_AUTO,
  .placement = PLACEMENT_FULL,
  .input_path = NULL,
  .output_path = NULL
};

struct image {
  int w, h;
  union color { // Alpha channel is not used, it's just there to align it all
    struct rgba { uint8_t r, g, b, a; } rgba;
    uint32_t v;
  } *pixels;
};

bool parse_cmdline(int argc, char **argv);
void show_help(const char *progname, bool show_all, FILE *fp);
struct image *image_load(const char *fp);
struct image *image_new(int w, int h);
struct image *image_resize(struct image *original, int new_w, int new_h);
struct image *image_dither(struct image *original, union color *colors, size_t n_colors);
void image_unload(struct image *img);

const char *known_file_extensions[] = {
  ".png", ".jpg", ".jpeg", ".jfif", ".jpg", ".gif",
  ".tga", ".bmp", ".hdr", ".pnm", 0
};

static const struct optiondocs {
  char shortopt;
  char *longopt;
  char *target;
  char *doc;
  struct optiondocs_choice { char *value; char *doc; } *choices;
} optiondocs[] = {
  { 'h', "help",        0,            "Show help", 0 },
  { 't', "textmode",    0,            "Output Lua script instead of binary", 0 },
  { 'W', "width",       "width",      "Width in characters", 0 },
  { 'h', "height",      "height",     "Height in characters", 0 },
  { 'V', "cpi_version", "version",    "Force specific version of CPI",
    (struct optiondocs_choice[]) {
      { "-1", "Choose best available" },
      { "0", "OG CPI, 255x255, uncompressed" },
      { "1", "CPIv1, huge images, uncompressed" },
      { "255", "In-dev version, may not work" },
      { 0, 0 } } },
  { 'p', "placement",   "placement",  "Image placement mode (same as in hsetroot)",
    (struct optiondocs_choice[]){
      { "center", "Render image centered on the canvas" },
      { "cover",  "Centered on screen, scaled to fill fully" },
      { "tile",   "Render image tiled" },
      { "full",   "Use maximum aspect ratio" },
      { "extend", "Same as \"full\", but filling borders" },
      { "fill",   "Stretch to fill" },
      { 0, 0 } } },
  { 0,   0,             "input.*",    "Input file path", 0 },
  { 0,   0,             "output.cpi", "Output file path", 0 },
  { 0 }
};

int main(int argc, char **argv) {
  if (!parse_cmdline(argc, argv)) {
    show_help(argv[0], false, stderr);
    fprintf(stderr, "Fatal error occurred, exiting.\n");
    return EXIT_FAILURE;
  }

  struct image *src_image = image_load(args.input_path);
  if (!src_image) {
    fprintf(stderr, "Error: failed to open the file\n");
    return EXIT_FAILURE;
  }

  struct image *canvas = image_new(args.width * 2, args.height * 3);
  if (!canvas) {
    fprintf(stderr, "Error: failed to allocate second image buffer\n");
    return EXIT_FAILURE;
  }

  // TODO: actually do stuff

  image_unload(src_image);
  image_unload(canvas);
  return EXIT_SUCCESS;
}

bool parse_cmdline(int argc, char **argv) {
  static struct option options[] = {
    { "help",         no_argument,        0, 'h' },
    { "textmode",     no_argument,        0, 't' },
    { "width",        required_argument,  0, 'W' },
    { "height",       required_argument,  0, 'H' },
    { "cpi_version",  required_argument,  0, 'V' },
    { "placement",    required_argument,  0, 'p' },
    { 0,              0,                  0,  0  }
  };

  while (true) {
    int option_index = 0;
    int c = getopt_long(argc, argv, "htW:H:V:p:", options, &option_index);
    if (c == -1) break;
    if (c == 0) c = options[option_index].val;
    if (c == '?') break;

    switch (c) {
      case 'h':
        show_help(argv[0], true, stdout);
        exit(EXIT_SUCCESS);
        break;
      case 't':
        args.text_mode = true;
        if (args.cpi_version != CPI_VERSION_AUTO) {
          fprintf(stderr, "Warning: text mode ignores version\n");
        }
        break;
      case 'W':
        args.width = atoi(optarg);
        break;
      case 'H':
        args.height = atoi(optarg);
        break;
      case 'V':
        {
          int v = atoi(optarg);
          if ((v < -1 || v > 1) && v != 255) {
            fprintf(stderr, "Error: Invalid CPI version: %d\n", args.cpi_version);
            return false;
          }
          args.cpi_version = v == -1 ? CPI_VERSION_AUTO : v;
        }
        break;
      case 'p':
        if (0 == strcmp(optarg, "center")) {
          args.placement = PLACEMENT_CENTER;
        } else if (0 == strcmp(optarg, "cover")) {
          args.placement = PLACEMENT_COVER;
        } else if (0 == strcmp(optarg, "tile")) {
          args.placement = PLACEMENT_TILE;
        } else if (0 == strcmp(optarg, "full")) {
          args.placement = PLACEMENT_FULL; }
        else if (0 == strcmp(optarg, "extend")) {
          args.placement = PLACEMENT_EXTEND;
        } else if (0 == strcmp(optarg, "fill")) {
          args.placement = PLACEMENT_FILL;
        } else {
          fprintf(stderr, "Error: invaild placement %s\n", optarg);
          return false;
        }
        break;
    }
  }

  if (optind == argc) {
    fprintf(stderr, "Error: no input file provided\n");
    return false;
  } else if (optind + 1 == argc) {
    fprintf(stderr, "Error: no output file provided\n");
    return false;
  } else if ((argc - optind) != 2) {
    fprintf(stderr, "Error: too many arguments\n");
    return false;
  }

  args.input_path = argv[optind];
  args.output_path = argv[optind + 1];

  const char *extension = strrchr(args.input_path, '.');
  if (!extension) {
    fprintf(stderr, "Warning: no file extension, reading may fail!\n");
  } else {
    bool known = false;
    for (int i = 0; known_file_extensions[i] != 0; i++) {
      if (0 == strcasecmp(known_file_extensions[i], extension)) {
        known = true;
        break;
      }
    }
    if (!known) {
      fprintf(stderr, "Warning: unknown file extension %s, reading may fail!\n", extension);
    }
  }

  return true;
}

void show_help(const char *progname, bool show_all, FILE *fp) {
  fprintf(fp, "usage: %s", progname);
  for (int i = 0; optiondocs[i].doc != 0; i++) {
    struct optiondocs doc = optiondocs[i];
    fprintf(fp, " [");
    if (doc.shortopt) fprintf(fp, "-%c", doc.shortopt);
    if (doc.shortopt && doc.longopt) fprintf(fp, "|");
    if (doc.longopt) fprintf(fp, "--%s", doc.longopt);
    if (doc.target) {
      if (doc.shortopt || doc.longopt) fprintf(fp, " ");
      fprintf(fp, "%s", doc.target);
    }
    fprintf(fp, "]");
  }
  fprintf(fp, "\n");

  if (!show_all) return;

  fprintf(fp, "\n");
  fprintf(fp, "ComputerCraft Palette Image converter\n");
  fprintf(fp, "\n");
  fprintf(fp, "positional arguments:\n");
  for (int i = 0; optiondocs[i].doc != 0; i++) {
    struct optiondocs doc = optiondocs[i];
    if (!doc.shortopt && !doc.longopt) {
      fprintf(fp, "  %s\t%s\n", doc.target, doc.doc);
    }
  }
  fprintf(fp, "\n");
  fprintf(fp, "options:\n");
  for (int i = 0; optiondocs[i].doc != 0; i++) {
    struct optiondocs doc = optiondocs[i];
    if (!doc.shortopt && !doc.longopt) { continue; }
    fprintf(fp, "  ");
    int x = 2;
    if (doc.shortopt) { fprintf(fp, "-%c", doc.shortopt); x += 2; }
    if (doc.shortopt && doc.longopt) { fprintf(fp, ", "); x += 2; }
    if (doc.longopt) { fprintf(fp, "--%s", doc.longopt); x += strlen(doc.longopt) + 2; }
    if (doc.choices) {
      fprintf(fp, " {");
      for (int j = 0; doc.choices[j].value != 0; j++) {
        if (j > 0) { fprintf(fp, ","); x += 1; }
        fprintf(fp, "%s", doc.choices[j].value);
        x += strlen(doc.choices[j].value);
      }
      fprintf(fp, "}");
      x += 3;
    } else if (doc.target) {
      fprintf(fp, " ");
      fprintf(fp, "%s", doc.target);
      x += strlen(doc.target) + 1;
    }
    if (x > 24) fprintf(fp, "\n%24c", ' ');
    else fprintf(fp, "%*c", 24 - x, ' ');
    fprintf(fp, "%s\n", doc.doc);
    if (doc.choices) {
      for (int j = 0; doc.choices[j].value != 0; j++) {
        fprintf(fp, "%26c", ' ');
        if (doc.shortopt) fprintf(fp, "-%c ", doc.shortopt);
        else if (doc.longopt) fprintf(fp, "--%s", doc.longopt);
        fprintf(fp, "%-12s %s\n", doc.choices[j].value, doc.choices[j].doc);
      }
    }
  }
}

struct image *image_load(const char *fp) {
  struct image *img = calloc(1, sizeof(struct image));
  if (!img) return NULL;
  img->pixels = (union color*)stbi_load(fp, &img->w, &img->h, 0, 4);
  if (!img->pixels) {
    free(img);
    return NULL;
  }
  return img;
}

struct image *image_new(int w, int h) {
  struct image *img = calloc(1, sizeof(struct image));
  if (!img) return NULL;
  img->pixels = calloc(h, sizeof(union color) * w);
  img->w = w;
  img->h = h;
  if (!img->pixels) {
    free(img);
    return NULL;
  }
  return img;
}

struct image *image_resize(struct image *original, int new_w, int new_h) {
  struct image *resized = image_new(new_w, new_h);
  if (!resized) return NULL;
  stbir_resize_uint8_srgb((unsigned char *)original->pixels, original->w, original->h, 0,
                          (unsigned char *)resized->pixels, resized->w, resized->h, 0,
                          STBIR_RGBA);
  return resized;
}

void image_unload(struct image *img) {
  free(img->pixels);
  free(img);
}