#define STB_IMAGE_IMPLEMENTATION
#include "../include/stb_image.h"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <strings.h>
#include <sys/stat.h>

#include "../include/chroma.h"

// Check if file exists and is readable
static int file_exists(const char *path) {
  struct stat st;
  return (stat(path, &st) == 0 && S_ISREG(st.st_mode));
}

// Get file size
static long get_file_size(const char *path) {
  struct stat st;
  if (stat(path, &st) != 0) {
    return -1;
  }
  return st.st_size;
}

// Calculate optimal image size based on output dimensions
static void calculate_optimal_size(int original_width, int original_height,
                                   int max_output_width, int max_output_height,
                                   int *optimal_width, int *optimal_height) {
  // If image is smaller than outputs, keep original size
  if (original_width <= max_output_width &&
      original_height <= max_output_height) {
    *optimal_width = original_width;
    *optimal_height = original_height;
    return;
  }

  // Calculate scale factor to fit within max output dimensions
  float scale_x = (float)max_output_width / original_width;
  float scale_y = (float)max_output_height / original_height;
  float scale = (scale_x < scale_y) ? scale_x : scale_y;

  // Apply scale factor with minimum size to avoid too small images
  scale = (scale > 1.0f) ? 1.0f : scale;
  scale = (scale < 0.25f) ? 0.25f : scale; // XXX: don't scale below 25%

  *optimal_width = (int)(original_width * scale);
  *optimal_height = (int)(original_height * scale);

  // Ensure even dimensions for better GPU alignment
  *optimal_width = (*optimal_width / 2) * 2;
  *optimal_height = (*optimal_height / 2) * 2;
}

// FIXME: this is a very simple way of implementing box filter downsampling for
// memory efficiency Could be better, but this is good enough *for the time
// being*. Must be revisited in the future to see how it stands as the program
// evolves.
static int downsample_image(unsigned char *src_data, int src_width,
                            int src_height, unsigned char *dst_data,
                            int dst_width, int dst_height) {
  if (!src_data || !dst_data) {
    return -1;
  }

  float x_ratio = (float)src_width / dst_width;
  float y_ratio = (float)src_height / dst_height;

  for (int y = 0; y < dst_height; y++) {
    for (int x = 0; x < dst_width; x++) {
      // Calculate corresponding source pixel
      int src_x = (int)(x * x_ratio);
      int src_y = (int)(y * y_ratio);

      // Ensure we're within bounds
      src_x = (src_x >= src_width) ? src_width - 1 : src_x;
      src_y = (src_y >= src_height) ? src_height - 1 : src_y;

      // Copy pixel (RGBA)
      int src_idx = (src_y * src_width + src_x) * 4;
      int dst_idx = (y * dst_width + x) * 4;

      dst_data[dst_idx + 0] = src_data[src_idx + 0]; // R
      dst_data[dst_idx + 1] = src_data[src_idx + 1]; // G
      dst_data[dst_idx + 2] = src_data[src_idx + 2]; // B
      dst_data[dst_idx + 3] = src_data[src_idx + 3]; // A
    }
  }

  return 0;
}

// Load image from file with configurable downsampling
int chroma_image_load(chroma_image_t *image, const char *path,
                      const chroma_config_t *config) {
  if (!image || !path) {
    chroma_log("ERROR", "Invalid parameters for image loading");
    return CHROMA_ERROR_INIT;
  }

  // Initialize image structure
  memset(image, 0, sizeof(chroma_image_t));
  strncpy(image->path, path, MAX_PATH_LEN - 1);
  image->path[MAX_PATH_LEN - 1] = '\0';

  // Check if file exists
  if (!file_exists(path)) {
    chroma_log("ERROR", "Image file does not exist: %s", path);
    return CHROMA_ERROR_IMAGE;
  }

  // Get file size for logging
  long file_size = get_file_size(path);
  if (file_size > 0) {
    chroma_log("DEBUG", "Loading image: %s (%.2f MB)", path,
               (double)file_size / (1024.0 * 1024.0));
  }

  // Load image data using stb_image, force RGBA format to avoid conversion
  stbi_set_flip_vertically_on_load(0); // keep images right-side up

  image->data =
      stbi_load(path, &image->width, &image->height, &image->channels, 4);
  image->channels = 4; // always RGBA after forced conversion
  if (!image->data) {
    chroma_log("ERROR", "Failed to load image %s: %s", path,
               stbi_failure_reason());
    return CHROMA_ERROR_IMAGE;
  }

  // Validate image dimensions
  if (image->width <= 0 || image->height <= 0) {
    chroma_log("ERROR", "Invalid image dimensions: %dx%d", image->width,
               image->height);
    chroma_image_free(image);
    return CHROMA_ERROR_IMAGE;
  }

  // Validate we have RGBA data (should always be true with forced conversion)
  if (image->channels != 4) {
    chroma_log("ERROR", "Failed to load image as RGBA: got %d channels",
               image->channels);
    chroma_image_free(image);
    return CHROMA_ERROR_IMAGE;
  }

  // Store original dimensions before potential downsampling
  int original_width = image->width;
  int original_height = image->height;

  // Apply intelligent downsampling if enabled
  bool should_downsample = false;
  int optimal_width = original_width;
  int optimal_height = original_height;

  if (config && config->enable_downsampling) {
    calculate_optimal_size(original_width, original_height,
                           config->max_output_width, config->max_output_height,
                           &optimal_width, &optimal_height);

    // Apply minimum scale factor constraint
    float scale_x = (float)optimal_width / original_width;
    float scale_y = (float)optimal_height / original_height;
    float scale = (scale_x < scale_y) ? scale_x : scale_y;

    if (scale < config->min_scale_factor) {
      scale = config->min_scale_factor;
      optimal_width = (int)(original_width * scale);
      optimal_height = (int)(original_height * scale);

      // Ensure even dimensions
      optimal_width = (optimal_width / 2) * 2;
      optimal_height = (optimal_height / 2) * 2;
    }

    should_downsample =
        (optimal_width < original_width || optimal_height < original_height);
  }

  // Downsamp if needed and enabled
  if (should_downsample) {
    chroma_log("INFO",
               "Downsampling image from %dx%d to %dx%d (%.1f%% of original)",
               original_width, original_height, optimal_width, optimal_height,
               (float)(optimal_width * optimal_height) /
                   (original_width * original_height) * 100.0f);

    size_t optimal_size = (size_t)optimal_width * optimal_height * 4;
    unsigned char *downsampled_data = malloc(optimal_size);
    if (!downsampled_data) {
      chroma_log("ERROR", "Failed to allocate memory for downsampled image");
      chroma_image_free(image);
      return CHROMA_ERROR_MEMORY;
    }

    if (downsample_image(image->data, original_width, original_height,
                         downsampled_data, optimal_width,
                         optimal_height) != 0) {
      chroma_log("ERROR", "Failed to downsample image");
      free(downsampled_data);
      chroma_image_free(image);
      return CHROMA_ERROR_IMAGE;
    }

    stbi_image_free(image->data);
    image->data = downsampled_data;
    image->width = optimal_width;
    image->height = optimal_height;

    chroma_log("DEBUG", "Successfully downsampled image to %dx%d",
               optimal_width, optimal_height);
  } else if (config && !config->enable_downsampling) {
    chroma_log("DEBUG",
               "Downsampling disabled, keeping original resolution %dx%d",
               original_width, original_height);
  }

  image->loaded = true;

  // Calculate and log memory allocation
  size_t image_size = (size_t)image->width * image->height * image->channels;
  chroma_log_resource_allocation("image_data", image_size, path);

  chroma_log("INFO", "Loaded image: %s (%dx%d, %d channels, %.2f MB)%s", path,
             image->width, image->height, image->channels,
             (double)image_size / (1024.0 * 1024.0),
             should_downsample ? " (downsampled)" : "");

  return CHROMA_OK;
}

// Free image data
void chroma_image_free(chroma_image_t *image) {
  if (!image) {
    return;
  }

  if (image->data) {
    // Log memory deallocation before freeing
    size_t image_size = (size_t)image->width * image->height * image->channels;
    chroma_log_resource_deallocation("image_data", image_size, image->path);

    // Always use stbi_image_free since we load directly with stbi_load
    stbi_image_free(image->data);
    image->data = NULL;
  }

  image->width = 0;
  image->height = 0;
  image->channels = 0;
  image->loaded = false;

  if (strlen(image->path) > 0) {
    chroma_log("DEBUG", "Freed image: %s", image->path);
  }

  memset(image->path, 0, sizeof(image->path));
}

// Find image by path in state
chroma_image_t *chroma_image_find_by_path(chroma_state_t *state,
                                          const char *path) {
  if (!state || !path) {
    return NULL;
  }

  for (int i = 0; i < state->image_count; i++) {
    if (strcmp(state->images[i].path, path) == 0) {
      return &state->images[i];
    }
  }

  return NULL;
}

// Load image if not already loaded
chroma_image_t *chroma_image_get_or_load(chroma_state_t *state,
                                         const char *path) {
  if (!state || !path) {
    return NULL;
  }

  // Check if already loaded
  chroma_image_t *existing = chroma_image_find_by_path(state, path);
  if (existing && existing->loaded) {
    chroma_log("DEBUG", "Using cached image: %s", path);
    return existing;
  }

  // Find empty slot or reuse existing
  chroma_image_t *image = existing;
  if (!image) {
    if (state->image_count >= MAX_OUTPUTS) {
      chroma_log("ERROR", "Maximum number of images reached");
      return NULL;
    }
    image = &state->images[state->image_count];
    state->image_count++;
  }

  // Load the image with configuration
  if (chroma_image_load(image, path, &state->config) != CHROMA_OK) {
    // If this was a new slot, decrement count
    if (!existing) {
      state->image_count--;
    }
    return NULL;
  }

  return image;
}

// Validate image file format
int chroma_image_validate(const char *path) {
  if (!path || !file_exists(path)) {
    return CHROMA_ERROR_IMAGE;
  }

  // Check file extension (basic validation)
  const char *ext = strrchr(path, '.');
  if (!ext) {
    return CHROMA_ERROR_IMAGE;
  }

  ext++; // Skip the dot

  // Check supported extensions
  if (strcasecmp(ext, "jpg") == 0 || strcasecmp(ext, "jpeg") == 0 ||
      strcasecmp(ext, "png") == 0 || strcasecmp(ext, "bmp") == 0 ||
      strcasecmp(ext, "tga") == 0 || strcasecmp(ext, "psd") == 0 ||
      strcasecmp(ext, "gif") == 0 || strcasecmp(ext, "hdr") == 0 ||
      strcasecmp(ext, "pic") == 0 || strcasecmp(ext, "ppm") == 0 ||
      strcasecmp(ext, "pgm") == 0) {
    return CHROMA_OK;
  }

  chroma_log("WARN", "Potentially unsupported image format: %s", ext);
  return CHROMA_ERROR_IMAGE;
}

// Get image info without loading full data
int chroma_image_get_info(const char *path, int *width, int *height,
                          int *channels) {
  if (!path || !width || !height || !channels) {
    return CHROMA_ERROR_INIT;
  }

  if (!file_exists(path)) {
    return CHROMA_ERROR_IMAGE;
  }

  if (!stbi_info(path, width, height, channels)) {
    chroma_log("ERROR", "Failed to get image info for %s: %s", path,
               stbi_failure_reason());
    return CHROMA_ERROR_IMAGE;
  }

  return CHROMA_OK;
}

// Cleanup all images in state
void chroma_images_cleanup(chroma_state_t *state) {
  if (!state) {
    return;
  }

  chroma_log("DEBUG", "Cleaning up %d images", state->image_count);

  for (int i = 0; i < state->image_count; i++) {
    chroma_image_free(&state->images[i]);
  }

  state->image_count = 0;
  chroma_log("INFO", "Cleaned up all images");
  chroma_log_memory_stats("post-image-cleanup");
}

// Preload common image formats for validation
void chroma_image_init_stb(void) {
  // Set stb_image options
  stbi_set_flip_vertically_on_load(0);

  // FIXME: these could be made configurable
  stbi_ldr_to_hdr_gamma(2.2f);
  stbi_ldr_to_hdr_scale(1.0f);

  chroma_log("DEBUG", "Initialized stb_image library");
}