#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "array_list.h"
#include "chunk.h"
#include "compression.h"
#include "data.h"
#include "file.h"
#include "log.h"
#include "metadata.h"
#include "protocol.h"

/* Maximum individual file data size within a chunk (64 MB) */
#define MAX_FILE_DATA_SIZE (64ULL * 1024 * 1024)

Chunk* chunk_create(File** items, int element_count) {
  Chunk* chunk = (Chunk*)malloc(sizeof(Chunk));
  if (chunk == NULL) {
    perror("ERROR: Could not allocate memory for chunk structure");
    return NULL;
  }

  chunk->items = (File**)malloc(element_count * sizeof(File*));
  if (chunk->items == NULL) {
    free(chunk);
    return NULL;
  }

  for (int i = 0; i < element_count; i++) {
    chunk->items[i] = items[i];
  }
  chunk->element_count = element_count;
  return chunk;
}

void chunk_destroy(void* item) {
  if (item == NULL) {
    return;
  }
  Chunk* chunk = (Chunk*)item;
  for (int i = 0; i < chunk->element_count; ++i) {
    if (chunk->items[i] != NULL) {
      file_destroy(chunk->items[i]);
    }
  }
  free(chunk->items);
  free(chunk);
}

static unsigned long long per_file_serialize_size(File* file, bool use_metadata) {
  return sizeof(size_t) + strlen(file->path) +
         (use_metadata ? sizeof(int) + (file->metadata ? FILE_METADATA_WIRE_SIZE : 0) : 0) +
         sizeof(size_t) + file->data->size;
}

Data* chunk_serialize(Chunk* chunk, bool use_metadata) {
  unsigned long long data_size = 0;
  for (int i = 0; i < chunk->element_count; i++) {
    data_size += per_file_serialize_size(chunk->items[i], use_metadata);
  }
  Data* data = data_create_empty(data_size);
  if (data == NULL) {
    log_message(LOG_LEVEL_ERROR, "Could not allocate memory for chunk serialization");
    return NULL;
  }
  char* data_pointer = data->data;
  for (int i = 0; i < chunk->element_count; i++) {
    File* file = chunk->items[i];
    size_t path_len = strlen(file->path);
    memcpy(data_pointer, &path_len, sizeof(size_t));
    data_pointer += sizeof(size_t);
    memcpy(data_pointer, file->path, path_len);
    data_pointer += path_len;

    if (use_metadata)
      metadata_to_buf(&data_pointer, file->metadata);

    size_t file_data_size = file->data->size;
    memcpy(data_pointer, &file_data_size, sizeof(size_t));
    data_pointer += sizeof(size_t);
    memcpy(data_pointer, file->data->data, file_data_size);
    data_pointer += file_data_size;
  }
  return data;
}

Chunk* chunk_deserialize(Data* data, bool use_metadata) {
  ArrayList* files = array_list_create(file_destroy);
  char* data_pointer = data->data;
  size_t remaining_size = data->size;

  while (remaining_size > 0) {
    if (remaining_size < sizeof(size_t)) {
      log_message(LOG_LEVEL_ERROR, "Invalid chunk format: not enough data for path length");
      array_list_delete(files);
      return NULL;
    }

    size_t path_len;
    memcpy(&path_len, data_pointer, sizeof(size_t));
    data_pointer += sizeof(size_t);
    remaining_size -= sizeof(size_t);

    if (remaining_size < path_len) {
      log_message(LOG_LEVEL_ERROR, "Invalid chunk format: not enough data for path");
      array_list_delete(files);
      return NULL;
    }

    char* path = malloc(path_len + 1);
    if (path == NULL) {
      perror("Could not allocate memory for file path");
      array_list_delete(files);
      return NULL;
    }
    memcpy(path, data_pointer, path_len);
    path[path_len] = '\0';
    data_pointer += path_len;
    remaining_size -= path_len;

    File* file = file_create(path);
    free(path);

    if (use_metadata) {
      if (remaining_size < sizeof(int)) {
        log_message(LOG_LEVEL_ERROR, "Invalid chunk format: not enough data for metadata");
        array_list_delete(files);
        return NULL;
      }
      // Peek at present flag to determine total size needed before reading
      int present_flag;
      memcpy(&present_flag, data_pointer, sizeof(int));
      if (present_flag && remaining_size < sizeof(int) + FILE_METADATA_WIRE_SIZE) {
        log_message(LOG_LEVEL_ERROR, "Invalid chunk format: not enough data for metadata body");
        array_list_delete(files);
        return NULL;
      }
      file->metadata = metadata_from_buf(&data_pointer);
      remaining_size -= sizeof(int);
      if (file->metadata)
        remaining_size -= FILE_METADATA_WIRE_SIZE;
    }

    if (remaining_size < sizeof(size_t)) {
      log_message(LOG_LEVEL_ERROR, "Invalid chunk format: not enough data for data size");
      array_list_delete(files);
      return NULL;
    }

    size_t file_data_size;
    memcpy(&file_data_size, data_pointer, sizeof(size_t));
    data_pointer += sizeof(size_t);
    remaining_size -= sizeof(size_t);

    if (remaining_size < file_data_size) {
      log_message(LOG_LEVEL_ERROR, "Invalid chunk format: not enough data for file content");
      array_list_delete(files);
      return NULL;
    }

    // Reject individual file data larger than the maximum allowed size.
    if (file_data_size > MAX_FILE_DATA_SIZE) {
      log_message(LOG_LEVEL_ERROR, "File data size %zu exceeds maximum %llu", file_data_size,
                  (unsigned long long)MAX_FILE_DATA_SIZE);
      array_list_delete(files);
      return NULL;
    }

    void* file_data = malloc(file_data_size);
    if (file_data == NULL) {
      perror("Could not allocate memory for file data");
      array_list_delete(files);
      return NULL;
    }
    memcpy(file_data, data_pointer, file_data_size);
    data_destroy(file->data);
    file->data = data_create(file_data, file_data_size);
    data_pointer += file_data_size;
    remaining_size -= file_data_size;

    array_list_add(files, file);
  }

  File** file_array = (File**)array_list_to_array(files);
  Chunk* chunk = chunk_create(file_array, files->size);

  free(file_array);
  files->item_destroyer = NULL;
  array_list_delete(files);

  return chunk;
}

Data* chunk_compress(Chunk* chunk, int compression_level, bool use_metadata) {
  log_message(LOG_LEVEL_DEBUG, "Starting to compress chunk");
  Data* serialized = chunk_serialize(chunk, use_metadata);
  if (serialized == NULL)
    return NULL;
  Data* compressed = data_compress(serialized, compression_level);
  data_destroy(serialized);
  if (compressed == NULL)
    return NULL;
  log_message(LOG_LEVEL_DEBUG, "Chunk successfully compressed");
  return compressed;
}

Chunk* receive_chunk_data(int fd, const Config* config) {
  Data* chunk_data = receive_data(fd);
  if (chunk_data == NULL) {
    log_message(LOG_LEVEL_ERROR, "Failed to receive chunk data");
    return NULL;
  }
  Data* data_to_process = chunk_data;
  if (config->use_compression) {
    data_to_process = data_decompress(chunk_data);
    data_destroy(chunk_data);
    if (data_to_process == NULL) {
      log_message(LOG_LEVEL_ERROR, "Failed to decompress chunk");
      return NULL;
    }
  }

  // Reject chunks larger than the maximum allowed size to prevent OOM.
  if (data_to_process->size > MAX_CHUNK_SIZE) {
    log_message(LOG_LEVEL_ERROR, "Chunk size %zu exceeds maximum %llu", data_to_process->size,
                (unsigned long long)MAX_CHUNK_SIZE);
    data_destroy(data_to_process);
    return NULL;
  }

  Chunk* chunk = chunk_deserialize(data_to_process, config->use_metadata);
  data_destroy(data_to_process);
  if (chunk == NULL)
    log_message(LOG_LEVEL_ERROR, "Failed to deserialize chunk, skipping");
  return chunk;
}