#include <filesystem.h>

#include <assert.h>
#include <stdlib.h>
#include <string.h>

size_t get_file_size(FILE* file) {
  assert(file);
  const long int starting_pos = ftell(file);
  if (starting_pos == -1) {
    return (size_t)-1;
  }
  if (fseek(file, 0, SEEK_END) != 0) {
    return (size_t)-1;
  }
  const size_t file_size = ftell(file);
  if (file_size == (size_t)-1) {
    return (size_t)-1;
  }
  if (fseek(file, starting_pos, SEEK_SET) != 0) {
    return (size_t)-1;
  }
  return file_size;
}

void* read_file(const char* filepath) {
  assert(filepath);

  void* data = 0;

  FILE* file = fopen(filepath, "rb");
  if (!file) {
    return 0;
  }
  const size_t file_size = get_file_size(file);
  if (file_size == (size_t)-1) {
    goto cleanup;
  }

  data = calloc(1, file_size);
  if (!data) {
    goto cleanup;
  }
  if (fread(data, 1, file_size, file) != file_size) {
    goto cleanup;
  }

  return data;

cleanup:
  fclose(file);
  if (data) {
    free(data);
  }
  return 0;
}

bool make_relative_path(
    size_t max_path_length, const char* filepath, const char* path,
    char* relative) {
  assert(filepath);
  assert(path);
  assert(relative);

  // Handle empty filepath.
  const size_t filepath_len = strlen(filepath);
  if (filepath_len == 0) {
    memcpy(relative, path, max_path_length);
    return true;
  }

  memcpy(relative, filepath, max_path_length);
  // Search for the last / in the tile map file path to get its parent
  // directory.
  assert(filepath_len > 0);
  size_t tm_dir_len = 0;
  for (tm_dir_len = strlen(filepath) - 1; tm_dir_len > 0; --tm_dir_len) {
    if (filepath[tm_dir_len] == '/') {
      break;
    }
  }
  tm_dir_len++; // Preserve the backslash.

  // Copy the tile set file path where the parent dir ends.
  // Make sure there is enough space in the output.
  const size_t path_len = strlen(path);
  if ((tm_dir_len + path_len + 1) >= max_path_length) {
    return false;
  }
  memcpy(&relative[tm_dir_len], path, path_len);
  return true;
}