/* SPDX-License-Identifier: GPL-3.0-or-later */
/*
 * vfetch - neofetch but the ascii part is a video
 *
 * Copyright (C) 2026  Doan Luu Duc Tai
 *
 */

#include "core.h"
#include <glib.h>
#include <glib/gstdio.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <errno.h>
#include <inttypes.h>
#include <limits.h>
#include <math.h>
#include <miniaudio.h>
#include <poll.h>
#include <pthread.h>
#include <signal.h>
#include <stdatomic.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include "args.h"
#include "audio.h"
#include "fetch.h"
#include "pl_mpeg.h"
#include "state.h"
#include "utils.h"
#include "video.h"
#include "video_defs.h"

static void free_cache_paths(CacheFilePaths *paths) {
  g_free(paths->data_file_path);
  g_free(paths->meta_file_path);
}

static VfetchError build_cache_paths(const char *cache_dir,
                                     CacheFilePaths *paths) {
  paths->data_file_path = g_build_filename(cache_dir, "frames.dat", NULL);
  paths->meta_file_path = g_build_filename(cache_dir, "frames.meta", NULL);

  if (!paths->data_file_path || !paths->meta_file_path) {
    log_vfetch_error(VFETCH_ERROR_MEMORY_ALLOCATION,
                     "Failed to construct cache file paths.");
    free_cache_paths(paths);
    return VFETCH_ERROR_MEMORY_ALLOCATION;
  }
  return VFETCH_SUCCESS;
}

static VfetchError read_metadata_files(AnimationResources *res,
                                       const CacheFilePaths *paths) {
  res->meta_stream = fopen(paths->meta_file_path, "rb");
  if (!res->meta_stream) {
    return VFETCH_ERROR_FILE_IO;
  }

  if (fseek(res->meta_stream, 0, SEEK_END) != 0) {
    return VFETCH_ERROR_FILE_IO;
  }

  long file_size = ftell(res->meta_stream);
  if (file_size < 0) {
    return VFETCH_ERROR_FILE_IO;
  }

  if (fseek(res->meta_stream, 0, SEEK_SET) != 0) {
    return VFETCH_ERROR_FILE_IO;
  }

  if ((size_t)file_size % sizeof(FrameMetadata) != 0) {
    return VFETCH_ERROR_CACHE_INVALID;
  }

  res->anim_args.num_frames = (size_t)file_size / sizeof(FrameMetadata);

  if (res->anim_args.num_frames == 0) {
    return VFETCH_ERROR_CACHE_INVALID;
  }

  res->anim_args.frames =
      malloc(res->anim_args.num_frames * sizeof(FrameMetadata));
  if (!res->anim_args.frames) {
    return VFETCH_ERROR_MEMORY_ALLOCATION;
  }

  if (fread(res->anim_args.frames,
            sizeof(FrameMetadata),
            res->anim_args.num_frames,
            res->meta_stream) != res->anim_args.num_frames) {
    return VFETCH_ERROR_FILE_IO;
  }

  return VFETCH_SUCCESS;
}

static VfetchError map_frame_data_file(AnimationResources *res,
                                       const char *data_file_path) {
  GError *gerr = NULL;

  res->mapped_file = g_mapped_file_new(data_file_path, FALSE, &gerr);

  if (!res->mapped_file) {
    if (gerr) {
      (void)fprintf(stderr, "ERROR: Memory map failed: %s\n", gerr->message);
      g_error_free(gerr);
    }
    return VFETCH_ERROR_MMAP_FAILED;
  }

  res->anim_args.data_map = g_mapped_file_get_contents(res->mapped_file);
  res->data_file_size = (off_t)g_mapped_file_get_length(res->mapped_file);

  if (res->data_file_size <= 0) {
    g_mapped_file_unref(res->mapped_file);
    res->mapped_file = NULL;
    return VFETCH_ERROR_CACHE_INVALID;
  }

  return VFETCH_SUCCESS;
}

static bool
validate_cache_file(const gchar *path, GStatBuf *st_out, bool check_non_empty) {
  if (g_stat(path, st_out) != 0) {
    return false;
  }

  if (check_non_empty && st_out->st_size == 0) {
    return false;
  }

  return true;
}

static gboolean validate_all_cache_files(const gchar *cache_dir_path,
                                         const CacheValidationStats *stats) {
  struct {
    const gchar *filename;
    GStatBuf *st_out;
    gboolean check_non_empty;
  } validation_rules[] = {
      {.filename = "_SUCCESS",
       .st_out = stats->st_success,
       .check_non_empty = FALSE},
      {.filename = "frames.dat",
       .st_out = stats->st_data,
       .check_non_empty = TRUE},
      {.filename = "frames.meta",
       .st_out = stats->st_meta,
       .check_non_empty = TRUE},
  };

  gchar *file_path = NULL;

  for (size_t idx = 0;
       idx < sizeof(validation_rules) / sizeof(validation_rules[0]);
       ++idx) {
    file_path =
        g_build_filename(cache_dir_path, validation_rules[idx].filename, NULL);

    if (!validate_cache_file(file_path,
                             validation_rules[idx].st_out,
                             validation_rules[idx].check_non_empty != FALSE)) {
      g_free(file_path);
      return FALSE;
    }

    g_free(file_path);
  }

  return TRUE;
}

static size_t verify_cache_file_integrity(const char *meta_path,
                                          const GStatBuf *st_data,
                                          const VfetchArgs *args) {
  FILE *meta_fp = fopen(meta_path, "rb");
  if (!meta_fp) {
    return 0;
  }

  if (fseek(meta_fp, 0, SEEK_END) != 0) {
    (void)fclose(meta_fp);
    return 0;
  }

  long meta_size = ftell(meta_fp);
  if (meta_size <= 0 || (size_t)meta_size % sizeof(FrameMetadata) != 0) {
    log_debug(
        args->debug,
        "Cache invalid: Meta file size is not a multiple of a frame entry.");
    (void)fclose(meta_fp);
    return 0;
  }

  long last_entry_pos = meta_size - (long)sizeof(FrameMetadata);
  if (fseek(meta_fp, last_entry_pos, SEEK_SET) != 0) {
    (void)fclose(meta_fp);
    return 0;
  }

  FrameMetadata last_frame = {0};
  if (fread(&last_frame, sizeof(FrameMetadata), 1, meta_fp) != 1) {
    (void)fclose(meta_fp);
    return 0;
  }
  (void)fclose(meta_fp);

  uint64_t expected_data_size = last_frame.offset + last_frame.length;

  if ((uint64_t)st_data->st_size != expected_data_size) {
    log_debug(args->debug,
              "Cache corrupted: Data file size mismatch. Expected %" PRIu64
              ", got %" PRIu64,
              expected_data_size,
              (uint64_t)st_data->st_size);
    return 0;
  }

  return (size_t)meta_size / sizeof(FrameMetadata);
}

static VfetchError perform_cache_validation(AppState *state,
                                            const gchar *cache_dir_path,
                                            const VfetchArgs *args,
                                            const CacheValidationStats *stats,
                                            uint32_t *num_frames_out) {
  if (!validate_all_cache_files(cache_dir_path, stats)) {
    return VFETCH_ERROR_CACHE_INVALID;
  }

  char *meta_path = g_build_filename(cache_dir_path, "frames.meta", NULL);
  if (!meta_path) {
    return VFETCH_ERROR_MEMORY_ALLOCATION;
  }

  size_t frame_count =
      verify_cache_file_integrity(meta_path, stats->st_data, args);
  free(meta_path);

  if (frame_count == 0) {
    return VFETCH_ERROR_CACHE_INVALID;
  }

  if (frame_count > INT_MAX) {
    log_verbose(state,
                args->verbose,
                args->debug,
                "Error: Frame count (%zu) exceeds INT_MAX.",
                frame_count);
    return VFETCH_ERROR_CACHE_INVALID;
  }

  log_verbose(state,
              args->verbose,
              args->debug,
              "Cache is valid with %zu frames.",
              frame_count);
  *num_frames_out = (uint32_t)frame_count;

  return VFETCH_SUCCESS;
}

static VfetchError is_cache_valid(AppState *state,
                                  const gchar *cache_dir_path,
                                  const VfetchArgs *args,
                                  uint32_t *num_frames) {
  VfetchError err = VFETCH_ERROR_CACHE_INVALID;

  *num_frames = 0;

  CacheValidationStats *stats = malloc(sizeof(CacheValidationStats));
  if (!stats) {
    return VFETCH_ERROR_MEMORY_ALLOCATION;
  }

  stats->st_success = g_new0(GStatBuf, 1);
  stats->st_data = g_new0(GStatBuf, 1);
  stats->st_meta = g_new0(GStatBuf, 1);
  if (!stats->st_success || !stats->st_data || !stats->st_meta) {
    err = VFETCH_ERROR_MEMORY_ALLOCATION;
  } else {
    err = perform_cache_validation(
        state, cache_dir_path, args, stats, num_frames);
  }

  free(stats->st_success);
  free(stats->st_data);
  free(stats->st_meta);
  free(stats);

  return err;
}

static VfetchError setup_cache_directory(AppState *state,
                                         const VfetchArgs *args) {
  GStatBuf file_stat = {0};
  gchar *base_cache_dir = NULL;
  gchar *video_filename = NULL;
  gchar *video_cache_dirname = NULL;

  base_cache_dir = g_build_filename(g_get_user_cache_dir(), "vfetch", NULL);

  if (g_mkdir_with_parents(base_cache_dir, S_IRWXU) != 0) {
    log_vfetch_error(VFETCH_ERROR_MKDIR_FAILED, base_cache_dir);
    g_free(base_cache_dir);
    return VFETCH_ERROR_MKDIR_FAILED;
  }

  if (g_stat(args->filename, &file_stat) != 0) {
    log_vfetch_error(VFETCH_ERROR_STAT_FAILED, args->filename);
    g_free(base_cache_dir);
    return VFETCH_ERROR_STAT_FAILED;
  }

  video_filename = g_path_get_basename(args->filename);

  video_cache_dirname =
      g_strdup_printf("%s_dev%" G_GINT64_FORMAT "_ino%" G_GINT64_FORMAT,
                      video_filename,
                      (gint64)file_stat.st_dev,
                      (gint64)file_stat.st_ino);

  state->video_specific_cache_root =
      g_build_filename(base_cache_dir, video_cache_dirname, NULL);

  g_free(base_cache_dir);
  g_free(video_filename);
  g_free(video_cache_dirname);

  if (!state->video_specific_cache_root) {
    return VFETCH_ERROR_MEMORY_ALLOCATION;
  }

  return VFETCH_SUCCESS;
}

#define VFETCH_CACHE_VERSION 1
static VfetchError build_cache_key(const VfetchArgs *args, CacheKey *key) {
  (void)memset(key, 0, sizeof(CacheKey));

  GStatBuf file_stat = {0};
  if (g_stat(args->filename, &file_stat) != 0) {
    return VFETCH_ERROR_STAT_FAILED;
  }

  key->file_size = file_stat.st_size;
  key->file_mtime = file_stat.st_mtime;
  key->width = args->width;
  key->height = args->height;
  key->fps = args->fps;
  key->cell_aspect_ratio = args->cell_aspect_ratio;
  key->version_tag = VFETCH_CACHE_VERSION;

  hash_string_to_bytes(args->format_arg, key->format_md5);
  hash_string_to_bytes(args->colors_arg, key->colors_md5);

  char *symbols = g_hash_table_lookup(args->chafa_options, "--symbols");
  hash_string_to_bytes(symbols ? symbols : "all", key->symbols_md5);

  char *serialized_opts = serialize_map_for_hashing(args->chafa_options);
  hash_string_to_bytes(serialized_opts, key->chafa_opts_md5);
  g_free(serialized_opts);

  return VFETCH_SUCCESS;
}
#undef VFETCH_CACHE_VERSION

static VfetchError
generate_cache_hash(AppState *state, VfetchArgs *args, gchar **out_hash_str) {
  CacheKey key = {0};
  VfetchError err = build_cache_key(args, &key);
  if (err != VFETCH_SUCCESS) {
    return err;
  }

  *out_hash_str = hash_cache_key(&key);

  state->current_args_cache_dir =
      g_build_filename(state->video_specific_cache_root, *out_hash_str, NULL);
  return VFETCH_SUCCESS;
}

static VfetchError initialize_pipeline_resources(const VfetchArgs *args,
                                                 size_t *total_frames_out) {
  VfetchError err =
      get_video_frame_count(args->filename, args->fps, total_frames_out);
  if (err) {
    log_vfetch_error(err, args->filename);
    return err;
  }

  if (*total_frames_out == 0) {
    log_vfetch_error(VFETCH_ERROR_AV_STREAM_INFO,
                     "Video has zero or negative duration");
    return VFETCH_ERROR_AV_STREAM_INFO;
  }

  return VFETCH_SUCCESS;
}

static VfetchError open_cache_files_for_writing(CacheFiles *files,
                                                const gchar *cache_dir,
                                                gchar **data_path,
                                                gchar **meta_path) {
  *data_path = g_build_filename(cache_dir, "frames.dat", NULL);
  *meta_path = g_build_filename(cache_dir, "frames.meta", NULL);

  if (!*data_path || !*meta_path) {
    return VFETCH_ERROR_MEMORY_ALLOCATION;
  }

  files->data_file = fopen(*data_path, "wb");
  files->meta_file = fopen(*meta_path, "wb");

  if (!files->data_file || !files->meta_file) {
    return VFETCH_ERROR_FILE_IO;
  }
  return VFETCH_SUCCESS;
}

static VfetchError generate_ascii_cache(AppState *state,
                                        const VfetchArgs *args) {
  gchar *data_file_path = NULL;
  gchar *meta_file_path = NULL;
  WorkerResources res = {0};
  CacheFiles files = {0};
  unsigned long current_offset = 0;
  VfetchError err = VFETCH_SUCCESS;

  err = initialize_worker_resources(&res, args);
  if (err != VFETCH_SUCCESS) {
    cleanup_worker_resources(&res);
    return err;
  }

  err = open_cache_files_for_writing(
      &files, state->current_args_cache_dir, &data_file_path, &meta_file_path);

  if (err == VFETCH_SUCCESS) {
    err = populate_frame_cache_loop(&res, state, &files, &current_offset);
  }

  if (files.data_file) {
    (void)fclose(files.data_file);
  }
  if (files.meta_file) {
    (void)fclose(files.meta_file);
  }
  g_free(data_file_path);
  g_free(meta_file_path);
  cleanup_worker_resources(&res);
  return err;
}

static VfetchError run_processing_pipeline(AppState *state,
                                           const VfetchArgs *args,
                                           size_t total_frames) {
  ProgressThreadArgs *progress_args = NULL;
  pthread_t progress_thread_id = 0;
  VfetchError err = VFETCH_SUCCESS;

  progress_args = malloc(sizeof(ProgressThreadArgs));
  if (!progress_args) {
    log_vfetch_error(VFETCH_ERROR_MEMORY_ALLOCATION, "progress thread args");
    return VFETCH_ERROR_MEMORY_ALLOCATION;
  }
  progress_args->state = state;
  progress_args->total_frames = total_frames;
  if (pthread_create(&progress_thread_id,
                     NULL,
                     progress_display_thread_func,
                     progress_args) != 0) {
    log_vfetch_error(VFETCH_ERROR_THREAD_CREATION, "progress display thread");
    free(progress_args);
    return VFETCH_ERROR_THREAD_CREATION;
  }

  err = generate_ascii_cache(state, args);

  atomic_store_explicit(
      &state->processing_finished, true, memory_order_release);

  if (progress_thread_id != 0) {
    (void)pthread_join(progress_thread_id, NULL);
  }

  return err;
}

static VfetchError finalize_cache(const AppState *state) {
  GStatBuf st_dat = {0};
  VfetchError err = VFETCH_SUCCESS;

  gchar *data_file_path =
      g_build_filename(state->current_args_cache_dir, "frames.dat", NULL);
  if (g_stat(data_file_path, &st_dat) != 0 &&
      state->ascii_frames_completed > 0) {
    log_vfetch_error(VFETCH_ERROR_CACHE_INVALID,
                     "Could not stat data file, but frames were written");
    g_free(data_file_path);
    return VFETCH_ERROR_CACHE_INVALID;
  }
  g_free(data_file_path);

  char *success_file_path =
      g_build_filename(state->current_args_cache_dir, "_SUCCESS", NULL);
  FILE *success_file = fopen(success_file_path, "w");
  if (success_file) {
    (void)fclose(success_file);
  } else {
    err = VFETCH_ERROR_FILE_IO;
    log_vfetch_error(err, success_file_path);
  }
  g_free(success_file_path);

  return err;
}

static VfetchError handle_cache_regeneration(AppState *state,
                                             VfetchArgs *args) {
  size_t total_frames = 0;

  if (!rm_rf(state->current_args_cache_dir)) {
    die(VFETCH_ERROR_FILE_IO, "Failed to clear cache directory");
  }
  if (g_mkdir_with_parents(state->current_args_cache_dir, S_IRWXU) != 0) {
    log_vfetch_error(VFETCH_ERROR_MKDIR_FAILED, state->current_args_cache_dir);
    return VFETCH_ERROR_MKDIR_FAILED;
  }

  VfetchError err = initialize_pipeline_resources(args, &total_frames);
  if (err) {
    return err;
  }

  err = run_processing_pipeline(state, args, total_frames);

  if (atomic_load_explicit(&state->exit_requested, memory_order_acquire)) {
    (void)fputs("\nCaching cancelled. Cleaning up partial cache.\n", stderr);
    (void)rm_rf(state->current_args_cache_dir);
    return VFETCH_SUCCESS_EXIT_EARLY;
  }

  if (err != VFETCH_SUCCESS) {
    (void)fputs("\nPipeline encountered a technical error. Cleaning up partial "
                "cache.\n",
                stderr);
    (void)rm_rf(state->current_args_cache_dir);
    return err;
  }

  args->num_frames = (uint32_t)atomic_load_explicit(
      &state->ascii_frames_completed, memory_order_relaxed);
  log_verbose(state,
              args->verbose,
              args->debug,
              "Cache finalized with %u frames.",
              args->num_frames);

  return finalize_cache(state);
}

static VfetchError prepare_animation_assets(AppState *state,
                                            VfetchArgs *args,
                                            bool *cache_was_newly_created) {
  gchar *current_args_hash_str = NULL;
  uint32_t num_frames_from_cache = 0;

  VfetchError err = validate_fps(args);
  if (err != VFETCH_SUCCESS) {
    return err;
  }
  err = setup_cache_directory(state, args);
  if (err != VFETCH_SUCCESS) {
    return err;
  }
  err = generate_cache_hash(state, args, &current_args_hash_str);
  if (err != VFETCH_SUCCESS) {
    return err;
  }

  *cache_was_newly_created = false;
  if (is_cache_valid(
          state, state->current_args_cache_dir, args, &num_frames_from_cache) ==
      VFETCH_SUCCESS) {
    args->num_frames = num_frames_from_cache;
    log_verbose(state,
                args->verbose,
                args->debug,
                "Loaded settings from a valid and integral cache.");
    g_free(current_args_hash_str);
    return VFETCH_SUCCESS;
  }

  *cache_was_newly_created = true;
  log_verbose(state,
              args->verbose,
              args->debug,
              "Cache invalid or not found, re-rendering.");

  err = handle_cache_regeneration(state, args);

  g_free(current_args_hash_str);

  return err;
}

static void cleanup_animation_resources(AnimationResources *res) {
  if (res->mapped_file) {
    g_mapped_file_unref(res->mapped_file);
    res->mapped_file = NULL;
    res->anim_args.data_map = NULL;
  }

  if (res->meta_stream) {
    (void)fclose(res->meta_stream);
    res->meta_stream = NULL;
  }

  free(res->anim_args.frames);
  res->anim_args.frames = NULL;

  free(res->anim_args.screen_buffer);
  res->anim_args.screen_buffer = NULL;
}

static VfetchError load_animation_data(const gchar *cache_dir,
                                       AnimationResources *res) {
  CacheFilePaths paths = {0};
  VfetchError err = VFETCH_SUCCESS;

  if (build_cache_paths(cache_dir, &paths) != VFETCH_SUCCESS) {
    return VFETCH_ERROR_MEMORY_ALLOCATION;
  }

  err = read_metadata_files(res, &paths);
  if (err == VFETCH_SUCCESS) {
    err = map_frame_data_file(res, paths.data_file_path);
  }

  free_cache_paths(&paths);
  return err;
}

static VfetchError handle_animation_events(AppState *state,
                                           size_t *last_displayed_idx_ptr) {
  const char k_clear_command[] = "\x1b[H\x1b[2J\x1b[3J";

  if (atomic_load_explicit(&state->terminal_resized, memory_order_acquire)) {
    if (write(STDOUT_FILENO, k_clear_command, sizeof(k_clear_command) - 1) <
        0) {
      return VFETCH_ERROR_FILE_IO;
    }

    atomic_store_explicit(
        &state->terminal_resized, false, memory_order_release);
    *last_displayed_idx_ptr = (size_t)-1;
  }

  return VFETCH_SUCCESS;
}

static void handle_input_char(AppState *state, char char_typed) {
  if (char_typed == 'q' || char_typed == 'Q') {
    atomic_store_explicit(&state->exit_requested, true, memory_order_release);
  } else if (char_typed == 'p' || char_typed == 'P') {
    bool current = atomic_load_explicit(&state->paused, memory_order_acquire);
    atomic_store_explicit(&state->paused, (bool)!current, memory_order_release);
  }
}

static long perform_blocking_pause(AppState *state, struct pollfd *pfd) {
  gint64 p_start = 0;
  gint64 p_end = 0;

  (void)pthread_mutex_lock(&state->audio_state_mutex);
  if (state->audio_state.device.pContext) {
    ma_device_stop(&state->audio_state.device);
  }
  (void)pthread_mutex_unlock(&state->audio_state_mutex);

  p_start = g_get_monotonic_time();

  while (atomic_load_explicit(&state->paused, memory_order_acquire) &&
         !atomic_load_explicit(&state->exit_requested, memory_order_acquire)) {
    if (poll(pfd, 1, -1) > 0) {
      char char_typed = 0;
      if (pfd->revents & POLLIN && read(STDIN_FILENO, &char_typed, 1) > 0) {
        handle_input_char(state, char_typed);
      }
    }
  }

  p_end = g_get_monotonic_time();

  (void)pthread_mutex_lock(&state->audio_state_mutex);
  if (state->audio_state.device.pContext &&
      !atomic_load_explicit(&state->exit_requested, memory_order_acquire)) {
    ma_device_start(&state->audio_state.device);
  }
  (void)pthread_mutex_unlock(&state->audio_state_mutex);

  return p_end - p_start;
}

#define K_MICROSECONDS_IN_MILLISECOND 1000L
static long wait_for_input(AppState *state, long delay_us) {
  struct pollfd pfd = {0};
  pfd.fd = STDIN_FILENO;
  pfd.events = POLLIN;

  int timeout_ms = (int)(delay_us / K_MICROSECONDS_IN_MILLISECOND);
  if (timeout_ms < 0) {
    timeout_ms = 0;
  }

  if (poll(&pfd, 1, timeout_ms) > 0) {
    char char_typed = 0;
    if (pfd.revents & POLLIN && read(STDIN_FILENO, &char_typed, 1) > 0) {
      handle_input_char(state, char_typed);
    }
  }

  if (atomic_load_explicit(&state->paused, memory_order_acquire)) {
    return perform_blocking_pause(state, &pfd);
  }

  return 0;
}
#undef K_MICROSECONDS_IN_MILLISECOND

static VfetchError render_frame(size_t frame_idx,
                                size_t *last_displayed_idx_ptr,
                                VideoAnimationArgs *anim_args,
                                AppState *state,
                                const VfetchArgs *args) {
  const char ansi_hide_cursor[] = "\x1b[?25l";
  size_t final_len = 0;

  if (anim_args->num_frames == 0 || frame_idx >= anim_args->num_frames) {
    log_vfetch_error(VFETCH_ERROR_INVALID_ARGUMENT,
                     "Attempted to render an out-of-bounds frame index.");
    return VFETCH_ERROR_INVALID_ARGUMENT;
  }

  if (frame_idx == *last_displayed_idx_ptr) {
    return VFETCH_SUCCESS;
  }

  int written = snprintf(
      anim_args->screen_buffer, anim_args->screen_buffer_size, "\x1b[H");
  if (written > 0) {
    final_len = (size_t)written;
  }

  FrameMetadata current_frame = anim_args->frames[frame_idx];
  if (current_frame.offset + current_frame.length >
      (uint64_t)anim_args->data_file_size) {
    log_vfetch_error(VFETCH_ERROR_CACHE_INVALID,
                     "Frame index data is out of bounds.");
    return VFETCH_ERROR_CACHE_INVALID;
  }

  const char *frame_data_ptr = anim_args->data_map + current_frame.offset;
  append_block_to_buffer(anim_args->screen_buffer,
                         anim_args->screen_buffer_size,
                         &final_len,
                         args->pad_x,
                         args->pad_y,
                         frame_data_ptr,
                         current_frame.length);

  render_fetch_panel(anim_args->screen_buffer,
                     anim_args->screen_buffer_size,
                     &final_len,
                     state,
                     args);

  if (final_len + sizeof(ansi_hide_cursor) < anim_args->screen_buffer_size) {
    (void)snprintf(anim_args->screen_buffer + final_len,
                   anim_args->screen_buffer_size - final_len,
                   "%s",
                   ansi_hide_cursor);
  }

  (void)pthread_mutex_lock(&state->stdout_mutex);
  ssize_t bytes_written = write(STDOUT_FILENO,
                                anim_args->screen_buffer,
                                strlen(anim_args->screen_buffer));
  (void)pthread_mutex_unlock(&state->stdout_mutex);

  if (bytes_written < 0 && errno != EINTR) {
    return VFETCH_ERROR_FILE_IO;
  }

  *last_displayed_idx_ptr = frame_idx;
  return VFETCH_SUCCESS;
}

#define K_MICROSECONDS_IN_SECOND 1000000L
static VfetchError run_continuous_animation_loop(VideoAnimationArgs *anim_args,
                                                 AppState *state,
                                                 const VfetchArgs *args) {
  const char k_clear_command[] = "\x1b[H\x1b[2J\x1b[3J";
  VfetchError err = VFETCH_SUCCESS;
  gint64 start_time = 0;
  size_t last_displayed_idx = (size_t)-1;

  if (anim_args->num_frames == 0) {
    return VFETCH_SUCCESS;
  }

  double total_duration = anim_args->frames[anim_args->num_frames - 1].pts;
  start_time = g_get_monotonic_time();

  size_t target_frame_idx = 0;
  if (write(STDOUT_FILENO, k_clear_command, sizeof(k_clear_command) - 1) < 0) {
    return VFETCH_ERROR_FILE_IO;
  }

  for (;;) {
    if (atomic_load_explicit(&state->exit_requested, memory_order_acquire)) {
      break;
    }

    err = handle_animation_events(state, &last_displayed_idx);
    if (err) {
      break;
    }

    gint64 current_time = g_get_monotonic_time();
    double master_media_clock =
        (double)(current_time - start_time) / K_MICROSECONDS_IN_SECOND;

    if (master_media_clock >= total_duration) {
      if (args->loop) {
        start_time = current_time;
        target_frame_idx = 0;
        last_displayed_idx = (size_t)-1;
        master_media_clock = 0.0;
      } else {
        break;
      }
    }

    while (target_frame_idx < anim_args->num_frames - 1 &&
           anim_args->frames[target_frame_idx + 1].pts < master_media_clock) {
      target_frame_idx++;
    }

    err = render_frame(
        target_frame_idx, &last_displayed_idx, anim_args, state, args);
    if (err) {
      atomic_store_explicit(&state->exit_requested, true, memory_order_release);
      break;
    }

    long refresh_delay_us = K_MICROSECONDS_IN_SECOND / args->refresh_rate;
    long paused_duration = wait_for_input(state, refresh_delay_us);

    if (paused_duration > 0) {
      start_time += paused_duration;
    }
  }

  return err;
}
#undef K_MICROSECONDS_IN_SECOND

static void update_frame_index_from_clock(size_t *current_frame_idx,
                                          double master_media_clock,
                                          const VideoAnimationArgs *anim_args,
                                          AppState *state) {
  if (anim_args->num_frames == 0) {
    return;
  }
  double total_duration = anim_args->frames[anim_args->num_frames - 1].pts;

  double current_loop_clock = fmod(master_media_clock, total_duration);

  if (current_loop_clock < anim_args->frames[*current_frame_idx].pts) {
    *current_frame_idx = 0;
  }

  while (*current_frame_idx < anim_args->num_frames - 1 &&
         anim_args->frames[*current_frame_idx + 1].pts <= current_loop_clock) {
    if (atomic_load_explicit(&state->exit_requested, memory_order_acquire)) {
      break;
    }
    (*current_frame_idx)++;
  }
}

#define K_MICROSECONDS_IN_SECOND 1000000.0
#define K_MAX_SYNC_DRIFT_SECONDS 2.0
static double calculate_media_clock_for_sync(AppState *state) {
  const double sample_rate =
      (double)state->audio_state.device.playback.internalSampleRate;
  const double audio_latency = state->audio_state.output_latency_seconds;

  uint64_t frames_consumed = atomic_load_explicit(
      &state->audio_state.frames_consumed, memory_order_acquire);
  double consumption_clock =
      (sample_rate > 0) ? (double)frames_consumed / sample_rate : 0.0;

  gint64 current_wall_time = g_get_monotonic_time();

  if (state->media_sync_start_time == 0) {
    state->media_sync_start_time =
        current_wall_time - (gint64)((consumption_clock - audio_latency) *
                                     K_MICROSECONDS_IN_SECOND);
  }

  double wall_clock =
      (double)(current_wall_time - state->media_sync_start_time) /
      K_MICROSECONDS_IN_SECOND;

  double max_allowed = consumption_clock;
  double min_allowed = consumption_clock - K_MAX_SYNC_DRIFT_SECONDS;
  if (min_allowed < 0.0) {
    min_allowed = 0.0;
  }

  if (wall_clock > max_allowed) {
    wall_clock = max_allowed;
    state->media_sync_start_time =
        current_wall_time - (gint64)(wall_clock * K_MICROSECONDS_IN_SECOND);
  } else if (wall_clock < min_allowed) {
    wall_clock = min_allowed;
    state->media_sync_start_time =
        current_wall_time - (gint64)(wall_clock * K_MICROSECONDS_IN_SECOND);
  }

  return wall_clock;
}
#undef K_MICROSECONDS_IN_SECOND
#undef K_MAX_SYNC_DRIFT_SECONDS

#define K_MICROSECONDS_IN_SECOND 1000000L
static VfetchError run_animation_with_sync(VideoAnimationArgs *anim_args,
                                           AppState *state,
                                           const VfetchArgs *args) {
  size_t last_displayed_idx = (size_t)-1;
  const char k_clear_command[] = "\x1b[H\x1b[2J\x1b[3J";
  VfetchError err = VFETCH_SUCCESS;

  if (anim_args->num_frames == 0) {
    return VFETCH_SUCCESS;
  }

  double total_duration = anim_args->frames[anim_args->num_frames - 1].pts;

  size_t current_frame_idx = 0;
  if (write(STDOUT_FILENO, k_clear_command, sizeof(k_clear_command) - 1) < 0) {
    return VFETCH_ERROR_FILE_IO;
  }

  for (;;) {
    if (atomic_load_explicit(&state->exit_requested, memory_order_acquire)) {
      break;
    }

    err = handle_animation_events(state, &last_displayed_idx);
    if (err) {
      break;
    }

    double master_media_clock = calculate_media_clock_for_sync(state);

    if (master_media_clock >= total_duration) {
      if (args->loop) {
        (void)pthread_mutex_lock(&state->audio_state_mutex);
        plm_rewind(state->audio_state.plm);
        atomic_store_explicit(
            &state->audio_state.frames_consumed, 0, memory_order_release);
        (void)pthread_mutex_unlock(&state->audio_state_mutex);

        current_frame_idx = 0;
        last_displayed_idx = (size_t)-1;
        continue;
      }
      break;
    }

    update_frame_index_from_clock(
        &current_frame_idx, master_media_clock, anim_args, state);

    if (current_frame_idx != last_displayed_idx) {
      err = render_frame(
          current_frame_idx, &last_displayed_idx, anim_args, state, args);
      if (err) {
        break;
      }
    }

    long sleep_us = K_MICROSECONDS_IN_SECOND / args->refresh_rate;
    wait_for_input(state, sleep_us);
  }
  return err;
}
#undef K_MICROSECONDS_IN_SECOND

static VfetchError run_animation_extract_audio(AppState *state,
                                               const VfetchArgs *args,
                                               VideoAnimationArgs *anim_args) {
  VfetchError err = VFETCH_SUCCESS;

  const char *audio_source = args->filename;
  err = initialize_audio(state, audio_source);

  if (err) {
    bool was_interrupted =
        atomic_load_explicit(&state->exit_requested, memory_order_acquire);

    if (was_interrupted) {
      shutdown_audio(state);
      return VFETCH_SUCCESS;
    }

    log_vfetch_error(err, "Could not initialize audio from video file.");
    return err;
  }
  err = run_animation_with_sync(anim_args, state, args);

  shutdown_audio(state);
  return err;
}

static VfetchError select_and_run_animation(AppState *state,
                                            const VfetchArgs *args,
                                            VideoAnimationArgs *anim_args) {
  if (args->audio) {
    return run_animation_extract_audio(state, args, anim_args);
  }
  return run_continuous_animation_loop(anim_args, state, args);
}

#define K_SCREEN_BUFFER_SIZE (2 * 1024 * 1024)
static VfetchError run_animation_loop(AppState *state, const VfetchArgs *args) {
  atomic_store_explicit(
      &state->animation_has_started, true, memory_order_release);

  AnimationResources res = {0};
  res.mapped_file = NULL;

  VfetchError err = load_animation_data(state->current_args_cache_dir, &res);
  if (err) {
    cleanup_animation_resources(&res);
    log_vfetch_error(err, "Failed to load animation data from cache");
    return err;
  }

  res.anim_args.data_file_size = res.data_file_size;
  res.anim_args.screen_buffer_size = (long)K_SCREEN_BUFFER_SIZE;
  res.anim_args.screen_buffer = malloc(res.anim_args.screen_buffer_size);
  if (!res.anim_args.screen_buffer) {
    err = VFETCH_ERROR_MEMORY_ALLOCATION;
    log_vfetch_error(err, "Failed to allocate screen buffer.");
    cleanup_animation_resources(&res);
    return err;
  }

  err = select_and_run_animation(state, args, &res.anim_args);

  cleanup_animation_resources(&res);

  return err;
}
#undef K_SCREEN_BUFFER_SIZE

static VfetchError initialize_paths_and_geometry(VfetchArgs *args) {

  gchar *abs_path = g_canonicalize_filename(args->filename, NULL);
  if (abs_path == NULL) {
    return VFETCH_ERROR_PATH_FAILED;
  }
  g_free(args->filename);
  args->filename = abs_path;

  VfetchError err = resolve_geometry(args);
  if (err) {
    return err;
  }

  return VFETCH_SUCCESS;
}

static VfetchError initialize_app_state(AppState *state) {
  global_signal_handler_state_ptr = state;

  if (pthread_mutex_init(&state->fetch_mutex, NULL) != 0 ||
      pthread_mutex_init(&state->audio_state_mutex, NULL) != 0 ||
      pthread_mutex_init(&state->stdout_mutex, NULL) != 0) {
    return VFETCH_ERROR_MUTEX_INIT;
  }

  atomic_store_explicit(
      &state->processing_finished, false, memory_order_release);

  return VFETCH_SUCCESS;
}

static VfetchError setup_environment(AppState *state) {
  struct sigaction sig_action = {0};
  VfetchError err = VFETCH_SUCCESS;

  setup_terminal(state);
  set_cursor_visible(state, false);

  if (pipe(global_signal_pipe) == -1) {
    err = VFETCH_ERROR_PIPE_CREATION;
    log_vfetch_error(err, "Failed to create signal pipe.");
    return err;
  }

  (void)memset(&sig_action, 0, sizeof(sig_action));

  sig_action.sa_flags = SA_SIGINFO;
  sig_action.sa_sigaction = app_signal_handler;
  (void)sigaction(SIGINT, &sig_action, NULL);
  (void)sigaction(SIGTERM, &sig_action, NULL);

  sig_action.sa_flags = SA_RESTART | SA_SIGINFO;
  sig_action.sa_sigaction = app_resize_handler;
  (void)sigaction(SIGWINCH, &sig_action, NULL);

  return err;
}

static VfetchError run_core_logic(AppState *state, VfetchArgs *args) {
  bool cache_was_newly_created = false;

  VfetchError err = initialize_paths_and_geometry(args);
  if (err) {
    log_vfetch_error(err, "Failed to initialize paths and geometry");
    return err;
  }

  if (!args->fetch_tool_arg || strcmp(args->fetch_tool_arg, "none") != 0) {
    err = initialize_fetch_utility(state, args);
    if (err) {
      return err;
    }
  }

  err = prepare_animation_assets(state, args, &cache_was_newly_created);
  if (err == VFETCH_SUCCESS_EXIT_EARLY) {
    return VFETCH_SUCCESS;
  }
  if (err) {
    return err;
  }

  bool should_exit =
      atomic_load_explicit(&state->exit_requested, memory_order_acquire);
  if (should_exit) {
    (void)fputs("\nOperation cancelled during asset preparation.\n", stderr);
    err = VFETCH_SUCCESS;
    return err;
  }

  err = start_fetch_thread(state, args);
  if (err) {
    return err;
  }

  err = run_animation_loop(state, args);

  return err;
}

static void teardown_threads_and_pipes(AppState *state) {
  atomic_store_explicit(&state->exit_requested, true, memory_order_release);

  if (global_signal_pipe[1] != -1) {
    (void)close(global_signal_pipe[1]);
    global_signal_pipe[1] = -1;
  }
  if (state->signal_monitor_thread_id != 0) {
    (void)pthread_join(state->signal_monitor_thread_id, NULL);
  }
  if (global_signal_pipe[0] != -1) {
    (void)close(global_signal_pipe[0]);
    global_signal_pipe[0] = -1;
  }
}

static void cleanup_args_resources(VfetchArgs *args) {
  if (!args) {
    return;
  }

  g_free(args->filename);
  g_free(args->colors_arg);
  g_free(args->fg_color_arg);
  g_free(args->bg_color_arg);
  g_free(args->format_arg);
  g_free(args->fetch_tool_arg);

  if (args->chafa_options) {
    g_hash_table_destroy(args->chafa_options);
  }
}

VfetchError execute_program(int argc,
                            const char *argv[],
                            AppState *state,
                            VfetchArgs *args) {
  VfetchError err = initialize_arguments(args);
  if (err) {
    return err;
  }

  err = parse_arguments(argc, argv, args);
  if (err) {
    return err;
  }

  err = initialize_app_state(state);
  if (err) {
    return err;
  }

  state->args = args;

  err = setup_environment(state);
  if (err) {
    return err;
  }

  if (pthread_create(&state->signal_monitor_thread_id,
                     NULL,
                     signal_monitor_thread_func,
                     state) != 0) {
    err = VFETCH_ERROR_THREAD_CREATION;
    log_vfetch_error(err, "signal monitor thread");
    return err;
  }

  err = run_core_logic(state, args);

  return err;
}

void cleanup_application(AppState *state, VfetchArgs *args) {
  if (state) {
    teardown_threads_and_pipes(state);
    restore_terminal();

    if (state->audio_state.device.pContext != NULL) {
      shutdown_audio(state);
    }

    pthread_mutex_destroy(&state->fetch_mutex);
    pthread_mutex_destroy(&state->audio_state_mutex);

    g_free(state->video_specific_cache_root);
    g_free(state->current_args_cache_dir);
    g_free(state->live_fetch_output);
    g_free(state->fetch_command);
  }

  global_signal_handler_state_ptr = NULL;
  cleanup_args_resources(args);
}