#include "platform.h"

// ----------------------------- Globals ------------------------------------
static atomic_uint_fast64_t g_bytes_processed = 0;
FileEntry *g_entries = NULL;
size_t g_entry_count = 0;
size_t g_entry_capacity = 0;

// ----------------------------- Utils --------------------------------------
static void perror_exit(const char *msg) {
  perror(msg);
  exit(1);
}

static void *xmalloc(size_t n) {
  void *p = malloc(n);
  if (!p)
    perror_exit("malloc");
  return p;
}

static void add_entry(const FileEntry *src) {
  if (g_entry_count + 1 > g_entry_capacity) {
    g_entry_capacity = g_entry_capacity ? g_entry_capacity * 2 : 1024;
    g_entries = realloc(g_entries, sizeof(FileEntry) * g_entry_capacity);
    if (!g_entries)
      perror_exit("realloc");
  }

  FileEntry *dst = &g_entries[g_entry_count++];
  memset(dst, 0, sizeof(*dst));

  dst->size_bytes = src->size_bytes;
  dst->created_time = src->created_time;
  dst->modified_time = src->modified_time;

  if (src->path)
    dst->path = strdup(src->path);

  strncpy(dst->owner, src->owner, sizeof(dst->owner) - 1);
  dst->owner[sizeof(dst->owner) - 1] = '\0';
}

static void free_entries(void) {
  for (size_t i = 0; i < g_entry_count; ++i) {
    free(g_entries[i].path);
  }

  free(g_entries);
  g_entries = NULL;
  g_entry_count = 0;
  g_entry_capacity = 0;
}

// ----------------------------- Owner lookup ------------------------------
static void get_file_owner(uid_t uid, char *out, size_t out_sz) {
  struct passwd *pw = getpwuid(uid);
  if (pw) {
    snprintf(out, out_sz, "%s", pw->pw_name);
  } else {
    snprintf(out, out_sz, "UNKNOWN");
  }
}

// ----------------------------- Format time helper -------------------------
static void format_time(uint64_t t, char *out, size_t out_sz) {
  if (t == 0) {
    snprintf(out, out_sz, "N/A");
    return;
  }

  time_t tt = (time_t)t;
  struct tm tm;

#if PLATFORM_WINDOWS
  localtime_s(&tm, &tt);
#else
  localtime_r(&tt, &tm);
#endif

  strftime(out, out_sz, "%Y-%m-%d %H:%M:%S", &tm);
}

// --------------- parallel directory scanning ----------------

// Add queue helper functions
static void dirqueue_push(DirQueue *q, const char *path) {
  DirJob *job = malloc(sizeof(*job));
  job->path = strdup(path);
  job->next = NULL;

  pthread_mutex_lock(&q->mutex);

  if (q->tail)
    q->tail->next = job;
  else
    q->head = job;

  q->tail = job;

  pthread_cond_signal(&q->cond);
  pthread_mutex_unlock(&q->mutex);
}

static char *dirqueue_pop(DirQueue *q) {
  pthread_mutex_lock(&q->mutex);
  while (!q->head && !q->stop)
    pthread_cond_wait(&q->cond, &q->mutex);

  if (q->stop) {
    pthread_mutex_unlock(&q->mutex);
    return NULL;
  }

  DirJob *job = q->head;
  q->head = job->next;
  if (!q->head)
    q->tail = NULL;

  q->active_workers++;
  pthread_mutex_unlock(&q->mutex);

  char *path = job->path;
  free(job);
  return path;
}

static void dirqueue_done(DirQueue *q) {
  pthread_mutex_lock(&q->mutex);
  q->active_workers--;

  if (!q->head && q->active_workers == 0) {
    q->stop = 1;
    pthread_cond_broadcast(&q->cond);
  }
  pthread_mutex_unlock(&q->mutex);
}

// Scanning directory worker thread function
static void scan_worker(void *arg) {
  DirQueue *q = arg;

  for (;;) {
    char *dir = dirqueue_pop(q);
    if (!dir)
      break;

    scan_folder_posix_parallel(dir, q);

    free(dir);
    dirqueue_done(q);
  }
}

// Scanning directory function
void scan_folder_posix_parallel(const char *base, DirQueue *q) {
  DIR *d = opendir(base);
  if (!d)
    return;

  struct dirent *ent;
  while ((ent = readdir(d))) {
    if (!strcmp(ent->d_name, ".") || !strcmp(ent->d_name, ".."))
      continue;

    char full[MAX_PATHLEN];
    snprintf(full, sizeof(full), "%s/%s", base, ent->d_name);

    struct stat st;
    if (lstat(full, &st) != 0)
      continue;

    if (S_ISDIR(st.st_mode)) {
      dirqueue_push(q, full);
    } else if (S_ISREG(st.st_mode)) {
      FileEntry fe;
      memset(&fe, 0, sizeof(fe));

      normalize_path(full);

      fe.path = full;
      fe.size_bytes = (uint64_t)st.st_size;
      fe.created_time = (uint64_t)st.st_ctime;
      fe.modified_time = (uint64_t)st.st_mtime;

      get_file_owner(st.st_uid, fe.owner, sizeof(fe.owner));

      add_entry(&fe);
    }
  }
  closedir(d);
}

// ----------------------------- Job queue ----------------------------------
static void jobqueue_init(JobQueue *q) {
  q->head = q->tail = NULL;
  atomic_store(&q->count, 0);
  q->stop = 0;
  pthread_mutex_init(&q->mutex, NULL);
  pthread_cond_init(&q->cond, NULL);
}

static void jobqueue_push(JobQueue *q, Job *job) {
  pthread_mutex_lock(&q->mutex);
  job->next = NULL;
  if (q->tail)
    q->tail->next = job;
  else
    q->head = job;
  q->tail = job;
  atomic_fetch_add(&q->count, 1);
  pthread_cond_signal(&q->cond);
  pthread_mutex_unlock(&q->mutex);
}

static Job *jobqueue_pop(JobQueue *q) {
  pthread_mutex_lock(&q->mutex);
  while (!q->head && !q->stop)
    pthread_cond_wait(&q->cond, &q->mutex);
  if (q->stop && !q->head) {
    pthread_mutex_unlock(&q->mutex);
    return NULL;
  }
  Job *j = q->head;
  q->head = j->next;
  if (!q->head)
    q->tail = NULL;
  pthread_mutex_unlock(&q->mutex);
  if (j)
    atomic_fetch_sub(&q->count, 1);
  return j;
}

static void jobqueue_stop(JobQueue *q) {
  pthread_mutex_lock(&q->mutex);
  q->stop = 1;
  pthread_cond_broadcast(&q->cond);
  pthread_mutex_unlock(&q->mutex);
}

// ----------------------------- Hashing helpers -----------------------------
static void xxh3_hash_file_stream(const char *path, char *out_hex) {
  // compute XXH3_128 over file. POSIX and Windows use standard reads in this
  // helper.
  int fd = open(path, O_RDONLY);
  if (fd < 0) {
    strcpy(out_hex, "ERROR");
    return;
  }
  XXH128_hash_t h;
  XXH3_state_t *state = XXH3_createState();
  XXH3_128bits_reset(state);
  unsigned char *buf = (unsigned char *)malloc(READ_BLOCK);
  ssize_t r;
  while ((r = read(fd, buf, READ_BLOCK)) > 0) {
    XXH3_128bits_update(state, buf, (size_t)r);
    atomic_fetch_add(&g_bytes_processed, (uint64_t)r);
  }

  h = XXH3_128bits_digest(state);
  XXH3_freeState(state);
  close(fd);
  free(buf);
  snprintf(out_hex, HASH_STRLEN, "%016llx%016llx", (unsigned long long)h.high64,
           (unsigned long long)h.low64);
}

// ----------------------------- Worker --------------------------------------
static void *worker_thread_posix(void *argp) {
  WorkerArg *w = (WorkerArg *)argp;
  JobQueue *q = w->queue;
  for (;;) {
    Job *job = jobqueue_pop(q);
    if (!job)
      break;
    char hex[HASH_STRLEN];
    xxh3_hash_file_stream(job->file->path, hex);

    // append to file_hashes.txt atomically: we will store results to a temp
    // buffer and write them at the end (to avoid synchronization issues). But
    // for simplicity, here we append directly using a file lock (fopen+fwrite
    // guarded by mutex). We'll store results in job->file->path? Instead,
    // simple global append with a mutex. Using a file-level append lock:
    static pthread_mutex_t append_mutex = PTHREAD_MUTEX_INITIALIZER;
    pthread_mutex_lock(&append_mutex);
    FILE *hf = fopen(FILE_HASHES_TXT, "a");
    if (hf) {
      char created[32], modified[32];

      format_time(job->file->created_time, created, sizeof(created));
      format_time(job->file->modified_time, modified, sizeof(modified));
      double size_kib = (double)job->file->size_bytes / (1024.0);

      fprintf(hf, "%s\t%s\t%.2f\t%s\t%s\t%s\n", hex, job->file->path, size_kib,
              created, modified, job->file->owner);
      fclose(hf);
    }
    pthread_mutex_unlock(&append_mutex);

    atomic_fetch_add(w->done_counter, 1);
    free(job);
  }
  atomic_fetch_sub(w->live_workers, 1);
  return NULL;
}

// ----------------------------- Progress display ---------------------------
static void print_progress(size_t done, size_t total) {
  const int barw = 40;
  double pct = total ? (double)done / (double)total : 0.0;
  int filled = (int)(pct * barw + 0.5);
  printf("\r[");
  for (int i = 0; i < filled; ++i)
    putchar('#');
  for (int i = filled; i < barw; ++i)
    putchar(' ');
  printf("] %6.2f%%  (%zu / %zu)  ", pct * 100.0, done, total);
  fflush(stdout);
}

// ----------------------------- Helpers: load/save --------------------------
static int file_exists(const char *path) {
  struct stat st;
  return (stat(path, &st) == 0);
}

static void save_file_list(const char *list_path) {
  FILE *f = fopen(list_path, "w");
  if (!f) {
    perror("fopen file_list");
    return;
  }
  for (size_t i = 0; i < g_entry_count; ++i) {
    fprintf(f, "%s\n", g_entries[i].path);
  }
  fclose(f);
}

static void load_file_list(const char *list_path) {
  FILE *f = fopen(list_path, "r");
  if (!f)
    return;

  char line[MAX_PATHLEN];

  while (fgets(line, sizeof(line), f)) {
    line[strcspn(line, "\r\n")] = 0;

    FileEntry fe;
    memset(&fe, 0, sizeof(fe));

    fe.path = line;

    /* Populate metadata from filesystem */
    platform_get_file_times(line, &fe.created_time, &fe.modified_time);

    platform_get_file_owner(line, fe.owner, sizeof(fe.owner));

    add_entry(&fe);
  }

  fclose(f);
}

// Read existing hashes into memory map for resume
// Simple linear search mapping: returns 1 if path has hash found (and writes
// into out_hex)
static int find_hash_in_file(const char *hashfile, const char *path,
                             char *out_hex) {
  FILE *f = fopen(hashfile, "r");
  if (!f)
    return 0;
  char p[MAX_PATHLEN];
  char h[128];
  int found = 0;
  while (fscanf(f, "%4095s %127s", p, h) == 2) {
    if (strcmp(p, path) == 0) {
      strncpy(out_hex, h, HASH_STRLEN);
      out_hex[HASH_STRLEN - 1] = 0;
      found = 1;
      break;
    }
  }
  fclose(f);
  return found;
}
// ----------------------------- Get file metadata -------------------------
void platform_get_file_times(const char *path, uint64_t *out_created,
                             uint64_t *out_modified) {
  struct stat st;
  if (stat(path, &st) == 0) {
    *out_created = (uint64_t)st.st_ctime;
    *out_modified = (uint64_t)st.st_mtime;
  } else {
    *out_created = 0;
    *out_modified = 0;
  }
}

void platform_get_file_owner(const char *path, char *out_owner,
                             size_t out_owner_size) {
  struct stat st;
  if (stat(path, &st) == 0) {
    get_file_owner(st.st_uid, out_owner, out_owner_size);
  } else {
    snprintf(out_owner, out_owner_size, "UNKNOWN");
  }
}

// ----------------------------- Main ---------------------------------------
int main(int argc, char **argv) {
  char folders[64][MAX_PATHLEN]; // up to 64 input folders
  int folder_count = 0;
  int resume = 0;

  // -------------------------------
  // Parse arguments
  // -------------------------------
  for (int i = 1; i < argc; ++i) {
    if (strcmp(argv[i], "-resume") == 0) {
      resume = 1;
    } else {
      if (folder_count < 64) {
        strncpy(folders[folder_count], argv[i], MAX_PATHLEN - 1);
        folders[folder_count][MAX_PATHLEN - 1] = 0;
        folder_count++;
      }
    }
  }

  // -------------------------------
  // Ask user if no folders provided
  // -------------------------------
  if (folder_count == 0 && !resume) {
    printf("Enter folder to process (Enter = current folder): ");
    fflush(stdout);

    char buf[MAX_PATHLEN];
    if (!fgets(buf, sizeof(buf), stdin))
      return 1;
    buf[strcspn(buf, "\r\n")] = 0;

    if (buf[0] == 0)
      strcpy(folders[0], ".");
    else
      strncpy(folders[0], buf, MAX_PATHLEN - 1);

    folder_count = 1;
  } else if (folder_count == 0 && resume) {
    strcpy(folders[0], ".");
    folder_count = 1;
  }

  // -------------------------------
  // Display selected folders
  // -------------------------------
  printf("Processing %d folder(s):\n", folder_count);
  for (int i = 0; i < folder_count; ++i) {
    printf("  - %s\n", folders[i]);
  }

  // -------------------------------
  // Detect hardware threads (CPU cores)
  // -------------------------------
  size_t hw_threads = 1;
  long cpus = sysconf(_SC_NPROCESSORS_ONLN);
  if (cpus > 0)
    hw_threads = (size_t)cpus;

  // Add some extra threads to overlap I/O more aggressively
  size_t num_threads = hw_threads * 2;
  if (num_threads < 2)
    num_threads = 2;

  // -------------------------------
  // Step 1: Scan all folders
  // -------------------------------
  if (!resume) {
    DirQueue q = {0};
    pthread_mutex_init(&q.mutex, NULL);
    pthread_cond_init(&q.cond, NULL);

    // Seed queue
    for (int i = 0; i < folder_count; ++i)
      dirqueue_push(&q, folders[i]);

    pthread_t *threads = malloc(sizeof(pthread_t) * num_threads);

    for (size_t i = 0; i < num_threads; ++i)
      pthread_create(&threads[i], NULL, (void *(*)(void *))scan_worker, &q);

    for (size_t i = 0; i < num_threads; ++i)
      pthread_join(threads[i], NULL);

    free(threads);

    pthread_mutex_destroy(&q.mutex);
    pthread_cond_destroy(&q.cond);

    printf("Found %zu files. Saving to %s\n", g_entry_count, FILE_LIST_TXT);
    save_file_list(FILE_LIST_TXT);
  } else {
    if (!file_exists(FILE_LIST_TXT)) {
      fprintf(stderr, "Resume requested but %s not found\n", FILE_LIST_TXT);
      return 1;
    }
    load_file_list(FILE_LIST_TXT);
    printf("Loaded %zu files from %s\n", g_entry_count, FILE_LIST_TXT);
  }

  if (g_entry_count == 0) {
    printf("No files to process.\n");
    return 0;
  }

  // If resume: create map of which files are already hashed
  char **existing_hash = calloc(g_entry_count, sizeof(char *));
  for (size_t i = 0; i < g_entry_count; ++i)
    existing_hash[i] = NULL;

  if (resume && file_exists(FILE_HASHES_TXT)) {
    // For simplicity we parse hash file and match lines to list entries.
    for (size_t i = 0; i < g_entry_count; ++i) {
      char hex[HASH_STRLEN] = {0};
      if (find_hash_in_file(FILE_HASHES_TXT, g_entries[i].path, hex)) {
        existing_hash[i] = strdup(hex);
      }
    }
  }

  // Prepare job queue of only missing files (or all if not resume)
  JobQueue queue;
  jobqueue_init(&queue);

  size_t total_jobs = 0;
  for (size_t i = 0; i < g_entry_count; ++i) {
    if (resume && existing_hash[i])
      continue;
    Job *j = (Job *)malloc(sizeof(Job));
    j->file = &g_entries[i];
    j->next = NULL;
    jobqueue_push(&queue, j);
    ++total_jobs;
  }

  if (total_jobs == 0) {
    printf("Nothing to do — all files already hashed.\n");
    return 0;
  }

  // Remove old hashes file if we're recomputing from scratch.
  if (!resume) {
    // create/overwrite hashes file
    FILE *hf = fopen(FILE_HASHES_TXT, "w");
    if (hf)
      fclose(hf);
  } // if resume, we append only missing

  // Starting thread pool

  atomic_size_t done_counter;
  atomic_store(&done_counter, 0);
  atomic_int live_workers;
  atomic_store(&live_workers, (int)num_threads);

  WorkerArg warg = {.queue = &queue,
                    .done_counter = &done_counter,
                    .total_jobs = total_jobs,
                    .live_workers = &live_workers};

  printf("Starting thread pool: %zu threads (CPU cores: %zu)\n", num_threads,
         hw_threads);

  // Launch threads
  pthread_t *tids = malloc(sizeof(pthread_t) * num_threads);
  for (size_t i = 0; i < num_threads; ++i) {
    pthread_create(&tids[i], NULL, worker_thread_posix, &warg);
  }

  // Progress / timer
  struct timespec tstart, tnow;
  clock_gettime(CLOCK_MONOTONIC, &tstart);

  size_t last_done = 0;

  // ---------- Correct real-time MB/s (stable & accurate) ----------
  uint64_t last_bytes = atomic_load(&g_bytes_processed);
  double last_time = 0.0;
  double displayed_speed = 0.0;
  const double sample_interval = 0.5;
  char linebuf[256];

  for (;;) {
    size_t done = (size_t)atomic_load(&done_counter);

    // ---- monotonic time ----
    clock_gettime(CLOCK_MONOTONIC, &tnow);
    double now =
        (tnow.tv_sec - tstart.tv_sec) + (tnow.tv_nsec - tstart.tv_nsec) / 1e9;

    // ---- bytes so far ----
    uint64_t bytes = atomic_load(&g_bytes_processed);

    // ---- real sampler (independent of UI sleep) ----
    if (last_time == 0.0) {
      last_time = now;
      last_bytes = bytes;
    }

    double dt = now - last_time;
    if (dt >= sample_interval) {
      uint64_t db = bytes - last_bytes;

      if (db > 0 && dt > 0.0001) {
        displayed_speed = (double)db / (1024.0 * 1024.0) / dt;
      }

      last_bytes = bytes;
      last_time = now;
    }

    // ---- progress bar build ----
    const int barw = 40;
    double pct = total_jobs ? (double)done / (double)total_jobs : 0.0;
    int filled = (int)(pct * barw + 0.5);

    int p = 0;
    p += snprintf(linebuf + p, sizeof(linebuf) - p, "[");
    for (int i = 0; i < filled && p < (int)sizeof(linebuf); ++i)
      p += snprintf(linebuf + p, sizeof(linebuf) - p, "#");
    for (int i = filled; i < barw && p < (int)sizeof(linebuf); ++i)
      p += snprintf(linebuf + p, sizeof(linebuf) - p, ".");

    snprintf(linebuf + p, sizeof(linebuf) - p,
             "] %6.2f%% (%zu / %zu)  %8.2f MB/s", pct * 100.0, done, total_jobs,
             displayed_speed);

    printf("\r%s", linebuf);
    fflush(stdout);

    if (done >= total_jobs)
      break;

    usleep(100000);
  }

  printf("\n\n");

  // stop queue and join threads
  jobqueue_stop(&queue);
  for (size_t i = 0; i < num_threads; ++i)
    pthread_join(tids[i], NULL);

  // done time
  clock_gettime(CLOCK_MONOTONIC, &tnow);
  double elapsed =
      (tnow.tv_sec - tstart.tv_sec) + (tnow.tv_nsec - tstart.tv_nsec) / 1e9;

  printf("Completed hashing %zu files in %.2f seconds\n", total_jobs, elapsed);
  uint64_t total_bytes = (uint64_t)atomic_load(&g_bytes_processed);
  double total_mb = (double)total_bytes / (1024.0 * 1024.0);
  double avg_mbps = total_mb / elapsed;
  printf("Total: %.2f MB, Average: %.2f MB/s\n", total_mb, avg_mbps);

  // If resume: we appended missing entries. If not resume: we wrote all results
  // during workers. Note: This program appends hashes as workers finish. This
  // avoids holding all hashes in RAM.

  // Cleanup
  for (size_t i = 0; i < g_entry_count; ++i)
    if (existing_hash[i])
      free(existing_hash[i]);
  free(existing_hash);

  free_entries();

  return 0;
}