+ if (dirent->d_name[strlen(dirent->d_name)-1] != '~')
+ mnemon_load_category (mnemon, dirent->d_name);
+ }
+ }
+
+ closedir (dir);
+}
+
+static void
+mnemon_save (mnemon_t *mnemon)
+{
+ int i, err;
+ char *filename, *lock_filename;
+ FILE *file;
+ category_t *category;
+
+ for (i = 0; i < mnemon->num_categories; i++) {
+ category = &mnemon->categories[i];
+
+ xasprintf (&filename, "%s/%s",
+ mnemon->dir_name, category->name);
+ xasprintf (&lock_filename, "%s/.#%s",
+ mnemon->dir_name, category->name);
+
+ file = fopen (lock_filename, "w");
+ if (file == NULL) {
+ fprintf (stderr, "Error: Failed to open %s for writing: %s\n",
+ lock_filename, strerror (errno));
+ continue;
+ }
+
+ category_print (category, file);
+
+ fclose (file);
+
+ err = rename (lock_filename, filename);
+ if (err < 0) {
+ fprintf (stderr, "Error: Failed to rename %s to %s: %s\n",
+ lock_filename, filename, strerror (errno));
+ continue;
+ }
+
+ free (filename);
+ free (lock_filename);
+ }
+}
+
+/* Return a uniformly-distributed pseudo-random integer within the
+ * range:
+ *
+ * 0 <= result < num_values
+ */
+static int
+rand_within (int num_values)
+{
+ return (int) (num_values * (rand() / (RAND_MAX + 1.0)));
+}
+
+/* Return an exponentially-distributed pseudo-random integer within
+ * the range:
+ *
+ * 0 <= result < num_values
+ *
+ * The distribution is such that each successively larger value will
+ * occur with a probability of half of the previous value.
+ */
+static int
+rand_within_exponential (int num_values)
+{
+ static int r;
+ static uint32_t mask = 0;
+ int ones;
+ int bit;
+
+ /* Optimize the constant case. */
+ if (num_values == 1)
+ return 0;
+
+ ones = 0;
+
+ do {
+ if (mask == 0) {
+ r = rand ();
+ mask = 1 << 31;
+ while (mask > RAND_MAX)
+ mask >>= 1;
+ }
+ bit = r & mask;
+ mask >>= 1;
+ if (bit) {
+ ones++;
+ if (ones == num_values)
+ ones = 0;
+ }
+ } while (bit);
+
+ return ones;
+}
+
+/* Find the category to which an item belongs. */
+static category_t *
+mnemon_item_category (mnemon_t *mnemon,
+ item_t *item)
+{
+ category_t *category;
+ int i, item_index;
+
+ for (i = 0; i < mnemon->num_categories; i++) {
+ category = &mnemon->categories[i];
+ item_index = item - category->items;
+ if (item_index >= 0 && item_index < category->num_items)
+ return category;
+ }
+
+ assert (0);
+}
+
+typedef struct _item_in_category_closure
+{
+ mnemon_t *mnemon;
+ category_t *category;
+} item_in_category_closure_t;
+
+static int
+mnemon_item_in_category (void *closure, item_t *item)
+{
+ item_in_category_closure_t *iicc = closure;
+ mnemon_t *mnemon = iicc->mnemon;
+ category_t *category = iicc->category;
+
+ return (mnemon_item_category (mnemon, item) == category);
+}
+
+typedef struct _item_in_category_of_length_closure
+{
+ mnemon_t *mnemon;
+ category_t *category;
+ int length;
+} item_in_category_of_length_closure_t;
+
+static int
+mnemon_item_in_category_of_length (void *closure, item_t *item)
+{
+ item_in_category_of_length_closure_t *iicolc = closure;
+ mnemon_t *mnemon = iicolc->mnemon;
+ category_t *category = iicolc->category;
+ int length = iicolc->length;
+
+ if (mnemon_item_category (mnemon, item) != category)
+ return 0;
+
+ return strlen (item->challenge) == length;
+}
+
+static void
+mnemon_select_item (mnemon_t *mnemon,
+ bin_t **bin_ret,
+ int *item_index_ret)
+{
+ int bin_index, item_index;
+ bin_t *bin;
+
+ bin_index = rand_within_exponential (mnemon->num_bins);
+
+ bin = &mnemon->bins[bin_index];
+
+ item_index = rand_within (bin->num_items);
+
+ if (bin->score == 0) {
+ category_t *category;
+ item_t *item;
+
+ item = bin->items[item_index];
+
+ category = mnemon_item_category (mnemon, item);
+
+ if (category->order == CATEGORY_ORDER_SEQUENTIAL) {
+ item = category_next_bin_zero_item (category);
+ if (item)
+ item_index = bin_item_index (bin, item);
+ }
+ }
+
+ *bin_ret = bin;
+ *item_index_ret = item_index;
+}
+
+
+#define HISTOGRAM_ROW_FORMAT "%3d: %3d"
+#define HISTOGRAM_BAR_WIDTH 63
+
+static void
+print_histogram_bar (double size,
+ double max)
+{
+ int units_per_cell = (int) ceil (max / HISTOGRAM_BAR_WIDTH);
+ static char const *boxes[8] = {
+ "█", "▉", "▊", "▋",
+ "▌", "▍", "▎", "▏"
+ };
+
+ while (size > units_per_cell) {
+ printf(boxes[0]);
+ size -= units_per_cell;
+ }
+
+ size /= units_per_cell;
+
+ if (size > 7.5/8.0)
+ printf(boxes[0]);
+ else if (size > 6.5/8.0)
+ printf(boxes[1]);
+ else if (size > 5.5/8.0)
+ printf(boxes[2]);
+ else if (size > 4.5/8.0)
+ printf(boxes[3]);
+ else if (size > 3.5/8.0)
+ printf(boxes[4]);
+ else if (size > 2.5/8.0)
+ printf(boxes[5]);
+ else if (size > 1.5/8.0)
+ printf(boxes[6]);
+ else if (size > 0.5/8.0)
+ printf(boxes[7]);
+
+ printf ("\n");
+}
+
+static void
+mnemon_print_histogram (mnemon_t *mnemon,
+ const char *category_name,
+ int length)
+{
+ int i, last_score, max;
+ category_t *category = NULL;
+ bin_t *bin;
+ int num_items;
+ item_match_predicate_t *predicate = NULL;
+ void *closure = NULL;
+ item_in_category_closure_t item_in_category;
+ item_in_category_of_length_closure_t item_in_category_of_length;
+
+ if (mnemon->num_bins == 0)
+ return;
+
+ if (category_name) {
+ category = mnemon_get_category_if_exists (mnemon, category_name);
+ if (category) {
+ if (length) {
+ predicate = mnemon_item_in_category_of_length;
+ item_in_category_of_length.mnemon = mnemon;
+ item_in_category_of_length.category = category;
+ item_in_category_of_length.length = length;
+ closure = &item_in_category_of_length;
+ } else {
+ predicate = mnemon_item_in_category;
+ item_in_category.mnemon = mnemon;
+ item_in_category.category = category;
+ closure = &item_in_category;
+ }
+ }
+ }
+
+ for (i = 0; i < mnemon->num_bins; i++) {
+ num_items = bin_num_items_matching (&mnemon->bins[i],
+ predicate, closure);
+ if (i == 0 || num_items > max)
+ max = num_items;
+ }
+
+ for (i = 0; i < mnemon->num_bins; i++) {
+ bin = &mnemon->bins[i];
+ if (i != 0)
+ while (bin->score - last_score > 1)
+ printf (HISTOGRAM_ROW_FORMAT "\n", ++last_score, 0);
+ num_items = bin_num_items_matching (bin,
+ predicate, closure);
+ printf (HISTOGRAM_ROW_FORMAT " ", bin->score, num_items);
+ print_histogram_bar (num_items, max);
+ last_score = bin->score;
+ }
+}
+
+static void
+mnemon_handle_command (mnemon_t *mnemon,
+ const char *command)
+{
+ const char *arg;
+ int len;
+ switch (command[0]) {
+ case 'h':
+ {
+ char *category = NULL;
+ int length = 0;
+
+ arg = command + 1;
+ arg += strspn (arg, " \t");
+ len = strcspn (arg, " \t");
+ if (len) {
+ category = xstrndup (arg, len);
+ arg += len;
+ arg += strspn (arg, " \t");
+ if (*arg)
+ length = atoi (arg);
+ }
+ mnemon_print_histogram (mnemon, category, length);
+ }
+ break;
+ default:
+ printf ("Unknown command: %s\n", command);
+ break;
+ }
+}
+
+static void
+mnemon_handle_response (mnemon_t *mnemon,
+ bin_t *bin,
+ int item_index,
+ item_t *item,
+ const char *response)
+{
+ bool_t correct;
+
+ correct = (strcmp (response, item->response) == 0);
+
+ bin_remove_item (bin, item_index);
+
+ /* If the bin is now empty, we must remove it. Also if we just
+ * picked the last word we'll ever pick from the bin with
+ * score 0, then we can remove that as well. */
+ if (bin->num_items == 0 ||
+ (bin->score == 0 && mnemon->to_introduce == 0))
+ {
+ mnemon_remove_bin (mnemon, bin);
+ }
+
+ if (correct) {
+ item->score++;
+ /* We reserve an item score of 0 for an item that has
+ * never been asked. */
+ if (item->score == 0) {
+ item->score = 1;
+ mnemon->unlearned--;
+ printf ("You got it!");
+ } else if (item->score < 0) {
+ printf ("Yes---just give me %d more.",
+ - item->score);
+ } else if (item->score == 1) {
+ printf ("On your first try, no less!");
+ } else {
+ printf ("Masterful (%dx).", item->score);
+ if (mnemon->to_master)
+ mnemon->mastered++;
+ }
+ } else {
+ printf (" %s is the correct answer.",
+ item->response);
+ /* Penalize an incorrect response by forcing the score
+ * negative. */
+ if (item->score >= 0) {
+ if (item->score > 0)
+ printf ( " Oops, you knew that, right?\n ");
+ mnemon->unlearned++;
+ /* We go to -2 to force a little extra reinforcement
+ * when re-learning an item, (otherwise, it will often
+ * get asked again immediately where it is easy to get
+ * a correct response without any learning). */
+ item->score = -2;