fix(osd): show subtitle-annotation loading status during tokenization

src/main/runtime/subtitle-tokenization-main-deps.ts

@@ -66,8 +66,88 @@ export function createCreateMecabTokenizerAndCheckMainHandler<TMecab>(deps: {
 export function createPrewarmSubtitleDictionariesMainHandler(deps: {
   ensureJlptDictionaryLookup: () => Promise<void>;
   ensureFrequencyDictionaryLookup: () => Promise<void>;
+  showMpvOsd?: (message: string) => void;
+  shouldShowOsdNotification?: () => boolean;
+  setInterval?: (callback: () => void, delayMs: number) => unknown;
+  clearInterval?: (timer: unknown) => void;
 }) {
-  return async (): Promise<void> => {
-    await Promise.all([deps.ensureJlptDictionaryLookup(), deps.ensureFrequencyDictionaryLookup()]);
+  let prewarmed = false;
+  let prewarmPromise: Promise<void> | null = null;
+  let loadingOsdDepth = 0;
+  let loadingOsdFrame = 0;
+  let loadingOsdTimer: unknown = null;
+  const showMpvOsd = deps.showMpvOsd;
+  const shouldShowOsdNotification = deps.shouldShowOsdNotification ?? (() => false);
+  const setIntervalHandler =
+    deps.setInterval ??
+    ((callback: () => void, delayMs: number): unknown => setInterval(callback, delayMs));
+  const clearIntervalHandler =
+    deps.clearInterval ??
+    ((timer: unknown): void => clearInterval(timer as ReturnType<typeof setInterval>));
+  const spinnerFrames = ['|', '/', '-', '\\'];
+
+  const beginLoadingOsd = (): boolean => {
+    if (!showMpvOsd || !shouldShowOsdNotification()) {
+      return false;
+    }
+    loadingOsdDepth += 1;
+    if (loadingOsdDepth > 1) {
+      return true;
+    }
+
+    loadingOsdFrame = 0;
+    showMpvOsd(`Loading subtitle annotations ${spinnerFrames[loadingOsdFrame]}`);
+    loadingOsdFrame += 1;
+    loadingOsdTimer = setIntervalHandler(() => {
+      if (!showMpvOsd) {
+        return;
+      }
+      showMpvOsd(`Loading subtitle annotations ${spinnerFrames[loadingOsdFrame % spinnerFrames.length]}`);
+      loadingOsdFrame += 1;
+    }, 180);
+    return true;
+  };
+
+  const endLoadingOsd = (): void => {
+    if (!showMpvOsd || !shouldShowOsdNotification()) {
+      return;
+    }
+
+    loadingOsdDepth = Math.max(0, loadingOsdDepth - 1);
+    if (loadingOsdDepth > 0) {
+      return;
+    }
+
+    if (loadingOsdTimer) {
+      clearIntervalHandler(loadingOsdTimer);
+      loadingOsdTimer = null;
+    }
+    showMpvOsd('Subtitle annotations loaded');
+  };
+
+  return async (options?: { showLoadingOsd?: boolean }): Promise<void> => {
+    if (prewarmed) {
+      return;
+    }
+    const shouldTrackLoadingOsd = options?.showLoadingOsd === true;
+    const loadingOsdStarted = shouldTrackLoadingOsd ? beginLoadingOsd() : false;
+
+    if (!prewarmPromise) {
+      prewarmPromise = (async () => {
+        try {
+          await Promise.all([deps.ensureJlptDictionaryLookup(), deps.ensureFrequencyDictionaryLookup()]);
+          prewarmed = true;
+        } finally {
+          prewarmPromise = null;
+        }
+      })();
+    }
+    try {
+      await prewarmPromise;
+    } finally {
+      if (loadingOsdStarted) {
+        endLoadingOsd();
+      }
+    }
   };
 }