refactor: extract secondary subtitle mode runtime service

src/core/services/secondary-subtitle-service.ts

@@ -0,0 +1,32 @@
+import { SecondarySubMode } from "../../types";
+
+export interface CycleSecondarySubModeDeps {
+  getSecondarySubMode: () => SecondarySubMode;
+  setSecondarySubMode: (mode: SecondarySubMode) => void;
+  getLastSecondarySubToggleAtMs: () => number;
+  setLastSecondarySubToggleAtMs: (timestampMs: number) => void;
+  broadcastSecondarySubMode: (mode: SecondarySubMode) => void;
+  showMpvOsd: (text: string) => void;
+  now?: () => number;
+}
+
+const SECONDARY_SUB_CYCLE: SecondarySubMode[] = ["hidden", "visible", "hover"];
+const SECONDARY_SUB_TOGGLE_DEBOUNCE_MS = 120;
+
+export function cycleSecondarySubModeService(
+  deps: CycleSecondarySubModeDeps,
+): void {
+  const now = deps.now ? deps.now() : Date.now();
+  if (now - deps.getLastSecondarySubToggleAtMs() < SECONDARY_SUB_TOGGLE_DEBOUNCE_MS) {
+    return;
+  }
+  deps.setLastSecondarySubToggleAtMs(now);
+
+  const currentMode = deps.getSecondarySubMode();
+  const currentIndex = SECONDARY_SUB_CYCLE.indexOf(currentMode);
+  const nextMode =
+    SECONDARY_SUB_CYCLE[(currentIndex + 1) % SECONDARY_SUB_CYCLE.length];
+  deps.setSecondarySubMode(nextMode);
+  deps.broadcastSecondarySubMode(nextMode);
+  deps.showMpvOsd(`Secondary subtitle: ${nextMode}`);
+}