/**
 * Native video surface compositing, Android only.
 *
 * TRACES: UR-003, UR-004 | DR-150, DR-151
 *
 * On Android, ExoPlayer renders video into a SurfaceView that sits *behind* the
 * Tauri WebView (`setZOrderMediaOverlay(false)`, added at index 0 of the content
 * view by VideoOverlayManager). For that video to be visible, two independent
 * opaque layers have to be cleared:
 *
 *  1. The **WebView widget's own background** — reachable only from Kotlin, via
 *     the `AndroidVideoSurface` @JavascriptInterface installed by MainActivity.
 *  2. The **web page's backgrounds** — the `html`/`body` colour in app.css and
 *     the app shell's `bg-[var(--color-background)]`. Handled by the
 *     `data-native-video` attribute, which $lib/stores/nativeVideo.ts sets and
 *     app.css keys its transparency rules off.
 *
 * Clearing only one leaves a black screen with audio, which is exactly the
 * failure mode the old INTERIM override in VideoPlayer.svelte was working
 * around. Both must be toggled together, so this module owns both halves.
 *
 * Everything here is a no-op off Android — the bridge is simply absent.
 */

import { nativeVideoActive } from "$lib/stores/nativeVideo";

interface AndroidVideoSurfaceBridge {
  setTransparent(transparent: boolean): void;
  isSupported(): boolean;
}

declare global {
  interface Window {
    AndroidVideoSurface?: AndroidVideoSurfaceBridge;
  }
}

function bridge(): AndroidVideoSurfaceBridge | undefined {
  if (typeof window === "undefined") return undefined;
  return window.AndroidVideoSurface;
}

/**
 * Whether the native-surface bridge exists on this platform. This reports only
 * that the *plumbing* is present; whether native video should actually be used
 * is Rust's decision (`player_get_capabilities`) gated by the user's
 * `experimentalNativeVideo` flag.
 */
export function isNativeSurfaceBridgeAvailable(): boolean {
  try {
    return bridge()?.isSupported() ?? false;
  } catch (err) {
    console.warn("[videoSurface] isSupported check failed:", err);
    return false;
  }
}

/**
 * Make the webview transparent so the video surface behind it shows through.
 *
 * MUST be paired with {@link disableNativeVideoCompositing} on teardown — a
 * transparent window left behind shows the launcher through the whole app.
 */
export function enableNativeVideoCompositing(): void {
  // Page layer first: if the Kotlin call succeeded but this threw, the user
  // would see through the app to the home screen.
  nativeVideoActive.set(true);
  try {
    bridge()?.setTransparent(true);
  } catch (err) {
    console.warn("[videoSurface] setTransparent(true) failed:", err);
    nativeVideoActive.set(false);
  }
}

/** Restore the opaque webview background. Safe to call unconditionally. */
export function disableNativeVideoCompositing(): void {
  try {
    bridge()?.setTransparent(false);
  } catch (err) {
    console.warn("[videoSurface] setTransparent(false) failed:", err);
  }
  // Always clear the page layer, even if the bridge call failed, so the app is
  // never left rendering over a transparent window.
  nativeVideoActive.set(false);
}