优化项目结构

lib/services/epub/web/webview_bridge.dart

@@ -0,0 +1,119 @@
+import 'dart:async';
+
+import 'package:flutter/foundation.dart';
+import 'package:flutter_inappwebview/flutter_inappwebview.dart';
+
+/// Manages JS↔Dart communication over an [InAppWebViewController].
+///
+/// Provides token-based async call tracking so that callers can fire a JS
+/// method that will eventually invoke `FlutterBridge.onEventFinished(token)`,
+/// and await the result on the Dart side via [waitForEvent].
+///
+/// Typical usage:
+/// ```dart
+/// // Fire and forget the token; caller awaits separately.
+/// final token = await _bridge.call((t) => "window.api.loadFrame($t, ...)");
+/// await _bridge.waitForEvent(token);
+///
+/// // Fire and immediately await.
+/// await _bridge.callAndWait((t) => "window.api.jumpToPage($t, $idx)");
+/// ```
+class WebViewBridge {
+  InAppWebViewController? _controller;
+
+  int _currentToken = 0;
+  final Map<int, Completer<void>> _completers = {};
+
+  // ─── Controller lifecycle ──────────────────────────────────────────
+
+  /// Attaches a live [InAppWebViewController]. Call this in `onWebViewCreated`.
+  void attach(InAppWebViewController controller) {
+    _controller = controller;
+  }
+
+  /// Detaches the controller and cancels all pending completers.
+  void detach() {
+    _controller = null;
+    for (final completer in _completers.values) {
+      if (!completer.isCompleted) {
+        completer.completeError(StateError('WebViewBridge detached'));
+      }
+    }
+    _completers.clear();
+  }
+
+  // ─── JS evaluation ─────────────────────────────────────────────────
+
+  /// Evaluates [source] in the WebView. No-ops if no controller is attached.
+  Future<void> evaluate(String source) async {
+    await _controller?.evaluateJavascript(source: source);
+  }
+
+  // ─── Token management ──────────────────────────────────────────────
+
+  /// Allocates a new token and registers a [Completer] for it.
+  ///
+  /// Embed the returned token in the JS call so JS can resolve it via
+  /// `FlutterBridge.onEventFinished(token)`.
+  int issueToken() {
+    _currentToken++;
+    _completers[_currentToken] = Completer<void>();
+    return _currentToken;
+  }
+
+  /// Called by the `onEventFinished` JS handler to resolve a pending token.
+  ///
+  /// A [token] of `-1` is a sentinel for fire-and-forget notifications that
+  /// do not need to be tracked.
+  void resolveToken(int token) {
+    if (token == -1) return;
+    final completer = _completers.remove(token);
+    if (completer != null && !completer.isCompleted) {
+      completer.complete();
+    }
+  }
+
+  // ─── Awaiting ──────────────────────────────────────────────────────
+
+  /// Waits for [token] to be resolved, or times out after [timeoutMs] ms.
+  Future<void> waitForEvent(int token, [int timeoutMs = 10000]) async {
+    final completer = _completers[token];
+    if (completer == null) {
+      debugPrint('WebViewBridge: no completer for token $token');
+      return;
+    }
+    return completer.future.timeout(
+      Duration(milliseconds: timeoutMs),
+      onTimeout: () {
+        _completers.remove(token);
+        debugPrint('WebViewBridge: timeout for token $token');
+      },
+    );
+  }
+
+  /// Waits for all [tokens] to be resolved concurrently.
+  Future<void> waitForEvents(List<int> tokens, [int timeoutMs = 10000]) async {
+    await Future.wait(tokens.map((t) => waitForEvent(t, timeoutMs)));
+  }
+
+  // ─── Convenience helpers ───────────────────────────────────────────
+
+  /// Issues a token, evaluates the JS returned by [source], and returns the
+  /// token so the caller can [waitForEvent] later.
+  Future<int> call(String Function(int token) source) async {
+    final token = issueToken();
+    await evaluate(source(token));
+    return token;
+  }
+
+  /// Issues a token, evaluates the JS returned by [source], and immediately
+  /// awaits [waitForEvent] before returning.
+  Future<void> callAndWait(
+    String Function(int token) source, [
+    int timeoutMs = 10000,
+  ]) async {
+    final token = issueToken();
+    await evaluate(source(token));
+    await waitForEvent(token, timeoutMs);
+  }
+}