117 lines
3.1 KiB
Dart
117 lines
3.1 KiB
Dart
import 'dart:async';
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import 'dart:collection';
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import 'package:flutter/foundation.dart';
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final ServicePolicy servicePolicy = ServicePolicy._private();
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class ServicePolicy {
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final Map<Object, _Task> _paused = {};
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final Queue<_Task> _asapQueue = Queue(), _normalQueue = Queue(), _backgroundQueue = Queue();
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List<Queue<_Task>> _queues;
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_Task _running;
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ServicePolicy._private() {
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_queues = [_asapQueue, _normalQueue, _backgroundQueue];
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}
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Future<T> call<T>(
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Future<T> Function() platformCall, {
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ServiceCallPriority priority = ServiceCallPriority.normal,
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String debugLabel,
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Object key,
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}) {
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var task = _paused.remove(key);
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if (task != null) {
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debugPrint('resume task with key=$key');
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}
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var completer = task?.completer ?? Completer<T>();
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task ??= _Task(
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() async {
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// if (debugLabel != null) debugPrint('$runtimeType $debugLabel start');
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final result = await platformCall();
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completer.complete(result);
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// if (debugLabel != null) debugPrint('$runtimeType $debugLabel completed');
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_running = null;
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_pickNext();
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},
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completer,
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key,
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);
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_getQueue(priority).addLast(task);
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_pickNext();
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return completer.future;
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}
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Future<T> resume<T>(Object key, ServiceCallPriority priority) {
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var task = _paused.remove(key);
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if (task == null) return null;
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_getQueue(priority).addLast(task);
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_pickNext();
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return task.completer.future;
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}
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Queue<_Task> _getQueue(ServiceCallPriority priority) {
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Queue<_Task> queue;
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switch (priority) {
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case ServiceCallPriority.asap:
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queue = _asapQueue;
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break;
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case ServiceCallPriority.background:
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queue = _backgroundQueue;
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break;
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case ServiceCallPriority.normal:
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default:
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queue = _normalQueue;
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break;
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}
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return queue;
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}
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void _pickNext() {
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if (_running != null) return;
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final queue = _queues.firstWhere((q) => q.isNotEmpty, orElse: () => null);
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_running = queue?.removeFirst();
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_running?.callback?.call();
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}
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bool cancel(Object key, ServiceCallPriority priority) {
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var cancelled = false;
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final queue = _getQueue(priority);
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final tasks = queue.where((task) => task.key == key).toList();
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tasks.forEach((task) {
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if (queue.remove(task)) {
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cancelled = true;
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task.completer.completeError(CancelledException());
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}
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});
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return cancelled;
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}
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bool pause(Object key, ServiceCallPriority priority) {
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var paused = false;
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final queue = _getQueue(priority);
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final tasks = queue.where((task) => task.key == key).toList();
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tasks.forEach((task) {
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if (queue.remove(task)) {
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paused = true;
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_paused.putIfAbsent(key, () => task);
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}
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});
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return paused;
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}
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bool isPaused(Object key) => _paused.containsKey(key);
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}
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class _Task {
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final VoidCallback callback;
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final Completer completer;
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final Object key;
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const _Task(this.callback, this.completer, this.key);
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}
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class CancelledException {}
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enum ServiceCallPriority { asap, normal, background }
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