import 'dart:async';

import 'package:flutter_test/flutter_test.dart';
import 'package:pj_supermarket_cloud/common/utils/app/face_readiness_cache.dart';

void main() {
  test('已就绪的重复读取直接使用缓存，不再次加载', () async {
    final cache = FaceReadinessCache<String>();
    var calls = 0;
    Future<String> load() async {
      calls++;
      return 'ready';
    }

    expect(await cache.read(load, canCache: (_) => true), 'ready');
    expect(await cache.read(load, canCache: (_) => true), 'ready');
    expect(cache.value, 'ready');
    expect(calls, 1);
  });

  test('同一代次的并发读取只发起一次加载', () async {
    final cache = FaceReadinessCache<String>();
    final source = Completer<String>();
    var calls = 0;
    Future<String> load() {
      calls++;
      return source.future;
    }

    final first = cache.read(load, canCache: (_) => true);
    final second = cache.read(load, canCache: (_) => true);
    expect(identical(first, second), isTrue);
    expect(calls, 1);
    source.complete('ready');
    expect(await Future.wait([first, second]), ['ready', 'ready']);
    expect(cache.value, 'ready');
  });

  test('相同数量的样本替换仍会在失效后重新检查', () async {
    final cache = FaceReadinessCache<List<int>>();
    var sampleIds = <int>[1, 2];
    var calls = 0;
    Future<List<int>> load() async {
      calls++;
      return List.unmodifiable(sampleIds);
    }

    expect(await cache.read(load, canCache: (_) => true), [1, 2]);
    sampleIds = [1, 3];
    cache.invalidate();
    expect(cache.value, isNull);
    expect(await cache.read(load, canCache: (_) => true), [1, 3]);
    expect(calls, 2);
  });

  test('查询中失效会创建新查询，旧查询完成不能清除新查询', () async {
    final cache = FaceReadinessCache<String>();
    final oldSource = Completer<String>();
    final newSource = Completer<String>();
    var calls = 0;
    Future<String> load() {
      calls++;
      return calls == 1 ? oldSource.future : newSource.future;
    }

    final oldRead = cache.read(load, canCache: (_) => true);
    cache.invalidate();
    final newRead = cache.read(load, canCache: (_) => true);
    expect(identical(oldRead, newRead), isFalse);
    expect(calls, 2);

    oldSource.complete('old');
    expect(await oldRead, 'old');
    expect(cache.value, isNull);
    final joined = cache.read(load, canCache: (_) => true);
    expect(identical(joined, newRead), isTrue);
    expect(calls, 2);

    newSource.complete('new');
    expect(await newRead, 'new');
    expect(await joined, 'new');
    expect(cache.value, 'new');
  });

  test('旧查询晚于新查询完成时不能覆盖新缓存', () async {
    final cache = FaceReadinessCache<String>();
    final oldSource = Completer<String>();
    final oldRead = cache.read(() => oldSource.future, canCache: (_) => true);
    cache.invalidate();

    expect(await cache.read(() async => 'new', canCache: (_) => true), 'new');
    oldSource.complete('old');
    expect(await oldRead, 'old');
    expect(cache.value, 'new');
  });

  test('嵌套变更全部结束后才允许缓存，中途读到就绪也不缓存', () async {
    final cache = FaceReadinessCache<String>();
    var calls = 0;
    Future<String> load() async {
      calls++;
      return 'ready';
    }

    await cache.read(load, canCache: (_) => true);
    cache.beginMutation();
    cache.beginMutation();
    expect(cache.mutationDepth, 2);
    expect(cache.value, isNull);
    expect(await cache.read(load, canCache: (_) => true), 'ready');
    expect(cache.value, isNull);

    cache.endMutation();
    expect(cache.mutationDepth, 1);
    expect(await cache.read(load, canCache: (_) => true), 'ready');
    expect(cache.value, isNull);

    cache.endMutation();
    expect(cache.mutationDepth, 0);
    expect(await cache.read(load, canCache: (_) => true), 'ready');
    expect(cache.value, 'ready');
    expect(calls, 4);
    expect(cache.endMutation, throwsStateError);
    expect(cache.mutationDepth, 0);
  });

  test('变更期间发起的查询在变更结束后完成也不能缓存', () async {
    final cache = FaceReadinessCache<String>();
    cache.beginMutation();
    final source = Completer<String>();
    final duringMutation =
        cache.read(() => source.future, canCache: (_) => true);
    cache.endMutation();
    source.complete('ready');

    expect(await duringMutation, 'ready');
    expect(cache.value, isNull);
    expect(await cache.read(() async => 'checked', canCache: (_) => true),
        'checked');
    expect(cache.value, 'checked');
  });

  test('加载失败不缓存失败结果，下一次读取可以重试', () async {
    final cache = FaceReadinessCache<String>();
    var calls = 0;
    Future<String> load() async {
      calls++;
      if (calls == 1) throw StateError('sdk unavailable');
      return 'ready';
    }

    await expectLater(
        cache.read(load, canCache: (_) => true), throwsStateError);
    expect(cache.value, isNull);
    expect(await cache.read(load, canCache: (_) => true), 'ready');
    expect(calls, 2);
  });

  test('未就绪的正常结果不缓存，后续就绪结果才会缓存', () async {
    final cache = FaceReadinessCache<bool>();
    var calls = 0;
    Future<bool> load() async => ++calls > 1;

    expect(await cache.read(load, canCache: (ready) => ready), isFalse);
    expect(cache.value, isNull);
    expect(await cache.read(load, canCache: (ready) => ready), isTrue);
    expect(await cache.read(load, canCache: (ready) => ready), isTrue);
    expect(cache.value, isTrue);
    expect(calls, 2);
  });
}