#nullable enable
using System;
using System.Collections.Generic;
using NUnit.Framework;
using ShrinkContext;

namespace ShrinkContext.Tests
{
    /// <summary>
    /// 声明式加载器（论文 5.2 的原型子集）：
    /// 增量协调、幂等、退役、disabled 开关、组件/配置变化重建、依赖缺失等待、隔离域条目。
    /// </summary>
    public class LoaderTests
    {
        private ShrinkContextRuntime _runtime = null!;
        private ShrinkComponentCatalog _catalog = null!;
        private ShrinkContextLoader _loader = null!;

        [SetUp]
        public void SetUp()
        {
            _runtime = new ShrinkContextRuntime();
            _catalog = new ShrinkComponentCatalog();
            _catalog.Register("provider", () => new ConfigProviderComponent("provider", "svc"));
            _catalog.Register("provider.alt", () => new ConfigProviderComponent("provider.alt", "svc"));
            _catalog.Register("consumer", () => new ConsumerComponent("consumer", "svc"));
            _catalog.Register("failing", () => new FailingComponent("failing", "svc"));
            _catalog.Register("policy.provider", () => new PolicyProviderComponent("policy.service"));
            _catalog.Register("policy.consumer", () => new PolicyConsumerComponent("policy.service"));
            _loader = new ShrinkContextLoader(_runtime, _catalog);
        }

        [Test]
        public void Apply_CreatesEntriesAndActivates()
        {
            TestAwait.Run(_loader.ApplyAsync(new List<ShrinkLoaderEntry>
            {
                new("provider-entry", "provider", "v1"),
                new("consumer-entry", "consumer"),
            }));

            Assert.IsTrue(_loader.TryGetFiber("provider-entry", out var providerFiber));
            Assert.IsTrue(_loader.TryGetFiber("consumer-entry", out var consumerFiber));
            Assert.AreEqual(ShrinkFiberState.Active, providerFiber.State);
            Assert.AreEqual(ShrinkFiberState.Active, consumerFiber.State);
        }

        [Test]
        public void Apply_IsIdempotent_SecondApplyDoesNotReload()
        {
            var config = new List<ShrinkLoaderEntry>
            {
                new("provider-entry", "provider", "v1"),
                new("consumer-entry", "consumer"),
            };

            TestAwait.Run(_loader.ApplyAsync(config));
            Assert.IsTrue(_loader.TryGetFiber("provider-entry", out var firstFiber));

            TestAwait.Run(_loader.ApplyAsync(config));

            Assert.IsTrue(_loader.TryGetFiber("provider-entry", out var secondFiber));
            Assert.AreSame(firstFiber, secondFiber, "无变化的条目不得重建纤程");
            var providerComponent = (ConfigProviderComponent)secondFiber.Component;
            Assert.AreEqual(1, providerComponent.ApplyCount, "幂等协调不触发重载");
        }

        [Test]
        public void RemovedEntry_RetiresFiber_DependentDeactivatesButStaysManaged()
        {
            TestAwait.Run(_loader.ApplyAsync(new List<ShrinkLoaderEntry>
            {
                new("provider-entry", "provider", "v1"),
                new("consumer-entry", "consumer"),
            }));

            TestAwait.Run(_loader.ApplyAsync(new List<ShrinkLoaderEntry>
            {
                new("consumer-entry", "consumer"),
            }));

            Assert.IsFalse(_loader.TryGetFiber("provider-entry", out _), "消失的条目不再被管理");
            Assert.IsTrue(_loader.TryGetFiber("consumer-entry", out var consumerFiber));
            Assert.AreEqual(ShrinkFiberState.Inactive, consumerFiber.State,
                "提供者退役后依赖者被响应式停用，但条目仍被管理、等待依赖回归");

            // 依赖回归后无需重建条目即可重新激活
            TestAwait.Run(_loader.ApplyAsync(new List<ShrinkLoaderEntry>
            {
                new("provider-entry", "provider", "v1"),
                new("consumer-entry", "consumer"),
            }));
            Assert.AreEqual(ShrinkFiberState.Active, consumerFiber.State);
        }

        [Test]
        public void DisabledEntry_UnloadsAndReloadsOnEnable()
        {
            var enabled = new List<ShrinkLoaderEntry> { new("provider-entry", "provider", "v1") };
            TestAwait.Run(_loader.ApplyAsync(enabled));

            TestAwait.Run(_loader.ApplyAsync(new List<ShrinkLoaderEntry>
            {
                new("provider-entry", "provider", "v1", disabled: true),
            }));
            Assert.IsFalse(_loader.TryGetFiber("provider-entry", out _),
                "disabled 条目不持有纤程，但条目本身仍被管理");
            CollectionAssert.Contains(_loader.ManagedEntryIds, "provider-entry");

            TestAwait.Run(_loader.ApplyAsync(enabled));
            Assert.IsTrue(_loader.TryGetFiber("provider-entry", out var reloadedFiber));
            Assert.AreEqual(ShrinkFiberState.Active, reloadedFiber.State, "取消 disabled 后重新加载");
        }

        [Test]
        public void ComponentChange_RebuildsEntry()
        {
            TestAwait.Run(_loader.ApplyAsync(new List<ShrinkLoaderEntry>
            {
                new("provider-entry", "provider", "v1"),
                new("consumer-entry", "consumer"),
            }));
            Assert.IsTrue(_loader.TryGetFiber("provider-entry", out var firstFiber));

            TestAwait.Run(_loader.ApplyAsync(new List<ShrinkLoaderEntry>
            {
                new("provider-entry", "provider.alt", "v2"),
                new("consumer-entry", "consumer"),
            }));

            Assert.IsTrue(_loader.TryGetFiber("provider-entry", out var rebuiltFiber));
            Assert.AreNotSame(firstFiber, rebuiltFiber, "组件名变化必须重建条目（论文 id/url → 重建）");
            Assert.AreEqual(ShrinkFiberState.Active, rebuiltFiber.State);
            Assert.AreEqual("provider.alt", rebuiltFiber.Component.Name);

            Assert.IsTrue(_loader.TryGetFiber("consumer-entry", out var consumerFiber));
            Assert.AreEqual(ShrinkFiberState.Active, consumerFiber.State);
            var consumer = (ConsumerComponent)consumerFiber.Component;
            Assert.AreEqual("v2", consumer.LastSeen, "依赖者切换到重建后的新提供者");
        }

        [Test]
        public void ConfigChange_ReloadsEntryWithNewConfig()
        {
            TestAwait.Run(_loader.ApplyAsync(new List<ShrinkLoaderEntry>
            {
                new("provider-entry", "provider", "v1"),
                new("consumer-entry", "consumer"),
            }));
            Assert.IsTrue(_loader.TryGetFiber("provider-entry", out var firstFiber));

            TestAwait.Run(_loader.ApplyAsync(new List<ShrinkLoaderEntry>
            {
                new("provider-entry", "provider", "v2"),
                new("consumer-entry", "consumer"),
            }));

            // 原型语义：配置变化走重建（组件自决 diff 属后续阶段）
            Assert.AreEqual(ShrinkFiberState.Inactive, firstFiber.State);
            Assert.IsTrue(_loader.TryGetFiber("provider-entry", out var rebuiltFiber));
            Assert.AreNotSame(firstFiber, rebuiltFiber);
            Assert.AreEqual("v2", rebuiltFiber.Config, "重建后的纤程携带新配置");

            Assert.IsTrue(_loader.TryGetFiber("consumer-entry", out var consumerFiber));
            var consumer = (ConsumerComponent)consumerFiber.Component;
            Assert.AreEqual("v2", consumer.LastSeen, "依赖者看到新配置的值");
        }

        [Test]
        public void MissingDependency_WaitsWithoutError_ThenActivatesWhenProvided()
        {
            // 首轮只有消费者：不抛“依赖缺失”异常，条目保持被管理、纤程 Inactive
            TestAwait.Run(_loader.ApplyAsync(new List<ShrinkLoaderEntry>
            {
                new("consumer-entry", "consumer"),
            }));
            Assert.IsTrue(_loader.TryGetFiber("consumer-entry", out var consumerFiber));
            Assert.AreEqual(ShrinkFiberState.Inactive, consumerFiber.State);

            // 次轮补上提供者：依赖者被响应式激活，无需重发消费者条目
            TestAwait.Run(_loader.ApplyAsync(new List<ShrinkLoaderEntry>
            {
                new("consumer-entry", "consumer"),
                new("provider-entry", "provider", "late"),
            }));
            Assert.AreEqual(ShrinkFiberState.Active, consumerFiber.State);
            Assert.AreEqual("late", ((ConsumerComponent)consumerFiber.Component).LastSeen);
        }

        [Test]
        public void DuplicateEntryIds_Throw()
        {
            Assert.Throws<ShrinkLoaderException>(() => TestAwait.Run(_loader.ApplyAsync(new List<ShrinkLoaderEntry>
            {
                new("dup", "provider", "v1"),
                new("dup", "provider", "v2"),
            })));
        }

        [Test]
        public void UnknownComponent_ThrowsWithEntryContext()
        {
            var ex = Assert.Throws<ShrinkLoaderException>(() => TestAwait.Run(_loader.ApplyAsync(
                new List<ShrinkLoaderEntry> { new("entry", "no.such.component") })));
            StringAssert.Contains("no.such.component", ex!.Message);
            StringAssert.Contains("entry", ex.Message);
        }

        [Test]
        public void IsolatedEntries_SameKeyCoexistInDifferentRealms()
        {
            TestAwait.Run(_loader.ApplyAsync(new List<ShrinkLoaderEntry>
            {
                new("p1", "provider", "from-r1", isolate: new Dictionary<string, string> { ["svc"] = "r1" }),
                new("p2", "provider", "from-r2", isolate: new Dictionary<string, string> { ["svc"] = "r2" }),
                new("c2", "consumer", isolate: new Dictionary<string, string> { ["svc"] = "r2" }),
            }));

            Assert.IsTrue(_loader.TryGetFiber("p1", out var f1));
            Assert.IsTrue(_loader.TryGetFiber("p2", out var f2));
            Assert.AreEqual(ShrinkFiberState.Active, f1.State, "不同隔离域的同键供给互不冲突");
            Assert.AreEqual(ShrinkFiberState.Active, f2.State);

            Assert.IsTrue(_loader.TryGetFiber("c2", out var consumerFiber));
            Assert.AreEqual(ShrinkFiberState.Active, consumerFiber.State);
            Assert.AreEqual("from-r2", ((ConsumerComponent)consumerFiber.Component).LastSeen,
                "消费者按自身隔离域解析到 r2 的绑定");
        }

        [Test]
        public void IsolatedProviderReplacement_DoesNotReloadOtherRealmConsumer()
        {
            var isolateR1 = new Dictionary<string, string> { ["svc"] = "r1" };
            var isolateR2 = new Dictionary<string, string> { ["svc"] = "r2" };
            TestAwait.Run(_loader.ApplyAsync(new List<ShrinkLoaderEntry>
            {
                new("p1", "provider", "r1-v1", isolate: isolateR1),
                new("p2", "provider", "r2-v1", isolate: isolateR2),
                new("c2", "consumer", isolate: isolateR2),
            }));
            Assert.IsTrue(_loader.TryGetFiber("c2", out var consumerFiber));
            var consumer = (ConsumerComponent)consumerFiber.Component;
            Assert.AreEqual(1, consumer.LoadCount);

            TestAwait.Run(_loader.ApplyAsync(new List<ShrinkLoaderEntry>
            {
                new("p1", "provider", "r1-v2", isolate: isolateR1),
                new("p2", "provider", "r2-v1", isolate: isolateR2),
                new("c2", "consumer", isolate: isolateR2),
            }));

            Assert.AreEqual(1, consumer.LoadCount,
                "r1 提供者替换不得触发只解析 r2 的消费者重载");
            Assert.AreEqual("r2-v1", consumer.LastSeen);
        }

        [Test]
        public void InterceptUpdate_ChangesAccessWithoutReloadingFiber()
        {
            var suffixA = new Dictionary<string, IReadOnlyDictionary<string, object?>>
            {
                ["policy.service"] = new Dictionary<string, object?> { ["suffix"] = "-a" }
            };
            var suffixB = new Dictionary<string, IReadOnlyDictionary<string, object?>>
            {
                ["policy.service"] = new Dictionary<string, object?> { ["suffix"] = "-b" }
            };

            TestAwait.Run(_loader.ApplyAsync(new List<ShrinkLoaderEntry>
            {
                new("policy-provider", "policy.provider", "base"),
                new("policy-consumer", "policy.consumer", intercept: suffixA),
            }));
            Assert.IsTrue(_loader.TryGetFiber("policy-consumer", out var firstFiber));
            var consumer = (PolicyConsumerComponent)firstFiber.Component;
            Assert.AreEqual("base-a", consumer.Read());
            Assert.AreEqual(1, consumer.ApplyCount);

            TestAwait.Run(_loader.ApplyAsync(new List<ShrinkLoaderEntry>
            {
                new("policy-provider", "policy.provider", "base"),
                new("policy-consumer", "policy.consumer", intercept: suffixB),
            }));

            Assert.IsTrue(_loader.TryGetFiber("policy-consumer", out var sameFiber));
            Assert.AreSame(firstFiber, sameFiber);
            Assert.AreEqual(1, consumer.ApplyCount, "intercept 元数据变化不应触发 reload");
            Assert.AreEqual("base-b", consumer.Read(), "访问时应读取更新后的 metadata");
        }

        [Test]
        public void FailedReplacement_RestoresPreviousLoaderCompositionAndReportsTransaction()
        {
            TestAwait.Run(_loader.ApplyAsync(new List<ShrinkLoaderEntry>
            {
                new("provider-entry", "provider", "stable")
            }));

            Assert.Throws<ShrinkLoaderException>(() => TestAwait.Run(_loader.ApplyAsync(
                new List<ShrinkLoaderEntry> { new("provider-entry", "failing") })));

            Assert.IsTrue(_loader.TryGetFiber("provider-entry", out var restored));
            Assert.AreEqual(ShrinkFiberState.Active, restored.State);
            Assert.AreEqual("stable", restored.Config);
            Assert.IsNotNull(_loader.LastTransaction);
            Assert.AreEqual(ShrinkLoaderTransactionPhase.Failed, _loader.LastTransaction!.Phase);
            Assert.IsTrue(_loader.LastTransaction.RestoreAttempted);
            Assert.IsTrue(_loader.LastTransaction.PreviousCompositionRestored);
            StringAssert.Contains("failed during apply", _loader.LastTransaction.ErrorMessage);
        }
    }
}