using System.Reflection;
using GFramework.Core.Abstractions.state;
using GFramework.Core.state;
using NUnit.Framework;

namespace GFramework.Core.Tests.state;

/// <summary>
/// 测试状态机功能的单元测试类
/// </summary>
[TestFixture]
public class StateMachineTests
{
    /// <summary>
    /// 在每个测试方法执行前初始化状态机实例
    /// </summary>
    [SetUp]
    public void SetUp()
    {
        _stateMachine = new StateMachine();
    }

    private StateMachine _stateMachine = null!;

    /// <summary>
    /// 验证当没有活动状态时，当前状态应为null
    /// </summary>
    [Test]
    public void Current_Should_BeNull_When_NoState_Active()
    {
        Assert.That(_stateMachine.Current, Is.Null);
    }

    /// <summary>
    /// 验证注册状态后，状态会被添加到状态字典中
    /// </summary>
    [Test]
    public void Register_Should_AddState_To_StatesDictionary()
    {
        var state = new TestStateV2();
        _stateMachine.Register(state);

        Assert.That(_stateMachine.ContainsState<TestStateV2>(), Is.True);
    }

    /// <summary>
    /// 验证ChangeTo方法能够正确设置当前状态
    /// </summary>
    [Test]
    public void ChangeTo_Should_SetCurrentState()
    {
        var state = new TestStateV2();
        _stateMachine.Register(state);
        _stateMachine.ChangeTo<TestStateV2>();

        Assert.That(_stateMachine.Current, Is.SameAs(state));
    }

    /// <summary>
    /// 验证ChangeTo方法会调用OnEnter回调
    /// </summary>
    [Test]
    public void ChangeTo_Should_Invoke_OnEnter()
    {
        var state = new TestStateV2();
        _stateMachine.Register(state);
        _stateMachine.ChangeTo<TestStateV2>();

        Assert.That(state.EnterCalled, Is.True);
        Assert.That(state.EnterFrom, Is.Null);
    }

    /// <summary>
    /// 验证当存在当前状态时，切换到新状态会调用原状态的OnExit回调
    /// </summary>
    [Test]
    public void ChangeTo_When_CurrentStateExists_Should_Invoke_OnExit()
    {
        var state1 = new TestStateV2();
        var state2 = new TestStateV3();
        _stateMachine.Register(state1);
        _stateMachine.Register(state2);

        _stateMachine.ChangeTo<TestStateV2>();
        _stateMachine.ChangeTo<TestStateV3>();

        Assert.That(state1.ExitCalled, Is.True);
        Assert.That(state1.ExitTo, Is.SameAs(state2));
    }

    /// <summary>
    /// 验证当存在当前状态时，切换到新状态会调用新状态的OnEnter回调
    /// </summary>
    [Test]
    public void ChangeTo_When_CurrentStateExists_Should_Invoke_OnEnter()
    {
        var state1 = new TestStateV2();
        var state2 = new TestStateV3();
        _stateMachine.Register(state1);
        _stateMachine.Register(state2);

        _stateMachine.ChangeTo<TestStateV2>();
        _stateMachine.ChangeTo<TestStateV3>();

        Assert.That(state2.EnterCalled, Is.True);
        Assert.That(state2.EnterFrom, Is.SameAs(state1));
    }

    /// <summary>
    /// 验证切换到相同状态时不应调用回调方法
    /// </summary>
    [Test]
    public void ChangeTo_ToSameState_Should_NotInvoke_Callbacks()
    {
        var state = new TestStateV2();
        _stateMachine.Register(state);
        _stateMachine.ChangeTo<TestStateV2>();

        var enterCount = state.EnterCallCount;
        var exitCount = state.ExitCallCount;

        _stateMachine.ChangeTo<TestStateV2>();

        Assert.That(state.EnterCallCount, Is.EqualTo(enterCount));
        Assert.That(state.ExitCallCount, Is.EqualTo(exitCount));
    }

    /// <summary>
    /// 验证切换到未注册状态时应抛出InvalidOperationException异常
    /// </summary>
    [Test]
    public void ChangeTo_ToUnregisteredState_Should_ThrowInvalidOperationException()
    {
        Assert.Throws<InvalidOperationException>(() => _stateMachine.ChangeTo<TestStateV2>());
    }

    /// <summary>
    /// 验证当状态未注册时CanChangeTo方法应返回false
    /// </summary>
    [Test]
    public void CanChangeTo_WhenStateNotRegistered_Should_ReturnFalse()
    {
        var result = _stateMachine.CanChangeTo<TestStateV2>();
        Assert.That(result, Is.False);
    }

    /// <summary>
    /// 验证当状态已注册时CanChangeTo方法应返回true
    /// </summary>
    [Test]
    public void CanChangeTo_WhenStateRegistered_Should_ReturnTrue()
    {
        var state = new TestStateV2();
        _stateMachine.Register(state);

        var result = _stateMachine.CanChangeTo<TestStateV2>();
        Assert.That(result, Is.True);
    }

    /// <summary>
    /// 验证当当前状态拒绝转换时CanChangeTo方法应返回false
    /// </summary>
    [Test]
    public void CanChangeTo_WhenCurrentStateDeniesTransition_Should_ReturnFalse()
    {
        var state1 = new TestStateV2 { AllowTransition = false };
        var state2 = new TestStateV3();
        _stateMachine.Register(state1);
        _stateMachine.Register(state2);
        _stateMachine.ChangeTo<TestStateV2>();

        var result = _stateMachine.CanChangeTo<TestStateV3>();
        Assert.That(result, Is.False);
    }

    /// <summary>
    /// 验证当当前状态拒绝转换时不应发生状态变化
    /// </summary>
    [Test]
    public void ChangeTo_WhenCurrentStateDeniesTransition_Should_NotChange()
    {
        var state1 = new TestStateV2 { AllowTransition = false };
        var state2 = new TestStateV3();
        _stateMachine.Register(state1);
        _stateMachine.Register(state2);
        _stateMachine.ChangeTo<TestStateV2>();

        var oldState = _stateMachine.Current;
        _stateMachine.ChangeTo<TestStateV3>();

        Assert.That(_stateMachine.Current, Is.SameAs(oldState));
        Assert.That(_stateMachine.Current, Is.SameAs(state1));
        Assert.That(state2.EnterCalled, Is.False);
    }

    /// <summary>
    /// 验证注销状态后应从字典中移除该状态
    /// </summary>
    [Test]
    public void Unregister_Should_RemoveState_FromDictionary()
    {
        var state = new TestStateV2();
        _stateMachine.Register(state);
        _stateMachine.Unregister<TestStateV2>();

        Assert.That(_stateMachine.ContainsState<TestStateV2>(), Is.False);
    }

    /// <summary>
    /// 验证当活动状态被注销时应调用OnExit并清除当前状态
    /// </summary>
    [Test]
    public void Unregister_WhenStateIsActive_Should_Invoke_OnExit_AndClearCurrent()
    {
        var state = new TestStateV2();
        _stateMachine.Register(state);
        _stateMachine.ChangeTo<TestStateV2>();
        _stateMachine.Unregister<TestStateV2>();

        Assert.That(state.ExitCalled, Is.True);
        Assert.That(state.ExitTo, Is.Null);
        Assert.That(_stateMachine.Current, Is.Null);
    }

    /// <summary>
    /// 验证当非活动状态被注销时不应调用OnExit
    /// </summary>
    [Test]
    public void Unregister_WhenStateNotActive_Should_Not_Invoke_OnExit()
    {
        var state1 = new TestStateV2();
        var state2 = new TestStateV3();
        _stateMachine.Register(state1);
        _stateMachine.Register(state2);
        _stateMachine.ChangeTo<TestStateV2>();

        _stateMachine.Unregister<TestStateV3>();

        Assert.That(state1.ExitCalled, Is.False);
        Assert.That(_stateMachine.Current, Is.SameAs(state1));
    }

    /// <summary>
    /// 验证多次状态转换应正确调用回调方法
    /// </summary>
    [Test]
    public void MultipleStateChanges_Should_Invoke_Callbacks_Correctly()
    {
        var state1 = new TestStateV2();
        var state2 = new TestStateV3();
        var state3 = new TestStateV4();
        _stateMachine.Register(state1);
        _stateMachine.Register(state2);
        _stateMachine.Register(state3);

        _stateMachine.ChangeTo<TestStateV2>();
        _stateMachine.ChangeTo<TestStateV3>();
        _stateMachine.ChangeTo<TestStateV4>();

        Assert.That(state1.EnterCalled, Is.True);
        Assert.That(state1.ExitCalled, Is.True);
        Assert.That(state2.EnterCalled, Is.True);
        Assert.That(state2.ExitCalled, Is.True);
        Assert.That(state3.EnterCalled, Is.True);
        Assert.That(state3.ExitCalled, Is.False);
    }

    /// <summary>
    /// 验证ChangeTo方法应遵循CanTransitionTo逻辑
    /// </summary>
    [Test]
    public void ChangeTo_Should_Respect_CanTransitionTo_Logic()
    {
        var state1 = new TestStateV2();
        var state2 = new TestStateV3();
        var state3 = new TestStateV4();
        _stateMachine.Register(state1);
        _stateMachine.Register(state2);
        _stateMachine.Register(state3);

        _stateMachine.ChangeTo<TestStateV2>();
        _stateMachine.ChangeTo<TestStateV3>();

        Assert.That(state1.EnterCalled, Is.True);
        Assert.That(state1.ExitCalled, Is.True);
        Assert.That(state2.EnterCalled, Is.True);
    }
}

/// <summary>
/// 测试状态类V2版本，实现IState接口用于测试
/// </summary>
public sealed class TestStateV2 : IState
{
    public bool AllowTransition { get; set; } = true;
    public bool EnterCalled { get; private set; }
    public bool ExitCalled { get; private set; }
    public int EnterCallCount { get; private set; }
    public int ExitCallCount { get; private set; }
    public IState? EnterFrom { get; private set; }
    public IState? ExitTo { get; private set; }

    /// <summary>
    /// 进入状态时的回调方法
    /// </summary>
    /// <param name="from">从哪个状态进入</param>
    public void OnEnter(IState? from)
    {
        EnterCalled = true;
        EnterCallCount++;
        EnterFrom = from;
    }

    /// <summary>
    /// 离开状态时的回调方法
    /// </summary>
    /// <param name="to">离开到哪个状态</param>
    public void OnExit(IState? to)
    {
        ExitCalled = true;
        ExitCallCount++;
        ExitTo = to;
    }

    /// <summary>
    /// 判断是否可以转换到目标状态
    /// </summary>
    /// <param name="target">目标状态</param>
    /// <returns>是否允许转换</returns>
    public bool CanTransitionTo(IState target)
    {
        return AllowTransition;
    }
}

/// <summary>
/// 测试状态类V3版本，实现IState接口用于测试
/// </summary>
public sealed class TestStateV3 : IState
{
    public bool EnterCalled { get; private set; }
    public bool ExitCalled { get; private set; }
    public int EnterCallCount { get; private set; }
    public int ExitCallCount { get; private set; }
    public IState? EnterFrom { get; private set; }
    public IState? ExitTo { get; private set; }

    /// <summary>
    /// 进入状态时的回调方法
    /// </summary>
    /// <param name="from">从哪个状态进入</param>
    public void OnEnter(IState? from)
    {
        EnterCalled = true;
        EnterCallCount++;
        EnterFrom = from;
    }

    /// <summary>
    /// 离开状态时的回调方法
    /// </summary>
    /// <param name="to">离开到哪个状态</param>
    public void OnExit(IState? to)
    {
        ExitCalled = true;
        ExitCallCount++;
        ExitTo = to;
    }

    /// <summary>
    /// 判断是否可以转换到目标状态
    /// </summary>
    /// <param name="target">目标状态</param>
    /// <returns>是否允许转换</returns>
    public bool CanTransitionTo(IState target)
    {
        return true;
    }
}

/// <summary>
/// 测试状态类V4版本，实现IState接口用于测试
/// </summary>
public sealed class TestStateV4 : IState
{
    public bool EnterCalled { get; private set; }
    public bool ExitCalled { get; private set; }
    public int EnterCallCount { get; private set; }
    public int ExitCallCount { get; private set; }
    public IState? EnterFrom { get; private set; }
    public IState? ExitTo { get; private set; }

    /// <summary>
    /// 进入状态时的回调方法
    /// </summary>
    /// <param name="from">从哪个状态进入</param>
    public void OnEnter(IState? from)
    {
        EnterCalled = true;
        EnterCallCount++;
        EnterFrom = from;
    }

    /// <summary>
    /// 离开状态时的回调方法
    /// </summary>
    /// <param name="to">离开到哪个状态</param>
    public void OnExit(IState? to)
    {
        ExitCalled = true;
        ExitCallCount++;
        ExitTo = to;
    }

    /// <summary>
    /// 判断是否可以转换到目标状态
    /// </summary>
    /// <param name="target">目标状态</param>
    /// <returns>是否允许转换</returns>
    public bool CanTransitionTo(IState target)
    {
        return true;
    }
}

/// <summary>
/// 状态机扩展方法类
/// </summary>
public static class StateMachineExtensions
{
    /// <summary>
    /// 检查状态机是否包含指定类型的状态
    /// </summary>
    /// <typeparam name="T">要检查的状态类型</typeparam>
    /// <param name="stateMachine">状态机实例</param>
    /// <returns>如果包含指定类型的状态则返回true，否则返回false</returns>
    public static bool ContainsState<T>(this StateMachine stateMachine) where T : IState
    {
        return stateMachine.GetType().GetField("States", BindingFlags.NonPublic | BindingFlags.Instance)?
                   .GetValue(stateMachine) is Dictionary<Type, IState> states &&
               states.ContainsKey(typeof(T));
    }
}