using System;
using System.Threading;
using UnityEngine;
using UnityEngine.UI;

namespace AibisDream.FrameAnimation
{
    [DisallowMultipleComponent]
    public sealed class FrameAnimationPlayer : MonoBehaviour
    {
        [SerializeField] private FrameAnimationGraph graph;
        [SerializeField] private bool playOnEnable;
        [SerializeField] private float speed = 1f;

        private static long nextRequestId;

        private IFrameAnimationTarget target;
        private FrameAnimationPlaybackSession session;
        private FrameAnimationPlaybackHandle activeHandle;
        private FrameAnimationPlaybackState state = FrameAnimationPlaybackState.Stopped;
        private bool _skipInitialPlayOnEnable;
        private bool hasStartedPlayback;

        public FrameAnimationGraph Graph => graph;
        public bool PlayOnEnable => playOnEnable;
        public FrameAnimationPlaybackState State => state;
        public string CurrentPlayableId => session?.PlayableId ?? string.Empty;
        public string CurrentClipId => session?.CurrentClipId ?? string.Empty;
        public string CurrentNodeId => session?.CurrentNodeId ?? string.Empty;
        public int CurrentFrameIndex => session?.CurrentFrameIndex ?? -1;
        public float Speed => speed;

        private void Awake()
        {
            _skipInitialPlayOnEnable = playOnEnable;

            if (TryCreateTarget(out var resolvedTarget, out _))
            {
                target = resolvedTarget;
            }
        }

        private void OnEnable()
        {
            if (!playOnEnable)
            {
                return;
            }

            if (_skipInitialPlayOnEnable)
            {
                _skipInitialPlayOnEnable = false;
                return;
            }

            TryAutoPlay();
        }

        private void Start()
        {
            if (!playOnEnable)
            {
                return;
            }

            TryAutoPlay();
        }

        private void TryAutoPlay()
        {
            var handle = Play();
            if (handle.IsCompleted && handle.Result.Reason == FrameAnimationCompletionReason.Failed)
            {
                Debug.LogError($"FrameAnimationPlayer 自动播放失败：{handle.Result.Error}", this);
            }
        }

        private void Update()
        {
            if (state != FrameAnimationPlaybackState.Playing || session == null)
            {
                return;
            }

            if (target == null || !target.IsValid)
            {
                FailActive(FrameAnimationPlaybackErrorCode.TargetMissing, "播放期间显示目标失效。");
                return;
            }

            if (graph == null || session.CurrentClip == null)
            {
                FailActive(FrameAnimationPlaybackErrorCode.InvalidPlayableData, "播放期间 Graph 或 Clip 数据失效。");
                return;
            }

            if (!FrameAnimationValueUtility.IsValidSpeed(speed))
            {
                FailActive(FrameAnimationPlaybackErrorCode.InvalidSpeed, "播放期间 Player speed 变为无效值。");
                return;
            }

            var evaluation = session.Evaluate(Time.deltaTime, speed, ApplySprite);
            if (evaluation.IsFailed)
            {
                FailActive(evaluation.Error.Code, evaluation.Error.Message);
            }
            else if (evaluation.IsCompleted)
            {
                CompleteNaturally(evaluation.EndBehavior);
            }
        }

        private void OnDisable()
        {
            TerminateActive(FrameAnimationCompletionReason.Stopped, FrameAnimationPlaybackError.None);
        }

        private void OnDestroy()
        {
            TerminateActive(FrameAnimationCompletionReason.Stopped, FrameAnimationPlaybackError.None);
        }

        public FrameAnimationPlaybackHandle Play()
        {
            var playableId = graph?.Settings?.DefaultPlayableId ?? string.Empty;
            return PlayInternal(playableId, default);
        }

        public FrameAnimationPlaybackHandle Play(string playableId)
        {
            return PlayInternal(playableId, default);
        }

        public FrameAnimationPlaybackHandle Play(string playableId, FrameAnimationPlayOptions options)
        {
            return PlayInternal(playableId, options);
        }

        /// <summary>
        /// 等待当前播放请求完成首轮。非循环请求等待自然结束；终点为 Loop 的请求在
        /// 第一次回绕后结束等待，但播放请求本身保持活动并继续循环。
        /// </summary>
        public CustomYieldInstruction WaitForFirstPass(FrameAnimationPlaybackHandle playbackHandle)
        {
            if (playbackHandle == null)
            {
                throw new ArgumentNullException(nameof(playbackHandle));
            }

            return new FirstPassYieldInstruction(this, playbackHandle);
        }

        public bool TryBindGraph(
            FrameAnimationGraph value,
            out FrameAnimationPlaybackError error)
        {
            if (value == null)
            {
                error = new FrameAnimationPlaybackError(
                    FrameAnimationPlaybackErrorCode.GraphMissing,
                    "不能为 FrameAnimationPlayer 绑定空 Graph。");
                return false;
            }

            if (hasStartedPlayback ||
                state != FrameAnimationPlaybackState.Stopped ||
                session != null ||
                (activeHandle != null && !activeHandle.IsCompleted))
            {
                error = new FrameAnimationPlaybackError(
                    FrameAnimationPlaybackErrorCode.GraphBindingNotAllowed,
                    "FrameAnimationPlayer 开始播放后不允许绑定或替换 Graph。");
                return false;
            }

            if (graph != null && graph != value)
            {
                error = new FrameAnimationPlaybackError(
                    FrameAnimationPlaybackErrorCode.GraphBindingNotAllowed,
                    "FrameAnimationPlayer 已绑定其他 Graph。");
                return false;
            }

            graph = value;
            error = FrameAnimationPlaybackError.None;
            return true;
        }

        /// <summary>
        /// 非循环 playable 立即应用最后一帧及结束行为；Loop 从头重新播放。
        /// </summary>
        public FrameAnimationPlaybackHandle RestoreTerminalState(string playableId)
        {
            var requestId = Interlocked.Increment(ref nextRequestId);
            var handle = new FrameAnimationPlaybackHandle(requestId);

            if (!isActiveAndEnabled)
            {
                return CompleteFailed(
                    handle,
                    playableId,
                    FrameAnimationPlaybackErrorCode.PlayerNotReady,
                    "FrameAnimationPlayer 未启用或 GameObject 未激活。");
            }

            if (graph == null)
            {
                return CompleteFailed(
                    handle,
                    playableId,
                    FrameAnimationPlaybackErrorCode.GraphMissing,
                    "FrameAnimationPlayer 没有绑定 FrameAnimationGraph。");
            }

            if (!FrameAnimationValueUtility.IsValidSpeed(speed))
            {
                return CompleteFailed(
                    handle,
                    playableId,
                    FrameAnimationPlaybackErrorCode.InvalidSpeed,
                    "FrameAnimationPlayer speed 无效。");
            }

            if (!TryCreateTarget(out var resolvedTarget, out var targetError))
            {
                return CompleteFailed(handle, playableId, targetError.Code, targetError.Message);
            }

            if (!FrameAnimationResolver.TryResolve(
                    graph,
                    playableId,
                    default,
                    out var plan,
                    out var resolveError))
            {
                return CompleteFailed(handle, playableId, resolveError.Code, resolveError.Message);
            }

            if (activeHandle != null && !activeHandle.IsCompleted)
            {
                CompleteHandle(
                    activeHandle,
                    CurrentPlayableId,
                    FrameAnimationCompletionReason.Replaced,
                    FrameAnimationPlaybackError.None);
            }

            hasStartedPlayback = true;
            target = resolvedTarget;
            target.Enabled = true;
            var terminalStep = plan.Steps[plan.Steps.Count - 1];
            if (terminalStep.TerminalEndBehavior == FrameClipEndBehavior.Loop)
            {
                session = new FrameAnimationPlaybackSession(plan);
                activeHandle = handle;
                state = FrameAnimationPlaybackState.Playing;
                session.Start(ApplySprite);
                return handle;
            }

            var lastFrameIndex = terminalStep.Clip.FrameCount - 1;
            ApplySprite(terminalStep.Clip.Frames[lastFrameIndex]?.Sprite);
            ApplyEndBehavior(terminalStep.TerminalEndBehavior);
            session = null;
            activeHandle = null;
            state = FrameAnimationPlaybackState.Stopped;
            CompleteHandle(
                handle,
                playableId,
                FrameAnimationCompletionReason.Completed,
                FrameAnimationPlaybackError.None);
            return handle;
        }

        public void Stop(FrameAnimationStopMode mode = FrameAnimationStopMode.HoldCurrentFrame)
        {
            TerminateActive(FrameAnimationCompletionReason.Stopped, FrameAnimationPlaybackError.None);

            if (target == null || !target.IsValid)
            {
                if (!TryCreateTarget(out var resolvedTarget, out _))
                {
                    return;
                }

                target = resolvedTarget;
            }

            ApplyStopMode(mode);
        }

        public void Pause()
        {
            if (state == FrameAnimationPlaybackState.Playing && session != null)
            {
                state = FrameAnimationPlaybackState.Paused;
            }
        }

        public void Resume()
        {
            if (state == FrameAnimationPlaybackState.Paused && session != null)
            {
                state = FrameAnimationPlaybackState.Playing;
            }
        }

        public void SetSpeed(float value)
        {
            if (!FrameAnimationValueUtility.IsValidSpeed(value))
            {
                Debug.LogError($"FrameAnimationPlayer speed 必须是有限且不小于 0 的数值，收到：{value}", this);
                return;
            }

            speed = value;
        }

        internal void ConfigureForAuthoring(FrameAnimationGraph value, bool shouldPlayOnEnable, float playerSpeed)
        {
            graph = value;
            playOnEnable = shouldPlayOnEnable;
            speed = playerSpeed;
            hasStartedPlayback = false;
        }

        internal void EvaluateForTests(double deltaTimeSeconds)
        {
            if (state != FrameAnimationPlaybackState.Playing || session == null)
            {
                return;
            }

            var evaluation = session.Evaluate(deltaTimeSeconds, speed, ApplySprite);
            if (evaluation.IsFailed)
            {
                FailActive(evaluation.Error.Code, evaluation.Error.Message);
            }
            else if (evaluation.IsCompleted)
            {
                CompleteNaturally(evaluation.EndBehavior);
            }
        }

        private FrameAnimationPlaybackHandle PlayInternal(
            string playableId,
            FrameAnimationPlayOptions options)
        {
            var requestId = Interlocked.Increment(ref nextRequestId);
            var handle = new FrameAnimationPlaybackHandle(requestId);

            if (!isActiveAndEnabled)
            {
                return CompleteFailed(
                    handle,
                    playableId,
                    FrameAnimationPlaybackErrorCode.PlayerNotReady,
                    "FrameAnimationPlayer 未启用或 GameObject 未激活。");
            }

            if (graph == null)
            {
                return CompleteFailed(
                    handle,
                    playableId,
                    FrameAnimationPlaybackErrorCode.GraphMissing,
                    "FrameAnimationPlayer 没有绑定 FrameAnimationGraph。");
            }

            if (!FrameAnimationValueUtility.IsValidSpeed(speed))
            {
                return CompleteFailed(
                    handle,
                    playableId,
                    FrameAnimationPlaybackErrorCode.InvalidSpeed,
                    "FrameAnimationPlayer speed 无效。");
            }

            if (!TryCreateTarget(out var resolvedTarget, out var targetError))
            {
                return CompleteFailed(handle, playableId, targetError.Code, targetError.Message);
            }

            if (!FrameAnimationResolver.TryResolve(graph, playableId, options, out var plan, out var resolveError))
            {
                return CompleteFailed(handle, playableId, resolveError.Code, resolveError.Message);
            }

            hasStartedPlayback = true;

            if (activeHandle != null && !activeHandle.IsCompleted)
            {
                CompleteHandle(activeHandle, CurrentPlayableId, FrameAnimationCompletionReason.Replaced, FrameAnimationPlaybackError.None);
            }

            session = new FrameAnimationPlaybackSession(plan);
            activeHandle = handle;
            state = FrameAnimationPlaybackState.Playing;
            target = resolvedTarget;
            target.Enabled = true;
            session.Start(ApplySprite);
            return handle;
        }

        private bool TryCreateTarget(
            out IFrameAnimationTarget resolvedTarget,
            out FrameAnimationPlaybackError error)
        {
            var spriteRenderer = GetComponent<SpriteRenderer>();
            var image = GetComponent<Image>();
            if (spriteRenderer != null && image != null)
            {
                resolvedTarget = null;
                error = new FrameAnimationPlaybackError(
                    FrameAnimationPlaybackErrorCode.TargetConflict,
                    "FrameAnimationPlayer 所在对象不能同时包含 SpriteRenderer 和 Image。");
                return false;
            }

            if (spriteRenderer == null && image == null)
            {
                resolvedTarget = null;
                error = new FrameAnimationPlaybackError(
                    FrameAnimationPlaybackErrorCode.TargetMissing,
                    "FrameAnimationPlayer 所在对象缺少 SpriteRenderer 或 Image。");
                return false;
            }

            resolvedTarget = spriteRenderer != null
                ? new SpriteRendererFrameAnimationTarget(spriteRenderer)
                : new ImageFrameAnimationTarget(image);
            error = FrameAnimationPlaybackError.None;
            return true;
        }

        private FrameAnimationPlaybackHandle CompleteFailed(
            FrameAnimationPlaybackHandle handle,
            string playableId,
            FrameAnimationPlaybackErrorCode code,
            string message)
        {
            CompleteHandle(
                handle,
                playableId,
                FrameAnimationCompletionReason.Failed,
                new FrameAnimationPlaybackError(code, message));
            return handle;
        }

        private void CompleteNaturally(FrameClipEndBehavior endBehavior)
        {
            var handle = activeHandle;
            var playableId = CurrentPlayableId;
            ApplyEndBehavior(endBehavior);
            session = null;
            activeHandle = null;
            state = FrameAnimationPlaybackState.Stopped;
            CompleteHandle(
                handle,
                playableId,
                FrameAnimationCompletionReason.Completed,
                FrameAnimationPlaybackError.None);
        }

        private void FailActive(FrameAnimationPlaybackErrorCode code, string message)
        {
            var handle = activeHandle;
            var playableId = CurrentPlayableId;
            session = null;
            activeHandle = null;
            state = FrameAnimationPlaybackState.Stopped;
            CompleteHandle(
                handle,
                playableId,
                FrameAnimationCompletionReason.Failed,
                new FrameAnimationPlaybackError(code, message));
        }

        private void TerminateActive(
            FrameAnimationCompletionReason reason,
            FrameAnimationPlaybackError error)
        {
            if (activeHandle == null || activeHandle.IsCompleted)
            {
                session = null;
                activeHandle = null;
                state = FrameAnimationPlaybackState.Stopped;
                return;
            }

            var handle = activeHandle;
            var playableId = CurrentPlayableId;
            session = null;
            activeHandle = null;
            state = FrameAnimationPlaybackState.Stopped;
            CompleteHandle(handle, playableId, reason, error);
        }

        private static void CompleteHandle(
            FrameAnimationPlaybackHandle handle,
            string playableId,
            FrameAnimationCompletionReason reason,
            FrameAnimationPlaybackError error)
        {
            handle?.TryComplete(new FrameAnimationPlaybackResult(handle.RequestId, playableId, reason, error));
        }

        private void ApplySprite(Sprite sprite)
        {
            if (target != null && target.IsValid)
            {
                target.Sprite = sprite;
            }
        }

        private bool ShouldWaitForFirstPass(FrameAnimationPlaybackHandle playbackHandle)
        {
            if (playbackHandle.IsCompleted || activeHandle != playbackHandle || session == null)
            {
                return false;
            }

            return !session.HasCompletedFirstTerminalLoopCycle;
        }

        private sealed class FirstPassYieldInstruction : CustomYieldInstruction
        {
            private readonly FrameAnimationPlayer player;
            private readonly FrameAnimationPlaybackHandle playbackHandle;

            public FirstPassYieldInstruction(
                FrameAnimationPlayer player,
                FrameAnimationPlaybackHandle playbackHandle)
            {
                this.player = player;
                this.playbackHandle = playbackHandle;
            }

            public override bool keepWaiting =>
                player != null && player.ShouldWaitForFirstPass(playbackHandle);
        }

        private void ApplyEndBehavior(FrameClipEndBehavior endBehavior)
        {
            switch (endBehavior)
            {
                case FrameClipEndBehavior.HoldLastFrame:
                    break;
                case FrameClipEndBehavior.Clear:
                    if (target != null && target.IsValid)
                    {
                        target.Enabled = true;
                        target.Sprite = null;
                    }
                    break;
                case FrameClipEndBehavior.HideTarget:
                    if (target != null && target.IsValid)
                    {
                        target.Enabled = false;
                    }
                    break;
            }
        }

        private void ApplyStopMode(FrameAnimationStopMode mode)
        {
            switch (mode)
            {
                case FrameAnimationStopMode.HoldCurrentFrame:
                    break;
                case FrameAnimationStopMode.Clear:
                    target.Enabled = true;
                    target.Sprite = null;
                    break;
                case FrameAnimationStopMode.HideTarget:
                    target.Enabled = false;
                    break;
            }
        }
    }
}