using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.UI;

namespace ShrinkTutorial
{
    [DefaultExecutionOrder(-1500)]
    public class ShrinkTutorialManager : MonoBehaviour
    {
        private static ShrinkTutorialManager _instance;

        [SerializeField] private ShrinkTutorialSettings settingsOverride;

        private readonly List<string> _pendingTutorialIds = new();
        private readonly HashSet<string> _completedTutorials = new();
        private readonly HashSet<string> _skippedTutorials = new();
        private readonly List<RaycastResult> _pointerRaycastResults = new();

        private IShrinkTutorialStorage _storage;
        private Canvas _canvas;
        private ShrinkTutorialMask _mask;
        private ShrinkTutorialDialog _dialog;

        private Coroutine _runner;
        private ShrinkTutorialData _currentTutorial;
        private int _currentStepIndex = -1;
        private bool _isPaused;
        private bool _skipRequested;
        private bool _stepCompleted;
        private bool _stepCompletionQueued;
        private float _stepAutoTimer;
        private string _receivedCustomEvent = string.Empty;

        public static ShrinkTutorialManager Instance => _instance;

        public bool IsRunning => _currentTutorial != null;
        public string CurrentTutorialId => _currentTutorial ? _currentTutorial.tutorialId : string.Empty;

        public event Action<string> OnTutorialStarted;
        public event Action<string> OnTutorialCompleted;
        public event Action<string> OnTutorialSkipped;
        public event Action<string, int> OnStepChanged;
        public event Action<ShrinkTutorialSignalArgs> OnSignalTriggered;

        public static ShrinkTutorialManager EnsureInstance(ShrinkTutorialSettings settings = null)
        {
            if (_instance)
                return _instance;

            var existing = FindObjectOfType<ShrinkTutorialManager>();
            if (existing)
                return existing;

            var host = new GameObject("ShrinkTutorialManager");
            var manager = host.AddComponent<ShrinkTutorialManager>();
            manager.settingsOverride = settings;
            return manager;
        }

        public static void ResetStaticState()
        {
            _instance = null;
        }

        public bool HasCompleted(string tutorialId)
        {
            return !string.IsNullOrWhiteSpace(tutorialId) && _completedTutorials.Contains(tutorialId);
        }

        public bool HasSkipped(string tutorialId)
        {
            return !string.IsNullOrWhiteSpace(tutorialId) && _skippedTutorials.Contains(tutorialId);
        }

        public void ClearProgress(string tutorialId)
        {
            InitializeIfNeeded();

            if (string.IsNullOrWhiteSpace(tutorialId))
                return;

            var changed = _completedTutorials.Remove(tutorialId);
            changed = _skippedTutorials.Remove(tutorialId) || changed;
            if (changed)
                SaveProgress();
        }

        public void StartTutorial(string tutorialId)
        {
            InitializeIfNeeded();

            if (string.IsNullOrWhiteSpace(tutorialId) || HasCompleted(tutorialId))
                return;

            if (!TryGetDatabaseTutorial(tutorialId, out var tutorial))
            {
                Debug.LogWarning($"[ShrinkTutorial] 未找到教程: {tutorialId}");
                return;
            }

            if (!ArePrerequisitesSatisfied(tutorial) || _currentTutorial)
            {
                EnqueueTutorial(tutorialId);
                return;
            }

            LogDebug($"StartTutorial -> {tutorialId}");
            _runner = StartCoroutine(RunTutorialRoutine(tutorial));
        }

        public void CompleteStep(string customEventName = "")
        {
            if (_currentTutorial)
            {
                LogDebug($"CompleteStep signal received, tutorial={_currentTutorial.tutorialId}, step={_currentStepIndex}, event={customEventName}");
                _receivedCustomEvent = customEventName ?? string.Empty;
            }
        }

        public void SkipCurrent()
        {
            if (!_currentTutorial)
                return;

            _skipRequested = true;
            _stepCompleted = true;
        }

        public void PauseCurrent()
        {
            if (!_currentTutorial)
                return;

            _isPaused = true;
            SetUiVisible(false);
        }

        public void ResumeCurrent()
        {
            if (!_currentTutorial)
                return;

            _isPaused = false;
            SetUiVisible(true);
        }

        private void Awake()
        {
            if (_instance && _instance != this)
            {
                Destroy(gameObject);
                return;
            }

            _instance = this;
            InitializeIfNeeded();
        }

        private void InitializeIfNeeded()
        {
            if (_storage != null)
                return;

            var settings = ResolveSettings();
            _storage = new PlayerPrefsShrinkTutorialStorage(settings.playerPrefsStorageKey);

            var progress = _storage.Load();
            _completedTutorials.Clear();
            _skippedTutorials.Clear();

            foreach (var tutorialId in progress.completedTutorials)
            {
                if (!string.IsNullOrWhiteSpace(tutorialId))
                    _completedTutorials.Add(tutorialId);
            }

            foreach (var tutorialId in progress.skippedTutorials)
            {
                if (!string.IsNullOrWhiteSpace(tutorialId))
                    _skippedTutorials.Add(tutorialId);
            }

            if (settings.dontDestroyOnLoad)
                DontDestroyOnLoad(gameObject);

            EnsureEventSystem();
            EnsureUi();
        }

        private IEnumerator RunTutorialRoutine(ShrinkTutorialData tutorial)
        {
            _currentTutorial = tutorial;
            OnTutorialStarted?.Invoke(tutorial.tutorialId);

            for (var stepIndex = 0; stepIndex < tutorial.steps.Count; stepIndex++)
            {
                _currentStepIndex = stepIndex;
                _skipRequested = false;
                _stepCompleted = false;
                _stepCompletionQueued = false;
                _stepAutoTimer = tutorial.steps[stepIndex].autoDelay;
                _receivedCustomEvent = string.Empty;

                var step = tutorial.steps[stepIndex];
                LogDebug(
                    $"Enter step {stepIndex}, condition={step.completeCondition}, targetMode={step.targetMode}, " +
                    $"targetPath={step.targetPath}, anchorId={step.anchorId}, customEvent={step.customEventName}");
                OnStepChanged?.Invoke(tutorial.tutorialId, stepIndex);

                yield return WaitWhilePaused();

                Transform targetTransform = null;
                yield return ResolveTargetRoutine(step, value => targetTransform = value);

                if (step.RequiresTarget() && !targetTransform)
                {
                    Debug.LogWarning($"[ShrinkTutorial] 教程 {tutorial.tutorialId} 第 {stepIndex + 1} 步缺少目标，已跳过。");
                    continue;
                }

                if (targetTransform)
                    LogDebug($"Resolved target for step {stepIndex}: {GetTransformPath(targetTransform)}");

                EmitSignal(step.enterSignal);
                _dialog.SetSkipVisible(ResolveSettings().showSkipButton);

                while (!_stepCompleted && !_skipRequested)
                {
                    yield return WaitWhilePaused();

                    UpdateStepVisuals(step, targetTransform);
                    TickStepCompletion(step, targetTransform);
                    yield return null;
                }

                EmitSignal(step.exitSignal);
                _dialog.Hide();

                if (_skipRequested)
                {
                    MarkSkipped(tutorial.tutorialId);
                    CleanupAfterTutorial();
                    OnTutorialSkipped?.Invoke(tutorial.tutorialId);
                    yield break;
                }
            }

            MarkCompleted(tutorial.tutorialId);
            OnTutorialCompleted?.Invoke(tutorial.tutorialId);
            CleanupAfterTutorial();
        }

        private IEnumerator ResolveTargetRoutine(ShrinkTutorialStep step, Action<Transform> assignResult)
        {
            var elapsed = 0f;
            var target = ShrinkTutorialTargetUtility.ResolveTarget(step);

            while (!target && step.waitForTarget)
            {
                if (step.waitTimeout > 0f && elapsed >= step.waitTimeout)
                    break;

                elapsed += Time.unscaledDeltaTime;
                yield return null;
                target = ShrinkTutorialTargetUtility.ResolveTarget(step);
            }

            assignResult?.Invoke(target);
        }

        private IEnumerator WaitWhilePaused()
        {
            while (_isPaused)
                yield return null;
        }

        private void TickStepCompletion(ShrinkTutorialStep step, Transform targetTransform)
        {
            switch (step.completeCondition)
            {
                case ShrinkTutorialCompleteCondition.Auto:
                    _stepAutoTimer -= Time.unscaledDeltaTime;
                    if (_stepAutoTimer <= 0f)
                    {
                        LogDebug($"Auto step completed, tutorial={_currentTutorial?.tutorialId}, step={_currentStepIndex}");
                        _stepCompleted = true;
                    }
                    break;
                case ShrinkTutorialCompleteCondition.AnyClick:
                    if (WasPrimaryPointerPressedOutsideDialog())
                    {
                        LogDebug($"AnyClick step completed, tutorial={_currentTutorial?.tutorialId}, step={_currentStepIndex}");
                        _stepCompleted = true;
                    }
                    break;
                case ShrinkTutorialCompleteCondition.ClickTarget:
                    if (targetTransform &&
                        ShrinkTutorialTargetUtility.TryBuildScreenRect(targetTransform, out var targetRect) &&
                        WasPrimaryPointerReleased(targetRect, step.maskShape, out var screenPosition) &&
                        WasPointerReleaseRoutedToTarget(targetTransform, screenPosition))
                    {
                        LogDebug(
                            $"ClickTarget candidate accepted, tutorial={_currentTutorial?.tutorialId}, step={_currentStepIndex}, " +
                            $"pointer={screenPosition}, target={GetTransformPath(targetTransform)}");
                        QueueStepCompletion();
                    }
                    break;
                case ShrinkTutorialCompleteCondition.CustomEvent:
                case ShrinkTutorialCompleteCondition.DragToTarget:
                    if (MatchesCustomEvent(step.customEventName))
                    {
                        LogDebug(
                            $"CustomEvent step completed, tutorial={_currentTutorial?.tutorialId}, step={_currentStepIndex}, event={step.customEventName}");
                        _stepCompleted = true;
                    }
                    break;
            }
        }

        private void UpdateStepVisuals(ShrinkTutorialStep step, Transform targetTransform)
        {
            Rect targetRect = default;
            var hasTargetRect = targetTransform && ShrinkTutorialTargetUtility.TryBuildScreenRect(targetTransform, out targetRect);

            if (hasTargetRect && step.maskShape != ShrinkTutorialMaskShape.None)
                _mask.SetHighlight(targetRect, step.maskShape, step.maskPadding);
            else
                _mask.ClearHighlight();

            var tutorialText = ShrinkTutorialLocalization.Resolve(step.localizedTextKey, step.fallbackText);
            _dialog.Show(tutorialText, hasTargetRect ? targetRect : (Rect?)null, step.dialogAnchor, step.dialogOffset, step.showArrow);
        }

        private bool MatchesCustomEvent(string expectedEventName)
        {
            if (string.IsNullOrWhiteSpace(_receivedCustomEvent))
                return false;

            if (string.IsNullOrWhiteSpace(expectedEventName))
            {
                _receivedCustomEvent = string.Empty;
                return true;
            }

            if (!string.Equals(expectedEventName, _receivedCustomEvent, StringComparison.Ordinal))
                return false;

            _receivedCustomEvent = string.Empty;
            return true;
        }

        private bool WasPrimaryPointerPressedOutsideDialog()
        {
            var pressed = TryGetPointerDownPosition(out var screenPosition);
            return pressed && !_dialog.ContainsScreenPoint(screenPosition);
        }

        private bool WasPrimaryPointerReleased(Rect targetRect, ShrinkTutorialMaskShape maskShape, out Vector2 screenPosition)
        {
            if (!TryGetPointerUpPosition(out screenPosition))
                return false;

            if (_dialog.ContainsScreenPoint(screenPosition))
            {
                LogDebug($"Pointer release ignored because it hit dialog, pointer={screenPosition}");
                return false;
            }

            var insideTarget = maskShape == ShrinkTutorialMaskShape.Circle
                ? IsPointInsideCircle(targetRect, screenPosition)
                : targetRect.Contains(screenPosition);
            if (!insideTarget)
                LogDebug($"Pointer release outside target, pointer={screenPosition}, rect={targetRect}");

            return insideTarget;
        }

        private static bool IsPointInsideCircle(Rect targetRect, Vector2 screenPosition)
        {
            var center = targetRect.center;
            var radius = Mathf.Min(targetRect.width, targetRect.height) * 0.5f;
            return Vector2.SqrMagnitude(screenPosition - center) <= radius * radius;
        }

        private static bool TryGetPointerDownPosition(out Vector2 screenPosition)
        {
            if (Input.touchCount > 0)
            {
                var touch = Input.GetTouch(0);
                if (touch.phase == TouchPhase.Began)
                {
                    screenPosition = touch.position;
                    return true;
                }
            }

            if (Input.GetMouseButtonDown(0))
            {
                screenPosition = Input.mousePosition;
                return true;
            }

            screenPosition = default;
            return false;
        }

        private static bool TryGetPointerUpPosition(out Vector2 screenPosition)
        {
            if (Input.touchCount > 0)
            {
                var touch = Input.GetTouch(0);
                if (touch.phase == TouchPhase.Ended)
                {
                    screenPosition = touch.position;
                    return true;
                }
            }

            if (Input.GetMouseButtonUp(0))
            {
                screenPosition = Input.mousePosition;
                return true;
            }

            screenPosition = default;
            return false;
        }

        private bool WasPointerReleaseRoutedToTarget(Transform targetTransform, Vector2 screenPosition)
        {
            var eventSystem = EventSystem.current;
            if (!eventSystem)
                return true;

            _pointerRaycastResults.Clear();
            var pointerEventData = new PointerEventData(eventSystem)
            {
                position = screenPosition
            };
            eventSystem.RaycastAll(pointerEventData, _pointerRaycastResults);

            foreach (var result in _pointerRaycastResults)
            {
                var hitTransform = result.gameObject ? result.gameObject.transform : null;
                if (IsSameOrNestedTarget(hitTransform, targetTransform))
                {
                    LogDebug(
                        $"Raycast matched target, pointer={screenPosition}, target={GetTransformPath(targetTransform)}, " +
                        $"hit={GetTransformPath(hitTransform)}");
                    return true;
                }
            }

            var hitSummary = _pointerRaycastResults.Count == 0
                ? "<none>"
                : string.Join(" | ", _pointerRaycastResults.Take(5).Select(result =>
                {
                    var hitTransform = result.gameObject ? result.gameObject.transform : null;
                    return GetTransformPath(hitTransform);
                }));
            LogDebug(
                $"Raycast missed target, pointer={screenPosition}, target={GetTransformPath(targetTransform)}, hits={hitSummary}");
            return false;
        }

        private static bool IsSameOrNestedTarget(Transform hitTransform, Transform targetTransform)
        {
            return hitTransform &&
                   targetTransform &&
                   (hitTransform == targetTransform ||
                    hitTransform.IsChildOf(targetTransform) ||
                    targetTransform.IsChildOf(hitTransform));
        }

        private void QueueStepCompletion()
        {
            if (_stepCompletionQueued || !_currentTutorial)
                return;

            LogDebug($"QueueStepCompletion, tutorial={_currentTutorial.tutorialId}, step={_currentStepIndex}");
            _stepCompletionQueued = true;
            StartCoroutine(CompleteStepAtEndOfFrame(_currentTutorial.tutorialId, _currentStepIndex));
        }

        private IEnumerator CompleteStepAtEndOfFrame(string tutorialId, int stepIndex)
        {
            yield return new WaitForEndOfFrame();
            _stepCompletionQueued = false;

            if (_currentTutorial &&
                !_skipRequested &&
                !_stepCompleted &&
                string.Equals(_currentTutorial.tutorialId, tutorialId, StringComparison.Ordinal) &&
                _currentStepIndex == stepIndex)
            {
                LogDebug($"Step completed at end of frame, tutorial={tutorialId}, step={stepIndex}");
                _stepCompleted = true;
            }
        }

        private void EmitSignal(string signalName)
        {
            if (string.IsNullOrWhiteSpace(signalName) || !_currentTutorial)
                return;

            OnSignalTriggered?.Invoke(new ShrinkTutorialSignalArgs(
                _currentTutorial.tutorialId,
                _currentStepIndex,
                signalName));
        }

        private void CleanupAfterTutorial()
        {
            _mask.ClearHighlight();
            _dialog.Hide();
            _currentTutorial = null;
            _currentStepIndex = -1;
            _runner = null;
            _stepCompletionQueued = false;

            TryStartQueuedTutorial();
        }

        private void EnsureUi()
        {
            if (_canvas && _mask && _dialog)
                return;

            var settings = ResolveSettings();
            var canvasObject = new GameObject("ShrinkTutorialCanvas", typeof(RectTransform), typeof(Canvas), typeof(CanvasScaler),
                typeof(GraphicRaycaster));
            canvasObject.transform.SetParent(transform, false);

            _canvas = canvasObject.GetComponent<Canvas>();
            _canvas.renderMode = RenderMode.ScreenSpaceOverlay;
            _canvas.sortingOrder = settings.canvasSortingOrder;

            var scaler = canvasObject.GetComponent<CanvasScaler>();
            scaler.uiScaleMode = CanvasScaler.ScaleMode.ScaleWithScreenSize;
            scaler.referenceResolution = new Vector2(1920f, 1080f);
            scaler.matchWidthOrHeight = 0.5f;

            var maskObject = new GameObject("Mask", typeof(RectTransform), typeof(CanvasRenderer), typeof(ShrinkTutorialMask));
            maskObject.transform.SetParent(canvasObject.transform, false);
            StretchFull(maskObject.GetComponent<RectTransform>());
            _mask = maskObject.GetComponent<ShrinkTutorialMask>();
            _mask.color = settings.maskColor;

            var dialogObject = new GameObject("Dialog", typeof(RectTransform), typeof(ShrinkTutorialDialog));
            dialogObject.transform.SetParent(canvasObject.transform, false);
            _dialog = dialogObject.GetComponent<ShrinkTutorialDialog>();
            _dialog.Initialize(canvasObject.transform, SkipCurrent);
            _dialog.Hide();
        }

        private void EnsureEventSystem()
        {
            if (FindObjectOfType<EventSystem>())
                return;

            var eventSystemObject = new GameObject("EventSystem", typeof(EventSystem), typeof(StandaloneInputModule));
            DontDestroyOnLoad(eventSystemObject);
        }

        private bool TryGetDatabaseTutorial(string tutorialId, out ShrinkTutorialData tutorial)
        {
            tutorial = null;
            var settings = ResolveSettings();
            return settings.database && settings.database.TryGetTutorial(tutorialId, out tutorial);
        }

        private ShrinkTutorialSettings ResolveSettings()
        {
            return settingsOverride ? settingsOverride : ShrinkTutorialSettings.Instance;
        }

        private bool ArePrerequisitesSatisfied(ShrinkTutorialData tutorial)
        {
            if (!tutorial || tutorial.prerequisiteIds == null)
                return true;

            foreach (var prerequisiteId in tutorial.prerequisiteIds)
            {
                if (string.IsNullOrWhiteSpace(prerequisiteId))
                    continue;

                if (!_completedTutorials.Contains(prerequisiteId))
                    return false;
            }

            return true;
        }

        private void EnqueueTutorial(string tutorialId)
        {
            if (_pendingTutorialIds.Contains(tutorialId))
                return;

            _pendingTutorialIds.Add(tutorialId);
            _pendingTutorialIds.Sort(ComparePendingTutorial);
        }

        private int ComparePendingTutorial(string leftId, string rightId)
        {
            var leftPriority = TryGetDatabaseTutorial(leftId, out var leftTutorial) ? leftTutorial.priority : 0;
            var rightPriority = TryGetDatabaseTutorial(rightId, out var rightTutorial) ? rightTutorial.priority : 0;
            return rightPriority.CompareTo(leftPriority);
        }

        private void TryStartQueuedTutorial()
        {
            for (var i = 0; i < _pendingTutorialIds.Count; i++)
            {
                var tutorialId = _pendingTutorialIds[i];
                if (!TryGetDatabaseTutorial(tutorialId, out var tutorial) || !ArePrerequisitesSatisfied(tutorial))
                    continue;

                _pendingTutorialIds.RemoveAt(i);
                StartTutorial(tutorialId);
                return;
            }
        }

        private void MarkCompleted(string tutorialId)
        {
            _completedTutorials.Add(tutorialId);
            _skippedTutorials.Remove(tutorialId);
            SaveProgress();
        }

        private void MarkSkipped(string tutorialId)
        {
            _skippedTutorials.Add(tutorialId);
            SaveProgress();
        }

        private void SaveProgress()
        {
            _storage.Save(new ShrinkTutorialProgress
            {
                completedTutorials = new List<string>(_completedTutorials),
                skippedTutorials = new List<string>(_skippedTutorials)
            });
        }

        private void SetUiVisible(bool visible)
        {
            if (_canvas)
                _canvas.enabled = visible;
        }

        private static void StretchFull(RectTransform rectTransform)
        {
            rectTransform.anchorMin = Vector2.zero;
            rectTransform.anchorMax = Vector2.one;
            rectTransform.offsetMin = Vector2.zero;
            rectTransform.offsetMax = Vector2.zero;
            rectTransform.pivot = new Vector2(0.5f, 0.5f);
        }

        [System.Diagnostics.Conditional("UNITY_EDITOR")]
        private static void LogDebug(string message)
        {
            if (!IsDebugLoggingEnabled())
                return;

            Debug.Log($"[ShrinkTutorial][Debug] {message}");
        }

        [System.Diagnostics.Conditional("UNITY_EDITOR")]
        private static void LogDebug(string format, params object[] args)
        {
            if (!IsDebugLoggingEnabled())
                return;

            Debug.LogFormat("[ShrinkTutorial][Debug] " + format, args);
        }

        private static bool IsDebugLoggingEnabled()
        {
            return false;
        }

        private static string GetTransformPath(Transform transform)
        {
            if (!transform)
                return "<null>";

            var path = transform.name;
            while (transform.parent)
            {
                transform = transform.parent;
                path = $"{transform.name}/{path}";
            }

            return path;
        }
    }

    public readonly struct ShrinkTutorialSignalArgs
    {
        public ShrinkTutorialSignalArgs(string tutorialId, int stepIndex, string signalName)
        {
            TutorialId = tutorialId;
            StepIndex = stepIndex;
            SignalName = signalName;
        }

        public string TutorialId { get; }
        public int StepIndex { get; }
        public string SignalName { get; }
    }
}