using UnityEngine;
using System.Collections.Generic;

public class PuzzleManager : MonoBehaviour
{
    private static PuzzleManager _instance;
    public static PuzzleManager Instance
    {
        get
        {
            if (_instance == null)
            {
                _instance = FindAnyObjectByType<PuzzleManager>();
                if (_instance == null)
                {
                    var go = new GameObject("PuzzleManager");
                    _instance = go.AddComponent<PuzzleManager>();
                    DontDestroyOnLoad(go);
                }
            }
            return _instance;
        }
    }

    private HashSet<PuzzleStepSO> completedSteps = new HashSet<PuzzleStepSO>();
    private HashSet<PuzzleStepSO> unlockedSteps = new HashSet<PuzzleStepSO>();

    // Registration for ObjectiveStepBehaviour
    private Dictionary<PuzzleStepSO, ObjectiveStepBehaviour> stepBehaviours = new Dictionary<PuzzleStepSO, ObjectiveStepBehaviour>();

    // Runtime dependency graph
    private Dictionary<PuzzleStepSO, List<PuzzleStepSO>> runtimeDependencies = new Dictionary<PuzzleStepSO, List<PuzzleStepSO>>();

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

    public void RegisterStepBehaviour(ObjectiveStepBehaviour behaviour)
    {
        if (behaviour?.stepData == null) return;
        if (!stepBehaviours.ContainsKey(behaviour.stepData))
        {
            stepBehaviours.Add(behaviour.stepData, behaviour);
            Debug.Log($"[Puzzles] Registered step: {behaviour.stepData.stepId} on {behaviour.gameObject.name}");
        }
    }

    public void UnregisterStepBehaviour(ObjectiveStepBehaviour behaviour)
    {
        if (behaviour?.stepData == null) return;
        stepBehaviours.Remove(behaviour.stepData);
        Debug.Log($"[Puzzles] Unregistered step: {behaviour.stepData.stepId} on {behaviour.gameObject.name}");
    }

    void Start()
    {
        BuildRuntimeDependencies();
        UnlockInitialSteps();
    }

    private void BuildRuntimeDependencies()
    {
        runtimeDependencies.Clear();
        foreach (var step in stepBehaviours.Keys)
        {
            runtimeDependencies[step] = new List<PuzzleStepSO>();
        }
        foreach (var step in stepBehaviours.Keys)
        {
            foreach (var unlocked in step.unlocks)
            {
                if (!runtimeDependencies.ContainsKey(unlocked))
                    runtimeDependencies[unlocked] = new List<PuzzleStepSO>();
                runtimeDependencies[unlocked].Add(step);
                Debug.Log($"[Puzzles] Step {unlocked.stepId} depends on {step.stepId}");
            }
        }
        Debug.Log($"[Puzzles] Runtime dependencies built. Total steps: {stepBehaviours.Count}");
    }

    private void UnlockInitialSteps()
    {
        foreach (var step in stepBehaviours.Keys)
        {
            if (runtimeDependencies[step].Count == 0)
            {
                Debug.Log($"[Puzzles] Initial step unlocked: {step.stepId}");
                UnlockStep(step);
            }
        }
    }

    public void OnStepCompleted(PuzzleStepSO step)
    {
        if (completedSteps.Contains(step)) return;
        completedSteps.Add(step);
        Debug.Log($"[Puzzles] Step completed: {step.stepId}");
        foreach (var unlock in step.unlocks)
        {
            if (AreRuntimeDependenciesMet(unlock))
            {
                Debug.Log($"[Puzzles] Unlocking step {unlock.stepId} after completing {step.stepId}");
                UnlockStep(unlock);
            }
            else
            {
                Debug.Log($"[Puzzles] Step {unlock.stepId} not unlocked yet, waiting for other dependencies");
            }
        }
        CheckPuzzleCompletion();
    }

    private bool AreRuntimeDependenciesMet(PuzzleStepSO step)
    {
        if (!runtimeDependencies.ContainsKey(step) || runtimeDependencies[step].Count == 0) return true;
        foreach (var dep in runtimeDependencies[step])
        {
            if (!completedSteps.Contains(dep)) return false;
        }
        return true;
    }

    private void UnlockStep(PuzzleStepSO step)
    {
        if (unlockedSteps.Contains(step)) return;
        unlockedSteps.Add(step);
        if (stepBehaviours.TryGetValue(step, out var behaviour))
        {
            behaviour.UnlockStep();
        }
        Debug.Log($"[Puzzles] Step unlocked: {step.stepId}");
    }

    private void CheckPuzzleCompletion()
    {
        if (completedSteps.Count == stepBehaviours.Count)
        {
            Debug.Log("[Puzzles] Puzzle complete! All steps finished.");
            // TODO: Fire puzzle complete event or trigger outcome logic
        }
    }
}