using System;
using System.Collections;
using System.Collections.Generic;
using TMPro;
using UnityEngine;
using UnityEngine.Events;
using UnityEngine.SceneManagement;
using UnityEngine.UI;
#if UNITY_EDITOR
using UnityEditor;
#endif

[DisallowMultipleComponent]
public sealed class SceneSelectorMenu : MonoBehaviour
{
    [Serializable]
    public sealed class SceneButtonBinding
    {
        [Tooltip("Optional UI label override. If empty, scene name from path is used.")]
        public string displayName;

        [SerializeField]
        private string scenePath;

#if UNITY_EDITOR
        [Tooltip("Editor helper for selecting a scene asset. scenePath is synced from this field.")]
        public SceneAsset sceneAsset;
#endif

        [Tooltip("UI Button for this scene.")]
        public Button button;

        [Tooltip("Optional text component for the button label.")]
        public TMP_Text buttonLabel;

        [Tooltip("Optional text component for availability hints.")]
        public TMP_Text availabilityLabel;

        public string ScenePath => scenePath;

        public string EffectiveLabel
        {
            get
            {
                if (!string.IsNullOrWhiteSpace(displayName))
                {
                    return displayName;
                }

                if (string.IsNullOrWhiteSpace(scenePath))
                {
                    return "<missing scene>";
                }

                int slash = scenePath.LastIndexOf('/');
                int dot = scenePath.LastIndexOf('.');
                if (dot <= slash)
                {
                    dot = scenePath.Length;
                }

                return scenePath.Substring(slash + 1, dot - slash - 1);
            }
        }

#if UNITY_EDITOR
        public void SyncScenePathFromAsset()
        {
            if (sceneAsset == null)
            {
                return;
            }

            string path = AssetDatabase.GetAssetPath(sceneAsset);
            if (!string.IsNullOrWhiteSpace(path))
            {
                scenePath = path;
            }
        }
#endif
    }

    [SerializeField]
    private List<SceneButtonBinding> sceneButtons = new();

    [SerializeField]
    private TMP_Text statusLabel;

    [SerializeField]
    private bool disableButtonsWhileLoading = true;

    [SerializeField]
    private string missingPathText = "No scene assigned";

    [SerializeField]
    private string missingBuildSettingsText = "Not in Build Settings";

    [SerializeField]
    private string loadingPrefix = "Loading ";

    private readonly List<UnityAction> clickActions = new();
    private bool isLoading;

    private void OnEnable()
    {
        BindButtons();
        RefreshBindings();
    }

    private void OnDisable()
    {
        UnbindButtons();
    }

    private void OnValidate()
    {
#if UNITY_EDITOR
        for (int i = 0; i < sceneButtons.Count; i++)
        {
            sceneButtons[i].SyncScenePathFromAsset();
        }
#endif
        RefreshBindingVisuals();
    }

    public void RefreshBindings()
    {
        RefreshBindingVisuals();
        SetStatus(string.Empty);
    }

    public void LoadSceneByPath(string scenePath)
    {
        int buildIndex = SceneUtility.GetBuildIndexByScenePath(scenePath);
        if (buildIndex < 0)
        {
            SetStatus($"{missingBuildSettingsText}: {scenePath}");
            Debug.LogWarning($"[SceneSelector] Scene not in build settings: {scenePath}");
            return;
        }

        StartLoad(buildIndex, scenePath);
    }

    private void BindButtons()
    {
        UnbindButtons();
        clickActions.Clear();

        for (int i = 0; i < sceneButtons.Count; i++)
        {
            SceneButtonBinding binding = sceneButtons[i];
            if (binding.button == null)
            {
                clickActions.Add(null);
                continue;
            }

            int capturedIndex = i;
            UnityAction action = () => OnSceneButtonPressed(capturedIndex);
            clickActions.Add(action);
            binding.button.onClick.AddListener(action);
        }
    }

    private void UnbindButtons()
    {
        int count = Mathf.Min(sceneButtons.Count, clickActions.Count);
        for (int i = 0; i < count; i++)
        {
            SceneButtonBinding binding = sceneButtons[i];
            UnityAction action = clickActions[i];
            if (binding.button != null && action != null)
            {
                binding.button.onClick.RemoveListener(action);
            }
        }

        clickActions.Clear();
    }

    private void OnSceneButtonPressed(int index)
    {
        if (isLoading)
        {
            return;
        }

        if (index < 0 || index >= sceneButtons.Count)
        {
            return;
        }

        SceneButtonBinding binding = sceneButtons[index];
        string scenePath = binding.ScenePath;
        string label = binding.EffectiveLabel;

        if (string.IsNullOrWhiteSpace(scenePath))
        {
            SetStatus($"{missingPathText}: {label}");
            return;
        }

        int buildIndex = SceneUtility.GetBuildIndexByScenePath(scenePath);
        if (buildIndex < 0)
        {
            SetStatus($"{missingBuildSettingsText}: {label}");
            Debug.LogWarning($"[SceneSelector] Scene not in build settings: {scenePath}");
            RefreshBindingVisuals();
            return;
        }

        StartLoad(buildIndex, label);
    }

    private void StartLoad(int buildIndex, string label)
    {
        if (isLoading)
        {
            return;
        }

        StartCoroutine(LoadSceneRoutine(buildIndex, label));
    }

    private IEnumerator LoadSceneRoutine(int buildIndex, string label)
    {
        isLoading = true;
        RefreshBindingVisuals();
        SetStatus($"{loadingPrefix}{label}...");

        AsyncOperation op = SceneManager.LoadSceneAsync(buildIndex, LoadSceneMode.Single);
        if (op == null)
        {
            isLoading = false;
            SetStatus($"Load failed: {label}");
            RefreshBindingVisuals();
            yield break;
        }

        while (!op.isDone)
        {
            yield return null;
        }
    }

    private void RefreshBindingVisuals()
    {
        for (int i = 0; i < sceneButtons.Count; i++)
        {
            SceneButtonBinding binding = sceneButtons[i];
            string label = binding.EffectiveLabel;
            bool hasPath = !string.IsNullOrWhiteSpace(binding.ScenePath);
            bool inBuildSettings = hasPath && SceneUtility.GetBuildIndexByScenePath(binding.ScenePath) >= 0;
            bool available = hasPath && inBuildSettings;

            if (binding.buttonLabel != null)
            {
                binding.buttonLabel.text = label;
            }

            if (binding.availabilityLabel != null)
            {
                if (!hasPath)
                {
                    binding.availabilityLabel.text = missingPathText;
                }
                else if (!inBuildSettings)
                {
                    binding.availabilityLabel.text = missingBuildSettingsText;
                }
                else
                {
                    binding.availabilityLabel.text = string.Empty;
                }
            }

            if (binding.button != null)
            {
                bool interactable = available;
                if (disableButtonsWhileLoading && isLoading)
                {
                    interactable = false;
                }

                binding.button.interactable = interactable;
            }
        }
    }

    private void SetStatus(string message)
    {
        if (statusLabel != null)
        {
            statusLabel.text = message;
        }
    }
}