using System;
using System.Collections;
using System.Collections.Generic;
using System.IO;
using UnityEngine;
using UnityEngine.AddressableAssets;
using UnityEngine.ResourceManagement.AsyncOperations;

public class GeoTileAddressablesLoader : MonoBehaviour
{
    [Header("References")]
    [SerializeField] private Transform player;
    [SerializeField] private Transform tilesParent;

    [Header("Paths")]
    [SerializeField] private string tileBundleFolderName = "TileBundles";
    [SerializeField] private string manifestFileName = "TileManifest.json";
    [SerializeField] private string buildTargetFolderOverride = "";

    [Header("Streaming")]
    [SerializeField] private float loadRadiusMeters = 1500f;
    [SerializeField] private float unloadRadiusMeters = 2000f;
    [SerializeField] private float updateInterval = 0.5f;
    [SerializeField] private int maxConcurrentLoads = 2;
    [SerializeField] private bool verboseLogging = false;

    private TileManifest manifest;
    private readonly Dictionary<string, TileEntry> tiles = new Dictionary<string, TileEntry>();
    private readonly Dictionary<string, GameObject> loaded = new Dictionary<string, GameObject>();
    private readonly HashSet<string> loading = new HashSet<string>();
    private readonly HashSet<string> queued = new HashSet<string>();
    private readonly Queue<string> loadQueue = new Queue<string>();

    private bool initialized;
    private float nextUpdateTime;

    private void OnValidate()
    {
        if (unloadRadiusMeters < loadRadiusMeters)
            unloadRadiusMeters = loadRadiusMeters;
        if (maxConcurrentLoads < 1)
            maxConcurrentLoads = 1;
        if (updateInterval < 0.05f)
            updateInterval = 0.05f;
    }

    private void Awake()
    {
        if (tilesParent == null)
        {
            var parent = new GameObject("Geo_Tile_Addressables");
            tilesParent = parent.transform;
        }
    }

    private void Start()
    {
        if (player == null && Camera.main != null)
            player = Camera.main.transform;

        StartCoroutine(Initialize());
    }

    private IEnumerator Initialize()
    {
        var buildTargetFolder = string.IsNullOrWhiteSpace(buildTargetFolderOverride)
            ? GetBuildTargetFolderName()
            : buildTargetFolderOverride;

        var basePath = Path.Combine(Application.persistentDataPath, tileBundleFolderName, buildTargetFolder);
        var manifestPath = Path.Combine(basePath, manifestFileName);

        Log($"Initializing loader. BasePath={basePath}");
        Log($"ManifestPath={manifestPath}");

        if (!File.Exists(manifestPath))
        {
            Debug.LogError($"[GeoTileAddressablesLoader] Manifest not found: {manifestPath}");
            yield break;
        }

        manifest = JsonUtility.FromJson<TileManifest>(File.ReadAllText(manifestPath));
        if (manifest == null || manifest.tiles == null || manifest.tiles.Length == 0)
        {
            Debug.LogError("[GeoTileAddressablesLoader] Manifest is empty or invalid.");
            yield break;
        }

        tiles.Clear();
        foreach (var tile in manifest.tiles)
        {
            if (!string.IsNullOrWhiteSpace(tile.tileId))
                tiles[tile.tileId] = tile;
        }

        Log($"Manifest loaded. Tiles={tiles.Count} CatalogFile={manifest.catalogFile}");

        var catalogPath = Path.Combine(basePath, manifest.catalogFile);
        if (!File.Exists(catalogPath))
        {
            Debug.LogError($"[GeoTileAddressablesLoader] Catalog not found: {catalogPath}");
            yield break;
        }

        Log($"Loading catalog: {catalogPath}");
        var handle = Addressables.LoadContentCatalogAsync(ToFileUri(catalogPath), true);
        yield return handle;

        if (handle.Status != AsyncOperationStatus.Succeeded)
        {
            Debug.LogError($"[GeoTileAddressablesLoader] Catalog load failed: {handle.OperationException}");
            yield break;
        }

        Log("Catalog loaded successfully.");
        initialized = true;
        nextUpdateTime = Time.time;
    }

    private void Update()
    {
        if (!initialized || player == null)
            return;

        if (Time.time < nextUpdateTime)
            return;

        nextUpdateTime = Time.time + updateInterval;

        UpdateTileSet();
        ProcessQueue();
    }

    private void UpdateTileSet()
    {
        var playerPos = player.position;
        var tileSize = manifest.tileSizeMeters;

        foreach (var kvp in tiles)
        {
            var tile = kvp.Value;
            var tileCenter = new Vector3(
                tile.offsetX + tileSize * 0.5f,
                tile.baseY,
                tile.offsetZ + tileSize * 0.5f);
            var distance = Vector2.Distance(
                new Vector2(playerPos.x, playerPos.z),
                new Vector2(tileCenter.x, tileCenter.z));

            if (distance <= loadRadiusMeters)
            {
                EnqueueTileLoad(tile.tileId);
            }
            else if (distance >= unloadRadiusMeters)
            {
                UnloadTile(tile.tileId);
            }
        }
    }

    private void EnqueueTileLoad(string tileId)
    {
        if (loaded.ContainsKey(tileId) || loading.Contains(tileId) || queued.Contains(tileId))
            return;

        loadQueue.Enqueue(tileId);
        queued.Add(tileId);
    }

    private void ProcessQueue()
    {
        while (loading.Count < maxConcurrentLoads && loadQueue.Count > 0)
        {
            var tileId = loadQueue.Dequeue();
            queued.Remove(tileId);
            StartLoad(tileId);
        }
    }

    private void StartLoad(string tileId)
    {
        if (!tiles.TryGetValue(tileId, out var tile))
            return;

        loading.Add(tileId);
        Log($"Loading tile {tileId}...");

        var handle = Addressables.InstantiateAsync(tileId, tilesParent);
        handle.Completed += op =>
        {
            loading.Remove(tileId);

            if (op.Status != AsyncOperationStatus.Succeeded)
            {
                Debug.LogError($"[GeoTileAddressablesLoader] Load failed for {tileId}: {op.OperationException}");
                return;
            }

            var instance = op.Result;
            instance.name = tileId;
            instance.transform.position = new Vector3(tile.offsetX, tile.baseY, tile.offsetZ);
            loaded[tileId] = instance;
            Log($"Loaded tile {tileId}. LoadedCount={loaded.Count}");
        };
    }

    private void UnloadTile(string tileId)
    {
        if (!loaded.TryGetValue(tileId, out var instance))
            return;

        Addressables.ReleaseInstance(instance);
        loaded.Remove(tileId);
        Log($"Unloaded tile {tileId}. LoadedCount={loaded.Count}");
    }

    private static string GetBuildTargetFolderName()
    {
        switch (Application.platform)
        {
            case RuntimePlatform.Android:
                return "Android";
            case RuntimePlatform.WindowsPlayer:
            case RuntimePlatform.WindowsEditor:
                return "Windows";
            case RuntimePlatform.LinuxPlayer:
            case RuntimePlatform.LinuxEditor:
                return "Linux";
            case RuntimePlatform.OSXPlayer:
            case RuntimePlatform.OSXEditor:
                return "OSX";
            default:
                return "Android";
        }
    }

    private static string ToFileUri(string path)
    {
        var normalized = path.Replace("\\", "/");
        return normalized.StartsWith("file://", StringComparison.OrdinalIgnoreCase)
            ? normalized
            : "file://" + normalized;
    }

    private void OnDestroy()
    {
        foreach (var instance in loaded.Values)
            Addressables.ReleaseInstance(instance);

        loaded.Clear();
        loading.Clear();
        queued.Clear();
        loadQueue.Clear();
    }

    private void Log(string message)
    {
        if (verboseLogging)
            Debug.Log($"[GeoTileAddressablesLoader] {message}");
    }
}