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

/// <summary>
/// Spawns monsters into the maze based on MazeConfig settings.
///
/// Spawning rules
/// ─────────────
/// • Monster rooms  (RoomType.Boss + Normal rooms chosen by MonsterAreaDensity %)
///     → 2–4 monsters, difficulty multiplier scales with room distance from start.
///
/// • Hallway tiles  (walkable tiles not inside any room)
///     → sparse single monsters; much lower density, difficulty ≤ 1.
///
/// Monster prefab is a red sphere identical in size to a solo agent.
///
/// Exposes a static room-threat lookup so AIAgents can query danger before entering.
/// </summary>
public class MonsterSpawner : MonoBehaviour
{
    // ------------------------------------------------------------------ //
    //  Inspector                                                           //
    // ------------------------------------------------------------------ //
    [Header("Prefab (auto-created if null)")]
    [SerializeField] private GameObject monsterPrefab;

    [Header("Room spawn")]
    [Tooltip("Min monsters in a monster room")]
    [SerializeField] private int minMonstersPerRoom = 2;
    [Tooltip("Max monsters in a monster room")]
    [SerializeField] private int maxMonstersPerRoom = 4;
    [Tooltip("Extra monsters added per Boss room")]
    [SerializeField] private int bossRoomBonusMonsters = 3;
    [Tooltip("Difficulty multiplier range for deepest rooms (1 = weakest, 2 = strongest)")]
    [SerializeField] private float maxDifficultyMultiplier = 2f;

    [Header("Hallway spawn")]
    [Tooltip("Probability that any given hallway tile spawns a monster (0–1)")]
    [SerializeField][Range(0f, 0.05f)] private float hallwaySpawnChance = 0.005f;
    [Tooltip("Difficulty multiplier cap for hallway monsters")]
    [SerializeField] private float hallwayMaxDifficulty = 1f;

    // ------------------------------------------------------------------ //
    //  Runtime                                                             //
    // ------------------------------------------------------------------ //
    private MazeData maze;
    private MazeConfig config;

    /// <summary>
    /// Room ID → list of living monsters. Agents can query this to assess danger.
    /// Hallway monsters are stored under key -1.
    /// </summary>
    private static readonly Dictionary<int, List<Monster>> roomMonsters = new();

    // ------------------------------------------------------------------ //
    //  Public entry point – called by MazeController after generation     //
    // ------------------------------------------------------------------ //

    /// <summary>
    /// Called by MazeController once the maze has been fully generated.
    /// Destroys any previously spawned monsters and re-spawns for the new maze.
    /// </summary>
    public void SpawnForMaze(MazeData mazeData, MazeConfig mazeConfig)
    {
        // Destroy any monsters left over from a previous maze
        foreach (var m in FindObjectsByType<Monster>())
            Destroy(m.gameObject);

        maze = mazeData;
        config = mazeConfig;

        if (maze == null) { Debug.LogError("MonsterSpawner: Maze is null!"); return; }

        if (monsterPrefab == null) monsterPrefab = CreateDefaultMonsterPrefab();

        roomMonsters.Clear();
        SpawnRoomMonsters();
        SpawnHallwayMonsters();
        Debug.Log("[MonsterSpawner] Spawning complete.");
    }

    // ------------------------------------------------------------------ //
    //  Public query API                                                    //
    // ------------------------------------------------------------------ //

    /// <summary>
    /// Total threat in a room (sum of living-monster health).
    /// Returns 0 for rooms with no monsters or already cleared.
    /// </summary>
    public static int GetRoomThreat(int roomId)
    {
        if (!roomMonsters.TryGetValue(roomId, out var list)) return 0;
        return list.Where(m => m != null && !m.IsDead).Sum(m => m.ThreatValue);
    }

    /// <summary>How many living monsters are in a room.</summary>
    public static int GetLivingMonsterCount(int roomId)
    {
        if (!roomMonsters.TryGetValue(roomId, out var list)) return 0;
        return list.Count(m => m != null && !m.IsDead);
    }

    // ------------------------------------------------------------------ //
    //  Spawning                                                            //
    // ------------------------------------------------------------------ //

    private void SpawnRoomMonsters()
    {
        if (!config.UseMonsterAreas) return;

        var allRooms = maze.Rooms;
        if (allRooms.Count == 0) return;

        // Build a "depth" estimate: BFS distance from start rooms.
        var depthMap = BuildRoomDepthMap();
        float maxDepth = depthMap.Values.Count > 0 ? depthMap.Values.Max() : 1f;

        // Rooms eligible for monsters
        var eligibleRooms = allRooms.Where(r =>
            r.Type != MazeRoom.RoomType.Safe &&
            r.Type != MazeRoom.RoomType.End &&
            !r.IsStart
        ).ToList();

        // Filter down by MonsterAreaDensity %
        int targetCount = Mathf.RoundToInt(eligibleRooms.Count * (config.MonsterAreaDensity / 100f));
        Shuffle(eligibleRooms);
        var chosenRooms = eligibleRooms.Take(targetCount).ToList();

        // Always include all Boss rooms in the chosen set
        foreach (var boss in allRooms.Where(r => r.Type == MazeRoom.RoomType.Boss))
            if (!chosenRooms.Contains(boss)) chosenRooms.Add(boss);

        foreach (var room in chosenRooms)
        {
            int count = Random.Range(minMonstersPerRoom, maxMonstersPerRoom + 1);
            if (room.Type == MazeRoom.RoomType.Boss) count += bossRoomBonusMonsters;

            // Difficulty: rooms farther from start are harder
            float depth = depthMap.TryGetValue(room.Id, out float d) ? d : 0f;
            float t = maxDepth > 0 ? depth / maxDepth : 0f;
            float difficulty = Mathf.Lerp(1f, maxDifficultyMultiplier, t);

            SpawnMonstersInRoom(room, count, difficulty);
        }
    }

    private void SpawnHallwayMonsters()
    {
        if (!config.UseMonsterAreas) return;

        // Iterate walkable tiles that are NOT inside any room
        for (int x = 0; x < maze.Width; x++)
        {
            for (int y = 0; y < maze.Height; y++)
            {
                if (!maze.IsWalkable(x, y)) continue;
                if (maze.GetRoomAtTile(x, y) != null) continue; // skip room tiles

                if (Random.value > hallwaySpawnChance) continue;

                float difficulty = Random.Range(1f, hallwayMaxDifficulty);
                SpawnSingleMonster(null, new Vector3(x + 0.5f, 1f, y + 0.5f), difficulty);
            }
        }
    }

    private void SpawnMonstersInRoom(MazeRoom room, int count, float difficulty)
    {
        for (int i = 0; i < count; i++)
        {
            Vector2Int tile = room.GetRandomPoint();
            Vector3 worldPos = new Vector3(tile.x + 0.5f, 1f, tile.y + 0.5f);
            SpawnSingleMonster(room, worldPos, difficulty);
        }
    }

    private void SpawnSingleMonster(MazeRoom room, Vector3 worldPos, float difficulty)
    {
        GameObject go = Instantiate(monsterPrefab, worldPos, Quaternion.Euler(90, 0, 0));
        var monster = go.GetComponent<Monster>();
        if (monster == null) monster = go.AddComponent<Monster>();

        // Use a placeholder room for hallway monsters so Init doesn't crash
        MazeRoom spawnRoom = room ?? new MazeRoom(-1, 0, 0, 0, 0);
        monster.Init(spawnRoom, maze, difficulty);

        // Track in lookup
        int key = room?.Id ?? -1;
        if (!roomMonsters.ContainsKey(key)) roomMonsters[key] = new List<Monster>();
        roomMonsters[key].Add(monster);

        // Remove from list on death
        monster.OnMonsterKilled += m => { roomMonsters[key]?.Remove(m); };
    }

    // ------------------------------------------------------------------ //
    //  Helpers                                                             //
    // ------------------------------------------------------------------ //

    /// <summary>BFS from all start-rooms to compute depth per room.</summary>
    private Dictionary<int, float> BuildRoomDepthMap()
    {
        var depth = new Dictionary<int, float>();
        var queue = new Queue<int>();

        foreach (var room in maze.Rooms.Where(r => r.IsStart))
        {
            depth[room.Id] = 0f;
            queue.Enqueue(room.Id);
        }

        // Build adjacency via room connectivity (rooms that share hallway tiles)
        var adj = BuildRoomAdjacency();

        while (queue.Count > 0)
        {
            int id = queue.Dequeue();
            if (!adj.TryGetValue(id, out var neighbours)) continue;
            foreach (int nId in neighbours)
            {
                if (!depth.ContainsKey(nId))
                {
                    depth[nId] = depth[id] + 1f;
                    queue.Enqueue(nId);
                }
            }
        }

        return depth;
    }

    private Dictionary<int, List<int>> BuildRoomAdjacency()
    {
        var adj = new Dictionary<int, List<int>>();

        foreach (var room in maze.Rooms)
            adj[room.Id] = new List<int>();

        // For each walkable non-room tile, check if it borders two different rooms
        for (int x = 0; x < maze.Width; x++)
        {
            for (int y = 0; y < maze.Height; y++)
            {
                if (!maze.IsWalkable(x, y)) continue;
                MazeRoom r1 = maze.GetRoomAtTile(x, y);
                if (r1 == null) continue;

                Vector2Int[] dirs = { new(x + 1, y), new(x - 1, y), new(x, y + 1), new(x, y - 1) };
                foreach (var d in dirs)
                {
                    if (!maze.IsInBounds(d.x, d.y) || !maze.IsWalkable(d.x, d.y)) continue;
                    MazeRoom r2 = maze.GetRoomAtTile(d.x, d.y);
                    if (r2 == null || r2.Id == r1.Id) continue;
                    if (!adj[r1.Id].Contains(r2.Id)) adj[r1.Id].Add(r2.Id);
                    if (!adj[r2.Id].Contains(r1.Id)) adj[r2.Id].Add(r1.Id);
                }
            }
        }

        return adj;
    }

    private static void Shuffle<T>(List<T> list)
    {
        for (int i = list.Count - 1; i > 0; i--)
        {
            int j = Random.Range(0, i + 1);
            (list[i], list[j]) = (list[j], list[i]);
        }
    }

    // ------------------------------------------------------------------ //
    //  Prefab factory                                                      //
    // ------------------------------------------------------------------ //

    private GameObject CreateDefaultMonsterPrefab()
    {
        var go = new GameObject("MonsterPrefab");
        go.transform.localScale = Vector3.one * 0.5f;

        go.AddComponent<SphereCollider>().radius = 1f;

        var mf = go.AddComponent<MeshFilter>();
        mf.mesh = Resources.GetBuiltinResource<Mesh>("Sphere.fbx");

        var mr = go.AddComponent<MeshRenderer>();
        var mat = new Material(Shader.Find("Universal Render Pipeline/Lit")
                  ?? Shader.Find("Standard"));
        mat.color = Color.red;
        mr.material = mat;

        go.AddComponent<Monster>();
        return go;
    }
}