using System.Collections.Generic;
using UnityEngine;

public class EnemyMovement : MonoBehaviour
{
    #region Statication

    public static EnemyMovement instance;

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

    #endregion
    private Queue<TileObject> frontier = new();
    private HashSet<TileObject> visited = new();
    private Dictionary<TileObject, TileObject> currentPaths = new();
    
    public void PathfindToTarget(TileObject target, Entity selectedEntity)
    {
        frontier.Clear();
        visited.Clear();
        currentPaths.Clear();
        GetTilesInRange(selectedEntity);
        TileObject requestedTile = GetPathToTarget(target, selectedEntity);
        selectedEntity.currentTile = requestedTile;
        selectedEntity.transform.position = requestedTile.transform.position;
    }
    private void GetTilesInRange(Entity selectedEntity)
    {
        frontier.Enqueue(selectedEntity.currentTile);
        while (frontier.Count > 0)
        {
            TileObject currentTile = frontier.Dequeue();
            foreach (TileObject neighboringTiles in currentTile.neighbors)
            {
                if (!visited.Contains(neighboringTiles))
                {
                    visited.Add(neighboringTiles);
                    frontier.Enqueue(neighboringTiles);
                    currentPaths.TryAdd(neighboringTiles, currentTile);
                }
            }
        }
        Debug.Log(frontier.Count);
    }

    private TileObject GetPathToTarget(TileObject target, Entity selectedEntity)
    {
        TileObject currentTile = target; 
        List<TileObject> pathToTarget = new();
        while (currentTile != selectedEntity.currentTile)
        {
            pathToTarget.Add(currentTile);
            currentTile = currentPaths[currentTile];
        }
        pathToTarget.Reverse();
        int validMovementRange = Mathf.Min(pathToTarget.Count, selectedEntity.maxMovement) - 1;
        return pathToTarget[validMovementRange];
    }
}