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 List<TileObject> pathRequested;
    public void PathfindToTarget(TileObject target, Entity selectedEntity)
    {
        frontier.Clear();
        visited.Clear();
        currentPaths.Clear();
        GetTilesInRange(selectedEntity);
        GetPathToTarget(GridManager.instance.FindClosestEmptyTile(target), selectedEntity);
        selectedEntity.currentTile.hasUnit = null;
        selectedEntity.currentTile.hasUnit = selectedEntity;
        StartCoroutine(selectedEntity.MoveToLocation(pathRequested.ToArray()));
    }
    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) && (!neighboringTiles.hasUnit && !neighboringTiles.blocked))
                {
                    visited.Add(neighboringTiles);
                    frontier.Enqueue(neighboringTiles);
                    currentPaths.TryAdd(neighboringTiles, currentTile);
                }
            }
        }
    }

    private void GetPathToTarget(TileObject target, Entity selectedEntity)
    {
        TileObject currentTile = target; 
        pathRequested.Clear();
        while (currentTile != selectedEntity.currentTile)
        {
            pathRequested.Add(currentTile);
            currentTile = currentPaths[currentTile];
        }
        pathRequested.Reverse();
        int validMovementRange = Mathf.Min(pathRequested.Count, selectedEntity.maxMovement) - 1;
        if (pathRequested.Count > selectedEntity.maxMovement)
        {
            int tilesToRemove = pathRequested.Count - selectedEntity.maxMovement;
            pathRequested.RemoveRange(selectedEntity.maxMovement, tilesToRemove);
        }
    }
}