using System.Collections.Generic;
using UnityEngine;

public static class TargetFinder
{
    static SimpleHeap<Entity> entitiesHeap = new SimpleHeap<Entity>();

    public static IList<Vector2> GetRandom(Bounds bounds, int maxCount)
    {
        var areaSize = BattleMgr.Instance.GetBgSize();

        var result = new List<Vector2>();
        for(int i = 0; i < maxCount; i++)
        {
            float rndX = Random.Range(bounds.min.x, bounds.max.x);
            float rndY = Random.Range(bounds.min.y, bounds.max.y);

            rndX = Mathf.Clamp(rndX, areaSize.bounds.min.x, areaSize.bounds.max.x);
            rndY = Mathf.Clamp(rndY, areaSize.bounds.min.y, areaSize.bounds.max.y);

            result.Add(new Vector2(rndX, rndY));
        }

        return result;
    }

    public static List<IBattleEntity> GetNears(Vector2 pivot, Bitset32.Mask filterTags, int maxCount = -1, ICollection<IBattleEntity> except = null, bool ignoreExcepIfNoTarget = false)
    {
        entitiesHeap.Clear();
        entitiesHeap.SetCompareFunc((a, b) =>
        {
            float distA = (pivot - (Vector2)a.transform.position).sqrMagnitude;
            float distB = (pivot - (Vector2)b.transform.position).sqrMagnitude;

            return distA < distB;
        });

        if(except is null)
        {
            BattleMgr.Instance.LoopAllBattleEntities((battleEntity) =>
            {
                var entity = battleEntity as Entity;
                if (entity.HasTagsAny(filterTags))
                {
                    entitiesHeap.Push(entity);
                }
                return true;
            });
        }
        else if (!ignoreExcepIfNoTarget)
        {
            BattleMgr.Instance.LoopAllBattleEntities((battleEntity) =>
            {
                var entity = battleEntity as Entity;
                if (entity.HasTagsAny(filterTags) && !except.Contains(battleEntity))
                {
                    entitiesHeap.Push(entity);
                }
                return true;
            });
        }
        else
        {
            var targetCandidates = new List<Entity>();
            BattleMgr.Instance.LoopAllBattleEntities((battleEntity) =>
            {
                var entity = battleEntity as Entity;

                if(entity.HasTagsAny(filterTags))
                {
                    if(!except.Contains(battleEntity))
                        entitiesHeap.Push(entity);
                    else
                        targetCandidates.Add(entity);
                }

                return true;
            });

            if (entitiesHeap.IsEmpty())
            {
                for(int i = 0; i < targetCandidates.Count; i++)
                {
                    entitiesHeap.Push(targetCandidates[i]);
                }
            }
        }

        var result = new List<IBattleEntity>();

        if(maxCount < 0)
            maxCount = entitiesHeap.Count;

        while (entitiesHeap.Count > 0 && result.Count < maxCount)
        {
            result.Add(entitiesHeap.Pop() as IBattleEntity);
        }

        return result;
    }
    
    public static bool TryFindNearest(Vector2 pivot, Bitset32.Mask filterTags, out IBattleEntity result, ICollection<IBattleEntity> except = null, bool ignoreExcepIfNoTarget = false)
    {
        result = null;

        var nearests = GetNears(pivot, filterTags, 1, except, ignoreExcepIfNoTarget);
        if (nearests.Count > 0)
            result = nearests[0];

        return result != null;
    }

    public static bool TryFindNearest(Vector2 pivot, Bounds bound, Bitset32.Mask filterTags, out IBattleEntity result, ICollection<IBattleEntity> except = null, bool ignoreExcepIfNoTarget = false)
    {
        result = null;

        var nearests = GetNears(pivot, filterTags, -1, except, ignoreExcepIfNoTarget);
        for(int i = 0; i < nearests.Count; i++)
        {
            if (bound.Contains((nearests[i] as Entity).transform.position))
            {
                result = nearests[i];
                break;
            }
        }

        return result != null;
    }
}