using UnityEngine;
using System.Collections;
using BehaviorDesigner.Runtime;
using BehaviorDesigner.Runtime.Tasks;
using UnityEngine.AI;

/// <summary>
/// 跟随目标
/// </summary>
public class ActionFollowTarget : Action
{
    /// <summary>
    /// 跟随的最近距离
    /// </summary>
    public float followDistance = 2.0f;

    /// <summary>
    /// 跟随的目标
    /// </summary>
    public SharedTransform target;

    /// <summary>
    /// 角色
    /// </summary>
    private Role role = null;

    /// <summary>
    /// 跟随距离
    /// </summary>
    private float sqrFollowDistance = 0;

    public override void OnAwake()
    {
        role = GetComponent<Role>();
    }

    public override void OnStart()
    {
        sqrFollowDistance = followDistance * followDistance;

        //启用导航组件
        role.mNavMeshAgent.enabled = true;

        if (target != null && target.Value != null)
        {
            role.mNavMeshAgent.destination = target.Value.position;
        }
    }

    public override void OnEnd()
    {
        role.mNavMeshAgent.enabled = false;
    }

    //如果抢夺者在视野内，就追， 否则就认为防御成功
    public override TaskStatus OnUpdate()
    {
        //做一个安全的校验
        if (target == null && target.Value == null)
        {
            return TaskStatus.Failure;
        }

        float sqrDistance = (target.Value.position - transform.position).sqrMagnitude;
        if (sqrDistance > sqrFollowDistance)
        {
            if (role.mNavMeshAgent.destination != target.Value.position)
            {
                role.mNavMeshAgent.destination = target.Value.position;
            }

            return TaskStatus.Running;
        }
        else
        {
            return TaskStatus.Success;
        }
    }
}