using UnityEngine;

using System.Collections;

[RequireComponent(typeof(Character))]

public class Enemy : MonoBehaviour {

public enum EnemyState
    {
    searching,
    following
    }

//time in seconds till the character determines a new heading.

public float timeToChangeDirection=5.0f;

//amount of damage to do to the player

public int damage=5;

//how fast this can deal damage

public float damageFrequency=1.0f;

//internal timer to track last time dealt damage.

private float damageTimer;

//reference to the character script.

private Character character;

//internal timer to keep track of elapsed time.

private float internalTimer=0.0f;

//direction relative to the character to head.

private Vector2 heading;

private EnemyState currentState;

private GameObject target;

private GameObject spawnedBy;

/// <summary>

/// Used for initializing your script component

/// </summary>

private void Awake () {

//cache the character script

this.character = this.GetComponent<Character>();

//set an initial heading.

this.createNewHeading();

//set internal timer for damagefrequency

this.damageTimer=this.damageFrequency;

this.currentState=EnemyState.searching;

}

/// <summary>

/// called after all awakes are called.

/// </summary>

private void Start()

{

this.character.SetDeathFunction(() => {

//destroy the game object.

Destroy(this.gameObject);

});

}



/// <summary>

/// Update that is called once per frame.

/// </summary>

private void Update () {

//increment our damage timer by the time it took to complete the last frame.

this.damageTimer+=Time.deltaTime;

}

/// <summary>

/// Update that is kept in sync with physics.

/// </summary>

private void FixedUpdate()

{

//if we are searching, call the search function

if(this.currentState==EnemyState.searching)

{

this.Search();

}else if(this.currentState==EnemyState.following)

{

//if we are following, call the follow function

this.Follow();

}

}

/// <summary>

/// The enemy follows the player.

/// </summary>

private void Follow()

{

//vector math says position to go minus current position = vector we should head in.

Vector3 nTransform=this.target.transform.position-this.transform.position;

//make sure its of magnitude 1.

nTransform.Normalize();

//move that direction

character.Move(nTransform);

}

/// <summary>

/// The enemy searches for the player.

/// </summary>

private void Search()

{

//increase the internal timer by

//the amount of time that has passed.

this.internalTimer+=Time.deltaTime;

//determine if we need to create a new heading.

if (this.internalTimer>this.timeToChangeDirection)

{

//create a new heading

this.createNewHeading();

//reset the timer.

this.internalTimer=0.0f;

}

//move the character in the direction of its heading

character.Move(heading);

}

/// <summary>

/// Generates a new random heading for the character

/// and applies that heading immediately.

/// </summary>

private void createNewHeading()

{

//I used -100 to 100 to give an equal chance for any direction

float xCoord=Random.Range(-100.0f, 100.0f);

float yCoord=Random.Range(-100.0f, 100.0f);

//set our heading to the random headings.

heading=new Vector2(xCoord, yCoord);

//make sure the magnitude of our heading is 1

heading.Normalize();

}

/// <summary>

/// Called when a collision happens between the character

/// and something else.

/// </summary>

/// <param name=“other”>What you collided with.</param>

private void OnCollisionEnter2D(Collision2D other)

{

//make sure we don’t do too much damage to the player

if (other.gameObject.tag=="Player" && this.damageTimer>this.damageFrequency)

{

//deal some damage!

other.gameObject.GetComponent<Character>().AdjustHealth(-1*this.damage);

//reset the timer so we don’t damage too much again.

this.damageTimer=0.0f;

}

//create a new heading, you ran into something.

this.createNewHeading();

}

public void SetSpawnedBy(GameObject o)

{

this.spawnedBy=o;

}

public GameObject GetSpawnedBy()

{

return this.spawnedBy;

}

/// <summary>

/// Occurs when something enters its trigger zone.

/// </summary>

/// <param name=“other”></param>

private void OnTriggerEnter2D(Collider2D other)

{

//check to see what this thing is

if (other.gameObject.tag=="Player")

{

//Its the player! FOLLOW IT!

this.currentState=EnemyState.following;

//set the target.

this.target=other.gameObject;

}

}

/// <summary>

/// Occurs when something enters its trigger zone.

/// </summary>

/// <param name=“other”></param>

private void OnTriggerExit2D(Collider2D other)

{

//Check to see what it is

if (other.gameObject.tag=="Player")

{

//Its the player, I can’t see it anymore, stop following.

this.currentState=EnemyState.searching;

}

}

}