// Laser Shot C# Script (version: 1.02)
// SPACE UNITY - Space Scene Construction Kit
// http://www.spaceunity.com
// (c) 2013 Stefan Persson

// DESCRIPTION:
// Laser shot script for demo purposes. Moves the transform with a velocity and
// uses raycast to check for hit and spawn impact effect. It also randomly destroys
// objects it hits. The reason for randomness is just to allow impact effect and you
// would most likely want to implement a "hit points" script for targets where you
// can deduct hitpoints on impact until it is destroyed rather than using the random
// demo function in this script.

// INSTRUCTIONS:
// This script is attached to the LaserShot prefab for demo purposes.

// Version History
// 1.02 - Prefixed with SU_LaserShot to avoid naming conflicts.
//        Added documentation.
// 1.01 - Initial Release.

using UnityEngine;
using System.Collections;

public class SU_LaserShot : MonoBehaviour 
{	
	// Default life of laser beam
	public float life = 2.0f;
	// Default velocity of laser beam
	public float velocity = 1000.0f;
	// Reference to impact effect prefab to spawn upon impact
	public Transform impactEffect;
	// Reference to explosion effect prefab to spawn if object is destroyed
	public Transform explosionEffect;
	// "Fired By" Reference to ignore collision detection for the ship that fired the laser
	public Transform firedBy {get; set;}
	
	// Private variables
	private Vector3 _velocity;
	private Vector3 _newPos;
	private Vector3 _oldPos;	
	private float hitpower = 5;
	void Start () {
		// Set the new position to the current position of the transform
		_newPos = transform.position;
		// Set the old position to the same value
		_oldPos = _newPos;			
		// Set the velocity vector 3 to the specified velocity and set the direction to face forward of the transform
		_velocity = velocity * transform.forward;
		// Set the gameobject to destroy after period "life"
		Destroy(gameObject, life);
	}
	
	void Update () {
		// Change new position by the velocity magnitude (in the direction of transform.forward) and since
		// we are in the update function we need to multiply by deltatime.
		_newPos += transform.forward * _velocity.magnitude * Time.deltaTime;
		// SDet direction to the difference between new position and old position
		Vector3 _direction = _newPos - _oldPos;
		// Get the distance which is the magnitude of the direction vector
		float _distance = _direction.magnitude;
				
		// If distance is greater than nothing...
		if (_distance > 0) {
			// Define a RayCast
			RaycastHit _hit;
			// If the raycast from previous position in the specified direction at (or before) the distance...
			if (Physics.Raycast(_oldPos, _direction, out _hit, _distance)) {
				// and if the transform we hit isn't a the ship that fired the weapon and the collider isn't just a trigger...
				if (_hit.transform != firedBy && !_hit.collider.isTrigger) {		
					// Set the rotation of the impact effect to the normal of the impact surface (we wan't the impact effect to
					// throw particles out from the object we just hit...
					Quaternion _rotation = Quaternion.FromToRotation(Vector3.up, _hit.normal);
					// Instantiate the imapct effect at impact position

					Instantiate(impactEffect, _hit.point, _rotation);

					// Call GameManager to handle weapon hit (damange, explosion, etc..)
					GameManager.HandleWeaponHit(_hit, hitpower, firedBy, explosionEffect, _rotation);
					
					// Destroy the laser shot game object
					Destroy(gameObject);
				}
			}
		}
		// Set the old position tho the current position
		_oldPos = transform.position;
		// Set the actual position to the new position
		transform.position = _newPos;		
	}
}