﻿using UnityEngine;
using Academy.HoloToolkit.Unity;

/// <summary>
/// Determines when the occluded version of the planet should be visible.
/// This script allows us to do selective occlusion, so the occlusionObject
/// will only be rendered when a Spatial Mapping surface is occluding the planet,
/// not when another hologram is responsible for the occlusion.
/// </summary>
public class PlanetOcclusion : MonoBehaviour
{
    [Tooltip("Object to display when the planet is occluded.")]
    public GameObject occlusionObject;

    /// <summary>
    /// Points to raycast to when checking for occlusion.
    /// </summary>
    private Vector3[] checkPoints;

    // Use this for initialization
    void Start()
    {
        occlusionObject.SetActive(false);

        // Set the check points to use when testing for occlusion.
        MeshFilter filter = gameObject.GetComponent<MeshFilter>();
        Vector3 extents = filter.mesh.bounds.extents;
        Vector3 center = filter.mesh.bounds.center;
        Vector3 top = new Vector3(center.x, center.y + extents.y, center.z);
        Vector3 left = new Vector3(center.x - extents.x, center.y, center.z);
        Vector3 right = new Vector3(center.x + extents.x, center.y, center.z);
        Vector3 bottom = new Vector3(center.x, center.y - extents.y, center.z);

        checkPoints = new Vector3[] { center, top, left, right, bottom };
    }

    // Update is called once per frame
    void Update()
    {
        /* TODO: 5.a DEVELOPER CODING EXERCISE 5.a */

        // Check to see if any of the planet's boundary points are occluded.
        for (int i = 0; i < checkPoints.Length; i++)
        {
            // 5.a: Convert the current checkPoint to world coordinates.
            // Call gameObject.transform.TransformPoint(checkPoints[i]).
            // Assign the result to a new Vector3 variable called 'checkPt'.
            Vector3 checkPt = gameObject.transform.TransformPoint(checkPoints[i]);

            // 5.a: Call Vector3.Distance() to calculate the distance
            // between the Main Camera's position and 'checkPt'.
            // Assign the result to a new float variable called 'distance'.
            float distance = Vector3.Distance(Camera.main.transform.position, checkPt);

            // 5.a: Take 'checkPt' and subtract the Main Camera's position from it.
            // Assign the result to a new Vector3 variable called 'direction'.
            Vector3 direction = checkPt - Camera.main.transform.position;

            // Used to indicate if the call to Physics.Raycast() was successful.
            bool raycastHit = false;

            // 5.a: Check if the planet is occluded by a spatial mapping surface.
            // Call Physics.Raycast() with the following arguments:
            // - Pass in the Main Camera's position as the origin.
            // - Pass in 'direction' for the direction.
            // - Pass in 'distance' for the maxDistance.
            // - Pass in SpatialMappingManager.Instance.LayerMask as layerMask.
            // Assign the result to 'raycastHit'.
            raycastHit = Physics.Raycast(Camera.main.transform.position,
                direction,
                distance,
                SpatialMappingManager.Instance.LayerMask);
            
            if (raycastHit)
            {
                // 5.a: Our raycast hit a surface, so the planet is occluded.
                // Set the occlusionObject to active.
                occlusionObject.SetActive(true);

                // At least one point is occluded, so break from the loop.
                break;
            }
            else
            {
                // 5.a: The Raycast did not hit, so the planet is not occluded.
                // Deactivate the occlusionObject.
                occlusionObject.SetActive(false);
            }
        }
    }
}