// Copyright 2015 Nicholas Costello <NicholasJCostello@gmail.com>

using UnityEngine;

namespace Assets.Scripts.Extensions
{
    /// <summary>
    /// Camera frustum extensions
    /// </summary>
    public static class CameraFrustumExtensions
    {
        /// <summary>
        /// Returns the frustum's height at the given distance from the camera.
        /// This returns the entire height from top to bottom, so if your camera is at 0,0
        /// the frustums top is at: Frustrumheight/2 and bottom is at: -Frustrumheight/2
        /// </summary>
        /// <param name="camera"></param>
        /// <param name="distance"></param>
        /// <returns></returns>
        public static float FrustumHeightAtDistace(this Camera camera, float distance)
        {
            return 2.0f * distance * Mathf.Tan(camera.fieldOfView * 0.5f * Mathf.Deg2Rad);
        }

        /// <summary>
        /// Returns the distance from camera a given frustrum height can be found
        /// </summary>
        /// <param name="camera"></param>
        /// <param name="frustumHeight"></param>
        /// <returns></returns>
        public static float DistanceAtFrustumHeight(this Camera camera, float frustumHeight)
        {
            return frustumHeight*0.5f/Mathf.Tan(camera.fieldOfView*0.5f*Mathf.Deg2Rad);
        }

        /// <summary>
        /// Returns the frustum's width at a given distance from the camera.
        /// </summary>
        /// <param name="camera"></param>
        /// <param name="frustumHeight"></param>
        /// <returns></returns>
        public static float FrustumWidthAtFrustumHeight(this Camera camera, float frustumHeight)
        {
            return frustumHeight*camera.aspect;
        }
    }
}