import { OrthographicCamera } from "../cameras/OrthographicCamera.js";
import { LightShadow } from "./LightShadow.js";

/**
 * This is used internally by {@link DirectionalLight | DirectionalLights} for calculating shadows.
 * Unlike the other shadow classes, this uses an {@link THREE.OrthographicCamera | OrthographicCamera} to calculate the shadows,
 * rather than a {@link THREE.PerspectiveCamera | PerspectiveCamera}
 * @remarks
 * This is because light rays from a {@link THREE.DirectionalLight | DirectionalLight} are parallel.
 * @example
 * ```typescript
 * //Create a WebGLRenderer and turn on shadows in the renderer
 * const renderer = new THREE.WebGLRenderer();
 * renderer.shadowMap.enabled = true;
 * renderer.shadowMap.type = THREE.PCFSoftShadowMap; // default THREE.PCFShadowMap
 * //Create a DirectionalLight and turn on shadows for the light
 * const light = new THREE.DirectionalLight(0xffffff, 1);
 * light.position.set(0, 1, 0); //default; light shining from top
 * light.castShadow = true; // default false
 * scene.add(light);
 * //Set up shadow properties for the light
 * light.shadow.mapSize.width = 512; // default
 * light.shadow.mapSize.height = 512; // default
 * light.shadow.camera.near = 0.5; // default
 * light.shadow.camera.far = 500; // default
 * //Create a sphere that cast shadows (but does not receive them)
 * const sphereGeometry = new THREE.SphereGeometry(5, 32, 32);
 * const sphereMaterial = new THREE.MeshStandardMaterial({
 *     color: 0xff0000
 * });
 * const sphere = new THREE.Mesh(sphereGeometry, sphereMaterial);
 * sphere.castShadow = true; //default is false
 * sphere.receiveShadow = false; //default
 * scene.add(sphere);
 * //Create a plane that receives shadows (but does not cast them)
 * const planeGeometry = new THREE.PlaneGeometry(20, 20, 32, 32);
 * const planeMaterial = new THREE.MeshStandardMaterial({
 *     color: 0x00ff00
 * })
 * const plane = new THREE.Mesh(planeGeometry, planeMaterial);
 * plane.receiveShadow = true;
 * scene.add(plane);
 * //Create a helper for the shadow camera (optional)
 * const helper = new THREE.CameraHelper(light.shadow.camera);
 * scene.add(helper);
 * ```
 * @see {@link https://threejs.org/docs/index.html#api/en/lights/shadows/DirectionalLightShadow | Official Documentation}
 * @see {@link https://github.com/mrdoob/three.js/blob/master/src/lights/DirectionalLightShadow.js | Source}
 */
export class DirectionalLightShadow extends LightShadow<OrthographicCamera> {
    /**
     * Create a new instance of {@link DirectionalLightShadow}
     */
    constructor();

    /**
     * Read-only flag to check if a given object is of type {@link DirectionalLightShadow}.
     * @remarks This is a _constant_ value
     * @defaultValue `true`
     */
    readonly isDirectionalLightShadow: true;

    /**
     * The light's view of the world.
     * @remarks This is used to generate a depth map of the scene; objects behind other objects from the light's perspective will be in shadow.
     * @defaultValue is an {@link THREE.OrthographicCamera | OrthographicCamera} with
     * {@link OrthographicCamera.left | left} and {@link OrthographicCamera.bottom | bottom} set to -5,
     * {@link OrthographicCamera.right | right} and {@link OrthographicCamera.top | top} set to 5,
     * the {@link OrthographicCamera.near | near} clipping plane at 0.5 and
     * the {@link OrthographicCamera.far | far} clipping plane at 500.
     */
    camera: OrthographicCamera;
}