import BoxGeometry from "../Core/BoxGeometry.js";
import Cartesian3 from "../Core/Cartesian3.js";
import defaultValue from "../Core/defaultValue.js";
import defined from "../Core/defined.js";
import destroyObject from "../Core/destroyObject.js";
import DeveloperError from "../Core/DeveloperError.js";
import GeometryPipeline from "../Core/GeometryPipeline.js";
import Matrix4 from "../Core/Matrix4.js";
import VertexFormat from "../Core/VertexFormat.js";
import BufferUsage from "../Renderer/BufferUsage.js";
import CubeMap from "../Renderer/CubeMap.js";
import DrawCommand from "../Renderer/DrawCommand.js";
import loadCubeMap from "../Renderer/loadCubeMap.js";
import RenderState from "../Renderer/RenderState.js";
import ShaderProgram from "../Renderer/ShaderProgram.js";
import ShaderSource from "../Renderer/ShaderSource.js";
import VertexArray from "../Renderer/VertexArray.js";
import SkyBoxFS from "../Shaders/SkyBoxFS.js";
import SkyBoxVS from "../Shaders/SkyBoxVS.js";
import BlendingState from "./BlendingState.js";
import SceneMode from "./SceneMode.js";

/**
 * A sky box around the scene to draw stars.  The sky box is defined using the True Equator Mean Equinox (TEME) axes.
 * <p>
 * This is only supported in 3D.  The sky box is faded out when morphing to 2D or Columbus view.  The size of
 * the sky box must not exceed {@link Scene#maximumCubeMapSize}.
 * </p>
 *
 * @alias SkyBox
 * @constructor
 *
 * @param {Object} options Object with the following properties:
 * @param {Object} [options.sources] The source URL or <code>Image</code> object for each of the six cube map faces.  See the example below.
 * @param {Boolean} [options.show=true] Determines if this primitive will be shown.
 *
 *
 * @example
 * scene.skyBox = new Cesium.SkyBox({
 *   sources : {
 *     positiveX : 'skybox_px.png',
 *     negativeX : 'skybox_nx.png',
 *     positiveY : 'skybox_py.png',
 *     negativeY : 'skybox_ny.png',
 *     positiveZ : 'skybox_pz.png',
 *     negativeZ : 'skybox_nz.png'
 *   }
 * });
 *
 * @see Scene#skyBox
 * @see Transforms.computeTemeToPseudoFixedMatrix
 */
function SkyBox(options) {
  /**
   * The sources used to create the cube map faces: an object
   * with <code>positiveX</code>, <code>negativeX</code>, <code>positiveY</code>,
   * <code>negativeY</code>, <code>positiveZ</code>, and <code>negativeZ</code> properties.
   * These can be either URLs or <code>Image</code> objects.
   *
   * @type Object
   * @default undefined
   */
  this.sources = options.sources;
  this._sources = undefined;

  /**
   * Determines if the sky box will be shown.
   *
   * @type {Boolean}
   * @default true
   */
  this.show = defaultValue(options.show, true);

  this._command = new DrawCommand({
    modelMatrix: Matrix4.clone(Matrix4.IDENTITY),
    owner: this,
  });
  this._cubeMap = undefined;

  this._attributeLocations = undefined;
  this._useHdr = undefined;
}

/**
 * Called when {@link Viewer} or {@link CesiumWidget} render the scene to
 * get the draw commands needed to render this primitive.
 * <p>
 * Do not call this function directly.  This is documented just to
 * list the exceptions that may be propagated when the scene is rendered:
 * </p>
 *
 * @exception {DeveloperError} this.sources is required and must have positiveX, negativeX, positiveY, negativeY, positiveZ, and negativeZ properties.
 * @exception {DeveloperError} this.sources properties must all be the same type.
 */
SkyBox.prototype.update = function (frameState, useHdr) {
  const that = this;

  if (!this.show) {
    return undefined;
  }

  if (
    frameState.mode !== SceneMode.SCENE3D &&
    frameState.mode !== SceneMode.MORPHING
  ) {
    return undefined;
  }

  // The sky box is only rendered during the render pass; it is not pickable, it doesn't cast shadows, etc.
  if (!frameState.passes.render) {
    return undefined;
  }

  const context = frameState.context;

  if (this._sources !== this.sources) {
    this._sources = this.sources;
    const sources = this.sources;

    //>>includeStart('debug', pragmas.debug);
    if (
      !defined(sources.positiveX) ||
      !defined(sources.negativeX) ||
      !defined(sources.positiveY) ||
      !defined(sources.negativeY) ||
      !defined(sources.positiveZ) ||
      !defined(sources.negativeZ)
    ) {
      throw new DeveloperError(
        "this.sources is required and must have positiveX, negativeX, positiveY, negativeY, positiveZ, and negativeZ properties."
      );
    }

    if (
      typeof sources.positiveX !== typeof sources.negativeX ||
      typeof sources.positiveX !== typeof sources.positiveY ||
      typeof sources.positiveX !== typeof sources.negativeY ||
      typeof sources.positiveX !== typeof sources.positiveZ ||
      typeof sources.positiveX !== typeof sources.negativeZ
    ) {
      throw new DeveloperError(
        "this.sources properties must all be the same type."
      );
    }
    //>>includeEnd('debug');

    if (typeof sources.positiveX === "string") {
      // Given urls for cube-map images.  Load them.
      loadCubeMap(context, this._sources).then(function (cubeMap) {
        that._cubeMap = that._cubeMap && that._cubeMap.destroy();
        that._cubeMap = cubeMap;
      });
    } else {
      this._cubeMap = this._cubeMap && this._cubeMap.destroy();
      this._cubeMap = new CubeMap({
        context: context,
        source: sources,
      });
    }
  }

  const command = this._command;

  if (!defined(command.vertexArray)) {
    command.uniformMap = {
      u_cubeMap: function () {
        return that._cubeMap;
      },
    };

    const geometry = BoxGeometry.createGeometry(
      BoxGeometry.fromDimensions({
        dimensions: new Cartesian3(2.0, 2.0, 2.0),
        vertexFormat: VertexFormat.POSITION_ONLY,
      })
    );
    const attributeLocations = (this._attributeLocations = GeometryPipeline.createAttributeLocations(
      geometry
    ));

    command.vertexArray = VertexArray.fromGeometry({
      context: context,
      geometry: geometry,
      attributeLocations: attributeLocations,
      bufferUsage: BufferUsage.STATIC_DRAW,
    });

    command.renderState = RenderState.fromCache({
      blending: BlendingState.ALPHA_BLEND,
    });
  }

  if (!defined(command.shaderProgram) || this._useHdr !== useHdr) {
    const fs = new ShaderSource({
      defines: [useHdr ? "HDR" : ""],
      sources: [SkyBoxFS],
    });
    command.shaderProgram = ShaderProgram.fromCache({
      context: context,
      vertexShaderSource: SkyBoxVS,
      fragmentShaderSource: fs,
      attributeLocations: this._attributeLocations,
    });
    this._useHdr = useHdr;
  }

  if (!defined(this._cubeMap)) {
    return undefined;
  }

  return command;
};

/**
 * Returns true if this object was destroyed; otherwise, false.
 * <br /><br />
 * If this object was destroyed, it should not be used; calling any function other than
 * <code>isDestroyed</code> will result in a {@link DeveloperError} exception.
 *
 * @returns {Boolean} <code>true</code> if this object was destroyed; otherwise, <code>false</code>.
 *
 * @see SkyBox#destroy
 */
SkyBox.prototype.isDestroyed = function () {
  return false;
};

/**
 * Destroys the WebGL resources held by this object.  Destroying an object allows for deterministic
 * release of WebGL resources, instead of relying on the garbage collector to destroy this object.
 * <br /><br />
 * Once an object is destroyed, it should not be used; calling any function other than
 * <code>isDestroyed</code> will result in a {@link DeveloperError} exception.  Therefore,
 * assign the return value (<code>undefined</code>) to the object as done in the example.
 *
 * @exception {DeveloperError} This object was destroyed, i.e., destroy() was called.
 *
 *
 * @example
 * skyBox = skyBox && skyBox.destroy();
 *
 * @see SkyBox#isDestroyed
 */
SkyBox.prototype.destroy = function () {
  const command = this._command;
  command.vertexArray = command.vertexArray && command.vertexArray.destroy();
  command.shaderProgram =
    command.shaderProgram && command.shaderProgram.destroy();
  this._cubeMap = this._cubeMap && this._cubeMap.destroy();
  return destroyObject(this);
};
export default SkyBox;