/**
 * @license
 * Copyright 2017 Google Inc. All Rights Reserved.
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/**
 * @file Directivity/occlusion filter.
 * @author Andrew Allen <bitllama@google.com>
 */
'use strict';
// Internal dependencies.
import Utils from './utils.js';
/**
 * @class Directivity
 * @description Directivity/occlusion filter.
 * @param {AudioContext} context
 * Associated {@link
https://developer.mozilla.org/en-US/docs/Web/API/AudioContext AudioContext}.
 * @param {Object} options
 * @param {Number} options.alpha
 * Determines directivity pattern (0 to 1). See
 * {@link Directivity#setPattern setPattern} for more details. Defaults to
 * {@linkcode Utils.DEFAULT_DIRECTIVITY_ALPHA DEFAULT_DIRECTIVITY_ALPHA}.
 * @param {Number} options.sharpness
 * Determines the sharpness of the directivity pattern (1 to Inf). See
 * {@link Directivity#setPattern setPattern} for more details. Defaults to
 * {@linkcode Utils.DEFAULT_DIRECTIVITY_SHARPNESS
 * DEFAULT_DIRECTIVITY_SHARPNESS}.
 */
class Directivity {
    constructor(context, options) {
        // Public variables.
        /**
         * Mono (1-channel) input {@link
         * https://developer.mozilla.org/en-US/docs/Web/API/AudioNode AudioNode}.
         * @member {AudioNode} input
         * @memberof Directivity
         * @instance
         */
        /**
         * Mono (1-channel) output {@link
         * https://developer.mozilla.org/en-US/docs/Web/API/AudioNode AudioNode}.
         * @member {AudioNode} output
         * @memberof Directivity
         * @instance
         */
        // Use defaults for undefined arguments.
        if (options == undefined) {
            options = {};
        }
        if (options.alpha == undefined) {
            options.alpha = Utils.DEFAULT_DIRECTIVITY_ALPHA;
        }
        if (options.sharpness == undefined) {
            options.sharpness = Utils.DEFAULT_DIRECTIVITY_SHARPNESS;
        }
        // Create audio node.
        this._context = context;
        this._lowpass = context.createBiquadFilter();
        // Initialize filter coefficients.
        this._lowpass.type = 'lowpass';
        this._lowpass.Q.value = 0;
        this._lowpass.frequency.value = context.sampleRate * 0.5;
        this._cosTheta = 0;
        this.setPattern(options.alpha, options.sharpness);
        // Input/Output proxy.
        this.input = this._lowpass;
        this.output = this._lowpass;
    }
    /**
     * Compute the filter using the source's forward orientation and the listener's
     * position.
     * @param {Float32Array} forward The source's forward vector.
     * @param {Float32Array} direction The direction from the source to the
     * listener.
     */
    computeAngle(forward, direction) {
        let forwardNorm = Utils.normalizeVector(forward);
        let directionNorm = Utils.normalizeVector(direction);
        let coeff = 1;
        if (this._alpha > Utils.EPSILON_FLOAT) {
            let cosTheta = forwardNorm[0] * directionNorm[0] +
                forwardNorm[1] * directionNorm[1] + forwardNorm[2] * directionNorm[2];
            coeff = (1 - this._alpha) + this._alpha * cosTheta;
            coeff = Math.pow(Math.abs(coeff), this._sharpness);
        }
        this._lowpass.frequency.value = this._context.sampleRate * 0.5 * coeff;
    }
    /**
     * Set source's directivity pattern (defined by alpha), where 0 is an
     * omnidirectional pattern, 1 is a bidirectional pattern, 0.5 is a cardiod
     * pattern. The sharpness of the pattern is increased exponenentially.
     * @param {Number} alpha
     * Determines directivity pattern (0 to 1).
     * @param {Number} sharpness
     * Determines the sharpness of the directivity pattern (1 to Inf).
     * DEFAULT_DIRECTIVITY_SHARPNESS}.
     */
    setPattern(alpha, sharpness) {
        // Clamp and set values.
        this._alpha = Math.min(1, Math.max(0, alpha));
        this._sharpness = Math.max(1, sharpness);
        // Update angle calculation using new values.
        this.computeAngle([this._cosTheta * this._cosTheta, 0, 0], [1, 0, 0]);
    }
}
export default Directivity;