Initial

resources/app/client-esm/audio/biquad.mjs

@@ -0,0 +1,74 @@
+/**
+ * A sound effect which applies a biquad filter.
+ * @see {@link https://developer.mozilla.org/en-US/docs/Web/API/BiquadFilterNode}
+ * @alias foundry.audio.BiquadFilterEffect
+ */
+export default class BiquadFilterEffect extends BiquadFilterNode {
+  /**
+   * A ConvolverEffect is constructed by passing the following parameters.
+   * @param {AudioContext} context      The audio context required by the BiquadFilterNode
+   * @param {object} [options]          Additional options which modify the BiquadFilterEffect behavior
+   * @param {BiquadFilterType} [options.type=lowpass]  The filter type to apply
+   * @param {number} [options.intensity=5]   The initial intensity of the effect
+   */
+  constructor(context, {type="lowpass", intensity=5, ...options}={}) {
+    if ( !BiquadFilterEffect.#ALLOWED_TYPES.includes(type) ) {
+      throw new Error(`Invalid BiquadFilterEffect type "${type}" provided`);
+    }
+    super(context, options);
+    this.#type = this.type = type;
+    this.#intensity = intensity;
+    this.update();
+  }
+
+  /**
+   * The allowed filter types supported by this effect class.
+   */
+  static #ALLOWED_TYPES = ["lowpass", "highpass", "bandpass", "lowshelf", "highshelf", "peaking", "notch"];
+
+  /**
+   * The original configured type of the effect.
+   * @type {BiquadFilterType}
+   */
+  #type;
+
+  /* -------------------------------------------- */
+
+  /**
+   * Adjust the intensity of the effect on a scale of 0 to 10.
+   * @type {number}
+   */
+  get intensity() {
+    return this.#intensity;
+  }
+
+  set intensity(intensity) {
+    this.update({intensity});
+  }
+
+  #intensity;
+
+  /* -------------------------------------------- */
+
+  /**
+   * Update the state of the effect node given the active flag and numeric intensity.
+   * @param {object} options            Options which are updated
+   * @param {number} [options.intensity]  A new effect intensity
+   * @param {BiquadFilterType} [options.type] A new filter type
+   */
+  update({intensity, type} = {}) {
+    if ( Number.isFinite(intensity) ) this.#intensity = Math.clamp(intensity, 1, 10);
+    if ( BiquadFilterEffect.#ALLOWED_TYPES.includes(type) ) this.#type = type;
+    this.type = this.#type;
+    switch ( this.#type ) {
+      case "lowpass":
+        this.frequency.value = 1100 - (100 * this.#intensity); // More intensity cuts at a lower frequency
+        break;
+      case "highpass":
+        this.frequency.value = 100 * this.#intensity; // More intensity cuts at higher frequency
+        break;
+      default:
+        throw new Error(`BiquadFilterEffect type "${this.#type}" not yet configured`);
+    }
+  }
+}