added initial support for dialogflow

lib/tasks/dialogflow/digit-buffer.js

@@ -0,0 +1,70 @@
+const Emitter = require('events');
+
+/**
+ * A dtmf collector
+ * @class
+ */
+class DigitBuffer extends Emitter {
+  /**
+   * Creates a DigitBuffer
+   * @param {*} logger - a pino logger
+   * @param {*} opts - dtmf collection instructions
+   */
+  constructor(logger, opts) {
+    super();
+    this.logger = logger;
+    this.minDigits = opts.min || 1;
+    this.maxDigits = opts.max || 99;
+    this.termDigit = opts.term;
+    this.interdigitTimeout = opts.idt || 8000;
+    this.template = opts.template;
+    this.buffer = '';
+    this.logger.debug(`digitbuffer min: ${this.minDigits} max: ${this.maxDigits} term digit: ${this.termDigit}`);
+  }
+
+  /**
+   * process a received dtmf digit
+   * @param {String} a single digit entered by the caller
+   */
+  process(digit) {
+    this.logger.debug(`digitbuffer process: ${digit}`);
+    if (digit === this.termDigit) return this._fulfill();
+    this.buffer += digit;
+    if (this.buffer.length === this.maxDigits) return this._fulfill();
+    if (this.buffer.length >= this.minDigits) this._startInterDigitTimer();
+    this.logger.debug(`digitbuffer buffer: ${this.buffer}`);
+  }
+
+  /**
+   * clear the digit buffer
+   */
+  flush() {
+    if (this.idtimer) clearTimeout(this.idtimer);
+    this.buffer = '';
+  }
+
+  _fulfill() {
+    this.logger.debug(`digit buffer fulfilled with ${this.buffer}`);
+    if (this.template && this.template.includes('${digits}')) {
+      const text = this.template.replace('${digits}', this.buffer);
+      this.logger.info(`reporting dtmf as ${text}`);
+      this.emit('fulfilled', text);
+    }
+    else {
+      this.emit('fulfilled', this.buffer);
+    }
+    this.flush();
+  }
+
+  _startInterDigitTimer() {
+    if (this.idtimer) clearTimeout(this.idtimer);
+    this.idtimer = setTimeout(this._onInterDigitTimeout.bind(this), this.interdigitTimeout);
+  }
+
+  _onInterDigitTimeout() {
+    this.logger.debug('digit buffer timeout');
+    this._fulfill();
+  }
+}
+
+module.exports = DigitBuffer;