/*
 * Copyright 2020 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.
 */

export interface Metric {
  // The name of the metric (in acronym form).
  name: 'CLS' | 'FCP' | 'FID' | 'LCP' | 'TTFB';

  // The current value of the metric.
  value: number;

  // The delta between the current value and the last-reported value.
  // On the first report, `delta` and `value` will always be the same.
  delta: number;

  // A unique ID representing this particular metric that's specific to the
  // current page. This ID can be used by an analytics tool to dedupe
  // multiple values sent for the same metric, or to group multiple deltas
  // together and calculate a total.
  id: string;

  // `false` if the value of the metric may change in the future,
  // for the current page.
  isFinal: boolean;

  // Any performance entries used in the metric value calculation.
  // Note, entries will be added to the array as the value changes.
  entries: PerformanceEntry[];
}

export interface ReportHandler {
  (metric: Metric): void;
}