text: /*
   * Copyright 2020 Google LLC
   *
   * 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
   *
   *     https://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.
   */
  import { bindReporter } from './lib/bindReporter.js';
  import { finalMetrics } from './lib/finalMetrics.js';
  import { getFirstHidden } from './lib/getFirstHidden.js';
  import { initMetric } from './lib/initMetric.js';
  import { observe } from './lib/observe.js';
  import { onBFCacheRestore } from './lib/onBFCacheRestore.js';
  export const getFCP = (onReport, reportAllChanges) => {
      const firstHidden = getFirstHidden();
      let metric = initMetric('FCP');
      let report;
      const entryHandler = (entry) => {
          if (entry.name === 'first-contentful-paint') {
              if (po) {
                  po.disconnect();
              }
              // Only report if the page wasn't hidden prior to the first paint.
              if (entry.startTime < firstHidden.timeStamp) {
                  metric.value = entry.startTime;
                  metric.entries.push(entry);
                  finalMetrics.add(metric);
                  report();
              }
          }
      };
      // TODO(philipwalton): remove the use of `fcpEntry` once this bug is fixed.
      // https://bugs.webkit.org/show_bug.cgi?id=225305
      const fcpEntry = performance.getEntriesByName('first-contentful-paint')[0];
      const po = fcpEntry ? null : observe('paint', entryHandler);
      if (fcpEntry || po) {
          report = bindReporter(onReport, metric, reportAllChanges);
          if (fcpEntry) {
              entryHandler(fcpEntry);
          }
          onBFCacheRestore((event) => {
              metric = initMetric('FCP');
              report = bindReporter(onReport, metric, reportAllChanges);
              requestAnimationFrame(() => {
                  requestAnimationFrame(() => {
                      metric.value = performance.now() - event.timeStamp;
                      finalMetrics.add(metric);
                      report();
                  });
              });
          });
      }
  };
  