/*
 * Copyright 2022 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 { getBFCacheRestoreTime } from '../lib/bfcache.js';
import { getLoadState } from '../lib/getLoadState.js';
import { getNavigationEntry } from '../lib/getNavigationEntry.js';
import { onFCP as unattributedOnFCP } from '../onFCP.js';
const attributeFCP = (metric) => {
    // Use a default object if no other attribution has been set.
    let attribution = {
        timeToFirstByte: 0,
        firstByteToFCP: metric.value,
        loadState: getLoadState(getBFCacheRestoreTime()),
    };
    if (metric.entries.length) {
        const navigationEntry = getNavigationEntry();
        const fcpEntry = metric.entries[metric.entries.length - 1];
        if (navigationEntry) {
            const activationStart = navigationEntry.activationStart || 0;
            const ttfb = Math.max(0, navigationEntry.responseStart - activationStart);
            attribution = {
                timeToFirstByte: ttfb,
                firstByteToFCP: metric.value - ttfb,
                loadState: getLoadState(metric.entries[0].startTime),
                navigationEntry,
                fcpEntry,
            };
        }
    }
    // Use Object.assign to set property to keep tsc happy.
    const metricWithAttribution = Object.assign(metric, { attribution });
    return metricWithAttribution;
};
/**
 * Calculates the [FCP](https://web.dev/articles/fcp) value for the current page and
 * calls the `callback` function once the value is ready, along with the
 * relevant `paint` performance entry used to determine the value. The reported
 * value is a `DOMHighResTimeStamp`.
 */
export const onFCP = (onReport, opts) => {
    unattributedOnFCP((metric) => {
        const metricWithAttribution = attributeFCP(metric);
        onReport(metricWithAttribution);
    }, opts);
};
