/*
 * 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 { getNavigationEntry } from '../lib/getNavigationEntry.js';
import { getSelector } from '../lib/getSelector.js';
import { onLCP as unattributedOnLCP } from '../onLCP.js';
const attributeLCP = (metric) => {
    if (metric.entries.length) {
        const navigationEntry = getNavigationEntry();
        if (navigationEntry) {
            const activationStart = navigationEntry.activationStart || 0;
            const lcpEntry = metric.entries[metric.entries.length - 1];
            const lcpResourceEntry = lcpEntry.url &&
                performance
                    .getEntriesByType('resource')
                    .filter((e) => e.name === lcpEntry.url)[0];
            const ttfb = Math.max(0, navigationEntry.responseStart - activationStart);
            const lcpRequestStart = Math.max(ttfb, 
            // Prefer `requestStart` (if TOA is set), otherwise use `startTime`.
            lcpResourceEntry
                ? (lcpResourceEntry.requestStart || lcpResourceEntry.startTime) -
                    activationStart
                : 0);
            const lcpResponseEnd = Math.max(lcpRequestStart, lcpResourceEntry ? lcpResourceEntry.responseEnd - activationStart : 0);
            const lcpRenderTime = Math.max(lcpResponseEnd, lcpEntry ? lcpEntry.startTime - activationStart : 0);
            const attribution = {
                element: getSelector(lcpEntry.element),
                timeToFirstByte: ttfb,
                resourceLoadDelay: lcpRequestStart - ttfb,
                resourceLoadTime: lcpResponseEnd - lcpRequestStart,
                elementRenderDelay: lcpRenderTime - lcpResponseEnd,
                navigationEntry,
                lcpEntry,
            };
            // Only attribution the URL and resource entry if they exist.
            if (lcpEntry.url) {
                attribution.url = lcpEntry.url;
            }
            if (lcpResourceEntry) {
                attribution.lcpResourceEntry = lcpResourceEntry;
            }
            metric.attribution = attribution;
            return;
        }
    }
    // Set an empty object if no other attribution has been set.
    metric.attribution = {
        timeToFirstByte: 0,
        resourceLoadDelay: 0,
        resourceLoadTime: 0,
        elementRenderDelay: metric.value,
    };
};
/**
 * Calculates the [LCP](https://web.dev/lcp/) value for the current page and
 * calls the `callback` function once the value is ready (along with the
 * relevant `largest-contentful-paint` performance entry used to determine the
 * value). The reported value is a `DOMHighResTimeStamp`.
 *
 * If the `reportAllChanges` configuration option is set to `true`, the
 * `callback` function will be called any time a new `largest-contentful-paint`
 * performance entry is dispatched, or once the final value of the metric has
 * been determined.
 */
export const onLCP = (onReport, opts) => {
    unattributedOnLCP(((metric) => {
        attributeLCP(metric);
        onReport(metric);
    }), opts);
};
