wikimedia/mediawiki-core

/*!
 * Augment mw.loader to facilitate module-level profiling.
 *
 * @since 1.32
 */
/* global mw */
( function () {
    'use strict';

    var moduleTimes = Object.create( null );

    /**
     * Private hooks inserted into mw.loader code if MediaWiki configuration
     * `$wgResourceLoaderEnableJSProfiler` is `true`.
     *
     * To use this data, run `mw.inspect( 'time' )` from the browser console.
     * See mw#inspect().
     *
     * @private
     * @class
     * @singleton
     */
    mw.loader.profiler = {
        onExecuteStart: function ( moduleName ) {
            var time = performance.now();
            if ( moduleTimes[ moduleName ] ) {
                throw new Error( 'Unexpected perf record for "' + moduleName + '".' );
            }
            moduleTimes[ moduleName ] = {
                executeStart: time,
                executeEnd: null,
                scriptStart: null,
                scriptEnd: null
            };
        },
        onExecuteEnd: function ( moduleName ) {
            var time = performance.now();
            moduleTimes[ moduleName ].executeEnd = time;
        },
        onScriptStart: function ( moduleName ) {
            var time = performance.now();
            moduleTimes[ moduleName ].scriptStart = time;
        },
        onScriptEnd: function ( moduleName ) {
            var time = performance.now();
            moduleTimes[ moduleName ].scriptEnd = time;
        },

        /**
         * For internal use by inspect.reports#time.
         *
         * @private
         * @param {string} moduleName
         * @return {Object|null}
         * @throws {Error} If the perf record is incomplete.
         */
        getProfile: function ( moduleName ) {
            var times, key, execute, script, total;
            times = moduleTimes[ moduleName ];
            if ( !times ) {
                return null;
            }
            for ( key in times ) {
                if ( times[ key ] === null ) {
                    throw new Error( 'Incomplete perf record for "' + moduleName + '".', times );
                }
            }
            execute = times.executeEnd - times.executeStart;
            script = times.scriptEnd - times.scriptStart;
            total = execute + script;
            return {
                name: moduleName,
                execute: execute,
                script: script,
                total: total
            };
        }
    };

}() );