/*!
 * Tools for inspecting page composition and performance.
 *
 * @author Ori Livneh
 * @since 1.22
 */

/* eslint-disable no-console */

( function ( mw, $ ) {

	var inspect,
		byteLength = require( 'mediawiki.String' ).byteLength,
		hasOwn = Object.prototype.hasOwnProperty;

	function sortByProperty( array, prop, descending ) {
		var order = descending ? -1 : 1;
		return array.sort( function ( a, b ) {
			return a[ prop ] > b[ prop ] ? order : a[ prop ] < b[ prop ] ? -order : 0;
		} );
	}

	function humanSize( bytes ) {
		var i,
			units = [ '', ' KiB', ' MiB', ' GiB', ' TiB', ' PiB' ];

		if ( !$.isNumeric( bytes ) || bytes === 0 ) { return bytes; }

		for ( i = 0; bytes >= 1024; bytes /= 1024 ) { i++; }
		// Maintain one decimal for kB and above, but don't
		// add ".0" for bytes.
		return bytes.toFixed( i > 0 ? 1 : 0 ) + units[ i ];
	}

	/**
	 * @class mw.inspect
	 * @singleton
	 */
	inspect = {

		/**
		 * Return a map of all dependency relationships between loaded modules.
		 *
		 * @return {Object} Maps module names to objects. Each sub-object has
		 *  two properties, 'requires' and 'requiredBy'.
		 */
		getDependencyGraph: function () {
			var modules = inspect.getLoadedModules(),
				graph = {};

			modules.forEach( function ( moduleName ) {
				var dependencies = mw.loader.moduleRegistry[ moduleName ].dependencies || [];

				if ( !hasOwn.call( graph, moduleName ) ) {
					graph[ moduleName ] = { requiredBy: [] };
				}
				graph[ moduleName ].requires = dependencies;

				dependencies.forEach( function ( depName ) {
					if ( !hasOwn.call( graph, depName ) ) {
						graph[ depName ] = { requiredBy: [] };
					}
					graph[ depName ].requiredBy.push( moduleName );
				} );
			} );
			return graph;
		},

		/**
		 * Calculate the byte size of a ResourceLoader module.
		 *
		 * @param {string} moduleName The name of the module
		 * @return {number|null} Module size in bytes or null
		 */
		getModuleSize: function ( moduleName ) {
			var module = mw.loader.moduleRegistry[ moduleName ],
				args, i, size;

			if ( module.state !== 'ready' ) {
				return null;
			}

			if ( !module.style && !module.script ) {
				return 0;
			}

			function getFunctionBody( func ) {
				return String( func )
					// To ensure a deterministic result, replace the start of the function
					// declaration with a fixed string. For example, in Chrome 55, it seems
					// V8 seemingly-at-random decides to sometimes put a line break between
					// the opening brace and first statement of the function body. T159751.
					.replace( /^\s*function\s*\([^)]*\)\s*{\s*/, 'function(){' )
					.replace( /\s*}\s*$/, '}' );
			}

			// Based on the load.php response for this module.
			// For example: `mw.loader.implement("example", function(){}, {"css":[".x{color:red}"]});`
			// @see mw.loader.store.set().
			args = [
				moduleName,
				module.script,
				module.style,
				module.messages,
				module.templates
			];
			// Trim trailing null or empty object, as load.php would have done.
			// @see ResourceLoader::makeLoaderImplementScript and ResourceLoader::trimArray.
			i = args.length;
			while ( i-- ) {
				if ( args[ i ] === null || ( $.isPlainObject( args[ i ] ) && $.isEmptyObject( args[ i ] ) ) ) {
					args.splice( i, 1 );
				} else {
					break;
				}
			}

			size = 0;
			for ( i = 0; i < args.length; i++ ) {
				if ( typeof args[ i ] === 'function' ) {
					size += byteLength( getFunctionBody( args[ i ] ) );
				} else {
					size += byteLength( JSON.stringify( args[ i ] ) );
				}
			}

			return size;
		},

		/**
		 * Given CSS source, count both the total number of selectors it
		 * contains and the number which match some element in the current
		 * document.
		 *
		 * @param {string} css CSS source
		 * @return {Object} Selector counts
		 * @return {number} return.selectors Total number of selectors
		 * @return {number} return.matched Number of matched selectors
		 */
		auditSelectors: function ( css ) {
			var selectors = { total: 0, matched: 0 },
				style = document.createElement( 'style' );

			style.textContent = css;
			document.body.appendChild( style );
			$.each( style.sheet.cssRules, function ( index, rule ) {
				selectors.total++;
				// document.querySelector() on prefixed pseudo-elements can throw exceptions
				// in Firefox and Safari. Ignore these exceptions.
				// https://bugs.webkit.org/show_bug.cgi?id=149160
				// https://bugzilla.mozilla.org/show_bug.cgi?id=1204880
				try {
					if ( document.querySelector( rule.selectorText ) !== null ) {
						selectors.matched++;
					}
				} catch ( e ) {}
			} );
			document.body.removeChild( style );
			return selectors;
		},

		/**
		 * Get a list of all loaded ResourceLoader modules.
		 *
		 * @return {Array} List of module names
		 */
		getLoadedModules: function () {
			return mw.loader.getModuleNames().filter( function ( module ) {
				return mw.loader.getState( module ) === 'ready';
			} );
		},

		/**
		 * Print tabular data to the console, using console.table, console.log,
		 * or mw.log (in declining order of preference).
		 *
		 * @param {Array} data Tabular data represented as an array of objects
		 *  with common properties.
		 */
		dumpTable: function ( data ) {
			try {
				// Bartosz made me put this here.
				if ( window.opera ) { throw window.opera; }
				// Use Function.prototype#call to force an exception on Firefox,
				// which doesn't define console#table but doesn't complain if you
				// try to invoke it.
				// eslint-disable-next-line no-useless-call
				console.table.call( console, data );
				return;
			} catch ( e ) {}
			try {
				console.log( JSON.stringify( data, null, 2 ) );
				return;
			} catch ( e ) {}
			mw.log( data );
		},

		/**
		 * Generate and print one more reports. When invoked with no arguments,
		 * print all reports.
		 *
		 * @param {...string} [reports] Report names to run, or unset to print
		 *  all available reports.
		 */
		runReports: function () {
			var reports = arguments.length > 0 ?
				Array.prototype.slice.call( arguments ) :
				$.map( inspect.reports, function ( v, k ) { return k; } );

			reports.forEach( function ( name ) {
				inspect.dumpTable( inspect.reports[ name ]() );
			} );
		},

		/**
		 * @class mw.inspect.reports
		 * @singleton
		 */
		reports: {
			/**
			 * Generate a breakdown of all loaded modules and their size in
			 * kilobytes. Modules are ordered from largest to smallest.
			 *
			 * @return {Object[]} Size reports
			 */
			size: function () {
				// Map each module to a descriptor object.
				var modules = inspect.getLoadedModules().map( function ( module ) {
					return {
						name: module,
						size: inspect.getModuleSize( module )
					};
				} );

				// Sort module descriptors by size, largest first.
				sortByProperty( modules, 'size', true );

				// Convert size to human-readable string.
				modules.forEach( function ( module ) {
					module.sizeInBytes = module.size;
					module.size = humanSize( module.size );
				} );

				return modules;
			},

			/**
			 * For each module with styles, count the number of selectors, and
			 * count how many match against some element currently in the DOM.
			 *
			 * @return {Object[]} CSS reports
			 */
			css: function () {
				var modules = [];

				inspect.getLoadedModules().forEach( function ( name ) {
					var css, stats, module = mw.loader.moduleRegistry[ name ];

					try {
						css = module.style.css.join();
					} catch ( e ) { return; } // skip

					stats = inspect.auditSelectors( css );
					modules.push( {
						module: name,
						allSelectors: stats.total,
						matchedSelectors: stats.matched,
						percentMatched: stats.total !== 0 ?
							( stats.matched / stats.total * 100 ).toFixed( 2 ) + '%' : null
					} );
				} );
				sortByProperty( modules, 'allSelectors', true );
				return modules;
			},

			/**
			 * Report stats on mw.loader.store: the number of localStorage
			 * cache hits and misses, the number of items purged from the
			 * cache, and the total size of the module blob in localStorage.
			 *
			 * @return {Object[]} Store stats
			 */
			store: function () {
				var raw, stats = { enabled: mw.loader.store.enabled };
				if ( stats.enabled ) {
					$.extend( stats, mw.loader.store.stats );
					try {
						raw = localStorage.getItem( mw.loader.store.getStoreKey() );
						stats.totalSizeInBytes = byteLength( raw );
						stats.totalSize = humanSize( byteLength( raw ) );
					} catch ( e ) {}
				}
				return [ stats ];
			}
		},

		/**
		 * Perform a string search across the JavaScript and CSS source code
		 * of all loaded modules and return an array of the names of the
		 * modules that matched.
		 *
		 * @param {string|RegExp} pattern String or regexp to match.
		 * @return {Array} Array of the names of modules that matched.
		 */
		grep: function ( pattern ) {
			if ( typeof pattern.test !== 'function' ) {
				pattern = new RegExp( mw.RegExp.escape( pattern ), 'g' );
			}

			return inspect.getLoadedModules().filter( function ( moduleName ) {
				var module = mw.loader.moduleRegistry[ moduleName ];

				// Grep module's JavaScript
				if ( $.isFunction( module.script ) && pattern.test( module.script.toString() ) ) {
					return true;
				}

				// Grep module's CSS
				if (
					$.isPlainObject( module.style ) && Array.isArray( module.style.css ) &&
					pattern.test( module.style.css.join( '' ) )
				) {
					// Module's CSS source matches
					return true;
				}

				return false;
			} );
		}
	};

	if ( mw.config.get( 'debug' ) ) {
		mw.log( 'mw.inspect: reports are not available in debug mode.' );
	}

	mw.inspect = inspect;

}( mediaWiki, jQuery ) );
