/**
 * Special concat/build task to handle various jQuery build requirements
 * Concats AMD modules, removes their definitions, and includes/excludes specified modules
 */

module.exports = function( grunt ) {

	"use strict";

	var fs = require( "fs" ),
		requirejs = require( "requirejs" ),
		srcFolder = __dirname + "/../../src/",
		rdefineEnd = /\}\);[^}\w]*$/,
		config = {
			baseUrl: "src",
			name: "jquery",
			out: "dist/jquery.js",
			// We have multiple minify steps
			optimize: "none",
			// Include dependencies loaded with require
			findNestedDependencies: true,
			// Avoid breaking semicolons inserted by r.js
			skipSemiColonInsertion: true,
			wrap: {
				startFile: "src/intro.js",
				endFile: "src/outro.js"
			},
			paths: {
				sizzle: "../bower_modules/sizzle/dist/sizzle"
			},
			rawText: {},
			onBuildWrite: convert
		};

	/**
	 * Strip all definitions generated by requirejs
	 * Convert "var" modules to var declarations
	 * "var module" means the module only contains a return statement that should be converted to a var declaration
	 * This is indicated by including the file in any "var" folder
	 * @param {String} name
	 * @param {String} path
	 * @param {String} contents The contents to be written (including their AMD wrappers)
	 */
	function convert( name, path, contents ) {
		// Convert var modules
		if ( /.\/var\//.test( path ) ) {
			contents = contents
				.replace( /define\([\w\W]*?return/, "var " + (/var\/([\w-]+)/.exec(name)[1]) + " =" )
				.replace( rdefineEnd, "" );

		// Sizzle treatment
		} else if ( /^sizzle$/.test( name ) ) {
			contents = "var Sizzle =\n" + contents
				// Remove EXPOSE lines from Sizzle
				.replace( /\/\/\s*EXPOSE[\w\W]*\/\/\s*EXPOSE/, "return Sizzle;" );

		} else {

			// Ignore jQuery's exports (the only necessary one)
			if ( name !== "jquery" ) {
				contents = contents
					.replace( /\s*return\s+[^\}]+(\}\);[^\w\}]*)$/, "$1" )
					// Multiple exports
					.replace( /\s*exports\.\w+\s*=\s*\w+;/g, "" );
			}

			// Remove define wrappers, closure ends, and empty declarations
			contents = contents
				.replace( /define\([^{]*?{/, "" )
				.replace( rdefineEnd, "" );

			// Remove anything wrapped with
			// /* ExcludeStart */ /* ExcludeEnd */
			// or a single line directly after a // BuildExclude comment
			contents = contents
				.replace( /\/\*\s*ExcludeStart\s*\*\/[\w\W]*?\/\*\s*ExcludeEnd\s*\*\//ig, "" )
				.replace( /\/\/\s*BuildExclude\n\r?[\w\W]*?\n\r?/ig, "" );

			// Remove empty definitions
			contents = contents
				.replace( /define\(\[[^\]]+\]\)[\W\n]+$/, "" );
		}
		return contents;
	}

	grunt.registerMultiTask(
		"build",
		"Concatenate source, remove sub AMD definitions, (include/exclude modules with +/- flags), embed date/version",
	function() {
		var flag,
			done = this.async(),
			flags = this.flags,
			optIn = flags[ "*" ],
			name = this.data.dest,
			minimum = this.data.minimum,
			removeWith = this.data.removeWith,
			excluded = [],
			included = [],
			version = grunt.config( "pkg.version" ),
			/**
			 * Recursively calls the excluder to remove on all modules in the list
			 * @param {Array} list
			 * @param {String} [prepend] Prepend this to the module name. Indicates we're walking a directory
			 */
			excludeList = function( list, prepend ) {
				if ( list ) {
					prepend = prepend ? prepend + "/" : "";
					list.forEach(function( module ) {
						// Exclude var modules as well
						if ( module === "var" ) {
							excludeList( fs.readdirSync( srcFolder + prepend + module ), prepend + module );
							return;
						}
						if ( prepend ) {
							// Skip if this is not a js file and we're walking files in a dir
							if ( !(module = /([\w-\/]+)\.js$/.exec( module )) ) {
								return;
							}
							// Prepend folder name if passed
							// Remove .js extension
							module = prepend + module[1];
						}

						// Avoid infinite recursion
						if ( excluded.indexOf( module ) === -1 ) {
							excluder( "-" + module );
						}
					});
				}
			},
			/**
			 * Adds the specified module to the excluded or included list, depending on the flag
			 * @param {String} flag A module path relative to the src directory starting with + or - to indicate whether it should included or excluded
			 */
			excluder = function( flag ) {
				var m = /^(\+|\-|)([\w\/-]+)$/.exec( flag ),
					exclude = m[ 1 ] === "-",
					module = m[ 2 ];

				if ( exclude ) {
					// Can't exclude certain modules
					if ( minimum.indexOf( module ) === -1 ) {
						// Add to excluded
						if ( excluded.indexOf( module ) === -1 ) {
							grunt.log.writeln( flag );
							excluded.push( module );
							// Exclude all files in the folder of the same name
							// These are the removable dependencies
							// It's fine if the directory is not there
							try {
								excludeList( fs.readdirSync( srcFolder + module ), module );
							} catch( e ) {
								grunt.verbose.writeln( e );
							}
						}
						// Check removeWith list
						excludeList( removeWith[ module ] );
					} else {
						grunt.log.error( "Module \"" + module + "\" is a mimimum requirement.");
					}
				} else {
					grunt.log.writeln( flag );
					included.push( module );
				}
			};

		// append commit id to version
		if ( process.env.COMMIT ) {
			version += " " + process.env.COMMIT;
		}

		// figure out which files to exclude based on these rules in this order:
		//  dependency explicit exclude
		//  > explicit exclude
		//  > explicit include
		//  > dependency implicit exclude
		//  > implicit exclude
		// examples:
		//  *                  none (implicit exclude)
		//  *:*                all (implicit include)
		//  *:*:-css           all except css and dependents (explicit > implicit)
		//  *:*:-css:+effects  same (excludes effects because explicit include is trumped by explicit exclude of dependency)
		//  *:+effects         none except effects and its dependencies (explicit include trumps implicit exclude of dependency)
		delete flags[ "*" ];
		for ( flag in flags ) {
			excluder( flag );
		}

		grunt.verbose.writeflags( excluded, "Excluded" );
		grunt.verbose.writeflags( included, "Included" );

		// append excluded modules to version
		if ( excluded.length ) {
			version += " -" + excluded.join( ",-" );
			// set pkg.version to version with excludes, so minified file picks it up
			grunt.config.set( "pkg.version", version );
			grunt.verbose.writeln( "Version changed to " + version );
			// Have to use shallow or core will get excluded since it is a dependency
			config.excludeShallow = excluded;
		}
		config.include = included;

		/**
		 * Handle Final output from the optimizer
		 * @param {String} compiled
		 */
		config.out = function( compiled ) {
			compiled = compiled
				// Embed Version
				.replace( /@VERSION/g, version )
				// Embed Date
				// yyyy-mm-ddThh:mmZ
				.replace( /@DATE/g, ( new Date() ).toISOString().replace( /:\d+\.\d+Z$/, "Z" ) );

			// Write concatenated source to file
			grunt.file.write( name, compiled );
		};

		// Turn off opt-in if necessary
		if ( !optIn ) {
			// Overwrite the default inclusions with the explicit ones provided
			config.rawText.jquery = "define([" + (included.length ? included.join(",") : "") + "]);";
		}

		// Trace dependencies and concatenate files
		requirejs.optimize( config, function( response ) {
			grunt.verbose.writeln( response );
			grunt.log.ok( "File '" + name + "' created." );
			done();
		}, function( err ) {
			done( err );
		});
	});

	// Special "alias" task to make custom build creation less grawlix-y
	// Translation example
	//
	//   grunt custom:+ajax,-dimensions,-effects,-offset
	//
	// Becomes:
	//
	//   grunt build:*:*:+ajax:-dimensions:-effects:-offset
	grunt.registerTask( "custom", function() {
		var args = [].slice.call( arguments ),
			modules = args.length ? args[ 0 ].replace( /,/g, ":" ) : "";

		grunt.log.writeln( "Creating custom build...\n" );

		grunt.task.run([ "build:*:*:" + modules, "uglify", "dist" ]);
	});
};