source: Dev/trunk/src/client/util/build/transforms/optimizer/closure.js

define([
        "../../buildControl",
        "dojo/has!host-node?./sendJob:",
        "../../fs",
        "../../fileUtils",
        "./stripConsole",
        "dojo/_base/lang",
        "dojo/has"
], function(bc, sendJob, fs, fileUtils, stripConsole, lang, has){
        if(has("host-node")){
                return function(resource, text, copyright, optimizeSwitch, callback){
                        copyright = copyright || "";
                        if(bc.stripConsole){
                                var tempFilename = resource.dest + ".consoleStripped.js";
                                text = stripConsole(text);
                                fs.writeFile(tempFilename, bc.newlineFilter(text, resource, "closureStripConsole"), resource.encoding, function(err){
                                        if(!err){
                                                sendJob(tempFilename, resource.dest, optimizeSwitch, copyright);
                                        }
                                        callback(resource, err);
                                });
                                return callback;
                        }else{
                                sendJob(resource.dest + ".uncompressed.js", resource.dest, optimizeSwitch, copyright);
                                return 0;
                        }
                };
        }

        if(has("host-rhino")){
                var JSSourceFilefromCode,
                        closurefromCode,
                        jscomp = 0,
                        built = "//>>built" + bc.newline;

                var ccompile = function(text, dest, optimizeSwitch, copyright, useSourceMaps){
                        /*jshint rhino:true */
                        /*global com:false Packages:false */
                        if(!jscomp){
                                JSSourceFilefromCode = java.lang.Class.forName("com.google.javascript.jscomp.JSSourceFile").getMethod("fromCode", [ java.lang.String, java.lang.String ]);
                                closurefromCode = function(filename,content){
                                        return JSSourceFilefromCode.invoke(null, [filename, content]);
                                };
                                jscomp = com.google.javascript.jscomp;
                        }
                        //Fake extern
                        var externSourceFile = closurefromCode("fakeextern.js", " ");

                        //Set up source input
                        var destFilename = dest.split("/").pop(),
                                jsSourceFile = closurefromCode(destFilename + ".uncompressed.js", String(text));

                        //Set up options
                        var options = new jscomp.CompilerOptions();
                        lang.mixin(options, bc.optimizeOptions);
                        // Must have non-null path to trigger source map generation, also fix version
                        options.setSourceMapOutputPath("");
                        options.setSourceMapFormat(jscomp.SourceMap.Format.V3);
                        if(optimizeSwitch.indexOf(".keeplines") !== -1){
                                options.prettyPrint = true;
                        }
                        var FLAG_compilation_level = jscomp.CompilationLevel.SIMPLE_OPTIMIZATIONS;
                        FLAG_compilation_level.setOptionsForCompilationLevel(options);
                        var FLAG_warning_level = jscomp.WarningLevel.DEFAULT;
                        FLAG_warning_level.setOptionsForWarningLevel(options);

                        //Prevent too-verbose logging output
                        Packages.com.google.javascript.jscomp.Compiler.setLoggingLevel(java.util.logging.Level.SEVERE);

                        // Run the compiler
                        // File name and associated map name
                        var mapTag = useSourceMaps ? (bc.newline + "//# sourceMappingURL=" + destFilename + ".map") : "";
                        var compiler = new Packages.com.google.javascript.jscomp.Compiler(Packages.java.lang.System.err);
                        compiler.compile(externSourceFile, jsSourceFile, options);
                        var result = copyright + built + compiler.toSource() + mapTag;

                        if(useSourceMaps){
                                var sourceMap = compiler.getSourceMap();
                                sourceMap.setWrapperPrefix(copyright + built);
                                var sb = new java.lang.StringBuffer();
                                sourceMap.appendTo(sb, destFilename);
                                fs.writeFile(dest + ".map", sb.toString(), "utf-8");
                        }

                        return result;
                };

                return function(resource, text, copyright, optimizeSwitch, callback){
                        bc.log("optimize", ["module", resource.mid]);
                        copyright = copyright || "";
                        try{
                                var result = ccompile(stripConsole(text), resource.dest, optimizeSwitch, copyright, bc.useSourceMaps);
                                fs.writeFile(resource.dest, result, resource.encoding, function(err){
                                        if(err){
                                                bc.log("optimizeFailedWrite", ["filename", result.dest]);
                                        }
                                        callback(resource, err);
                                });
                        }catch(e){
                                bc.log("optimizeFailed", ["module identifier", resource.mid, "exception", e + ""]);
                                callback(resource, 0);
                        }
                        return callback;
                };
        }

        throw new Error("Unknown host environment: only nodejs and rhino are supported by closure optimizer.");
});