/**

  * Back 2 Browser Bytecode Translator

  * Copyright (C) 2012-2015 Jaroslav Tulach <jaroslav.tulach@apidesign.org>

  *

  * This program is free software: you can redistribute it and/or modify

  * it under the terms of the GNU General Public License as published by

  * the Free Software Foundation, version 2 of the License.

  *

  * This program is distributed in the hope that it will be useful,

  * but WITHOUT ANY WARRANTY; without even the implied warranty of

  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

  * GNU General Public License for more details.

  *

  * You should have received a copy of the GNU General Public License

  * along with this program. Look for COPYING file in the top folder.

  * If not, see http://opensource.org/licenses/GPL-2.0.

  */

 package org.apidesign.vm4brwsr;

 import java.io.IOException;

 import java.io.InputStream;

 /** Build your own virtual machine! Use methods in this class to generate

  * a skeleton JVM in JavaScript that contains pre-compiled classes of your

  * choice:

  * <pre>

  * Writer w = new {@link java.io.StringWriter}();

  * {@link #newCompiler() Bck2Brwsr.newCompiler}()

  *   .{@link #resources(org.apidesign.vm4brwsr.Bck2Brwsr.Resources)}

  *   .{@link #addRootClasses(java.lang.String...)}

  *   .{@link #addClasses(java.lang.String...)}

  *   .{@link #addExported(java.lang.String...)}

  *   .{@link #generate(java.lang.Appendable) generate(w)};

  * System.out.{@link java.io.PrintStream#print(java.lang.String) print(w.toString())};

  * </pre>

  * The generated script defines one JavaScript method that can

  * be used to bootstrap and load the virtual machine: <pre>

  * var vm = bck2brwsr();

  * var main = vm.loadClass('org.your.pkg.Main');

  * main.invoke('main');

  * </pre>

  * In case one wants to initialize the virtual machine with ability to

  * load classes lazily when needed, one can provide a loader function to

  * when creating the virtual machine: <pre>

  * var vm = bck2brwsr(function(resource) { 

  *   return null; // byte[] for the resource

  * });

  * </pre>

  * In this scenario, when a request for an unknown class is made, the loader

  * function is asked for its byte code and the system dynamically transforms

  * it to JavaScript.

  * <p>

  * Instead of a loader function, one can also provide a URL to a JAR file

  * or a library JavaScript file generated with {@link #library(java.lang.String...)}

  * option on.

  * The <code>bck2brwsr</code> system will do its best to download the file

  * and provide loader function for it automatically. In order to use

  * the JAR file <code>emul.zip</code> module needs to be available in the system.

  * <p>

  * One can provide as many loader functions and URL references as necessary.

  * Then the initialization code would look like:<pre>

  * var vm = bck2brwsr(url1, url2, fnctn1, url3, functn2);

  * </pre>

  * The provided URLs and loader functions will be consulted one by one.

  * <p>

  * The initialization of the <b>Bck2Brwsr</b> is done asynchronously since 

  * version 0.9. E.g. call to <pre>

  * var vm = bck2brwsr('myapp.js');

  * var main = vm.loadClass('org.your.pkg.Main');

  * main.invoke('main');

  * </pre>

  * returns immediately and the call to the static main method will happen

  * once the virtual machine is initialized and the class available.

  *

  * @author Jaroslav Tulach

  */

 public final class Bck2Brwsr {

     private final ObfuscationLevel level;

     private final StringArray exported;

     private final StringArray classes;

     private final StringArray resources;

     private final Resources res;

     private final Boolean extension;

     private final StringArray classpath;

     private final Flow.Analyzer flow;

     private Bck2Brwsr(

         ObfuscationLevel level, StringArray exported,

         StringArray classes, StringArray resources, Resources res,

         Boolean extension, StringArray classpath, Flow.Analyzer flow

     ) {

         this.level = level;

         this.exported = exported;

         this.classes = classes;

         this.resources = resources;

         this.res = res;

         this.extension = extension;

         this.classpath = classpath;

         this.flow = flow;

     }

     /** Helper method to generate virtual machine from bytes served by a <code>resources</code>

      * provider.

      *

      * @param out the output to write the generated JavaScript to

      * @param resources provider of class files to use

      * @param classes additional classes to include in the generated script

      * @throws IOException I/O exception can be thrown when something goes wrong

      */

     public static void generate(Appendable out, Resources resources, String... classes) throws IOException {

         newCompiler().resources(resources).addRootClasses(classes).generate(out);

     }

     /** Helper method to generate virtual machine from bytes served by a class loader.

      *

      * @param out the output to write the generated JavaScript to

      * @param loader class loader to load needed classes from

      * @param classes additional classes to include in the generated script

      * @throws IOException I/O exception can be thrown when something goes wrong

      */

     public static void generate(Appendable out, ClassLoader loader, String... classes) throws IOException {

         newCompiler().resources(loader).addRootClasses(classes).generate(out);

     }

     /** Creates new instance of Bck2Brwsr compiler which is ready to generate

      * empty Bck2Brwsr virtual machine. The instance can be further

      * configured by calling chain of methods. For example: 

      * <pre>

      * {@link #newCompiler()}.{@link #resources(org.apidesign.vm4brwsr.Bck2Brwsr.Resources) resources(loader)}.{@link #addRootClasses(java.lang.String[]) addRootClasses("your/Clazz")}.{@link #generate(java.lang.Appendable) generate(out)};

      * </pre>

      * 

      * @return new instance of the Bck2Brwsr compiler

      * @since 0.5

      */

     public static Bck2Brwsr newCompiler() {

         return new Bck2Brwsr(

             ObfuscationLevel.NONE, 

             new StringArray(), new StringArray(), new StringArray(), 

             null, false, null, null

         );

     }

     /** Adds exported classes or packages. If the string ends 

      * with slash, it is considered a name of package. If it does not,

      * it is a name of a class (without <code>.class</code> suffix).

      * The exported classes are prevented from being obfuscated. 

      * All public classes in exported packages are prevented from

      * being obfuscated. By listing the packages or classes in this 

      * method, these classes are not guaranteed to be included in

      * the generated script. Use {@link #addClasses} to include

      * the classes.

      * 

      * @param exported names of classes and packages to treat as exported

      * @return new instances of the Bck2Brwsr compiler which inherits

      *   all values from <code>this</code> except list of exported classes

      */

     public Bck2Brwsr addExported(String... exported) {

         return new Bck2Brwsr(

             level, this.exported.addAndNew(exported), 

             classes, resources, res, extension, classpath, flow

         );

     }

     /** Adds additional classes 

      * to the list of those that should be included in the generated

      * JavaScript file.

      * These classes are guaranteed to be available in the

      * generated virtual machine code accessible using their fully 

      * qualified name. This brings the same behavior as if the

      * classes were added by {@link #addClasses(java.lang.String...) } and

      * exported via {@link #addExported(java.lang.String...)}.

      * 

      * @param classes the classes to add to the compilation

      * @return new instance of the Bck2Brwsr compiler which inherits

      * all values from <code>this</code>

      */

     public Bck2Brwsr addRootClasses(String... classes) {

         if (classes.length == 0) {

             return this;

         } 

         return addExported(classes).addClasses(classes);

     }

     /** Adds additional classes 

      * to the list of those that should be included in the generated

      * JavaScript file. These classes are guaranteed to be present,

      * but they may not be accessible through their fully qualified

      * name.

      * 

      * @param classes the classes to add to the compilation

      * @return new instance of the Bck2Brwsr compiler which inherits

      * all values from <code>this</code>

      * @since 0.9

      */

     public Bck2Brwsr addClasses(String... classes) {

         if (classes.length == 0) {

             return this;

         } else {

             return new Bck2Brwsr(level, exported, 

                 this.classes.addAndNew(classes), resources, res,

                 extension, classpath, flow);

         }

     }

     /** These resources should be made available in the compiled file in

      * binary form. These resources can then be loaded

      * by {@link ClassLoader#getResource(java.lang.String)} and similar 

      * methods.

      * 

      * @param resources names of the resources to be loaded by {@link Resources#get(java.lang.String)}

      * @return new instance of the Bck2Brwsr compiler which inherits

      *   all values from <code>this</code> just adds few more resource names

      *   for processing

      * @since 0.9

      */

     public Bck2Brwsr addResources(String... resources) {

         if (resources.length == 0) {

             return this;

         } else {

             return new Bck2Brwsr(level, exported, this.classes, 

                 this.resources.addAndNew(resources), res, extension, classpath, flow

             );

         }

     }

     /** Changes the obfuscation level for the compiler by creating new instance

      * which inherits all values from <code>this</code> and adjust the level

      * of obfuscation.

      * 

      * @param level the new level of obfuscation

      * @return new instance of the compiler with changed level of obfuscation

      * @since 0.5

      */

     public Bck2Brwsr obfuscation(ObfuscationLevel level) {

         return new Bck2Brwsr(level, exported, classes, resources, res, extension, classpath, flow);

     }

     /** A way to change the provider of additional resources (classes) for the 

      * compiler. 

      * 

      * @param res the implementation of resources provider

      * @return new instance of the compiler with all values remaining the same, just 

      *   with different resources provider

      * @since 0.5

      */

     public Bck2Brwsr resources(Resources res) {

         return new Bck2Brwsr(

             level, exported, classes, resources, 

             res, extension, classpath, flow

         );

     }

     /** Should one generate a library? By default the system generates

      * all transitive classes needed by the the transitive closure of

      * {@link #addRootClasses(java.lang.String...)} and {@link #addClasses(java.lang.String...)}.

      * By turning on the library mode, only classes explicitly listed

      * will be included in the archive. The others will be referenced

      * as external ones.

      * <p>

      * A library archive may specify its <em>classpath</em> - e.g. link to

      * other libraries that should also be included in the application. 

      * One can specify the list of libraries as vararg to this method.

      * These are relative URL with respect to location of this library.

      * The runtime system then prefers seek for ".js" suffix of the library

      * and only then seeks for the classical ".jar" path.

      * 

      * @param classpath the array of JARs that are referenced by this library -

      *   by default gets turned into 

      * @return new instance of the compiler with library flag changed

      * @since 0.9

      */

     public Bck2Brwsr library(String... classpath) {

         return new Bck2Brwsr(

             level, exported, classes, 

             resources, res, true, 

             StringArray.asList(classpath), flow

         );

     }

     /** Turns on the standalone mode. E.g. does the opposite of

      * calling {@link #library(java.lang.String...)},

      * but also allows to specify whether the <em>Bck2Brwsr VM</em> should

      * be included at all. If not, only the skeleton of the launcher is

      * generated without any additional VM classes referenced.

      * 

      * @param includeVM should the VM be compiled in, or left out

      * @return new instance of the compiler with standalone mode on

      * @since 0.9

      */

     public Bck2Brwsr standalone(boolean includeVM) {

         return new Bck2Brwsr(

             level, exported, classes, resources, 

             res, includeVM ? false : null, null, flow

         );

     }

     /** A way to change the provider of additional resources (classes) for the 

      * compiler by specifying classloader to use for loading them.

      * 

      * @param loader class loader to load the resources from

      * @return new instance of the compiler with all values being the same, just 

      *   different resources provider

      * @since 0.5

      */

     public Bck2Brwsr resources(final ClassLoader loader) {

         return resources(loader, false);

     }

     /** A way to change the provider of additional resources (classes) for the 

      * compiler by specifying classloader to use for loading them.

      * 

      * @param loader class loader to load the resources from

      * @param ignoreBootClassPath <code>true</code> if classes loaded

      *    from <code>rt.jar</code> 

      * @return new instance of the compiler with all values being the same, just 

      *   different resources provider

      * @since 0.9

      */

     public Bck2Brwsr resources(final ClassLoader loader, boolean ignoreBootClassPath) {

         return resources(new LdrRsrcs(loader, ignoreBootClassPath));

     }

     /** A way to register flow analyzer. Such analyzer can optimize the

      * representation of cycles inside of method bodies.

      * 

      * @param flow the analyzer to be consulted with each method body

      * @return new instance of the compiler with all values being the same, just 

      *   different flow analyzer

      * @since 0.15

      */

     public Bck2Brwsr flowAnalyzer(Flow.Analyzer flow) {

         return new Bck2Brwsr(

             level, exported, classes, resources, res, 

             extension, classpath, flow

         );

     }

     /** Generates virtual machine based on previous configuration of the 

      * compiler.

      * 

      * @param out the output to write the generated JavaScript to

      * @throws IOException I/O exception can be thrown when something goes wrong

      * @since 0.5

      */

     public void generate(Appendable out) throws IOException {

         if (level != ObfuscationLevel.NONE) {

             try {

                 ClosureWrapper.produceTo(out, level, this);

                 return;

             } catch (IOException ex) {

                 throw ex;

             } catch (Throwable ex) {

                 out.append("/* Failed to obfuscate: " + ex.getMessage()

                                + " */\n");

             }

         }

         VM.compile(out, this);

     }

     //

     // Internal getters

     // 

     Resources getResources() {

         return res != null ? res : new LdrRsrcs(Bck2Brwsr.class.getClassLoader(), false);

     }

     StringArray allResources() {

         return resources;

     }

     StringArray classes() {

         return classes;

     }

     StringArray exported() {

         return exported;

     }

     boolean isExtension() {

         return Boolean.TRUE.equals(extension);

     }

     boolean includeVM() {

         return extension != null;

     }

     StringArray classpath() {

         return classpath;

     }

     Flow.Analyzer flow() {

         return flow;

     }

     /** Provider of resources (classes and other files). The 

      * {@link #generate(java.lang.Appendable, org.apidesign.vm4brwsr.Bck2Brwsr.Resources, java.lang.String[]) 

      * generator method} will call back here for all classes needed during

      * translation to JavaScript.

      */

     public interface Resources {

         /** Loads given resource (class or other file like image). The 

          * resource name to load bytes for the {@link String} class

          * would be <code>"java/lang/String.class"</code>.

          * 

          * @param resource path to resource to load

          * @return the input stream for the resource 

          * @throws IOException can be thrown if the loading fails on some error

          *   or the file cannot be found

          */

         public InputStream get(String resource) throws IOException;

     }

     /** Represents control flow inside single method.

      * Passed into {@link Analyzer#analyze(byte[], org.apidesign.vm4brwsr.Bck2Brwsr.Flow)}

      * method that can be registed via {@link Bck2Brwsr#flowAnalyzer(org.apidesign.vm4brwsr.Bck2Brwsr.Flow.Analyzer)}

      * method.

      * 

      * @since 0.15

      */

     public static final class Flow {

         private final byte[] byteCode;

         Flow(byte[] byteCode) {

             this.byteCode = byteCode;

         }

         /** Access to bytecode of the method to analyse.

          * 

          * @return unmodifiable bytecode of the instructions in the method body

          */

         public byte[] getMethodByteCode() {

             return byteCode;

         }

         public void registerCycle(int offset) {

         }

         public void registerIf(int offset) {

         }

         /** Provider of advanced analysis of the code flow inside of

          * method bodies. Register via {@link Bck2Brwsr#flowAnalyzer(org.apidesign.vm4brwsr.Bck2Brwsr.Flow.Analyzer)}

          * when constructing the {@link Bck2Brwsr#newCompiler() compiler}.

          * 

          * @since 0.15

          */

         public interface Analyzer {

             /** Called to analyze method bodies and offer better control flow.

              * 

              * 

              * @param request flow computation request and also a

              *    callback interface with methods to define the flow

              * @return <code>true</code> if the analysis was successful,

              *   <code>false</code> otherwise

              */

             public boolean analyze(Flow request);

         }

     }

 }