/**

 * Back 2 Browser Bytecode Translator

 * Copyright (C) 2012 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;

import org.apidesign.vm4brwsr.ByteCodeParser.ClassData;

/** Generator of JavaScript from bytecode of classes on classpath of the VM.

 *

 * @author Jaroslav Tulach <jtulach@netbeans.org>

 */

abstract class VM extends ByteCodeToJavaScript {

    protected final Bck2Brwsr.Resources resources;

    private final ExportedSymbols exportedSymbols;

    private VM(Appendable out, Bck2Brwsr.Resources resources) {

        super(out);

        this.resources = resources;

        this.exportedSymbols = new ExportedSymbols(resources);

    }

    static {

        // uses VMLazy to load dynamic classes

        boolean assertsOn = false;

        assert assertsOn = true;

        if (assertsOn) {

            VMLazy.init();

            Zips.init();

        }

    }

    @Override

    boolean debug(String msg) throws IOException {

        return false;

    }

    static void compileStandalone(Bck2Brwsr.Resources l, Appendable out, StringArray names) throws IOException {

        VM vm = new Standalone(out, l);

        vm.doCompile(names);

    }

    static void compileExtension(Bck2Brwsr.Resources l, Appendable out, StringArray names) throws IOException {

        VM vm = new Extension(out, l);

        vm.doCompile(names);

    }

    private void doCompile(StringArray names) throws IOException {

        generatePrologue();

        generateBody(names);

        generateEpilogue();

    }

    protected abstract void generatePrologue() throws IOException;

    protected abstract void generateEpilogue() throws IOException;

    protected abstract String generateClass(String className)

            throws IOException;

    protected abstract String getExportsObject();

    @Override

    protected final void declaredClass(ClassData classData, String mangledName)

            throws IOException {

        if (exportedSymbols.isExported(classData)) {

            out.append("\n").append(getExportsObject()).append("['")

                                               .append(mangledName)

                                               .append("'] = ")

                            .append(accessClass(mangledName))

               .append(";\n");

        }

    }

    private void generateBody(StringArray names) throws IOException {

        StringArray processed = new StringArray();

        StringArray initCode = new StringArray();

        for (String baseClass : names.toArray()) {

            references.add(baseClass);

            for (;;) {

                String name = null;

                for (String n : references.toArray()) {

                    if (processed.contains(n)) {

                        continue;

                    }

                    name = n;

                }

                if (name == null) {

                    break;

                }

                try {

                    String ic = generateClass(name);

                    processed.add(name);

                    initCode.add(ic == null ? "" : ic);

                } catch (RuntimeException ex) {

                    if (out instanceof CharSequence) {

                        CharSequence seq = (CharSequence)out;

                        int lastBlock = seq.length();

                        while (lastBlock-- > 0) {

                            if (seq.charAt(lastBlock) == '{') {

                                break;

                            }

                        }

                        throw new IOException("Error while compiling " + name + "\n"

                            + seq.subSequence(lastBlock + 1, seq.length()), ex

                        );

                    } else {

                        throw new IOException("Error while compiling " + name + "\n"

                            + out, ex

                        );

                    }

                }

            }

            for (String resource : scripts.toArray()) {

                while (resource.startsWith("/")) {

                    resource = resource.substring(1);

                }

                InputStream emul = resources.get(resource);

                if (emul == null) {

                    throw new IOException("Can't find " + resource);

                }

                readResource(emul, out);

            }

            scripts = new StringArray();

            StringArray toInit = StringArray.asList(references.toArray());

            toInit.reverse();

            for (String ic : toInit.toArray()) {

                int indx = processed.indexOf(ic);

                if (indx >= 0) {

                    final String theCode = initCode.toArray()[indx];

                    if (!theCode.isEmpty()) {

                        out.append(theCode).append("\n");

                    }

                    initCode.toArray()[indx] = "";

                }

            }

        }

    }

    private static void readResource(InputStream emul, Appendable out) throws IOException {

        try {

            int state = 0;

            for (;;) {

                int ch = emul.read();

                if (ch == -1) {

                    break;

                }

                if (ch < 0 || ch > 255) {

                    throw new IOException("Invalid char in emulation " + ch);

                }

                switch (state) {

                    case 0: 

                        if (ch == '/') {

                            state = 1;

                        } else {

                            out.append((char)ch);

                        }

                        break;

                    case 1:

                        if (ch == '*') {

                            state = 2;

                        } else {

                            out.append('/').append((char)ch);

                            state = 0;

                        }

                        break;

                    case 2:

                        if (ch == '*') {

                            state = 3;

                        }

                        break;

                    case 3:

                        if (ch == '/') {

                            state = 0;

                        } else {

                            state = 2;

                        }

                        break;

                }

            }

        } finally {

            emul.close();

        }

    }

    private static InputStream loadClass(Bck2Brwsr.Resources l, String name) throws IOException {

        return l.get(name + ".class"); // NOI18N

    }

    static String toString(String name) throws IOException {

        StringBuilder sb = new StringBuilder();

//        compile(sb, name);

        return sb.toString().toString();

    }

    private StringArray scripts = new StringArray();

    private StringArray references = new StringArray();

    @Override

    protected boolean requireReference(String cn) {

        if (references.contains(cn)) {

            return false;

        }

        references.add(cn);

        return true;

    }

    @Override

    protected void requireScript(String resourcePath) {

        scripts.add(resourcePath);

    }

    @Override

    String assignClass(String className) {

        return "vm." + className + " = ";

    }

    @Override

    String accessClass(String className) {

        return "vm." + className;

    }

    private static final class Standalone extends VM {

        private Standalone(Appendable out, Bck2Brwsr.Resources resources) {

            super(out, resources);

        }

        @Override

        protected void generatePrologue() throws IOException {

            out.append("(function VM(global) {var fillInVMSkeleton = function(vm) {");

        }

        @Override

        protected void generateEpilogue() throws IOException {

            out.append(

                  "  return vm;\n"

                + "  };\n"

                + "  var extensions = [];\n"

                + "  global.bck2brwsr = function() {\n"

                + "    var args = Array.prototype.slice.apply(arguments);\n"

                + "    var vm = fillInVMSkeleton({});\n"

                + "    for (var i = 0; i < extensions.length; ++i) {\n"

                + "      extensions[i](vm);\n"

                + "    }\n"

                + "    var loader = {};\n"

                + "    loader.vm = vm;\n"

                + "    loader.loadClass = function(name) {\n"

                + "      var attr = name.replace__Ljava_lang_String_2CC('.','_');\n"

                + "      var fn = vm[attr];\n"

                + "      if (fn) return fn(false);\n"

                + "      return vm.org_apidesign_vm4brwsr_VMLazy(false).\n"

                + "        load__Ljava_lang_Object_2Ljava_lang_Object_2Ljava_lang_String_2_3Ljava_lang_Object_2(loader, name, args);\n"

                + "    }\n"

                + "    if (vm.loadClass) {\n"

                + "      throw 'Cannot initialize the bck2brwsr VM twice!';\n"

                + "    }\n"

                + "    vm.loadClass = loader.loadClass;\n"

                + "    vm.loadBytes = function(name) {\n"

                + "      return vm.org_apidesign_vm4brwsr_VMLazy(false).\n"

                + "        loadBytes___3BLjava_lang_Object_2Ljava_lang_String_2_3Ljava_lang_Object_2(loader, name, args);\n"

                + "    }\n"

                + "    vm.java_lang_reflect_Array(false);\n"

                + "    vm.org_apidesign_vm4brwsr_VMLazy(false).\n"

                + "      loadBytes___3BLjava_lang_Object_2Ljava_lang_String_2_3Ljava_lang_Object_2(loader, null, args);\n"

                + "    return loader;\n"

                + "  };\n");

            out.append(

                  "  global.bck2brwsr.registerExtension"

                             + " = function(extension) {\n"

                + "    extensions.push(extension);\n"

                + "  };\n");

            out.append("}(this));");

        }

        @Override

        protected String generateClass(String className) throws IOException {

            InputStream is = loadClass(resources, className);

            if (is == null) {

                throw new IOException("Can't find class " + className);

            }

            return compile(is);

        }

        @Override

        protected String getExportsObject() {

            return "vm";

        }

    }

    private static final class Extension extends VM {

        private Extension(Appendable out, Bck2Brwsr.Resources resources) {

            super(out, resources);

        }

        @Override

        protected void generatePrologue() throws IOException {

            out.append("bck2brwsr.registerExtension(function(exports) {\n"

                           + "  var vm = {};\n");

            out.append("  function link(n, inst) {\n"

                           + "    var cls = n.replace__Ljava_lang_String_2CC("

                                                  + "'/', '_').toString();\n"

                           + "    var dot = n.replace__Ljava_lang_String_2CC("

                                                  + "'/', '.').toString();\n"

                           + "    exports.loadClass(dot);\n"

                           + "    vm[cls] = exports[cls];\n"

                           + "    return vm[cls](inst);\n"

                           + "  };\n");

        }

        @Override

        protected void generateEpilogue() throws IOException {

            out.append("});");

        }

        @Override

        protected String generateClass(String className) throws IOException {

            InputStream is = loadClass(resources, className);

            if (is == null) {

                out.append("\n").append(assignClass(

                                            className.replace('/', '_')))

                   .append("function() {\n  return link('")

                   .append(className)

                   .append("', arguments.length == 0 || arguments[0] === true);"

                               + "\n};");

                return null;

            }

            return compile(is);

        }

        @Override

        protected String getExportsObject() {

            return "exports";

        }

    }

}