/**

 * 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.ByteArrayInputStream;

import java.io.IOException;

import java.io.InputStream;

import org.apidesign.bck2brwsr.core.JavaScriptBody;

/**

 *

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

 */

final class VMLazy {

    private final Object loader;

    private final Object[] args;

    private VMLazy(Object loader, Object[] args) {

        this.loader = loader;

        this.args = args;

    }

    static void init() {

    }

    static Object load(Object loader, String name, Object[] arguments) 

    throws IOException, ClassNotFoundException {

        return new VMLazy(loader, arguments).load(name, false);

    }

    static Object reload(Object loader, String name, Object[] arguments, byte[] arr) 

    throws IOException, ClassNotFoundException {

        return new VMLazy(loader, arguments).defineClass(arr, name, false);

    }

    private Object load(String name, boolean instance)

    throws IOException, ClassNotFoundException {

        String res = name.replace('.', '/') + ".class";

        byte[] arr = ClassPath.loadFromCp(args, res, 0);

        if (arr == null) {

            throw new ClassNotFoundException(name);

        }

        return defineClass(arr, name, instance);

    }

    private Object defineClass(byte[] arr, String name, boolean instance) throws IOException {

        StringBuilder out = new StringBuilder(65535);

        out.append("var loader = arguments[0];\n");

        out.append("var vm = loader.vm;\n");

        int prelude = out.length();

        String initCode = new Gen(this, out).compile(new ByteArrayInputStream(arr));

        String code = out.toString().toString();

        String under = name.replace('.', '_');

        Object fn = applyCode(loader, under, code, instance);

        if (!initCode.isEmpty()) {

            out.setLength(prelude);

            out.append(initCode);

            code = out.toString().toString();

            applyCode(loader, null, code, false);

        }            

        return fn;

    }

    @JavaScriptBody(args = {"loader", "name", "script", "instance" }, body =

        "try {\n" +

        "  new Function(script)(loader, name);\n" +

        "} catch (ex) {\n" +

        "  throw 'Cannot compile ' + name + ' ' + ex + ' line: ' + ex.lineNumber + ' script:\\n' + script;\n" +

        "}\n" +

        "return name != null ? vm[name](instance) : null;\n"

    )

    private static native Object applyCode(Object loader, String name, String script, boolean instance);

    private static final class Gen extends ByteCodeToJavaScript {

        private final VMLazy lazy;

        public Gen(VMLazy vm, Appendable out) {

            super(out);

            this.lazy = vm;

        }

        @JavaScriptBody(args = {"n"},

        body =

        "var cls = n.replace__Ljava_lang_String_2CC('/','_').toString();"

        + "\nvar dot = n.replace__Ljava_lang_String_2CC('/','.').toString();"

        + "\nvar lazy = this._lazy();"

        + "\nvar loader = lazy._loader();"

        + "\nvar vm = loader.vm;"

        + "\nif (vm[cls]) return false;"

        + "\nvm[cls] = function() {"

        + "\n  var instance = arguments.length == 0 || arguments[0] === true;"

        + "\n  return lazy.load__Ljava_lang_Object_2Ljava_lang_String_2Z(dot, instance);"

        + "\n};"

        + "\nreturn true;")

        @Override

        protected boolean requireReference(String internalClassName) {

            throw new UnsupportedOperationException();

        }

        @Override

        protected void requireScript(String resourcePath) throws IOException {

            if (!resourcePath.startsWith("/")) {

                resourcePath = "/" + resourcePath;

            }

            String code = readCode(resourcePath);

            applyCode(lazy.loader, null, code, false);

        }

        private String readCode(String resourcePath) throws IOException {

            InputStream is = getClass().getResourceAsStream(resourcePath);

            StringBuilder sb = new StringBuilder();

            for (;;) {

                int ch = is.read();

                if (ch == -1) {

                    break;

                }

                sb.append((char)ch);

            }

            return sb.toString();

        }

        @Override

        String assignClass(String className) {

            return "vm[arguments[1]]=";

        }

        @Override

        String accessClass(String classOperation) {

            return "vm." + classOperation;

        }

    }

}