/*

 * Copyright (c) 2008, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * This code 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

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

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

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

import java.io.ByteArrayOutputStream;

import java.net.URI;

import java.net.URISyntaxException;

import java.util.ArrayList;

import java.util.HashMap;

import java.util.List;

import java.util.Map;

import javax.tools.FileObject;

import javax.tools.ForwardingJavaFileManager;

import javax.tools.JavaCompiler;

import javax.tools.JavaFileManager;

import javax.tools.JavaFileObject.Kind;

import javax.tools.SimpleJavaFileObject;

import javax.tools.ToolProvider;

public final class MemoryClassLoader extends ClassLoader {

    private final JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();

    private final MemoryFileManager manager = new MemoryFileManager(this.compiler);

    public Class<?> compile(String name, String content) {

        compile(new Source(name, content));

        try {

            return findClass(name);

        }

        catch (ClassNotFoundException exception) {

            throw new Error(exception);

        }

    }

    public void compile(Source... sources) {

        List<Source> list = new ArrayList<Source>();

        if (sources != null) {

            for (Source source : sources) {

                if (source != null) {

                    list.add(source);

                }

            }

        }

        synchronized (this.manager) {

            this.compiler.getTask(null, this.manager, null, null, null, list).call();

        }

    }

    @Override

    protected Class<?> findClass(String name) throws ClassNotFoundException {

        synchronized (this.manager) {

            Output mc = this.manager.map.remove(name);

            if (mc != null) {

                byte[] array = mc.toByteArray();

                return defineClass(name, array, 0, array.length);

            }

        }

        return super.findClass(name);

    }

    private static final class MemoryFileManager extends ForwardingJavaFileManager<JavaFileManager> {

        private final Map<String, Output> map = new HashMap<String, Output>();

        MemoryFileManager(JavaCompiler compiler) {

            super(compiler.getStandardFileManager(null, null, null));

        }

        @Override

        public Output getJavaFileForOutput(Location location, String name, Kind kind, FileObject source) {

            Output mc = this.map.get(name);

            if (mc == null) {

                mc = new Output(name);

                this.map.put(name, mc);

            }

            return mc;

        }

    }

    private static class MemoryFileObject extends SimpleJavaFileObject {

        MemoryFileObject(String name, Kind kind) {

            super(toURI(name, kind.extension), kind);

        }

        private static URI toURI(String name, String extension) {

            try {

                return new URI("mfm:///" + name.replace('.', '/') + extension);

            }

            catch (URISyntaxException exception) {

                throw new Error(exception);

            }

        }

    }

    private static final class Output extends MemoryFileObject {

        private final ByteArrayOutputStream baos = new ByteArrayOutputStream();

        Output(String name) {

            super(name, Kind.CLASS);

        }

        byte[] toByteArray() {

            return this.baos.toByteArray();

        }

        @Override

        public ByteArrayOutputStream openOutputStream() {

            this.baos.reset();

            return this.baos;

        }

    }

    public static final class Source extends MemoryFileObject {

        private final String content;

        Source(String name, String content) {

            super(name, Kind.SOURCE);

            this.content = content;

        }

        @Override

        public CharSequence getCharContent(boolean ignore) {

            return this.content;

        }

    }

}