/**

 * 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.bck2brwsr.aot;

import java.io.BufferedReader;

import java.io.File;

import java.io.IOException;

import java.io.InputStream;

import java.io.InputStreamReader;

import java.net.URL;

import java.util.ArrayList;

import java.util.Enumeration;

import java.util.HashMap;

import java.util.HashSet;

import java.util.List;

import java.util.Map;

import java.util.Set;

import java.util.jar.JarEntry;

import java.util.jar.JarFile;

import java.util.logging.Level;

import java.util.logging.Logger;

import java.util.zip.ZipEntry;

import org.apidesign.vm4brwsr.Bck2Brwsr;

/** Utilities to process JAR files and set a compiler

 * up.

 *

 * @since 0.9

 * @author Jaroslav Tulach

 */

public final class Bck2BrwsrJars {

    private static final Logger LOG = Logger.getLogger(Bck2BrwsrJars.class.getName());

    private Bck2BrwsrJars() {

    }

    /** Creates new compiler pre-configured from the content of 

     * provided JAR file. The compiler will compile all classes.

     * The system understands OSGi manifest entries and will export

     * all packages that are exported in the JAR file. The system

     * also recognizes META-INF/services and makes sure the class names

     * are not mangled.

     * 

     * @param c the compiler to {@link Bck2Brwsr#addClasses(java.lang.String...) add classes},

     *    {@link Bck2Brwsr#addResources(java.lang.String...) add resources} and

     *    {@link Bck2Brwsr#addExported(java.lang.String...) exported objects} to.

     *    Can be <code>null</code> - in such case an 

     *    {@link Bck2Brwsr#newCompiler() empty compiler} is constructed.

     * @param jar the file to process

     * @return newly configured compiler

     * @throws IOException if something goes wrong

     */

    public static Bck2Brwsr configureFrom(Bck2Brwsr c, File jar) throws IOException {

        final JarFile jf = new JarFile(jar);

        final List<String> classes = new ArrayList<>();

        List<String> resources = new ArrayList<>();

        Set<String> exported = new HashSet<>();

        class JarRes extends EmulationResources implements Bck2Brwsr.Resources {

            JarRes() {

                super(classes);

            }

            @Override

            public InputStream get(String resource) throws IOException {

                InputStream is = jf.getInputStream(new ZipEntry(resource));

                return is == null ? super.get(resource) : is;

            }

        }

        JarRes jarRes = new JarRes();

        listJAR(jf, jarRes, resources, exported);

        String cp = jf.getManifest().getMainAttributes().getValue("Class-Path"); // NOI18N

        String[] classpath = cp == null ? new String[0] : cp.split(" ");

        if (c == null) {

            c = Bck2Brwsr.newCompiler();

        }

        return c

            .library(classpath)

            .addClasses(classes.toArray(new String[classes.size()]))

            .addExported(exported.toArray(new String[exported.size()]))

            .addResources(resources.toArray(new String[resources.size()]))

            .resources(jarRes);

    }

    private static void listJAR(

        JarFile j, EmulationResources classes,

        List<String> resources, Set<String> keep

    ) throws IOException {

        Enumeration<JarEntry> en = j.entries();

        while (en.hasMoreElements()) {

            JarEntry e = en.nextElement();

            final String n = e.getName();

            if (n.endsWith("/")) {

                continue;

            }

            if (n.startsWith("META-INF/maven/")) {

                continue;

            }

            int last = n.lastIndexOf('/');

            String pkg = n.substring(0, last + 1);

            if (pkg.startsWith("java/")) {

                keep.add(pkg);

            }

            if (n.endsWith(".class")) {

                classes.addClassResource(n);

            } else {

                resources.add(n);

                if (n.startsWith("META-INF/services/") && keep != null) {

                    BufferedReader r = new BufferedReader(new InputStreamReader(j.getInputStream(e)));

                    for (;;) {

                        String l = r.readLine();

                        if (l == null) {

                            break;

                        }

                        if (l.startsWith("#")) {

                            continue;

                        }

                        keep.add(l.replace('.', '/'));

                    }

                }

            }

        }

        String exp = j.getManifest().getMainAttributes().getValue("Export-Package");

        if (exp != null && keep != null) {

            for (String def : exp.split(",")) {

                for (String sep : def.split(";")) {

                    keep.add(sep.replace('.', '/') + "/");

                    break;

                }

            }

        }

    }

    static byte[] readFrom(InputStream is) throws IOException {

        int expLen = is.available();

        if (expLen < 1) {

            expLen = 1;

        }

        byte[] arr = new byte[expLen];

        int pos = 0;

        for (;;) {

            int read = is.read(arr, pos, arr.length - pos);

            if (read == -1) {

                break;

            }

            pos += read;

            if (pos == arr.length) {

                byte[] tmp = new byte[arr.length * 2];

                System.arraycopy(arr, 0, tmp, 0, arr.length);

                arr = tmp;

            }

        }

        if (pos != arr.length) {

            byte[] tmp = new byte[pos];

            System.arraycopy(arr, 0, tmp, 0, pos);

            arr = tmp;

        }

        return arr;

    }

    static class EmulationResources implements Bck2Brwsr.Resources {

        private final List<String> classes;

        private final Map<String,byte[]> converted = new HashMap<>();

        private final BytecodeProcessor proc;

        protected EmulationResources(List<String> classes) {

            this.classes = classes;

            BytecodeProcessor p;

            try {

                Class<?> bpClass = Class.forName("org.apidesign.bck2brwsr.aot.RetroLambda");

                p = (BytecodeProcessor) bpClass.newInstance();

            } catch (Throwable t) {

                p = null;

            }

            this.proc = p;

        }

        @Override

        public InputStream get(String name) throws IOException {

            Enumeration<URL> en = Bck2BrwsrJars.class.getClassLoader().getResources(name);

            URL u = null;

            while (en.hasMoreElements()) {

                u = en.nextElement();

            }

            if (u == null) {

                LOG.log(Level.WARNING, "Cannot find {0}", name);

                return null;

            }

            if (u.toExternalForm().contains("/rt.jar!")) {

                LOG.log(Level.WARNING, "{0}No bootdelegation for ", name);

                return null;

            }

            return u.openStream();

        }

        private void addClassResource(String n) throws IOException {

            if (proc != null) {

                try (InputStream is = this.get(n)) {

                    Map<String, byte[]> conv = proc.process(n, readFrom(is), this);

                    if (conv != null) {

                        if (!conv.containsKey(n)) {

                            throw new IOException("Cannot find " + n + " among " + conv);

                        }

                        converted.putAll(conv);

                        return;

                    }

                }

            }

            classes.add(n.substring(0, n.length() - 6));

        }

    }

}