/**

 * 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 java.net.URL;

import org.apidesign.bck2brwsr.core.JavaScriptBody;

/** Conversion from classpath to load function.

 *

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

 */

final class ClassPath {

    private ClassPath() {

    }

    public static void init() {

    }

    @JavaScriptBody(args = { "arr" }, body = "return arr.length;")

    private static native int length(Object arr);

    @JavaScriptBody(args = { "arr", "index" }, body = "return arr[index];")

    private static native Object at(Object arr, int index);

    @JavaScriptBody(args = { "arr", "index", "value" }, body = "arr[index] = value; return value;")

    private static native Object set(Object arr, int index, Object value);

    public static byte[] loadFromCp(Object classpath, String res, int skip) 

    throws IOException, ClassNotFoundException {

        for (int i = 0; i < length(classpath); i++) {

            Object c = at(classpath, i);

            if (c instanceof String) {

                try {

                    String url = (String)c;

                    final Bck2Brwsr.Resources z = toZip(url);

                    c = set(classpath, i, z);

                    final byte[] man = readBytes(z, "META-INF/MANIFEST.MF");

                    if (man != null) {

                        String mainClass = processClassPathAttr(man, url, classpath);

//                        if (mainClass != null) {

//                            Class.forName(mainClass);

//                        }

                    }

                } catch (IOException ex) {

                    set(classpath, i, ex);

                    log("Cannot load " + c + " - " + ex.getClass().getName() + ":" + ex.getMessage());

                }

            }

            if (res != null) {

                byte[] checkRes;

                if (c instanceof Bck2Brwsr.Resources) {

                    checkRes = readBytes((Bck2Brwsr.Resources)c, res);

                    if (checkRes != null && --skip < 0) {

                        return checkRes;

                    }

                } else {

                    checkRes = callFunction(c, res, skip);

                    if (checkRes != null) {

                        return checkRes;

                    }

                }

            }

        }

        return null;

    }

    @JavaScriptBody(args = { "fn", "res", "skip" }, body = 

        "if (typeof fn === 'function') return fn(res, skip);\n"

      + "return null;"

    )

    private static native byte[] callFunction(Object fn, String res, int skip);

    @JavaScriptBody(args = { "msg" }, body = "if (typeof console !== 'undefined') console.log(msg.toString());")

    private static native void log(String msg);

    private static String processClassPathAttr(final byte[] man, String url, Object classpath) throws IOException {

        try (ParseMan is = new ParseMan(new ByteArrayInputStream(man))) {

            String cp = is.toString();

            if (cp != null) {

                cp = cp.trim();

                for (int p = 0; p < cp.length();) {

                    int n = cp.indexOf(' ', p);

                    if (n == -1) {

                        n = cp.length();

                    }

                    String el = cp.substring(p, n);

                    URL u = new URL(new URL(url), el);

                    classpath = addToArray(classpath, u.toString());

                    p = n + 1;

                }

            }

            return is.getMainClass();

        }

    }

    private static Object addToArray(Object arr, String value) {

        final int last = length(arr);

        Object ret = enlargeArray(arr, last + 1);

        set(ret, last, value);

        return ret;

    }

    @JavaScriptBody(args = { "arr", "len" }, body = "while (arr.length < len) arr.push(null); return arr;")

    private static native Object enlargeArray(Object arr, int len);

    private static Bck2Brwsr.Resources toZip(String path) throws IOException {

        URL u = new URL(path);

        byte[] zipData = (byte[]) u.getContent(new Class[]{byte[].class});

        Bck2Brwsr.Resources r;

        try {

            Class<?> fastJar = Class.forName("org.apidesign.bck2brwsr.vmzip.ZipResources");

            return (Bck2Brwsr.Resources) fastJar.getConstructor(byte[].class).newInstance(zipData);

        } catch (Exception ex) {

            log("Reading JARs is only possible with enum.zip module included: " + ex.getMessage());

            ex.printStackTrace();

            throw new IOException(ex);

        }

    }

    private static byte[] readBytes(Bck2Brwsr.Resources r, String res) throws IOException {

        InputStream is = r.get(res);

        if (is == null) {

            return null;

        }

        byte[] arr = new byte[is.available()];

        int off = 0;

        for (;;) {

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

            if (len == -1) {

                break;

            }

            off += len;

        }

        is.close();

        return arr;

    }

}