/**

  * 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;

     }

 }