/*
 * Copyright 2000-2014 JetBrains s.r.o.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.jetbrains.java.decompiler.struct.lazy;

import org.jetbrains.java.decompiler.main.extern.IBytecodeProvider;
import org.jetbrains.java.decompiler.struct.StructMethod;
import org.jetbrains.java.decompiler.struct.attr.StructGeneralAttribute;
import org.jetbrains.java.decompiler.struct.consts.ConstantPool;
import org.jetbrains.java.decompiler.util.DataInputFullStream;

import java.io.IOException;
import java.io.InputStream;
import java.util.HashMap;

public class LazyLoader {

  private HashMap<String, Link> mapClassLinks = new HashMap<String, Link>();

  private IBytecodeProvider provider;

  public LazyLoader(IBytecodeProvider provider) {
    this.provider = provider;
  }

  public void addClassLink(String classname, Link link) {
    mapClassLinks.put(classname, link);
  }

  public void removeClassLink(String classname) {
    mapClassLinks.remove(classname);
  }

  public Link getClassLink(String classname) {
    return mapClassLinks.get(classname);
  }


  public ConstantPool loadPool(String classname) {

    try {

      DataInputFullStream in = getClassStream(classname);
      if (in == null) {
        return null;
      }

      in.skip(8);

      return new ConstantPool(in);
    }
    catch (IOException ex) {
      throw new RuntimeException(ex);
    }
  }

  public byte[] loadBytecode(StructMethod mt, int code_fulllength) {

    try {

      DataInputFullStream in = getClassStream(mt.getClassStruct().qualifiedName);
      if (in == null) {
        return null;
      }

      byte[] res = null;

      in.skip(8);

      ConstantPool pool = mt.getClassStruct().getPool();
      if (pool == null) {
        pool = new ConstantPool(in);
      }
      else {
        ConstantPool.skipPool(in);
      }

      in.skip(2);
      int this_class = in.readUnsignedShort();
      in.skip(2);

      // interfaces
      in.skip(in.readUnsignedShort() * 2);

      // fields
      int size = in.readUnsignedShort();
      for (int i = 0; i < size; i++) {
        in.skip(6);
        skipAttributes(in);
      }

      // methods
      size = in.readUnsignedShort();
      for (int i = 0; i < size; i++) {
        in.skip(2);

        int name_index = in.readUnsignedShort();
        int descriptor_index = in.readUnsignedShort();

        String[] elem_arr = pool.getClassElement(ConstantPool.METHOD, this_class, name_index, descriptor_index);
        String name = elem_arr[0];

        if (mt.getName().equals(name)) {
          String descriptor = elem_arr[1];
          if (mt.getDescriptor().equals(descriptor)) {

            int len = in.readUnsignedShort();
            for (int j = 0; j < len; j++) {

              int attr_nameindex = in.readUnsignedShort();
              String attrname = pool.getPrimitiveConstant(attr_nameindex).getString();

              if (StructGeneralAttribute.ATTRIBUTE_CODE.equals(attrname)) {
                in.skip(12);

                res = new byte[code_fulllength];
                in.readFull(res);
                return res;
              }
              else {
                in.skip(in.readInt());
              }
            }

            return null;
          }
        }

        skipAttributes(in);
      }

      return null;
    }
    catch (IOException ex) {
      throw new RuntimeException(ex);
    }
  }

  public DataInputFullStream getClassStream(String externPath, String internPath) throws IOException {
    InputStream instream = provider.getBytecodeStream(externPath, internPath);
    return instream == null ? null : new DataInputFullStream(instream);
  }

  public DataInputFullStream getClassStream(String qualifiedClassName) throws IOException {
    Link link = mapClassLinks.get(qualifiedClassName);
    return link == null ? null : getClassStream(link.externPath, link.internPath);
  }

  private static void skipAttributes(DataInputFullStream in) throws IOException {

    int length = in.readUnsignedShort();
    for (int i = 0; i < length; i++) {
      in.skip(2);
      in.skip(in.readInt());
    }
  }


  public static class Link {

    public static final int CLASS = 1;
    public static final int ENTRY = 2;

    public int type;
    public String externPath;
    public String internPath;

    public Link(int type, String externPath, String internPath) {
      this.type = type;
      this.externPath = externPath;
      this.internPath = internPath;
    }
  }
}