/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.apache.uima.cas.impl;

import java.io.BufferedWriter;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStreamWriter;
import java.nio.charset.StandardCharsets;
import java.util.Arrays;
import java.util.regex.Pattern;

import org.apache.uima.internal.util.Misc;

import com.strobel.assembler.InputTypeLoader;
import com.strobel.assembler.metadata.Buffer;
import com.strobel.assembler.metadata.CompositeTypeLoader;
import com.strobel.assembler.metadata.ITypeLoader;
import com.strobel.decompiler.Decompiler;
import com.strobel.decompiler.DecompilerSettings;
import com.strobel.decompiler.PlainTextOutput;

//@formatter:off
/**
 * Decompiler
 *   - for testing
 *   - for locating customizations
 *
 * Operation:
 *   Make an instance, optionally setting
 *     - class loader to use (may pass byte array instead)
 *     - directory where to write output (may output to string instead)
 *     - class loader to use when resolving symbols during decompile
 * 
 *   call decompile
 *     - argument
 *         - class name (without .class or .java suffix, fully qualified) or
 *         - byte array
 *     - return value is a byte array output stream with UTF-8 encoded value
 * 
 * decompileToFile - writes decompiled output to a xxx.java file in output directory
 * 
 * Not thread safe
 */
//@formatter:on
public class UimaDecompiler {

  /**
   * special message issued by the decompiler if it fails to load the class
   */
  private final static byte[] errorMsg;
  static {
    errorMsg = "!!! ERROR: Failed to load class".getBytes(StandardCharsets.UTF_8);
  }

  private final DecompilerSettings decompilerSettings = DecompilerSettings.javaDefaults();
  // {
  // decompilerSettings.setMergeVariables(true);
  // decompilerSettings.setSimplifyMemberReferences(true);
  // }

  private final ClassLoader classLoader;

  private File outputDirectory = null;

  public UimaDecompiler() {
    classLoader = null;
  }

  public UimaDecompiler(ClassLoader classLoader, File outputDirectory) {
    this.classLoader = classLoader;
    this.outputDirectory = outputDirectory;
    if (classLoader != null) {
      setDecompilerSettingsForClassLoader();
    }
  }

  // /**
  // * decompile className, and use the byte array passed in instead of getting it from the
  // classpath
  // * @param className the dotted name of the class
  // * @param byteArray the compiled definition for this class to decompile
  // * @return the decompilation
  // */
  // public ByteArrayOutputStream decompile(String className, byte[] byteArray) {
  // setDecompilerSettingsForByteArray(className.replace('.', '/'), byteArray);
  // return decompileCommon(className);
  // }

  /**
   * decompile className, getting the compiled version from the classpath
   * 
   * @param className
   *          the dotted name of the class
   * @return the decompilation
   */
  public ByteArrayOutputStream decompile(String className) {
    setDecompilerSettingsForClassLoader();
    return decompileCommon(className);
  }

  /**
   * Common part for decompiling to a ByteArrayOutputStream the decompiler settings are set up to
   * get the compiled form by name
   * 
   * @param className
   *          the class to decompile
   * @return the decompilation
   */
  public ByteArrayOutputStream decompileCommon(String className) {

    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    PlainTextOutput plainTextOutput = null;
    BufferedWriter writer = null;
    try {
      plainTextOutput = new PlainTextOutput(
              writer = new BufferedWriter(new OutputStreamWriter(baos, "UTF-8")));
      Decompiler.decompile(className.replace('.', '/'), plainTextOutput, decompilerSettings);
      writer.close();
    } catch (IOException e) {
      throw new RuntimeException(); // can't happen
    }

    return baos;
  }

  /**
   * decompile className, getting the compiled version from the classpath
   * 
   * @param className
   *          the dotted or slashified name of the class
   * @return the decompilation
   */
  public String decompileToString(String className) {
    setDecompilerSettingsForClassLoader();
    return decompileToStringCommon(className);
  }

  private String decompileToStringCommon(String className) {
    PlainTextOutput pto = new PlainTextOutput();
    String classNameSlashes = className.replace('.', '/');
    Decompiler.decompile(classNameSlashes, pto, decompilerSettings);
    return pto.toString();
  }

  public String decompileToString(String className, byte[] byteArray) {
    setDecompilerSettingsForByteArray(className.replace('.', '/'), byteArray);
    return decompileToStringCommon(className);
  }

  /** pattern to extract name following class, interface, or enum */
  private static final Pattern cie_name = Pattern.compile("( class | interface | enum )\\s*(\\w*)");

  /**
   * Decompile from the file system, maybe in a Jar. This is a 2 pass operation, usually, to get the
   * classname from the decompilation, and then redo the decompilation with that extra bit of
   * configuration.
   * 
   * @param b
   *          the byte array representing the compiled file
   * @return the decompiled form as a string
   */

  public String decompile(byte[] b) {
    // PlainTextOutput pto = new PlainTextOutput();

    String classNameSlashes = Misc.classNameFromByteCode(b);
    // setDecompilerSettingsForByteArray(classNameSlashes, b);
    // Decompiler.decompile(classNameSlashes, pto, decompilerSettings);
    // String s = pto.toString();
    //
    // String packageName = "";
    // String className = "";
    // int ip = s.indexOf("package ");
    // if (ip >= 0) {
    // ip = ip + "package ".length(); // start of package name;
    // int ipe = s.indexOf(";", ip);
    // packageName = s.substring(ip, ipe).replace('.', '/') + "/";
    // }
    //
    // Matcher m = cie_name.matcher(s);
    // boolean ok = m.find();
    // className = ok
    // ? m.group(2)
    // : "";
    //
    // String classNameSlashes2 = packageName + className;
    //
    // if (!classNameSlashes2.equals(classNameSlashes)) {
    //// System.out.println("debug trying classname: " + classNameSlashes2);
    // System.out.println("debug uimadecompiler classname: " + classNameSlashes);
    return decompileToString(classNameSlashes);

    // pto = new PlainTextOutput();
    // setDecompilerSettingsForByteArray(classNameSlashes, b);
    // Decompiler.decompile(classNameSlashes, pto, decompilerSettings);
    // return pto.toString();
  }

  // use Misc.classNameFromByteCode
  // /**
  // * get the slashified form of the fully qualified class name, (minus the trailing .class)
  // * @param b the compiled form of the class
  // * @return fully qualified class name with slashes
  // */
  // public String extractClassNameSlashes(byte[] b) {
  // if (b[10] == 7 && b[13] == 1) { // a well known compiled form
  // int length = b[14] * 16 + b[15];
  // try {
  // String s = new String(b, 16, length, "UTF-8");
  // if (s.endsWith(".class")) {
  // s = s.substring(0, s.length() - ".class".length());
  // }
  // return s;
  // } catch (UnsupportedEncodingException e) {
  // throw new RuntimeException(e);
  // }
  // } else {
  // // class name not immediately findable in the compiled code, so decompile it (without knowing
  // the class name)
  // // this path is slow - has 2 decompiles per class (one just to find the package/class name).
  // PlainTextOutput pto = new PlainTextOutput();
  // setDecompilerSettingsForByteArray("", b);
  // // decompilerSettings.setTypeLoader(getClasspathTypeLoader());
  // Decompiler.decompile("", pto, decompilerSettings);
  // String s = pto.toString();
  //
  // String packageName = "";
  // String className = "";
  // int ip = s.indexOf("package ");
  // if (ip >= 0) {
  // ip = ip + "package ".length(); // start of package name;
  // int ipe = s.indexOf(";", ip);
  // packageName = s.substring(ip, ipe).replace('.', '/') + "/";
  // }
  //
  // Matcher m = cie_name.matcher(s);
  // boolean ok = m.find();
  // className = ok
  // ? m.group(2)
  // : "";
  //
  // String classNameSlashes = packageName + className;
  //// if (classNameSlashes.equals("")) {
  //// throw new RuntimeException("Couldn't find class name");
  //// }
  // return classNameSlashes;
  // }
  // }

  public boolean decompileToOutputDirectory(String className) {
    ByteArrayOutputStream baos = decompile(className);
    return writeIfOk(baos, className);
  }

  // public boolean decompileToOutputDirectory(String className, byte[] byteArray) {
  // ByteArrayOutputStream baos = decompile(className, byteArray);
  // return writeIfOk(baos, className);
  // }

  public boolean writeIfOk(ByteArrayOutputStream baos, String className) {
    if (!decompiledFailed(baos)) {
      Misc.toFile(baos, new File(outputDirectory, className));
      return true;
    }
    return false;
  }

  public boolean decompiledFailed(ByteArrayOutputStream baos) {
    return (baos.size() == errorMsg.length && Arrays.equals(errorMsg, baos.toByteArray()));
  }

  /**
   * A special type loader that substitutes the byteArray for the given class name
   * 
   * @param classNameSlashes
   *          the name to look for to substitute
   * @param byteArray
   *          the value to substitute
   */
  private void setDecompilerSettingsForByteArray(String classNameSlashes, byte[] byteArray) {
    ITypeLoader tl = new ITypeLoader() {

      @Override
      public boolean tryLoadType(String internalName, Buffer buffer) {
        if (classNameSlashes.equals(internalName)) {
          int length = byteArray.length;
          buffer.reset(length);
          System.arraycopy(byteArray, 0, buffer.array(), 0, length);
          return true;
        } else {
          return false;
        }
      }
    };
    ITypeLoader tc = new CompositeTypeLoader(tl, getClasspathTypeLoader(), new InputTypeLoader());
    decompilerSettings.setTypeLoader(tc);
  }

  private void setDecompilerSettingsForClassLoader() {
    ITypeLoader tc = new CompositeTypeLoader(getClasspathTypeLoader(), new InputTypeLoader());
    decompilerSettings.setTypeLoader(tc);
  }

  private ITypeLoader getClasspathTypeLoader() {
    return new ITypeLoader() {

      @Override
      public boolean tryLoadType(String internalName, Buffer buffer) {

        // read the class as a resource, and put into temporary byte array output stream
        // because we need to know the length
        // System.out.println("debug trying to load " + internalName);
        internalName = internalName.replace('.', '/') + ".class";
        InputStream stream = classLoader.getResourceAsStream(internalName);
        if (stream == null) {
          // System.out.println("debug failed to load " + internalName);
          return false;
        }
        ByteArrayOutputStream baos = new ByteArrayOutputStream(1024 * 16);
        byte[] b = new byte[1024 * 16];
        int numberRead;
        try {
          while (0 <= (numberRead = stream.read(b))) {
            baos.write(b, 0, numberRead);
          }
        } catch (IOException e) {
          throw new RuntimeException(e);
        }

        // Copy result (based on length) into output buffer spot
        int length = baos.size();
        b = baos.toByteArray();
        buffer.reset(length);
        System.arraycopy(b, 0, buffer.array(), 0, length);
        // System.out.println("debug OK loading " + internalName);
        return true;
      }
    };
  }
}
