/*
    * 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
    *
   *   https://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.bcel;
  
  import org.apache.bcel.generic.GOTO;
  import org.apache.bcel.generic.ILOAD;
  import org.apache.bcel.generic.InstructionHandle;
  import org.apache.bcel.generic.InstructionList;
  import org.apache.bcel.generic.NOP;
  import org.junit.jupiter.api.Test;
  
  /**
   * Test for https://issues.apache.org/jira/browse/BCEL-267 "Race conditions on static fields in BranchHandle and
   * InstructionHandle".
   */
  class HandleTest {
  
      static Throwable exception;
      static final int MAXI = 100;
      static final int MAXJ = 1000;
  
      /**
       * Asserts that branch handles can be added an instruction list, without corrupting the list.
       */
      static void branchHandles() {
          for (int i = 0; i < MAXI; i++) {
              final InstructionList list = new InstructionList();
              final InstructionHandle start = list.append(new NOP());
              try {
                  for (int j = 0; j < MAXJ; j++) {
                      list.append(new GOTO(start));
                  }
                  final InstructionHandle[] instructionHandles = list.getInstructionHandles();
                  for (int j = 0; j < instructionHandles.length; j++) {
                      final InstructionHandle handle = instructionHandles[j];
                      if (j > 0) {
                          checkLinkage(handle, j);
                          if (start != ((GOTO) handle.getInstruction()).getTarget()) {
                              final AssertionError error = new AssertionError("unexpected instruction at index " + j);
                              exception = error;
                              throw error;
                          }
                      }
                  }
                  if (exception != null) {
                      return;
                  }
              } catch (final NullPointerException e) {
                  System.out.println("NPE at i=" + i);
                  exception = e;
                  throw e;
              }
              list.dispose(); // this initializes caching of unused instruction handles
          }
      }
  
      /**
       * Assert that opposite next/prev pairs always match.
       */
      static void checkLinkage(final InstructionHandle ih, final int index) {
          final InstructionHandle prev = ih.getPrev();
          final InstructionHandle next = ih.getNext();
          if (prev != null && prev.getNext() != ih || next != null && next.getPrev() != ih) {
              final AssertionError error = new AssertionError("corrupt instruction list at index " + index);
              exception = error;
              throw error;
          }
      }
  
      /**
       * Asserts that instruction handles can be added an instruction list, without corrupting the list.
       */
      static void handles() {
          for (int i = 0; i < MAXI; i++) {
              final InstructionList list = new InstructionList();
              try {
                  for (int j = 0; j < MAXJ; j++) {
                      list.append(new ILOAD(j));
                  }
                  final InstructionHandle[] instructionHandles = list.getInstructionHandles();
                  for (int j = 0; j < instructionHandles.length; j++) {
                      final InstructionHandle handle = instructionHandles[j];
                     checkLinkage(handle, j);
                     if (j != ((ILOAD) handle.getInstruction()).getIndex()) {
                         final AssertionError error = new AssertionError("unexpected instruction at index " + j);
                         exception = error;
                         throw error;
                     }
                 }
                 if (exception != null) {
                     return;
                 }
             } catch (final NullPointerException e) {
                 System.out.println("NPE at i=" + i);
                 exception = e;
                 throw e;
             }
             list.dispose(); // this initializes caching of unused instruction handles
         }
     }
 
     /**
      * Concurrently run the given runnable in two threads.
      */
     private void perform(final Runnable r) throws Throwable {
         exception = null;
         final Thread t1 = new Thread(r);
         final Thread t2 = new Thread(r);
         t1.start();
         t2.start();
         t1.join();
         t2.join();
         if (exception != null) {
             throw exception;
         }
     }
 
     /**
      * Assert that two independent instruction lists can be modified concurrently. Here: inserting branch instructions.
      */
     @Test
     void testBranchHandle() throws Throwable {
         perform(HandleTest::branchHandles);
     }
 
     /**
      * Assert that two independent instruction lists can be modified concurrently. Here: inserting regular instructions.
      */
     @Test
     void testInstructionHandle() throws Throwable {
         perform(HandleTest::handles);
     }
 }