package org.apache.lucene.index;

/*
 * 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.
 */

import java.io.EOFException;
import java.io.IOException;
import java.util.Arrays;
import java.util.Collections;

import org.apache.lucene.analysis.MockAnalyzer;
import org.apache.lucene.store.BaseDirectoryWrapper;
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.IOContext;
import org.apache.lucene.store.IndexInput;
import org.apache.lucene.store.IndexOutput;
import org.apache.lucene.store.MockDirectoryWrapper;
import org.apache.lucene.util.LineFileDocs;
import org.apache.lucene.util.LuceneTestCase;
import org.apache.lucene.util.TestUtil;

/**
 * Test that a plain default detects index file truncation early (on opening a reader).
 */
public class TestAllFilesDetectTruncation extends LuceneTestCase {
  public void test() throws Exception {
    Directory dir = newDirectory();

    if (dir instanceof MockDirectoryWrapper) {
      // otherwise we can have unref'd files left in the index that won't be visited when opening a reader and lead to scary looking false failures:
      ((MockDirectoryWrapper) dir).setEnableVirusScanner(false);
    }

    IndexWriterConfig conf = newIndexWriterConfig(new MockAnalyzer(random()));
    conf.setCodec(TestUtil.getDefaultCodec());

    // Disable CFS 80% of the time so we can truncate individual files, but the other 20% of the time we test truncation of .cfs/.cfe too:
    if (random().nextInt(5) != 1) {
      conf.setUseCompoundFile(false);
      conf.getMergePolicy().setNoCFSRatio(0.0);
    }

    RandomIndexWriter riw = new RandomIndexWriter(random(), dir, conf);
    // Use LineFileDocs so we (hopefully) get most Lucene features
    // tested, e.g. IntPoint was recently added to it:
    LineFileDocs docs = new LineFileDocs(random());
    for (int i = 0; i < 100; i++) {
      riw.addDocument(docs.nextDoc());
      if (random().nextInt(7) == 0) {
        riw.commit();
      }
      if (random().nextInt(20) == 0) {
        riw.deleteDocuments(new Term("docid", Integer.toString(i)));
      }
      if (random().nextInt(15) == 0) {
        riw.updateNumericDocValue(new Term("docid", Integer.toString(i)), "docid_intDV", Long.valueOf(i));
      }
    }
    if (TEST_NIGHTLY == false) {
      riw.forceMerge(1);
    }
    riw.close();
    checkTruncation(dir);
    dir.close();
  }
  
  private void checkTruncation(Directory dir) throws IOException {
    for(String name : dir.listAll()) {
      truncateOneFile(dir, name);
    }
  }
  
  private void truncateOneFile(Directory dir, String victim) throws IOException {
    try (BaseDirectoryWrapper dirCopy = newDirectory()) {
      dirCopy.setCheckIndexOnClose(false);
      long victimLength = dir.fileLength(victim);
      int lostBytes = TestUtil.nextInt(random(), 1, (int) Math.min(100, victimLength));
      assert victimLength > 0;

      if (VERBOSE) {
        System.out.println("TEST: now truncate file " + victim + " by removing " + lostBytes + " of " + victimLength + " bytes");
      }

      for(String name : dir.listAll()) {
        if (name.equals(victim) == false) {
          dirCopy.copyFrom(dir, name, name, IOContext.DEFAULT);
        } else {
          try(IndexOutput out = dirCopy.createOutput(name, IOContext.DEFAULT);
              IndexInput in = dir.openInput(name, IOContext.DEFAULT)) {
              out.copyBytes(in, victimLength - lostBytes);
            }
        }
        dirCopy.sync(Collections.singleton(name));
      }

      try {
        // NOTE: we .close so that if the test fails (truncation not detected) we don't also get all these confusing errors about open files:
        DirectoryReader.open(dirCopy).close();
        fail("truncation not detected after removing " + lostBytes + " bytes out of " + victimLength + " for file " + victim);
      } catch (CorruptIndexException | EOFException e) {
        // expected
      }

      // CheckIndex should also fail:
      try {
        TestUtil.checkIndex(dirCopy, true, true);
        fail("truncation not detected after removing " + lostBytes + " bytes out of " + victimLength + " for file " + victim);
      } catch (CorruptIndexException | EOFException e) {
        // expected
      }
    }
  }
}