/**
 * 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.hadoop.hdfs;

import java.io.File;
import java.io.FileFilter;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.Callable;
import java.util.concurrent.ThreadLocalRandom;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicReference;

import org.apache.commons.io.FileUtils;
import org.junit.jupiter.api.Timeout;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FSDataOutputStream;
import org.apache.hadoop.fs.FileStatus;
import org.apache.hadoop.fs.FileUtil;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.hdfs.client.HdfsClientConfigKeys.BlockWrite.ReplaceDatanodeOnFailure;
import org.apache.hadoop.hdfs.server.namenode.NameNode;
import org.apache.hadoop.hdfs.server.namenode.TestFileTruncate;
import org.apache.hadoop.test.GenericTestUtils;
import org.junit.jupiter.api.AfterAll;
import org.junit.jupiter.api.BeforeAll;
import org.junit.jupiter.api.Test;

import org.apache.hadoop.util.Preconditions;
import org.slf4j.event.Level;

import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertFalse;
import static org.junit.jupiter.api.Assertions.assertTrue;

/**
 * Test randomly mixing append, snapshot and truncate operations.
 * Use local file system to simulate the each operation and verify
 * the correctness.
 */
public class TestAppendSnapshotTruncate {
  static {
    GenericTestUtils.setLogLevel(NameNode.stateChangeLog, Level.TRACE);
  }
  private static final Logger LOG =
      LoggerFactory.getLogger(TestAppendSnapshotTruncate.class);
  private static final int BLOCK_SIZE = 1024;
  private static final int DATANODE_NUM = 4;
  private static final short REPLICATION = 3;
  private static final int FILE_WORKER_NUM = 10;
  private static final long TEST_TIME_SECOND = 20;
  private static final long TEST_TIMEOUT_SECOND = TEST_TIME_SECOND + 60;

  static final int SHORT_HEARTBEAT = 1;
  static final String[] EMPTY_STRINGS = {};

  static Configuration conf;
  static MiniDFSCluster cluster;
  static DistributedFileSystem dfs;

  @BeforeAll
  public static void startUp() throws IOException {
    conf = new HdfsConfiguration();
    conf.setLong(DFSConfigKeys.DFS_NAMENODE_MIN_BLOCK_SIZE_KEY, BLOCK_SIZE);
    conf.setInt(DFSConfigKeys.DFS_BYTES_PER_CHECKSUM_KEY, BLOCK_SIZE);
    conf.setInt(DFSConfigKeys.DFS_HEARTBEAT_INTERVAL_KEY, SHORT_HEARTBEAT);
    conf.setLong(
        DFSConfigKeys.DFS_NAMENODE_RECONSTRUCTION_PENDING_TIMEOUT_SEC_KEY, 1);
    conf.setBoolean(ReplaceDatanodeOnFailure.BEST_EFFORT_KEY, true);
    cluster = new MiniDFSCluster.Builder(conf)
        .format(true)
        .numDataNodes(DATANODE_NUM)
        .waitSafeMode(true)
        .build();
    dfs = cluster.getFileSystem();
  }

  @AfterAll
  public static void tearDown() throws IOException {
    if(dfs != null) {
      dfs.close();
    }
    if(cluster != null) {
      cluster.shutdown();
    }
  }


  /** Test randomly mixing append, snapshot and truncate operations. */
  @Test
  @Timeout(TEST_TIMEOUT_SECOND)
  public void testAST() throws Exception {
    final String dirPathString = "/dir";
    final Path dir = new Path(dirPathString);
    dfs.mkdirs(dir);
    dfs.allowSnapshot(dir);

    final File localDir = GenericTestUtils.getTestDir(dirPathString);
    if (localDir.exists()) {
      FileUtil.fullyDelete(localDir);
    }
    localDir.mkdirs();

    final DirWorker w = new DirWorker(dir, localDir, FILE_WORKER_NUM);
    w.startAllFiles();
    w.start();
    Worker.sleep(TEST_TIME_SECOND * 1000);
    w.stop();
    w.stopAllFiles();
    w.checkEverything();
  }

  static final FileFilter FILE_ONLY = new FileFilter() {
    @Override
    public boolean accept(File f) {
      return f.isFile();
    }
  };

  static class DirWorker extends Worker {
    final Path dir;
    final File localDir;
    
    final FileWorker[] files;

    private Map<String, Path> snapshotPaths = new HashMap<String, Path>();
    private AtomicInteger snapshotCount = new AtomicInteger();

    DirWorker(Path dir, File localDir, int nFiles) throws IOException {
      super(dir.getName());
      this.dir = dir;
      this.localDir = localDir;

      this.files = new FileWorker[nFiles];
      for(int i = 0; i < files.length; i++) {
        files[i] = new FileWorker(dir, localDir, String.format("file%02d", i));
      }
    }

    static String getSnapshotName(int n) {
      return String.format("s%02d", n);
    }

    String createSnapshot(String snapshot) throws IOException {
      final StringBuilder b = new StringBuilder("createSnapshot: ")
          .append(snapshot).append(" for ").append(dir);

      {
        //copy all local files to a sub dir to simulate snapshot. 
        final File subDir = new File(localDir, snapshot);
        assertFalse(subDir.exists());
        subDir.mkdir();

        for(File f : localDir.listFiles(FILE_ONLY)) {
          FileUtils.copyFile(f, new File(subDir, f.getName()));
        }
      }
      
      final Path p = dfs.createSnapshot(dir, snapshot);
      snapshotPaths.put(snapshot, p);
      return b.toString();
    }

    String checkSnapshot(String snapshot) throws IOException {
      final StringBuilder b = new StringBuilder("checkSnapshot: ")
          .append(snapshot);

      final File subDir = new File(localDir, snapshot);
      assertTrue(subDir.exists());
      
      final File[] localFiles = subDir.listFiles(FILE_ONLY);
      final Path p = snapshotPaths.get(snapshot);
      final FileStatus[] statuses = dfs.listStatus(p);
      assertEquals(localFiles.length, statuses.length);
      b.append(p).append(" vs ").append(subDir).append(", ")
       .append(statuses.length).append(" entries");
      
      Arrays.sort(localFiles);
      Arrays.sort(statuses);
      for(int i = 0; i < statuses.length; i++) {
        FileWorker.checkFullFile(statuses[i].getPath(), localFiles[i]);
      }
      return b.toString();
    }

    String deleteSnapshot(String snapshot) throws IOException {
      final StringBuilder b = new StringBuilder("deleteSnapshot: ")
          .append(snapshot).append(" from ").append(dir);
      FileUtil.fullyDelete(new File(localDir, snapshot));
      dfs.deleteSnapshot(dir, snapshot);
      snapshotPaths.remove(snapshot);
      return b.toString();
    }

    
    @Override
    public String call() throws Exception {
      final int op = ThreadLocalRandom.current().nextInt(6);
      if (op <= 1) {
        pauseAllFiles();
        try {
          final String snapshot = getSnapshotName(snapshotCount.getAndIncrement());
          return createSnapshot(snapshot);
        } finally {
          startAllFiles();
        }
      } else if (op <= 3) {
        final String[] keys = snapshotPaths.keySet().toArray(EMPTY_STRINGS);
        if (keys.length == 0) {
          return "NO-OP";
        }
        final String snapshot = keys[ThreadLocalRandom.current()
            .nextInt(keys.length)];
        final String s = checkSnapshot(snapshot);
        
        if (op == 2) {
          return deleteSnapshot(snapshot);
        }
        return s;
      } else {
        return "NO-OP";
      }
    }

    void pauseAllFiles() {
      for(FileWorker f : files) { 
        f.pause();
      }

      for(int i = 0; i < files.length; ) {
        sleep(100);
        for(; i < files.length && files[i].isPaused(); i++);
      }
    }
    
    void startAllFiles() {
      for(FileWorker f : files) { 
        f.start();
      }
    }
    
    void stopAllFiles() throws InterruptedException {
      for(FileWorker f : files) { 
        f.stop();
      }
    }

    void checkEverything() throws IOException {
      LOG.info("checkEverything");
      for(FileWorker f : files) { 
        f.checkFullFile();
        f.checkErrorState();
      }
      for(String snapshot : snapshotPaths.keySet()) {
        checkSnapshot(snapshot);
      }
      checkErrorState();
    }
  }

  static class FileWorker extends Worker {
    final Path file;
    final File localFile;

    FileWorker(Path dir, File localDir, String filename) throws IOException {
      super(filename);
      this.file = new Path(dir, filename);
      this.localFile = new File(localDir, filename);

      localFile.createNewFile();
      dfs.create(file, false, 4096, REPLICATION, BLOCK_SIZE).close();
    }

    @Override
    public String call() throws IOException {
      final int op = ThreadLocalRandom.current().nextInt(9);
      if (op == 0) {
        return checkFullFile();
      } else {
        final int nBlocks = ThreadLocalRandom.current().nextInt(4) + 1;
        final int lastBlockSize = ThreadLocalRandom.current()
            .nextInt(BLOCK_SIZE) + 1;
        final int nBytes = nBlocks*BLOCK_SIZE + lastBlockSize;

        if (op <= 4) {
          return append(nBytes);
        } else if (op <= 6) {
          return truncateArbitrarily(nBytes);
        } else {
          return truncateToBlockBoundary(nBlocks);
        }
      }
    }

    String append(int n) throws IOException {
      final StringBuilder b = new StringBuilder("append ")
          .append(n).append(" bytes to ").append(file.getName());

      final byte[] bytes = new byte[n];
      ThreadLocalRandom.current().nextBytes(bytes);

      { // write to local file
        final FileOutputStream out = new FileOutputStream(localFile, true);
        out.write(bytes, 0, bytes.length);
        out.close();
      }

      {
        final FSDataOutputStream out = dfs.append(file);
        out.write(bytes, 0, bytes.length);
        out.close();
      }
      return b.toString();
    }
    
    String truncateArbitrarily(int nBytes) throws IOException {
      Preconditions.checkArgument(nBytes > 0);
      final int length = checkLength();
      final StringBuilder b = new StringBuilder("truncateArbitrarily: ")
          .append(nBytes).append(" bytes from ").append(file.getName())
          .append(", length=" + length);

      truncate(length > nBytes? length - nBytes: 0, b);
      return b.toString();
    }

    String truncateToBlockBoundary(int nBlocks) throws IOException {
      Preconditions.checkArgument(nBlocks > 0);
      final int length = checkLength();
      final StringBuilder b = new StringBuilder("truncateToBlockBoundary: ")
          .append(nBlocks).append(" blocks from ").append(file.getName())
          .append(", length=" + length);
      final int n =  (nBlocks - 1)*BLOCK_SIZE + (length%BLOCK_SIZE);
      Preconditions.checkState(truncate(length > n? length - n: 0, b), b);
      return b.toString();
    }

    private boolean truncate(long newLength, StringBuilder b) throws IOException {
      final RandomAccessFile raf = new RandomAccessFile(localFile, "rw");
      raf.setLength(newLength);
      raf.close();

      final boolean isReady = dfs.truncate(file, newLength);
      b.append(", newLength=").append(newLength)
       .append(", isReady=").append(isReady);
      if (!isReady) {
        TestFileTruncate.checkBlockRecovery(file, dfs, 100, 300L);
      }
      return isReady;
    }
    
    int checkLength() throws IOException {
      return checkLength(file, localFile);
    }

    static int checkLength(Path file, File localFile) throws IOException {
      final long length = dfs.getFileStatus(file).getLen();
      assertEquals(localFile.length(), length);
      assertTrue(length <= Integer.MAX_VALUE);
      return (int)length;
    }
    
    String checkFullFile() throws IOException {
      return checkFullFile(file, localFile);
    }

    static String checkFullFile(Path file, File localFile) throws IOException {
      final StringBuilder b = new StringBuilder("checkFullFile: ")
          .append(file.getName()).append(" vs ").append(localFile);
      final byte[] bytes = new byte[checkLength(file, localFile)];
      b.append(", length=").append(bytes.length);
      
      final FileInputStream in = new FileInputStream(localFile); 
      for(int n = 0; n < bytes.length; ) {
        n += in.read(bytes, n, bytes.length - n);
      }
      in.close();
      
      AppendTestUtil.checkFullFile(dfs, file, bytes.length, bytes,
          "File content mismatch: " + b, false);
      return b.toString();
    }
  }
  
  static abstract class Worker implements Callable<String> {
    enum State {
      IDLE(false), RUNNING(false), STOPPED(true), ERROR(true);
      
      final boolean isTerminated;

      State(boolean isTerminated) {
        this.isTerminated = isTerminated;
      }
    };

    final String name;
    final AtomicReference<State> state = new AtomicReference<State>(State.IDLE);
    final AtomicBoolean isCalling = new AtomicBoolean();
    final AtomicReference<Thread> thread = new AtomicReference<Thread>();

    private Throwable thrown = null;

    Worker(String name) {
      this.name = name;
    }

    State checkErrorState() {
      final State s = state.get();
      if (s == State.ERROR) {
        throw new IllegalStateException(name + " has " + s, thrown);
      }
      return s;
    }

    void setErrorState(Throwable t) {
      checkErrorState();

      LOG.error("Worker " + name + " failed.", t);
      state.set(State.ERROR);
      thrown = t;
    }

    void start() {
      Preconditions.checkState(state.compareAndSet(State.IDLE, State.RUNNING));
      
      if (thread.get() == null) {
        final Thread t = new Thread(null, new Runnable() {
          @Override
          public void run() {
            for(State s; !(s = checkErrorState()).isTerminated;) {
              if (s == State.RUNNING) {
                isCalling.set(true);
                try {
                  LOG.info(call());
                } catch(Throwable t) {
                  setErrorState(t);
                  return;
                }
                isCalling.set(false);
              }
              sleep(ThreadLocalRandom.current().nextInt(100) + 50);
            }
          }
        }, name);
        Preconditions.checkState(thread.compareAndSet(null, t));
        t.start();
      }
    }

    boolean isPaused() {
      final State s = checkErrorState();
      if (s == State.STOPPED) {
        throw new IllegalStateException(name + " is " + s);
      }
      return s == State.IDLE && !isCalling.get();
    }

    void pause() {
      checkErrorState();
      Preconditions.checkState(state.compareAndSet(State.RUNNING, State.IDLE),
          "%s: state=%s != %s", name, state.get(), State.RUNNING);
    }

    void stop() throws InterruptedException {
      checkErrorState();

      state.set(State.STOPPED);
      thread.get().join();
    }

    static void sleep(final long sleepTimeMs) {
      try {
        Thread.sleep(sleepTimeMs);
      } catch (InterruptedException e) {
        throw new RuntimeException(e);
      }
    }
  }
}
