/*
    * 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.eclipse.aether.spi.io;
  
  import java.io.BufferedInputStream;
  import java.io.BufferedOutputStream;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.InterruptedIOException;
  import java.io.OutputStream;
  import java.nio.ByteBuffer;
  import java.nio.charset.StandardCharsets;
  import java.nio.file.AccessDeniedException;
  import java.nio.file.AtomicMoveNotSupportedException;
  import java.nio.file.FileSystemException;
  import java.nio.file.Files;
  import java.nio.file.Path;
  import java.nio.file.StandardCopyOption;
  import java.nio.file.attribute.FileTime;
  import java.util.concurrent.ThreadLocalRandom;
  import java.util.concurrent.atomic.AtomicBoolean;
  
  import static java.util.Objects.requireNonNull;
  
  /**
   * Utility class serving as base of {@link PathProcessor} implementations. This class can be extended or replaced
   * (as component) when needed. Also, this class is published in Resolver implementation for path processor interface.
   *
   * @since 2.0.13
   */
  public class PathProcessorSupport implements PathProcessor {
      /**
       * Logic borrowed from Commons-Lang3: we really need only this, to decide do we NIO2 file ops or not.
       * On Windows the final move needs retry/staging logic, see {@link #retryingMove(Path, Path, StandardCopyOption[])}.
       */
      protected static final boolean IS_WINDOWS =
              System.getProperty("os.name", "unknown").startsWith("Windows");
  
      /**
       * Escape hatch if atomic move is not desired on system we run on.
       */
      protected static final boolean ATOMIC_MOVE =
              Boolean.parseBoolean(System.getProperty(PathProcessor.class.getName() + "ATOMIC_MOVE", "true"));
  
      /**
       * The number of attempts for the final move on Windows, where the move target may be transiently locked by a
       * virus scanner, an indexer or a concurrent reader.
       */
      protected static final int WINDOWS_MOVE_ATTEMPTS =
              Math.max(1, Integer.getInteger(PathProcessor.class.getName() + "WINDOWS_MOVE_ATTEMPTS", 5));
  
      /**
       * The delay in milliseconds applied between the move attempts on Windows.
       */
      protected static final long WINDOWS_MOVE_RETRY_DELAY =
              Long.getLong(PathProcessor.class.getName() + "WINDOWS_MOVE_RETRY_DELAY", 50L);
  
      @Override
      public boolean setLastModified(Path path, long value) throws IOException {
          try {
              Files.setLastModifiedTime(path, FileTime.fromMillis(value));
              return true;
          } catch (FileSystemException e) {
              // MRESOLVER-536: Java uses generic FileSystemException for some weird cases,
              // but some subclasses like AccessDeniedEx should be re-thrown
              if (e instanceof AccessDeniedException) {
                  throw e;
              }
              return false;
          }
      }
  
      @Override
      public void write(Path target, String data) throws IOException {
          writeFile(target, p -> Files.write(p, data.getBytes(StandardCharsets.UTF_8)), false);
      }
  
      @Override
      public void write(Path target, InputStream source) throws IOException {
          writeFile(target, p -> Files.copy(source, p, StandardCopyOption.REPLACE_EXISTING), false);
      }
  
      @Override
     public void writeWithBackup(Path target, String data) throws IOException {
         writeFile(target, p -> Files.write(p, data.getBytes(StandardCharsets.UTF_8)), true);
     }
 
     @Override
     public void writeWithBackup(Path target, InputStream source) throws IOException {
         writeFile(target, p -> Files.copy(source, p, StandardCopyOption.REPLACE_EXISTING), true);
     }
 
     /**
      * A file writer, that accepts a {@link Path} to write some content to. Note: the file denoted by path may exist,
      * hence implementation have to ensure it is able to achieve its goal ("replace existing" option or equivalent
      * should be used).
      */
     @FunctionalInterface
     public interface FileWriter {
         void write(Path path) throws IOException;
     }
 
     /**
      * Utility method to write out file to disk in "atomic" manner, with optional backups (".bak") if needed. This
      * ensures that no other thread or process will be able to read not fully written files. Finally, this method
      * may create the needed parent directories, if the passed in target parents does not exist.
      *
      * @param target   that is the target file (must be an existing or non-existing file, the path must have parent)
      * @param writer   the writer that will accept a {@link Path} to write content to
      * @param doBackup if {@code true}, and target file is about to be overwritten, a ".bak" file with old contents will
      *                 be created/overwritten
      * @throws IOException if at any step IO problem occurs
      */
     public void writeFile(Path target, FileWriter writer, boolean doBackup) throws IOException {
         requireNonNull(target, "target is null");
         requireNonNull(writer, "writer is null");
         Path parent = requireNonNull(target.getParent(), "target must have parent");
 
         try (CollocatedTempFile tempFile = newTempFile(target)) {
             writer.write(tempFile.getPath());
             if (doBackup && Files.isRegularFile(target)) {
                 Files.copy(target, parent.resolve(target.getFileName() + ".bak"), StandardCopyOption.REPLACE_EXISTING);
             }
             tempFile.move();
         }
     }
 
     @Override
     public long copy(Path source, Path target, ProgressListener listener) throws IOException {
         try (InputStream in = new BufferedInputStream(Files.newInputStream(source));
                 CollocatedTempFile tempTarget = newTempFile(target);
                 OutputStream out = new BufferedOutputStream(Files.newOutputStream(tempTarget.getPath()))) {
             long result = copy(out, in, listener);
             tempTarget.move();
             return result;
         }
     }
 
     private long copy(OutputStream os, InputStream is, ProgressListener listener) throws IOException {
         long total = 0L;
         byte[] buffer = new byte[1024 * 32];
         while (true) {
             int bytes = is.read(buffer);
             if (bytes < 0) {
                 break;
             }
 
             os.write(buffer, 0, bytes);
 
             total += bytes;
 
             if (listener != null && bytes > 0) {
                 try {
                     listener.progressed(ByteBuffer.wrap(buffer, 0, bytes));
                 } catch (Exception e) {
                     // too bad
                 }
             }
         }
 
         return total;
     }
 
     @Override
     public void move(Path source, Path target) throws IOException {
         final StandardCopyOption[] copyOption = ATOMIC_MOVE
                 ? new StandardCopyOption[] {
                     StandardCopyOption.ATOMIC_MOVE,
                     StandardCopyOption.REPLACE_EXISTING,
                     StandardCopyOption.COPY_ATTRIBUTES
                 }
                 : new StandardCopyOption[] {StandardCopyOption.REPLACE_EXISTING, StandardCopyOption.COPY_ATTRIBUTES};
         if (IS_WINDOWS) {
             retryingMove(source, target, copyOption);
         } else {
             Files.move(source, target, copyOption);
         }
         Files.deleteIfExists(source);
     }
 
     // Temp files
 
     @Override
     public TempFile newTempFile() throws IOException {
         Path tempFile = Files.createTempFile("resolver", "tmp");
         return new TempFile() {
             @Override
             public Path getPath() {
                 return tempFile;
             }
 
             @Override
             public void close() throws IOException {
                 Files.deleteIfExists(tempFile);
             }
         };
     }
 
     @Override
     public CollocatedTempFile newTempFile(Path file) throws IOException {
         Path parent = requireNonNull(file.getParent(), "file must have parent");
         Files.createDirectories(parent);
         Path tempFile = parent.resolve(file.getFileName() + "."
                 + Long.toUnsignedString(ThreadLocalRandom.current().nextLong()) + ".tmp");
         return new CollocatedTempFile() {
             private final AtomicBoolean wantsMove = new AtomicBoolean(false);
             private final StandardCopyOption[] copyOption = ATOMIC_MOVE
                     ? new StandardCopyOption[] {StandardCopyOption.ATOMIC_MOVE, StandardCopyOption.REPLACE_EXISTING}
                     : new StandardCopyOption[] {StandardCopyOption.REPLACE_EXISTING};
 
             @Override
             public Path getPath() {
                 return tempFile;
             }
 
             @Override
             public void move() {
                 wantsMove.set(true);
             }
 
             @Override
             public void close() throws IOException {
                 if (wantsMove.get()) {
                     if (IS_WINDOWS) {
                         retryingMove(tempFile, file, copyOption);
                     } else {
                         Files.move(tempFile, file, copyOption);
                     }
                 }
                 Files.deleteIfExists(tempFile);
             }
         };
     }
 
     /**
      * Moves the source file to the target path without ever truncating the target in place: the content visible at
      * the target path is either the old file or the complete new file, never a partially written one.
      * <p>
      * Historically, on Windows the final move was implemented by opening the target path with a truncating stream
      * and copying the source into it ({@link #classicCopy(Path, Path)}). That left a window during which a
      * concurrent reader (for example a forked JVM resolving the same artifact) or an untimely process kill would
      * observe, or durably leave behind, a truncated file at the final path - after checksum validation has already
      * happened, so the torn content would from then on be trusted as verified. Instead, this method attempts the
      * rename a bounded number of times ({@link #WINDOWS_MOVE_ATTEMPTS}, file locking by virus scanners, indexers or
      * concurrent readers is transient on Windows), and if the file system refuses an atomic move (for example when
      * source and target are on different stores), the source is first staged into a collocated temporary file next
      * to the target and then renamed into place - the target path itself is never opened for writing.
      */
     protected void retryingMove(Path source, Path target, StandardCopyOption[] copyOptions) throws IOException {
         FileSystemException lastException = null;
         for (int attempt = 0; attempt < WINDOWS_MOVE_ATTEMPTS; attempt++) {
             try {
                 fileSystemMove(source, target, copyOptions);
                 return;
             } catch (AtomicMoveNotSupportedException e) {
                 lastException = e;
                 break; // retrying will not help; stage a collocated copy instead, see below
             } catch (FileSystemException e) {
                 // covers AccessDeniedException and sharing violations: transient on Windows
                 lastException = e;
                 try {
                     Thread.sleep(WINDOWS_MOVE_RETRY_DELAY);
                 } catch (InterruptedException ie) {
                     Thread.currentThread().interrupt();
                     InterruptedIOException interrupted =
                             new InterruptedIOException("Interrupted while moving " + source + " to " + target);
                     interrupted.initCause(ie);
                     interrupted.addSuppressed(e);
                     throw interrupted;
                 }
             }
         }
         if (lastException instanceof AtomicMoveNotSupportedException) {
             Path staged = target.resolveSibling(target.getFileName() + "."
                     + Long.toUnsignedString(ThreadLocalRandom.current().nextLong()) + ".tmp");
             try {
                 classicCopy(source, staged);
                 fileSystemMove(staged, target, copyOptions);
                 return;
             } finally {
                 Files.deleteIfExists(staged);
             }
         }
         throw lastException;
     }
 
     /**
      * Testable seam for {@link Files#move(Path, Path, java.nio.file.CopyOption...)}.
      */
     protected void fileSystemMove(Path source, Path target, StandardCopyOption... copyOptions) throws IOException {
         Files.move(source, target, copyOptions);
     }
 
     /**
      * Pre-NIO2 way to copy files. Important: this method must never be pointed at a "final" (published) path, as it
      * opens the target with truncation; callers stage into a temporary file and rename into place instead.
      */
     protected void classicCopy(Path source, Path target) throws IOException {
         ByteBuffer buffer = ByteBuffer.allocate(1024 * 32);
         byte[] array = buffer.array();
         try (InputStream is = Files.newInputStream(source);
                 OutputStream os = Files.newOutputStream(target)) {
             while (true) {
                 int bytes = is.read(array);
                 if (bytes < 0) {
                     break;
                 }
                 os.write(array, 0, bytes);
             }
         }
     }
 }