/*
    * junixsocket
    *
    * Copyright 2009-2026 Christian Kohlschütter
    *
    * Licensed 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.newsclub.net.unix;
  
  import java.io.IOException;
  import java.nio.charset.StandardCharsets;
  import java.nio.file.FileAlreadyExistsException;
  import java.nio.file.Files;
  import java.nio.file.Path;
  import java.nio.file.Paths;
  import java.util.Objects;
  import java.util.Random;
  
  import com.kohlschutter.annotations.compiletime.SuppressFBWarnings;
  
  abstract class TempFileUtil {
    static final TempFileUtil INSTANCE = newInstance();
  
    private TempFileUtil() {
    }
  
    private static TempFileUtil newInstance() {
      if ("Astral".equals(System.getProperty("os.name", ""))) {
        return new MaxLengthInstance(14);
      }
      return new StandardInstance();
    }
  
    public static TempFileUtil getInstance() {
      return INSTANCE;
    }
  
    public abstract Path newPathForUnixDomainSocket(boolean delete) throws IOException;
  
    private static final class StandardInstance extends TempFileUtil {
      @Override
      public Path newPathForUnixDomainSocket(boolean delete) throws IOException {
        Path p = Files.createTempFile("jux", ".sock");
        if (!Files.deleteIfExists(p) && Files.exists(p)) {
          throw new IOException("Could not delete temporary file that we just created: " + p);
        }
        return p;
      }
    }
  
    @SuppressFBWarnings("PREDICTABLE_RANDOM")
    private static final class MaxLengthInstance extends TempFileUtil {
      private final int maxLength;
      private final Random random = new Random();
      private final byte[] bytesPrefix = "/tmp/".getBytes(StandardCharsets.US_ASCII);
      private final byte[] bytesSuffix = ".j".getBytes(StandardCharsets.US_ASCII);
      private final byte[] validCharacters = {
          'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', //
          'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', //
          'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', //
          'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', //
          '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '0', //
          '_', '-', //
      };
  
      public MaxLengthInstance(int maxLength) {
        super();
        this.maxLength = maxLength;
      }
  
      @Override
      public Path newPathForUnixDomainSocket(boolean delete) throws IOException {
        Path p = null;
  
        while (!Thread.interrupted()) {
          p = randomPath();
          if (Files.exists(p)) {
            continue;
          }
          try {
            Files.createFile(p);
            break;
          } catch (FileAlreadyExistsException e) {
            continue;
          }
        }
        Objects.requireNonNull(p);
        if (delete && !Files.deleteIfExists(p) && Files.exists(p)) {
          throw new IOException("Could not delete temporary file that we just created: " + p);
       }
       return p;
     }
 
     @SuppressFBWarnings("PATH_TRAVERSAL_IN")
     private Path randomPath() {
       byte[] bytes = new byte[maxLength];
       random.nextBytes(bytes);
       System.arraycopy(bytesPrefix, 0, bytes, 0, bytesPrefix.length);
       System.arraycopy(bytesSuffix, 0, bytes, bytes.length - bytesSuffix.length,
           bytesSuffix.length);
 
       for (int i = bytesPrefix.length, n = bytes.length - bytesSuffix.length; i < n; i++) {
         bytes[i] = validCharacters[Math.abs(bytes[i]) % validCharacters.length];
       }
       return Paths.get(new String(bytes, StandardCharsets.US_ASCII));
     }
   }
 }