content: /*
   * 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.beam.sdk.io;
  
  import java.io.IOException;
  import java.io.OutputStreamWriter;
  import java.nio.channels.Channels;
  import java.nio.channels.WritableByteChannel;
  import java.nio.charset.StandardCharsets;
  import org.apache.beam.sdk.io.fs.ResourceId;
  import org.apache.beam.sdk.options.ValueProvider;
  import org.apache.beam.sdk.util.MimeTypes;
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  /**
   * Implementation detail of {@link TextIO.Write}.
   *
   * <p>A {@link FileBasedSink} for text files. Produces text files with the newline separator {@code
   * '\n'} represented in {@code UTF-8} format as the record separator. Each record (including the
   * last) is terminated.
   */
  @SuppressWarnings({
    "nullness", // TODO(https://github.com/apache/beam/issues/20497)
    "rawtypes"
  })
  class TextSink<UserT, DestinationT> extends FileBasedSink<UserT, DestinationT, String> {
    private final @Nullable String header;
    private final @Nullable String footer;
    private final char[] delimiter;
  
    TextSink(
        ValueProvider<ResourceId> baseOutputFilename,
        DynamicDestinations<UserT, DestinationT, String> dynamicDestinations,
        char[] delimiter,
        @Nullable String header,
        @Nullable String footer,
        WritableByteChannelFactory writableByteChannelFactory) {
      super(baseOutputFilename, dynamicDestinations, writableByteChannelFactory);
      this.header = header;
      this.footer = footer;
      this.delimiter = delimiter;
    }
  
    @Override
    public WriteOperation<DestinationT, String> createWriteOperation() {
      return new TextWriteOperation<>(this, delimiter, header, footer);
    }
  
    /** A {@link WriteOperation WriteOperation} for text files. */
    private static class TextWriteOperation<DestinationT>
        extends WriteOperation<DestinationT, String> {
      private final @Nullable String header;
      private final @Nullable String footer;
      private final char[] delimiter;
  
      private TextWriteOperation(
          TextSink sink, char[] delimiter, @Nullable String header, @Nullable String footer) {
        super(sink);
        this.header = header;
        this.footer = footer;
        this.delimiter = delimiter;
      }
  
      @Override
      public Writer<DestinationT, String> createWriter() throws Exception {
        return new TextWriter<>(this, delimiter, header, footer);
      }
    }
  
    /** A {@link Writer Writer} for text files. */
    private static class TextWriter<DestinationT> extends Writer<DestinationT, String> {
      private final @Nullable String header;
      private final @Nullable String footer;
      private final char[] delimiter;
  
      // Initialized in prepareWrite
      private @Nullable OutputStreamWriter out;
  
      public TextWriter(
          WriteOperation<DestinationT, String> writeOperation,
          char[] delimiter,
          @Nullable String header,
          @Nullable String footer) {
        super(writeOperation, MimeTypes.TEXT);
        this.delimiter = delimiter;
        this.header = header;
        this.footer = footer;
      }
  
      /** Writes {@code value} followed by a newline character if {@code value} is not null. */
      private void writeIfNotNull(@Nullable String value) throws IOException {
        if (value != null) {
          writeLine(value);
        }
      }
  
      /** Writes {@code value} followed by the delimiter byte sequence. */
      private void writeLine(String value) throws IOException {
        out.write(value);
        out.write(delimiter);
      }
  
      @Override
      protected void prepareWrite(WritableByteChannel channel) throws Exception {
        out = new OutputStreamWriter(Channels.newOutputStream(channel), StandardCharsets.UTF_8);
      }
  
      @Override
      protected void writeHeader() throws Exception {
        writeIfNotNull(header);
      }
  
      @Override
      public void write(String value) throws Exception {
        writeLine(value);
      }
  
      @Override
      protected void writeFooter() throws Exception {
        writeIfNotNull(footer);
      }
  
      @Override
      protected void finishWrite() throws Exception {
        out.flush();
      }
    }
  }
  