/*
 * Copyright 2023 Google LLC
 *
 * 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 com.google.cloud.storage;

import com.google.api.core.ApiFuture;
import com.google.common.base.Preconditions;
import java.io.IOException;
import java.nio.channels.WritableByteChannel;

final class BlobWriteSessions {

  private BlobWriteSessions() {}

  static BlobWriteSession of(WritableByteChannelSession<?, BlobInfo> s) {
    return new WritableByteChannelSessionAdapter(s);
  }

  static final class WritableByteChannelSessionAdapter implements BlobWriteSession {
    private final WritableByteChannelSession<?, BlobInfo> delegate;
    private boolean open;

    private WritableByteChannelSessionAdapter(WritableByteChannelSession<?, BlobInfo> delegate) {
      this.delegate = delegate;
      open = false;
    }

    @Override
    public WritableByteChannel open() throws IOException {
      synchronized (this) {
        Preconditions.checkState(!open, "already open");
        open = true;
        return delegate.open();
      }
    }

    @Override
    public ApiFuture<BlobInfo> getResult() {
      return delegate.getResult();
    }
  }
}
