Copyright Microsoft Corporation
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.
/**
 * Copyright Microsoft Corporation
 *
 * 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.microsoft.azure.storage;

import com.microsoft.azure.storage.blob.SubStream;

import java.io.InputStream;
import java.util.Iterator;

public final class SubStreamGenerator implements Iterable<InputStream> {

    private final Object mutex = new Object();
    private final long blockSize;
    private final InputStream wrappedStream;
    private int currentBlock = 0;
    private long lastBlockSize;
    private int blocksPending;

    public SubStreamGenerator(InputStream wrappedStream, int totalBlocks, long blockSize) {
        this.wrappedStream = wrappedStream;
        this.blocksPending = totalBlocks;
        this.blockSize = blockSize;
        this.lastBlockSize = blockSize;
    }

    public void setLastBlockSize(long blockSize) {
        this.lastBlockSize = blockSize;
    }

    @Override
    public Iterator<InputStream> iterator() {
        return new SubStreamIterator();
    }

    private class SubStreamIterator implements Iterator<InputStream> {

        @Override
        public boolean hasNext() {
            return blocksPending > 0;
        }

        @Override
        public SubStream next() {
            blocksPending--;
            return new SubStream(
                    wrappedStream,
                    currentBlock++ * blockSize,
                    blocksPending > 0 ? blockSize : lastBlockSize,
                    mutex);
        }

        @Override
        public void remove() {
            // No-op
        }
    }
}