/*
 * 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
 *
 *   https://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.commons.compress.utils;

import java.io.IOException;
import java.io.InputStream;
import java.util.zip.CheckedInputStream;
import java.util.zip.Checksum;

/**
 * Verifies the checksum of the data read once the stream is exhausted.
 *
 * @NotThreadSafe
 * @since 1.7
 * @deprecated Use {@link org.apache.commons.io.input.ChecksumInputStream}.
 */
@Deprecated
public class ChecksumVerifyingInputStream extends CheckedInputStream {
    private long remaining;
    private final long expected;

    /**
     * Constructs a new instance.
     *
     * @param checksum         Checksum implementation.
     * @param in               the stream to wrap
     * @param size             the of the stream's content
     * @param expectedChecksum the expected checksum
     */
    public ChecksumVerifyingInputStream(final Checksum checksum, final InputStream in, final long size, final long expectedChecksum) {
        super(in, checksum);
        this.expected = expectedChecksum;
        this.remaining = size;
    }

    /**
     * Gets the byte count remaining to read.
     *
     * @return bytes remaining to read.
     * @since 1.21
     */
    public long getBytesRemaining() {
        return remaining;
    }

    /**
     * Reads a single byte from the stream
     *
     * @throws IOException if the underlying stream throws or the stream is exhausted and the Checksum doesn't match the expected value
     */
    @Override
    public int read() throws IOException {
        if (remaining <= 0) {
            return -1;
        }
        final int data = super.read();
        if (data >= 0) {
            --remaining;
        }
        verify();
        return data;
    }

    /**
     * Reads from the stream into a byte array.
     *
     * @throws IOException if the underlying stream throws or the stream is exhausted and the Checksum doesn't match the expected value
     */
    @Override
    public int read(final byte[] b, final int off, final int len) throws IOException {
        if (len == 0) {
            return 0;
        }
        final int readCount = super.read(b, off, len);
        if (readCount >= 0) {
            remaining -= readCount;
        }
        verify();
        return readCount;
    }

    private void verify() throws IOException {
        if (remaining <= 0 && expected != getChecksum().getValue()) {
            throw new IOException("Checksum verification failed");
        }
    }
}
