/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * See LICENSE.txt included in this distribution for the specific
 * language governing permissions and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at LICENSE.txt.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright (c) 2013, 2018, Oracle and/or its affiliates. All rights reserved.
 * Portions Copyright (c) 2018, Chris Fraire <cfraire@me.com>.
 */
package org.opengrok.indexer.analysis;

import java.io.BufferedInputStream;
import java.io.ByteArrayInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.nio.charset.StandardCharsets;

/**
 * This class lets you create {@code InputStream}s that read data from a
 * specific source. It could be used if you need to pass a stream as an
 * argument to a method where the stream may need to be read multiple times.
 * Instead of passing the stream directly, you pass a {@code StreamSource}
 * instance that generates the stream. The receiver may call
 * {@link #getStream()} multiple times, getting a fresh stream each time,
 * so that there may be multiple, concurrent readers that don't interfere
 * with each other.
 */
public abstract class StreamSource {
    /**
     * Get a stream that reads data from the input source. Every call should
     * return a new instance so that multiple readers can read from the source
     * without interfering with each other.
     *
     * @return an {@code InputStream}
     * @throws IOException if an error occurs when opening the stream
     */
    public abstract InputStream getStream() throws IOException;

    /**
     * Helper method that creates a {@code StreamSource} instance that
     * reads data from a file.
     *
     * @param file the data file
     * @return a stream source that reads from {@code file}
     */
    public static StreamSource fromFile(final File file) {
        return new StreamSource() {
            @Override
            public InputStream getStream() throws IOException {
                return new BufferedInputStream(new FileInputStream(file));
            }
        };
    }

    /**
     * Helper method that creates a {@code StreamSource} instance that
     * reads data from a String.
     * @param str the source string
     * @return a stream source that reads from {@code str}
     */
    public static StreamSource fromString(final String str) {
        return new StreamSource() {
            private final byte[] sbuf = str.getBytes(StandardCharsets.UTF_8);

            @Override
            public InputStream getStream() throws IOException {
                return new ByteArrayInputStream(sbuf);
            }
        };
    }
}