/*

 * Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

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 */

package jdk.nashorn.api.scripting;

import java.io.CharArrayReader;

import java.io.IOException;

import java.io.Reader;

import java.net.URL;

import java.nio.charset.Charset;

import java.util.Objects;

import jdk.nashorn.internal.runtime.Source;

/**

 * A Reader that reads from a URL. Used to make sure that the reader

 * reads content from given URL and can be trusted to do so.

 *

 * @since 1.8u40

 */

public final class URLReader extends Reader {

    // underlying URL

    private final URL url;

    // Charset used to convert

    private final Charset cs;

    // lazily initialized underlying reader for URL

    private Reader reader;

    /**

     * Constructor

     *

     * @param url URL for this URLReader

     * @throws NullPointerException if url is null

     */

    public URLReader(final URL url) {

        this(url, (Charset)null);

    }

    /**

     * Constructor

     *

     * @param url URL for this URLReader

     * @param charsetName  Name of the Charset used to convert bytes to chars

     * @throws NullPointerException if url is null

     */

    public URLReader(final URL url, final String charsetName) {

        this(url, Charset.forName(charsetName));

    }

    /**

     * Constructor

     *

     * @param url URL for this URLReader

     * @param cs  Charset used to convert bytes to chars

     * @throws NullPointerException if url is null

     */

    public URLReader(final URL url, final Charset cs) {

        this.url = Objects.requireNonNull(url);

        this.cs  = cs;

    }

    @Override

    public int read(final char cbuf[], final int off, final int len) throws IOException {

        return getReader().read(cbuf, off, len);

    }

    @Override

    public void close() throws IOException {

        getReader().close();

    }

    /**

     * URL of this reader

     * @return the URL from which this reader reads.

     */

    public URL getURL() {

        return url;

    }

    /**

     * Charset used by this reader

     *

     * @return the Charset used to convert bytes to chars

     */

    public Charset getCharset() {

        return cs;

    }

    // lazily initialize char array reader using URL content

    private Reader getReader() throws IOException {

        synchronized (lock) {

            if (reader == null) {

                reader = new CharArrayReader(Source.readFully(url, cs));

            }

        }

        return reader;

    }

}