/*
 * Copyright (c) 2012, 2017 Oracle and/or its affiliates. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0, which is available at
 * http://www.eclipse.org/legal/epl-2.0.
 *
 * This Source Code may also be made available under the following Secondary
 * Licenses when the conditions for such availability set forth in the
 * Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
 * version 2 with the GNU Classpath Exception, which is available at
 * https://www.gnu.org/software/classpath/license.html.
 *
 * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 */

package sun.security.ssl;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.LinkedHashSet;

enum {
   next_protocol_negotiation(13172), (65535)
} ExtensionType;
The "extension_data" field of a "next_protocol_negotiation" extension
in a "ClientHello" MUST be empty.
The "extension_data" field of a "next_protocol_negotiation" extension
in a "ServerHello" contains an optional list of protocols advertised
by the server.  Protocols are named by opaque, non-empty byte strings
and the list of protocols is serialized as a concatenation of 8-bit,
length prefixed byte strings.  Implementations MUST ensure that the
empty string is not included and that no byte strings are truncated.
/**
 * enum {
 *    next_protocol_negotiation(13172), (65535)
 * } ExtensionType;
 *
 * The "extension_data" field of a "next_protocol_negotiation" extension
 * in a "ClientHello" MUST be empty.
 *
 * The "extension_data" field of a "next_protocol_negotiation" extension
 * in a "ServerHello" contains an optional list of protocols advertised
 * by the server.  Protocols are named by opaque, non-empty byte strings
 * and the list of protocols is serialized as a concatenation of 8-bit,
 * length prefixed byte strings.  Implementations MUST ensure that the
 * empty string is not included and that no byte strings are truncated.
 */
final class NextProtocolNegotiationExtension extends HelloExtension {

    private static final LinkedHashSet<String> EMPTY = new LinkedHashSet<>(0);

    // registry value TBD - NPN Draft 03 defines 13172 (0x3374).
    public static final int EXTENSION_ID = 0x3374;

    LinkedHashSet<String> protocols;
    private byte[] outData;

    // ------------------------------------------------------------ Constructors

    public NextProtocolNegotiationExtension(final ExtensionType extensionType) {
        super(extensionType);
        protocols = EMPTY;
    }

    // --------------------------------------------- Methods from HelloExtension


    @Override
    int length() {
        // Length of the encoded extension, including the type and length fields
        // - Two bytes for the type
        // - Two bytes for the length of the encoded protocols
        // - length of the encoded protocols
        return 4 + outData.length;
    }

    @Override
    void send(HandshakeOutStream handshakeOutStream) throws IOException {
        handshakeOutStream.putInt16(EXTENSION_ID);
        handshakeOutStream.putInt16(outData.length);
        handshakeOutStream.write(outData);
    }

    @Override
    public String toString() {
        return String.format(
                "Next Protocol Negotiation Extension [0x%x/%d], protocols: %s, compressed data: %s",
                EXTENSION_ID,
                EXTENSION_ID,
                protocols.toString(),
                Debug.toString(outData));
    }


    // ------------------------------------------------- Package Private Methods

    static Builder builder() {
        return new Builder();
    }

    // --------------------------------------------------------- Private Methods


    // ---------------------------------------------------------- Nested Classes


    static final class Builder {

        private static final byte[] EMPTY_DATA = new byte[0];
        public static final String ISO_8859_1 = "ISO-8859-1";

        private final NextProtocolNegotiationExtension extension =
                new NextProtocolNegotiationExtension(ExtensionType.get(EXTENSION_ID));

        private HandshakeInStream in;
        private int len;

        Builder protocols(final LinkedHashSet<String> protocols) {
            extension.protocols = protocols;
            return this;
        }

        Builder handshakeIn(final HandshakeInStream in, final int len) {
            this.in = in;
            this.len = len;
            return this;
        }

        NextProtocolNegotiationExtension build() throws IOException {
            if (in != null) {
                if (len > 0) {
                    extension.protocols = new LinkedHashSet<>();
                    int read = 0;
                    while (read != len) {
                        // Draft-03, section 3 states:
                        //    "Protocols are named by opaque, non-empty byte strings
                        //     and the list of protocols is serialized as a concatenation
                        //     of 8-bit length prefixed byte strings."
                        byte[] protocol = new byte[in.getInt8()];
                        in.read(protocol);
                        // the character encoding isn't specified by Draft-03.
                        // Given the examples in the draft, and our current usage,
                        // ISO-8859-1 seems sufficient.
                        extension.protocols.add(new String(protocol, ISO_8859_1));
                        read += protocol.length + 1; // add one for the length prefix
                    }
                } else {
                    extension.protocols = EMPTY;
                }
            } else {
                if (extension.protocols.isEmpty()) {
                    extension.outData = EMPTY_DATA;
                } else {
                    ByteArrayOutputStream out = new ByteArrayOutputStream();
                    for (String protocol : extension.protocols) {
                        out.write(protocol.length());
                        out.write(protocol.getBytes(ISO_8859_1));
                    }
                    extension.outData = out.toByteArray();
                }
            }
            return extension;
        }

    } // END Builder

} // END NextProtocolNegotiationExtension