/*
 * 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
 *
 *      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 org.apache.commons.net;

import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.SocketException;
import java.nio.charset.Charset;
import java.time.Duration;
import java.util.Objects;

/**
 * The DatagramSocketClient provides the basic operations that are required of client objects accessing datagram sockets. It is meant to be subclassed to avoid
 * having to rewrite the same code over and over again to open a socket, close a socket, set timeouts, etc. Of special note is the
 * {@link #setDatagramSocketFactory setDatagramSocketFactory } method, which allows you to control the type of DatagramSocket the DatagramSocketClient creates
 * for network communications. This is especially useful for adding things like proxy support as well as better support for applets. For example, you could
 * create a {@link org.apache.commons.net.DatagramSocketFactory} that requests browser security capabilities before creating a socket. All classes derived from
 * DatagramSocketClient should use the {@link #_socketFactory_ _socketFactory_ } member variable to create DatagramSocket instances rather than instantiating
 * them by directly invoking a constructor. By honoring this contract you guarantee that a user will always be able to provide his own Socket implementations by
 * substituting his own SocketFactory.
 *
 *
 * @see DatagramSocketFactory
 */

public abstract class DatagramSocketClient implements AutoCloseable {
    /**
     * The default DatagramSocketFactory shared by all DatagramSocketClient instances.
     */
    private static final DatagramSocketFactory DEFAULT_SOCKET_FACTORY = new DefaultDatagramSocketFactory();

    /**
     * Charset to use for byte IO.
     */
    private Charset charset = Charset.defaultCharset();

    /** The timeout to use after opening a socket. */
    protected int _timeout_;

    /** The datagram socket used for the connection. */
    protected DatagramSocket _socket_;

    /**
     * A status variable indicating if the client's socket is currently open.
     */
    protected boolean _isOpen_;

    /** The datagram socket's DatagramSocketFactory. */
    protected DatagramSocketFactory _socketFactory_ = DEFAULT_SOCKET_FACTORY;

    /**
     * Default constructor for DatagramSocketClient. Initializes _socket_ to null, _timeout_ to 0, and _isOpen_ to false.
     */
    public DatagramSocketClient() {
    }

    /**
     * Gets the non-null DatagramSocket or throws {@link NullPointerException}.
     *
     * @return the non-null DatagramSocket.
     * @since 3.10.0
     */
    protected DatagramSocket checkOpen() {
        return Objects.requireNonNull(_socket_, "DatagramSocket");
    }

    /**
     * Closes the DatagramSocket used for the connection. You should call this method after you've finished using the class instance and also before you call
     * {@link #open open() } again. _isOpen_ is set to false and _socket_ is set to null.
     */
    @Override
    public void close() {
        if (_socket_ != null) {
            _socket_.close();
        }
        _socket_ = null;
        _isOpen_ = false;
    }

    /**
     * Gets the charset.
     *
     * @return the charset.
     * @since 3.3
     */
    public Charset getCharset() {
        return charset;
    }

    /**
     * Gets the charset name.
     *
     * @return the charset name.
     * @since 3.3
     * @deprecated Use {@link #getCharset()} instead
     */
    @Deprecated
    public String getCharsetName() {
        return charset.name();
    }

    /**
     * Gets the default timeout in milliseconds that is used when opening a socket.
     *
     * @return The default timeout in milliseconds that is used when opening a socket.
     */
    public int getDefaultTimeout() {
        return _timeout_;
    }

    /**
     * Gets the local address to which the client's socket is bound. If you call this method when the client socket is not open, a NullPointerException is
     * thrown.
     *
     * @return The local address to which the client's socket is bound.
     */
    public InetAddress getLocalAddress() {
        return checkOpen().getLocalAddress();
    }

    /**
     * Gets the port number of the open socket on the local host used for the connection. If you call this method when the client socket is not open, a
     * NullPointerException is thrown.
     *
     * @return The port number of the open socket on the local host used for the connection.
     */
    public int getLocalPort() {
        return checkOpen().getLocalPort();
    }

    /**
     * Gets the timeout in milliseconds of the currently opened socket. If you call this method when the client socket is not open, a NullPointerException is
     * thrown.
     *
     * @return The timeout in milliseconds of the currently opened socket.
     * @throws SocketException if an error getting the timeout.
     * @deprecated Use {@link #getSoTimeoutDuration()}.
     */
    @Deprecated
    public int getSoTimeout() throws SocketException {
        return checkOpen().getSoTimeout();
    }

    /**
     * Gets the timeout duration of the currently opened socket. If you call this method when the client socket is not open, a NullPointerException is
     * thrown.
     *
     * @return The timeout in milliseconds of the currently opened socket.
     * @throws SocketException if an error getting the timeout.
     */
    public Duration getSoTimeoutDuration() throws SocketException {
        return Duration.ofMillis(checkOpen().getSoTimeout());
    }

    /**
     * Gets true if the client has a currently open socket.
     *
     * @return True if the client has a currently open socket, false otherwise.
     */
    public boolean isOpen() {
        return _isOpen_;
    }

    /**
     * Opens a DatagramSocket on the local host at the first available port. Also sets the timeout on the socket to the default timeout set by
     * {@link #setDefaultTimeout setDefaultTimeout() }.
     * <p>
     * _isOpen_ is set to true after calling this method and _socket_ is set to the newly opened socket.
     *
     * @throws SocketException If the socket could not be opened or the timeout could not be set.
     */
    public void open() throws SocketException {
        _socket_ = _socketFactory_.createDatagramSocket();
        _socket_.setSoTimeout(_timeout_);
        _isOpen_ = true;
    }

    /**
     * Opens a DatagramSocket on the local host at a specified port. Also sets the timeout on the socket to the default timeout set by {@link #setDefaultTimeout
     * setDefaultTimeout() }.
     * <p>
     * _isOpen_ is set to true after calling this method and _socket_ is set to the newly opened socket.
     *
     * @param port The port to use for the socket.
     * @throws SocketException If the socket could not be opened or the timeout could not be set.
     */
    public void open(final int port) throws SocketException {
        _socket_ = _socketFactory_.createDatagramSocket(port);
        _socket_.setSoTimeout(_timeout_);
        _isOpen_ = true;
    }

    /**
     * Opens a DatagramSocket at the specified address on the local host at a specified port. Also sets the timeout on the socket to the default timeout set by
     * {@link #setDefaultTimeout setDefaultTimeout() }.
     * <p>
     * _isOpen_ is set to true after calling this method and _socket_ is set to the newly opened socket.
     *
     * @param port  The port to use for the socket.
     * @param localAddress The local address to use.
     * @throws SocketException If the socket could not be opened or the timeout could not be set.
     */
    public void open(final int port, final InetAddress localAddress) throws SocketException {
        _socket_ = _socketFactory_.createDatagramSocket(port, localAddress);
        _socket_.setSoTimeout(_timeout_);
        _isOpen_ = true;
    }

    /**
     * Sets the charset.
     *
     * @param charset the charset.
     * @since 3.3
     */
    public void setCharset(final Charset charset) {
        this.charset = charset;
    }

    /**
     * Sets the DatagramSocketFactory used by the DatagramSocketClient to open DatagramSockets. If the factory value is null, then a default factory is used
     * (only do this to reset the factory after having previously altered it).
     *
     * @param factory The new DatagramSocketFactory the DatagramSocketClient should use.
     */
    public void setDatagramSocketFactory(final DatagramSocketFactory factory) {
        if (factory == null) {
            _socketFactory_ = DEFAULT_SOCKET_FACTORY;
        } else {
            _socketFactory_ = factory;
        }
    }

    /**
     * Set the default timeout in to use when opening a socket. After a call to open, the timeout for the socket is set using this value. This
     * method should be used prior to a call to {@link #open open()} and should not be confused with {@link #setSoTimeout setSoTimeout()} which operates on the
     * currently open socket. _timeout_ contains the new timeout value.
     *
     * @param timeout The timeout durations to use for the datagram socket connection.
     */
    public void setDefaultTimeout(final Duration timeout) {
        _timeout_ = Math.toIntExact(timeout.toMillis());
    }

    /**
     * Set the default timeout in milliseconds to use when opening a socket. After a call to open, the timeout for the socket is set using this value. This
     * method should be used prior to a call to {@link #open open()} and should not be confused with {@link #setSoTimeout setSoTimeout()} which operates on the
     * currently open socket. _timeout_ contains the new timeout value.
     *
     * @param timeout The timeout in milliseconds to use for the datagram socket connection.
     * @deprecated Use {@link #setDefaultTimeout(Duration)}.
     */
    @Deprecated
    public void setDefaultTimeout(final int timeout) {
        _timeout_ = timeout;
    }

    /**
     * Set the timeout duration of a currently open connection. Only call this method after a connection has been opened by {@link #open open()}.
     *
     * @param timeout The timeout in milliseconds to use for the currently open datagram socket connection.
     * @throws SocketException if an error setting the timeout.
     * @since 3.10.0
     */
    public void setSoTimeout(final Duration timeout) throws SocketException {
        checkOpen().setSoTimeout(Math.toIntExact(timeout.toMillis()));
    }

    /**
     * Set the timeout in milliseconds of a currently open connection. Only call this method after a connection has been opened by {@link #open open()}.
     *
     * @param timeout The timeout in milliseconds to use for the currently open datagram socket connection.
     * @throws SocketException if an error setting the timeout.
     * @deprecated Use {@link #setSoTimeout(Duration)}.
     */
    @Deprecated
    public void setSoTimeout(final int timeout) throws SocketException {
        checkOpen().setSoTimeout(timeout);
    }
}
