/*
 * Copyright 2014 The Netty Project
 *
 * The Netty Project 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 io.netty.channel.epoll;

import io.netty.channel.Channel;
import io.netty.channel.ChannelException;
import io.netty.channel.socket.ServerSocketChannel;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.unix.FileDescriptor;
import io.netty.channel.unix.Socket;
import io.netty.util.concurrent.GlobalEventExecutor;
import io.netty.util.internal.PlatformDependent;

import java.io.IOException;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.net.SocketAddress;
import java.net.UnknownHostException;
import java.util.Collection;
import java.util.Collections;
import java.util.Map;
import java.util.concurrent.Executor;

import static io.netty.channel.unix.Socket.newSocketStream;

/**
 * {@link SocketChannel} implementation that uses linux EPOLL Edge-Triggered Mode for
 * maximal performance.
 */
public final class EpollSocketChannel extends AbstractEpollStreamChannel implements SocketChannel {

    private final EpollSocketChannelConfig config;

    private volatile InetSocketAddress local;
    private volatile InetSocketAddress remote;
    private InetSocketAddress requestedRemote;

    private volatile Collection<InetAddress> tcpMd5SigAddresses = Collections.emptyList();

    EpollSocketChannel(Channel parent, Socket fd, InetSocketAddress remote) {
        super(parent, fd);
        config = new EpollSocketChannelConfig(this);
        // Directly cache the remote and local addresses
        // See https://github.com/netty/netty/issues/2359
        this.remote = remote;
        local = fd.localAddress();

        if (parent instanceof EpollServerSocketChannel) {
            tcpMd5SigAddresses = ((EpollServerSocketChannel) parent).tcpMd5SigAddresses();
        }
    }

    public EpollSocketChannel() {
        super(newSocketStream(), false);
        config = new EpollSocketChannelConfig(this);
    }

    /**
     * @deprecated Use {@link #EpollSocketChannel(Socket, boolean)}.
     */
    @Deprecated
    public EpollSocketChannel(FileDescriptor fd) {
        super(fd);
        // As we create an EpollSocketChannel from a FileDescriptor we should try to obtain the remote and local
        // address from it. This is needed as the FileDescriptor may be bound/connected already.
        remote = fd().remoteAddress();
        local = fd().localAddress();
        config = new EpollSocketChannelConfig(this);
    }

    /**
     * Creates a new {@link EpollSocketChannel} from an existing {@link FileDescriptor}.
     */
    public EpollSocketChannel(Socket fd, boolean active) {
        super(fd, active);
        // As we create an EpollSocketChannel from a FileDescriptor we should try to obtain the remote and local
        // address from it. This is needed as the FileDescriptor may be bound/connected already.
        remote = fd.remoteAddress();
        local = fd.localAddress();
        config = new EpollSocketChannelConfig(this);
    }

    /**
     * Returns the {@code TCP_INFO} for the current socket. See <a href="http://linux.die.net/man/7/tcp">man 7 tcp</a>.
     */
    public EpollTcpInfo tcpInfo() {
        return tcpInfo(new EpollTcpInfo());
    }

    /**
     * Updates and returns the {@code TCP_INFO} for the current socket.
     * See <a href="http://linux.die.net/man/7/tcp">man 7 tcp</a>.
     */
    public EpollTcpInfo tcpInfo(EpollTcpInfo info) {
        try {
            Native.tcpInfo(fd().intValue(), info);
            return info;
        } catch (IOException e) {
            throw new ChannelException(e);
        }
    }

    @Override
    public InetSocketAddress remoteAddress() {
        return (InetSocketAddress) super.remoteAddress();
    }

    @Override
    public InetSocketAddress localAddress() {
        return (InetSocketAddress) super.localAddress();
    }

    @Override
    protected SocketAddress localAddress0() {
        return local;
    }

    @Override
    protected SocketAddress remoteAddress0() {
        return remote;
    }

    @Override
    protected void doBind(SocketAddress local) throws Exception {
        InetSocketAddress localAddress = (InetSocketAddress) local;
        fd().bind(localAddress);
        this.local = fd().localAddress();
    }

    @Override
    public EpollSocketChannelConfig config() {
        return config;
    }

    @Override
    public ServerSocketChannel parent() {
        return (ServerSocketChannel) super.parent();
    }

    @Override
    protected AbstractEpollUnsafe newUnsafe() {
        return new EpollSocketChannelUnsafe();
    }

    private static InetSocketAddress computeRemoteAddr(InetSocketAddress remoteAddr, InetSocketAddress osRemoteAddr) {
        if (osRemoteAddr != null) {
            if (PlatformDependent.javaVersion() >= 7) {
                try {
                    // Only try to construct a new InetSocketAddress if we using java >= 7 as getHostString() does not
                    // exists in earlier releases and so the retrieval of the hostname could block the EventLoop if a
                    // reverse lookup would be needed.
                    return new InetSocketAddress(InetAddress.getByAddress(remoteAddr.getHostString(),
                            osRemoteAddr.getAddress().getAddress()),
                            osRemoteAddr.getPort());
                } catch (UnknownHostException ignore) {
                    // Should never happen but fallback to osRemoteAddr anyway.
                }
            }
            return osRemoteAddr;
        }
        return remoteAddr;
    }

    @Override
    protected boolean doConnect(SocketAddress remoteAddress, SocketAddress localAddress) throws Exception {
        if (localAddress != null) {
            checkResolvable((InetSocketAddress) localAddress);
        }
        InetSocketAddress remoteAddr = (InetSocketAddress) remoteAddress;
        checkResolvable(remoteAddr);

        boolean connected = super.doConnect(remoteAddress, localAddress);
        if (connected) {
            remote = computeRemoteAddr(remoteAddr, fd().remoteAddress());
        } else {
            // Store for later usage in doFinishConnect()
            requestedRemote = remoteAddr;
        }
        // We always need to set the localAddress even if not connected yet as the bind already took place.
        //
        // See https://github.com/netty/netty/issues/3463
        local = fd().localAddress();
        return connected;
    }

    private final class EpollSocketChannelUnsafe extends EpollStreamUnsafe {
        @Override
        protected Executor prepareToClose() {
            try {
                // Check isOpen() first as otherwise it will throw a RuntimeException
                // when call getSoLinger() as the fd is not valid anymore.
                if (isOpen() && config().getSoLinger() > 0) {
                    // We need to cancel this key of the channel so we may not end up in a eventloop spin
                    // because we try to read or write until the actual close happens which may be later due
                    // SO_LINGER handling.
                    // See https://github.com/netty/netty/issues/4449
                    ((EpollEventLoop) eventLoop()).remove(EpollSocketChannel.this);
                    return GlobalEventExecutor.INSTANCE;
                }
            } catch (Throwable ignore) {
                // Ignore the error as the underlying channel may be closed in the meantime and so
                // getSoLinger() may produce an exception. In this case we just return null.
                // See https://github.com/netty/netty/issues/4449
            }
            return null;
        }

        @Override
        boolean doFinishConnect() throws Exception {
            if (super.doFinishConnect()) {
                remote = computeRemoteAddr(requestedRemote, fd().remoteAddress());
                requestedRemote = null;
                return true;
            }
            return false;
        }
    }

    void setTcpMd5Sig(Map<InetAddress, byte[]> keys) throws IOException {
        this.tcpMd5SigAddresses = TcpMd5Util.newTcpMd5Sigs(this, tcpMd5SigAddresses, keys);
    }
}
