// Copyright (C) 2009 The Android Open Source Project
//
// Licensed 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 com.google.gerrit.sshd.commands;

import static com.google.common.base.Preconditions.checkState;
import static com.google.gerrit.sshd.CommandMetaData.Mode.MASTER_OR_SLAVE;

import com.google.gerrit.common.TimeUtil;
import com.google.gerrit.common.data.GlobalCapability;
import com.google.gerrit.extensions.annotations.RequiresCapability;
import com.google.gerrit.server.CurrentUser;
import com.google.gerrit.server.IdentifiedUser;
import com.google.gerrit.server.ioutil.HexFormat;
import com.google.gerrit.sshd.CommandMetaData;
import com.google.gerrit.sshd.SshCommand;
import com.google.gerrit.sshd.SshDaemon;
import com.google.gerrit.sshd.SshSession;
import com.google.inject.Inject;
import java.io.IOException;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.net.SocketAddress;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.Date;
import java.util.List;
import java.util.Optional;
import org.apache.sshd.common.io.IoAcceptor;
import org.apache.sshd.common.io.IoSession;
import org.apache.sshd.common.io.mina.MinaAcceptor;
import org.apache.sshd.common.io.mina.MinaSession;
import org.apache.sshd.common.io.nio2.Nio2Acceptor;
import org.apache.sshd.common.session.helpers.AbstractSession;
import org.apache.sshd.server.Environment;
import org.kohsuke.args4j.Option;

/** Show the current SSH connections. */
@RequiresCapability(GlobalCapability.VIEW_CONNECTIONS)
@CommandMetaData(
    name = "show-connections",
    description = "Display active client SSH connections",
    runsAt = MASTER_OR_SLAVE)
final class ShowConnections extends SshCommand {
  @Option(
      name = "--numeric",
      aliases = {"-n"},
      usage = "don't resolve names")
  private boolean numeric;

  @Option(
      name = "--wide",
      aliases = {"-w"},
      usage = "display without line width truncation")
  private boolean wide;

  @Inject private SshDaemon daemon;

  private int hostNameWidth;
  private int columns = 80;

  @Override
  public void start(Environment env) throws IOException {
    String s = env.getEnv().get(Environment.ENV_COLUMNS);
    if (s != null && !s.isEmpty()) {
      try {
        columns = Integer.parseInt(s);
      } catch (NumberFormatException err) {
        columns = 80;
      }
    }
    super.start(env);
  }

  @Override
  protected void run() throws Failure {
    final IoAcceptor acceptor = daemon.getIoAcceptor();
    if (acceptor == null) {
      throw new Failure(1, "fatal: sshd no longer running");
    }

    final List<IoSession> list = new ArrayList<>(acceptor.getManagedSessions().values());
    Collections.sort(
        list,
        new Comparator<IoSession>() {
          @Override
          public int compare(IoSession arg0, IoSession arg1) {
            if (arg0 instanceof MinaSession) {
              MinaSession mArg0 = (MinaSession) arg0;
              MinaSession mArg1 = (MinaSession) arg1;
              if (mArg0.getSession().getCreationTime() < mArg1.getSession().getCreationTime()) {
                return -1;
              } else if (mArg0.getSession().getCreationTime()
                  > mArg1.getSession().getCreationTime()) {
                return 1;
              }
            }
            return (int) (arg0.getId() - arg1.getId());
          }
        });

    hostNameWidth = wide ? Integer.MAX_VALUE : columns - 9 - 9 - 10 - 32;

    if (getBackend().equals("mina")) {
      long now = TimeUtil.nowMs();
      stdout.print(
          String.format(
              "%-8s %8s %8s   %-15s %s\n", "Session", "Start", "Idle", "User", "Remote Host"));
      stdout.print("--------------------------------------------------------------\n");
      for (IoSession io : list) {
        checkState(io instanceof MinaSession, "expected MinaSession");
        MinaSession minaSession = (MinaSession) io;
        long start = minaSession.getSession().getCreationTime();
        long idle = now - minaSession.getSession().getLastIoTime();
        AbstractSession s = AbstractSession.getSession(io, true);
        SshSession sd = s != null ? s.getAttribute(SshSession.KEY) : null;

        stdout.print(
            String.format(
                "%8s %8s %8s   %-15.15s %s\n",
                id(sd),
                time(now, start),
                age(idle),
                username(sd),
                hostname(io.getRemoteAddress())));
      }
    } else {
      stdout.print(String.format("%-8s   %-15s %s\n", "Session", "User", "Remote Host"));
      stdout.print("--------------------------------------------------------------\n");
      for (IoSession io : list) {
        AbstractSession s = AbstractSession.getSession(io, true);
        SshSession sd = s != null ? s.getAttribute(SshSession.KEY) : null;

        stdout.print(
            String.format(
                "%8s   %-15.15s %s\n", id(sd), username(sd), hostname(io.getRemoteAddress())));
      }
    }

    stdout.print("--\n");
    stdout.print("SSHD Backend: " + getBackend() + "\n");
  }

  private String getBackend() {
    IoAcceptor acceptor = daemon.getIoAcceptor();
    if (acceptor == null) {
      return "";
    } else if (acceptor instanceof MinaAcceptor) {
      return "mina";
    } else if (acceptor instanceof Nio2Acceptor) {
      return "nio2";
    } else {
      return "unknown";
    }
  }

  private static String id(SshSession sd) {
    return sd != null ? HexFormat.fromInt(sd.getSessionId()) : "";
  }

  private static String time(long now, long time) {
    if (now - time < 24 * 60 * 60 * 1000L) {
      return new SimpleDateFormat("HH:mm:ss").format(new Date(time));
    }
    return new SimpleDateFormat("MMM-dd").format(new Date(time));
  }

  private static String age(long age) {
    age /= 1000;

    final int sec = (int) (age % 60);
    age /= 60;

    final int min = (int) (age % 60);
    age /= 60;

    final int hr = (int) (age % 60);
    return String.format("%02d:%02d:%02d", hr, min, sec);
  }

  private String username(SshSession sd) {
    if (sd == null) {
      return "";
    }

    final CurrentUser user = sd.getUser();
    if (user != null && user.isIdentifiedUser()) {
      IdentifiedUser u = user.asIdentifiedUser();

      if (!numeric) {
        Optional<String> name = u.getUserName();
        if (name.isPresent()) {
          return name.get();
        }
      }

      return "a/" + u.getAccountId().toString();
    }
    return "";
  }

  private String hostname(SocketAddress remoteAddress) {
    if (remoteAddress == null) {
      return "?";
    }
    String host = null;
    if (remoteAddress instanceof InetSocketAddress) {
      final InetSocketAddress sa = (InetSocketAddress) remoteAddress;
      final InetAddress in = sa.getAddress();
      if (numeric) {
        return in.getHostAddress();
      }
      if (in != null) {
        host = in.getCanonicalHostName();
      } else {
        host = sa.getHostName();
      }
    }
    if (host == null) {
      host = remoteAddress.toString();
    }

    if (host.length() > hostNameWidth) {
      return host.substring(0, hostNameWidth);
    }

    return host;
  }
}