/*
 * Copyright 2012-2014 Red Hat, Inc.
 *
 * This file is part of Thermostat.
 *
 * Thermostat is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published
 * by the Free Software Foundation; either version 2, or (at your
 * option) any later version.
 *
 * Thermostat 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 for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Thermostat; see the file COPYING.  If not see
 * <http://www.gnu.org/licenses/>.
 *
 * Linking this code with other modules is making a combined work
 * based on this code.  Thus, the terms and conditions of the GNU
 * General Public License cover the whole combination.
 *
 * As a special exception, the copyright holders of this code give
 * you permission to link this code with independent modules to
 * produce an executable, regardless of the license terms of these
 * independent modules, and to copy and distribute the resulting
 * executable under terms of your choice, provided that you also
 * meet, for each linked independent module, the terms and conditions
 * of the license of that module.  An independent module is a module
 * which is not derived from or based on this code.  If you modify
 * this code, you may extend this exception to your version of the
 * library, but you are not obligated to do so.  If you do not wish
 * to do so, delete this exception statement from your version.
 */

package com.redhat.thermostat.agent.proxy.server;

import java.io.File;
import java.io.IOException;
import java.rmi.RemoteException;
import java.util.Properties;
import java.util.Set;
import java.util.logging.Logger;

import javax.security.auth.Subject;

import com.sun.tools.attach.AgentInitializationException;
import com.sun.tools.attach.AgentLoadException;
import com.sun.tools.attach.AttachNotSupportedException;
import com.sun.tools.attach.VirtualMachine;

import com.redhat.thermostat.common.utils.LoggingUtils;

class AgentProxyControlImpl {
    
    private static final Logger logger = LoggingUtils.getLogger(AgentProxyControlImpl.class);

    private static final String CONNECTOR_ADDRESS_PROPERTY = "com.sun.management.jmxremote.localConnectorAddress";
    
    private final int pid;
    private final VirtualMachineUtils vmUtils;
    
    private VirtualMachine vm;
    private boolean attached;
    private String connectorAddress;
    
    AgentProxyControlImpl(int pid) {
        this(pid, new VirtualMachineUtils());
    }
    
    AgentProxyControlImpl(int pid, VirtualMachineUtils vmUtils) {
        this.pid = pid;
        this.vmUtils = vmUtils;
    }

    void attach(Subject user) throws RemoteException, SecurityException {
        authCheck(user);
        try {
            vm = vmUtils.attach(String.valueOf(pid));
            attached = true;
            
            Properties props = vm.getAgentProperties();
            connectorAddress = props.getProperty(CONNECTOR_ADDRESS_PROPERTY);
            if (connectorAddress == null) {
                String home = null;
                String agent = null;
                try {
                    props = vm.getSystemProperties();
                    home = props.getProperty("java.home");
                    agent = home + File.separator + "lib" + File.separator + "management-agent.jar";
                    logger.fine("Loading '" + agent + "' into VM (pid: " + pid + ")");
                    vm.loadAgent(agent);

                    props = vm.getAgentProperties();
                    connectorAddress = props.getProperty(CONNECTOR_ADDRESS_PROPERTY);
                } catch (IOException | AgentLoadException | AgentInitializationException e) {
                    throw new RemoteException("Failed to load agent ('" + agent + "', from home '" + home + "') into VM (pid: " + pid + ")", e);
                }
            }
        } catch (AttachNotSupportedException | IOException e) {
            throw new RemoteException("Failed to attach to VM (pid: " + pid + ")", e);
        }
    }

    boolean isAttached(Subject user) throws RemoteException, SecurityException {
        authCheck(user);
        return attached;
    }

    String getConnectorAddress(Subject user) throws RemoteException, SecurityException {
        authCheck(user);
        if (!attached) {
            throw new RemoteException("Agent not attached to target VM");
        }
        return connectorAddress;
    }

    void detach(Subject user) throws RemoteException, SecurityException {
        authCheck(user);
        try {
            if (attached) {
                vm.detach();
                attached = false;
            }
        } catch (IOException e) {
            throw new RemoteException("Failed to detach from VM", e);
        }
    }
    
    private void authCheck(Subject user) throws SecurityException {
        // If we've added our Principal, we've authenticated this user
        Set<AgentProxyPrincipal> principals = user.getPrincipals(AgentProxyPrincipal.class);
        if (principals.isEmpty()) {
            throw new SecurityException("Access Denied");
        }
    }
    
    static class VirtualMachineUtils {
        VirtualMachine attach(String pid) throws AttachNotSupportedException, IOException {
            return VirtualMachine.attach(pid);
        }
    }

}