/*
 * JobServServer
 *
 * v1.0
 *
 * May 18, 2019
 */

package JobServ;

import io.grpc.Server;
import io.grpc.ServerBuilder;
import io.grpc.netty.GrpcSslContexts;
import io.grpc.netty.NettyServerBuilder;
import io.netty.handler.ssl.ClientAuth;
import io.netty.handler.ssl.SslContext;
import io.netty.handler.ssl.SslContextBuilder;
import io.netty.handler.ssl.SslProvider;
import javax.net.ssl.SSLException;
import java.io.File;
import java.io.IOException;
import java.util.logging.Logger;

/*
 * The JobServServer class implements the JobServ protobuf API
 * It does this by extending the gRPC stub code.
 * Additionally, JobServServer starts and manages a daemon
 * Which accepts incoming connections from client.
 */
public class JobServServer {
    private static final Logger logger = Logger.getLogger(JobServServer.class.getName());

    private Server server;
    private final int port;
    private final SslContext ssl;

    /*
     * Constructor
     * Sets port and builds sslContext
     */
    public JobServServer(int port,
                         String serverCert,
                         String privateKey,
                         String trustStore) throws SSLException {
        this.port = port;
        SslContextBuilder sslContextBuilder = SslContextBuilder.forServer(new File(serverCert), new File(privateKey));

        // Mutual TLS trust store and require client auth
        sslContextBuilder.trustManager(new File(trustStore));
        sslContextBuilder.clientAuth(ClientAuth.REQUIRE);

        this.ssl = GrpcSslContexts.configure(sslContextBuilder).build();
    }

    /*
     * start()
     * this initializes the server
     */
    private void start() throws IOException {
        // TODO: this should be passed in from a configuration manager
        server = NettyServerBuilder.forPort(port)
            .addService(new ShellServerService())
            .sslContext(this.ssl)
            .build()
            .start();
        logger.info("Server initialized!");

        Runtime.getRuntime().addShutdownHook(new Thread() {
                @Override
                public void run() {
                    // JVM shutdown might break logger functionality
                    // so investigate this....
                    logger.info("Shutting down server");
                    JobServServer.this.stop();
                }
            });
    }

    /*
     * stop()
     * This is called when ctrl+c is pressed
     */
    private void stop() {
        if (server != null) {
            server.shutdown();
        }
    }

    /*
     * blockUntilShutdown()
     * This is more or less the main loop of the server.
     * It spins until shutdown is called.
     */
    private void blockUntilShutdown() throws InterruptedException {
        if (server != null) {
            server.awaitTermination();
        }
    }

    /*
     * main()
     * Entrypoint of hte server
     * parses args and initializes a server object.
     * calls server main loop.
     */
    public static void main(String[] args) throws IOException, InterruptedException {
        int port = 8448; // TODO: port and key/cert files should be handled by a config manager

        if(args.length < 3) {
            System.out.println("Usage: ./jobserv-server cert privatekey truststore");
            return;
        }

        JobServServer server;

        try{
            server = new JobServServer(8448, args[0], args[1], args[2]);
        } catch (SSLException e) {
            System.out.println(e.getMessage());
            return;
        }

        server.start();
        server.blockUntilShutdown();
    }
}