serene-simple/src/main/java/serene/simple/Main.java

/**
 * Serene (simple) - A PoC lisp to collect data on Serenes concepts
 * Copyright (C) 2019-2020 Sameer Rahmani <lxsameer@gnu.org>
 *
 * This program 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
 * of the License, or (at your option) any later version.
 *
 * This program 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 this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
 * MA  02110-1301, USA.
 */
package serene.simple;

import java.io.IOException;
import java.io.ByteArrayInputStream;
import java.io.Console;
import java.io.FileInputStream;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.net.ServerSocket;
import java.net.Socket;

/**
 * What is missing:
 *   * A namespace functionality. Because creating and compiling dynamic classes
 *     is a rabbit hole and tons of work which doesn't make sense for a toy
 *     project.
 *   * Unified function interface.
 *   * Requiring different namespaces
 *   * A sophisticated parser. My Reader implementation is really cheap that
 *     suits a toy project. It might worth investigating on different solutions
 *     including using a parser generator or a head of time read implementation.
 *   * Primitive functions in Serene. I implemented lots of primitive functions
 *     in java rather than Serene itself mostly because of two reasons. Lack of
 *     macros and namespaces.
 *   * Decent [functional] data structures. The only data structure I implemented
 *     is list.
 *   * Quality code. The general quality of this implementation is not great, I
 *     sacrificed quality for time.
 */
public class Main {
  private static int port = 5544;
  private static String host = "localhost";

  private static String licenseHeader = "\nSerene(simple), Copyright (C) 2019-2020 " +
    "Sameer Rahmani <lxsameer@gnu.org>\n" +
    "Serene(simple) comes with ABSOLUTELY NO WARRANTY;\n" +
    "This is free software, and you are welcome\n" +
    "to redistribute it under certain conditions; \n" +
    "for details take a look at the LICENSE file.\n";

  public static void main(String[] args) throws IOException, RuntimeException {

    if (args.length == 0) {
      startRepl();
      return;
    }

    if (args[0].equals("nrepl")) {
      nrepl();
      return;
    }

    runSerene(args[0]);
  }

  private static void startRepl() throws IOException {
    RootScope rootScope = new RootScope();

    Console console = System.console();

    System.out.println("Serene 'simple' v0.1.0");
    System.out.println(licenseHeader);

    while(true) {
      String inputData = console.readLine("serene-> ");

      if (inputData == null) break;

      ByteArrayInputStream inputStream = new ByteArrayInputStream(inputData.getBytes());


      try {
        ListNode<Node> nodes = Reader.read(inputStream);
        Object result = ListNode.EMPTY;

        for (Node n : nodes) {
          result = n.eval(rootScope);
        }

        System.out.print(";; ");
        if (result == null) {
          System.out.println("nil");
        }
        else {
          System.out.println(result.toString());
        }

      }
      catch(Exception e) {
        System.out.println("Error: ");
        e.printStackTrace(System.out);
      }

    }
  }

  /**
   * Serene's nRepl is super simple. It waits for a newline char and then evaluates the
   * given input. It sends back the result of the evaluation in `<status-char><value>` format.
   * `status-char` is either `0` or `1`. **Zero** means the evaluation was successful and the `value`
   * is the result of evaluation while **one** means there was an error during the evaluation and
   * the `value` is the traceback for the exception.
  */
  public static void nrepl() throws IOException {
    RootScope rootScope = new RootScope();
    ServerSocket socket = new ServerSocket(Main.port);;

    System.out.println("Serene 'simple' v0.1.0");
    System.out.println(licenseHeader);
    System.out.println(
      String.format("nRepl has been started on tcp://%s:%s", Main.host, Main.port));

    // NOTE: The nRepl server is too simple. It supports one connection at a time
    // and will terminate when the client disconnects.
    try {
      Socket clientSocket = socket.accept();

      PrintWriter out = new PrintWriter(clientSocket.getOutputStream(), true);
      BufferedReader in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));

      while(true) {
        String inputData = in.readLine();

        if (inputData == null) break;

        ByteArrayInputStream inputStream = new ByteArrayInputStream(inputData.getBytes());


        try {
          ListNode<Node> nodes = Reader.read(inputStream);
          Object result = ListNode.EMPTY;

          for (Node n : nodes) {
            result = n.eval(rootScope);
          }

          if (result == null) {
            out.println("0nil");
          }
          else {
            out.println(
              String.format("0%s", result.toString()));
          }

        }
        catch(Exception e) {
          StringWriter sw = new StringWriter();
          e.printStackTrace(new PrintWriter(sw));
          String exceptionAsString = sw.toString();
          out.println(
            String.format("1%s", exceptionAsString));
        }
      }

    }
    catch (IOException e) {
      System.out.println("Exception caught when trying to listen on port "
                         + Main.port + " or listening for a connection");
      System.out.println(e.getMessage());
    }
    finally {

      socket.close();
    }
  }

  private static void runSerene(String filePath) throws IOException {
    IScope rootScope = new RootScope();
    FileInputStream input = new FileInputStream(filePath);
    ListNode<Node> nodes = Reader.read(input);

    for (Node n : nodes) {
      n.eval(rootScope);
    }
  }
}