J REPL in Node

readme.md

This Node script creates a REPL for the J langage by calling out to the J shared lib (libj.so) via the node-ffi-napi.

I would like to be able to do syntax highlighting on the input (and perhaps output) using emphasize, which wraps highlight.js through lowlight to output ANSI syntax highlighting.

emphasize is "ESM only". I'm not a Node guy, so I'm not sure exactly what that means, apart from the fact that I can't simply do require('emphasize') in my Node script. Any help on how to get this working would be appreciated.

The highlight.js language definition for J is here.

jrepl.js

//!/usr/bin/env node

var ffi = require('ffi-napi');

const BIN = '/opt/j904/bin';
const LIB = `${BIN}/libj.so`;
const PRO = `${BIN}/profile.ijs`;

var libj = ffi.Library(LIB, {
  'JInit': [ 'pointer', [ ] ],
  'JDo':   [ 'int', [ 'pointer', 'string' ] ],
  'JGetR': [ 'string', [ 'pointer' ] ],
});

let j = libj.JInit();

libj.JDo(j, `0!:0<'${PRO}'[BINPATH_z_=:'${BIN}'[ARGV_z_=:''`);

var readline = require('readline');

var rl = readline.createInterface({
  input: process.stdin,
  output: process.stdout
});

rl.setPrompt('   ')
rl.prompt()

rl.on('line', expr => {
  libj.JDo(j, expr);
  var out = libj.JGetR(j);
  process.stdout.write(out);
}),

// force trigger of _writeToOutput on each keystroke
process.stdin.on(
  'keypress', (c, k) => {
    setTimeout(() => { rl._refreshLine() }, 0);
  },
);

rl._writeToOutput = function _writeToOutput(out) {
  // This is where the highlighting would occur
  // eg. rl.output.write(emphasize.highlight('J', out);
  rl.output.write(out)
};