esther-medina-quintero-parser-nearley/src/parse.js

Lab for language processors

'use strict';
const SPACE = require('./tokens.js');
const fs = require('fs');
const nearley = require("nearley");
const grammar = require("./grammar.js");
const { lexer } = require('./lex.js');

// Check parenthesis balance
function parBalance(line) {
  let stack = 0;
  lexer.reset(line);
  let tokens = lexer.tokens;
  /// console.log(tokens);
  for (let token of tokens) {
    if (!token || token.type == "EOF") break;
    if (token.type == "LP") stack++;
    else if (token.type == "RP") stack--;
  }
  return stack;
}

function parse(p) {
  // debugger
  const parser = new nearley.Parser(nearley.Grammar.fromCompiled(grammar));
  parser.feed(p);
  const ast = parser.results[0];
  return ast;
}

function parseFromFile(origin) {
  // debugger
  const parser = new nearley.Parser(nearley.Grammar.fromCompiled(grammar));
  const source = fs.readFileSync(origin, { encoding: 'utf8' });
  parser.feed(source);
  const ast = parser.results[0];
  return ast;
}

let getTokens = function(line) {
  debugger;
  lexer.reset(line);
  let result = [], t = null;
  do {
    try {
      t = lexer.next();
      result.push(t);
    } catch (e) {
      console.error(e);
      result.push({ type: "ERROR", text: e.message});
      break;
    }
  } while(t);
  return result;
}

module.exports = {
  lex: lexer,
  parse,
  SPACE,
  parseFromFile,
  parBalance,
  getTokens
}