repl.js

import readline from 'readline'
import {parser as parserExpr} from './parsers/expr'
import {NodeInfo} from './common'

function parse(src) {
  const tree = parserExpr.parse(src)
  let hasError = false

  const stack = [new NodeInfo()]

  tree.iterate({
    // from: 0,
    // to: tree.length,
    enter(...args) {
      const node = new NodeInfo(...args)
      stack.push(node)
      if (node.error) {
        hasError = true
      }
      // console.log('enter', nodeTypeRepr(node.type), start, end)
    },
    leave() {
      const node = stack.pop()
      const parent = stack[stack.length - 1]
      parent.children.push(node)
      // console.log('leave', nodeTypeRepr(node.type), start, end)
    },
  })

  function getExpr(node, level=0) {
    const arr = []
    const repr = `${node.repr()}: "${src.substring(node.start, node.end)}"`
    const indent = ' '.repeat(level * 2) + '* '

    if (node.error) {
      // id == 0 can be treated as an error?
      arr.push(indent + '[ERROR] ' + repr)
    } else {
      arr.push(indent + repr)
    }

    // is it terminal?

    node.children.forEach(child => {
      getExpr(child, level + 1).forEach(token => {
          arr.push(token)
      })
    })
    return arr
  }

  const treeRoot = stack[0].children[0]
  getExpr(treeRoot).forEach(ln => console.log(ln))

  // returns if the syntax is "correct"
  return !hasError
}

// parse('(8 + 9) * 17 + 20 * 20 - ')

function mainLoop() {
  const rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout,
  })

  rl.on('close', () => {
    console.log()
  })

  const thunk = () => new Promise(resolve => {
    rl.question('> ', src => {
      resolve(parse(src))
    })
  })

  const tForever = () => thunk().then(tForever)
  return tForever()
}

mainLoop()