Effects refactoring example (UNC COMP 523)

before.js

// Goal: assign students to seats
// Usage: node before.js
// Context: UNC COMP 523 (https://comp523.cs.unc.edu)
// Exercise: refactor to manage effects better

const makePref = ([pid, section, isVip]) =>
  ({pid, section, isVip, isAssigned: false})

const makePrefs = (rows) => rows.map(makePref)

const prefs = makePrefs([
  ['111222333', 'front', false],
  ['111222444', 'front', true],
  ['111222555', 'middle', false],
  ['111222666', 'front', true],
  ['111222777', 'back', false],
  ['111222888', 'back', true],
])

let seatsBySection = {
  'front': 2,
  'middle': 2,
  'back': 2,
}

let assignments = {
  'front': [],
  'middle': [],
  'back': [],
  'overflow': [],
}

for (var i = 0; i < prefs.length; i++) {
  const {pid, section, isVip, isAssigned} = prefs[i]
  if (isAssigned) continue
  if (!isVip) continue
  if (seatsBySection[section] > 0) {
    seatsBySection[section] -= 1
    assignments[section].push(pid)
    prefs[i].isAssigned = true
  } else {
    assignments.overflow.push(pid)
    prefs[i].isAssigned = true
  }
}

for (var i = 0; i < prefs.length; i++) {
  const {pid, section, isVip, isAssigned} = prefs[i]
  if (isAssigned) continue
  if (seatsBySection[section] > 0) {
    seatsBySection[section] -= 1
    assignments[section].push(pid)
    prefs[i].isAssigned = true
  } else {
    assignments.overflow.push(pid)
    prefs[i].isAssigned = true
  }
}

for (var section in assignments) {
  console.log(`PIDs in '${section}' section: ` + assignments[section].join(', '));
}