hub.js

// a hub world corresponds to a partial order on levels
//
// an example play sequence is:
// 1. the player starts in the hub world,
//    - which several open (or unlocked) doors and several closed (or locked) doors
// 2. the player chooses an open door, and plays through a level, and fails
// 3. the player is returned to the hub world
// 4. the player chooses the same open door, plays through the same level, and succeeds
// 5. the player is returned to the hub world, but there is a change:
//    - the door they went through may be open or closed but it is definitely marked differently
//    - one or more doors that were closed (locked) have become open
// 
function PartialOrder(items) {
  this.items = items;
  this.done = {};
}

PartialOrder.prototype.open = function PartialOrder_open(door) {
  if (!this.items[door]) {
    return false;
  }
  if (this.done[door]) {
    return false; // return true here if you prefer doors to stay open for replaying
  }
  var prereqs = this.items[door].prereqs;
  for (var i = 0; i < prereqs.length; i += 1) {
    var prereq = prereqs[i];
    if (!this.done[prereq]) {
      return false;
    }
  }
  return true;
}

// here's an example of using this class, in a node.js context
po = new PartialOrder({
  a: { prereqs: [] },
  b: { prereqs: [] },
  c: { prereqs: ['a'] },
  d: { prereqs: ['a', 'b'] },
  e: { prereqs: ['c'] },
  f: { prereqs: ['d'] },
  g: { prereqs: ['e', 'f'] },
  h: { prereqs: ['f'] }
});

for (var count_done = 0; count_done < process.argv.length - 2; count_done += 1) {
  console.log('Here are your options:')
  for (var k in po.items) {
    if (po.open(k)) {
      console.log(k);
    }
  }
  var it = process.argv[count_done + 2];
  console.log('btw, it is ' + it);
  if (po.open(it)) {
    po.done[it] = true;
  } else {
    console.log('ERR: ' + it + ' is closed!');
  }
}

console.log('all done!')

// an example of running this demo:
//
// $ js hub.js a b c d e f g h
// here are your options:
// a
// b
// btw, it is a
// here are your options:
// b
// c
// btw, it is b
// here are your options:
// c
// d
// btw, it is c
// here are your options:
// d
// e
// btw, it is d
// here are your options:
// e
// f
// btw, it is e
// here are your options:
// f
// btw, it is f
// here are your options:
// g
// h
// btw, it is g
// here are your options:
// h
// btw, it is h
// all done!