gistfile1.js

// ======================================
// Gilded Rose Requirements Specification
// ======================================

// We are a small inn with a prime location in a prominent city ran by a friendly innkeeper named Allison. 
// We also buy and sell only the finest goods.
// Unfortunately, our goods are constantly degrading in quality as they approach their sell by date. We
// have a system in place that updates our inventory for us.

// First an introduction to our system:

// 	- All items have a SellIn value which denotes the number of days we have to sell the item
// 	- All items have a Quality value which denotes how valuable the item is
// 	- At the end of each day our system lowers both values for every item

// Pretty simple, right? Well this is where it gets interesting:

// 	- The Quality of an item is never negative;
// 	- "Aged Brie" actually increases in Quality the older it gets;
// 	- The Quality of an item is never more than 50;
// 	- "Backstage passes", like "Aged Brie", increases in Quality as its SellIn value approaches;
// 	- "Sulfuras", being a legendary item, never has to be sold or decreases in Quality.

// Just for clarification, an item can never have its Quality increase above 50, however "Sulfuras" is a
// legendary item and as such its Quality is 80 and it never alters.

// Suppose you have the following data amostration for items:

var data = [
  {
    name: '+5 Dexterity Vest',
    sell_in: 10,
    quality: 20
  }, {
    name: 'Aged Brie',
    sell_in: 2,
    quality: 0
  }, {
    name: 'Elixir of the Mongoose',
    sell_in: 5,
    quality: 7
  }, {
    name: 'Sulfuras',
    sell_in: 0,
    quality: 80
  }, {
    name: 'Backstage Passes',
    sell_in: 15,
    quality: 20
  }, {
    name: 'Conjured Mana Cake',
    sell_in: 3,
    quality: 6
  }
];

// The proposed solution is:

function update_quality(items) {
  for (var i = 0; i < items.length; i++) {
    if (items[i].name != 'Aged Brie' && items[i].name != 'Backstage passes') {
      if (items[i].quality > 0) {
        if (items[i].name != 'Sulfuras') {
          items[i].quality = items[i].quality - 1;
        }
      }
    } else {
      if (items[i].quality < 50) {
        items[i].quality = items[i].quality + 1;
        if (items[i].name == 'Backstage passes') {
          if (items[i].quality < 50) {
            items[i].quality = items[i].quality + 1;
          }
        }
      }
    }
    if (items[i].name != 'Sulfuras') {
      items[i].sell_in = items[i].sell_in - 1;
    }
    if (items[i].sell_in < 0) {
      if (items[i].name != 'Aged Brie') {
        if (items[i].name != 'Backstage passes') {
          if (items[i].quality > 0) {
            if (items[i].name != 'Sulfuras') {
              items[i].quality = items[i].quality - 1;
            }
          }
        } else {
          items[i].quality = items[i].quality + 1;
        }
      } else {
        if (items[i].quality < 50) {
          items[i].quality = items[i].quality + 1;
        }
      }
    }
  }
}

update_quality(data);