Gilded Rose Kata—Look-up approach in TypeScript

README.md

Gilded Rose Kata—Look-up approach in TypeScript

Inspired by “it's a table driven problem, it's not an object oriented problem, it's not even a control flow problem”.

• Gilded Rose Requirements
• Original TypeScript starting point
• TypeScript Playground with updateQualityBefore(item: Item) and updateQualityAfter(item: Item)

---

/*
 * RUN Script
 */
tests(updateQualityBefore);

[LOG]: "tests DONE" 

---

/*
 * RUN Script
 */
tests(updateQualityAfter);

[LOG]: "tests DONE" 

---

/*
 * RUN Script
 */
demo(updateQualityBefore);

[LOG]: "-------- day 0 --------" 
[LOG]: "name, sellIn, quality" 
[LOG]: "+5 Dexterity Vest 10 20" 
[LOG]: "Aged Brie 2 0" 
[LOG]: "Elixir of the Mongoose 5 7" 
[LOG]: "Sulfuras, Hand of Ragnaros 0 80" 
[LOG]: "Sulfuras, Hand of Ragnaros -1 80" 
[LOG]: "Backstage passes to a TAFKAL80ETC concert 15 20" 
[LOG]: "Backstage passes to a TAFKAL80ETC concert 10 49" 
[LOG]: "Backstage passes to a TAFKAL80ETC concert 5 49" 
[LOG]: 
[LOG]: "-------- day 1 --------" 
[LOG]: "name, sellIn, quality" 
[LOG]: "+5 Dexterity Vest 9 19" 
[LOG]: "Aged Brie 1 1" 
[LOG]: "Elixir of the Mongoose 4 6" 
[LOG]: "Sulfuras, Hand of Ragnaros 0 80" 
[LOG]: "Sulfuras, Hand of Ragnaros -1 80" 
[LOG]: "Backstage passes to a TAFKAL80ETC concert 14 21" 
[LOG]: "Backstage passes to a TAFKAL80ETC concert 9 50" 
[LOG]: "Backstage passes to a TAFKAL80ETC concert 4 50" 

---

/*
 * RUN Script
 */
demo(updateQualityAfter);

[LOG]: "-------- day 0 --------" 
[LOG]: "name, sellIn, quality" 
[LOG]: "+5 Dexterity Vest 10 20" 
[LOG]: "Aged Brie 2 0" 
[LOG]: "Elixir of the Mongoose 5 7" 
[LOG]: "Sulfuras, Hand of Ragnaros 0 80" 
[LOG]: "Sulfuras, Hand of Ragnaros -1 80" 
[LOG]: "Backstage passes to a TAFKAL80ETC concert 15 20" 
[LOG]: "Backstage passes to a TAFKAL80ETC concert 10 49" 
[LOG]: "Backstage passes to a TAFKAL80ETC concert 5 49" 
[LOG]: "Conjured Mana Cake 3 6" 
[LOG]: 
[LOG]: "-------- day 1 --------" 
[LOG]: "name, sellIn, quality" 
[LOG]: "+5 Dexterity Vest 9 19" 
[LOG]: "Aged Brie 1 1" 
[LOG]: "Elixir of the Mongoose 4 6" 
[LOG]: "Sulfuras, Hand of Ragnaros 0 80" 
[LOG]: "Sulfuras, Hand of Ragnaros -1 80" 
[LOG]: "Backstage passes to a TAFKAL80ETC concert 14 21" 
[LOG]: "Backstage passes to a TAFKAL80ETC concert 9 50" 
[LOG]: "Backstage passes to a TAFKAL80ETC concert 4 50" 
[LOG]: "Conjured Mana Cake 2 4"  

gilded-rose.ts

// File: gilded-rose.ts
// For: https://gist.github.com/peerreynders/146d5a2c7d6adf5358580da5054c76b4

type Item = {
  name: string;
  sellIn: number;
  quality: number;
};

function makeItem(name: string, sellIn: number, quality: number): Item {
  return {
    name,
    sellIn,
    quality,
  };
}

type UpdateQuality = (item: Item) => void;

/*
 * BEFORE implementation
 *
 * Original:
 * https://github.com/emilybache/GildedRose-Refactoring-Kata/blob/main/TypeScript/app/gilded-rose.ts
 *
 */
function updateQualityBefore(item: Item) {
  if (
    item.name != 'Aged Brie' &&
    item.name != 'Backstage passes to a TAFKAL80ETC concert'
  ) {
    if (item.quality > 0) {
      if (item.name != 'Sulfuras, Hand of Ragnaros') {
        item.quality = item.quality - 1;
      }
    }
  } else {
    if (item.quality < 50) {
      item.quality = item.quality + 1;
      if (item.name == 'Backstage passes to a TAFKAL80ETC concert') {
        if (item.sellIn < 11) {
          if (item.quality < 50) {
            item.quality = item.quality + 1;
          }
        }
        if (item.sellIn < 6) {
          if (item.quality < 50) {
            item.quality = item.quality + 1;
          }
        }
      }
    }
  }
  if (item.name != 'Sulfuras, Hand of Ragnaros') {
    item.sellIn = item.sellIn - 1;
  }
  if (item.sellIn < 0) {
    if (item.name != 'Aged Brie') {
      if (item.name != 'Backstage passes to a TAFKAL80ETC concert') {
        if (item.quality > 0) {
          if (item.name != 'Sulfuras, Hand of Ragnaros') {
            item.quality = item.quality - 1;
          }
        }
      } else {
        item.quality = item.quality - item.quality;
      }
    } else {
      if (item.quality < 50) {
        item.quality = item.quality + 1;
      }
    }
  }
}

/*
 * AFTER implementation
 *
 * Requirements:
 * https://github.com/emilybache/GildedRose-Refactoring-Kata/blob/main/GildedRoseRequirements.txt
 *
 */
type QualityAdjustmentFn = (item: Item) => number;

// - At the end of each day our system lowers both values for every item
// - Once the sell by date has passed, Quality degrades twice as fast
const qualityAdjustment: QualityAdjustmentFn = ({ sellIn }) =>
  sellIn > 0 ? -1 : -2;

// - "Aged Brie" actually increases in Quality the older it gets
const brieAdjustment: QualityAdjustmentFn = (item) => -qualityAdjustment(item);

// - "Backstage passes", like aged brie,
//  increases in Quality as its SellIn value approaches;
//  Quality increases by 2 when there are 10 days or less and
//  by 3 when there are 5 days or less but Quality
//  drops to 0 after the concert
const passesAdjustment: QualityAdjustmentFn = (item) =>
  item.sellIn > 10
    ? -qualityAdjustment(item)
    : item.sellIn > 5
    ? -2 * qualityAdjustment(item)
    : item.sellIn > 0
    ? -3 * qualityAdjustment(item)
    : -item.quality;

// - "Conjured" items degrade in Quality twice as fast as normal items
const conjuredAdjustment: QualityAdjustmentFn = (item) =>
  2 * qualityAdjustment(item);

const clamp = (min: number, max: number, value: number) =>
  value > max ? max : value < min ? min : value;

// - At the end of each day our system lowers both values for every item
// - The Quality of an item is never negative
// - The Quality of an item is never more than 50
function updateItem(item: Item, fn: QualityAdjustmentFn) {
  const quality = clamp(0, 50, item.quality + fn(item));

  item.sellIn -= 1;
  item.quality = quality;
}

type ConfigEntry = [name: string, update: UpdateQuality];

function selectUpdate(itemName: string, config: ConfigEntry[]) {
  for (let i = 1; i < config.length; i += 1) {
    const [name, update] = config[i];
    if (itemName.startsWith(name)) return update;
  }
  return config[0][1];
}

const NAME_BRIE = 'Aged Brie';
const NAME_SULFARAS = 'Sulfuras';
const NAME_PASSES = 'Backstage passes';
const NAME_CONJURED = 'Conjured';

const config2: ConfigEntry[] = [
  ['', (item: Item) => updateItem(item, qualityAdjustment)],
  [NAME_BRIE, (item: Item) => updateItem(item, brieAdjustment)],
  [NAME_SULFARAS, (item: Item) => void 0],
  [NAME_PASSES, (item: Item) => updateItem(item, passesAdjustment)],
  [NAME_CONJURED, (item: Item) => updateItem(item, conjuredAdjustment)],
];

const updateQualityAfter = (item: Item) =>
  selectUpdate(item.name, config2)(item);

/*
 * TESTS
 */
function tests(updateQuality: UpdateQuality) {
  // NOTE:
  // Assertion failures show in the
  // Developer Tools Console NOT the `Logs` panel
  const assert = console.assert;
  const isExpected = (item: Item, sellIn: number, quality: number) =>
    item.sellIn === sellIn && item.quality === quality;

  const test01 = () => {
    const title = 'Both sellIn and quality are lowered';
    const item = makeItem('Elixir of the Mongoose', 5, 7);
    updateQuality(item);
    assert(
      isExpected(item, 4, 6),
      `${title}: sellIn ${item.sellIn} and/or quality ${item.quality} don't match lower values`
    );
  };
  test01();

  const test02 = () => {
    const title = 'Quality degrades twice as fast once past sellIn';
    const item = makeItem('Elixir of the Mongoose', 0, 7);
    updateQuality(item);
    assert(
      isExpected(item, -1, 5),
      `${title}: quality ${item.quality} doesn't match degraded value`
    );
  };
  test02();

  const test03 = () => {
    const title = 'Quality is never negative';
    const item = makeItem('Elixir of the Mongoose', 5, 0);
    updateQuality(item);
    assert(
      isExpected(item, 4, 0),
      `${title}: quality ${item.quality} isn't zero`
    );
  };
  test03();

  const test04 = () => {
    const title = 'Aged Brie increases in quality';
    const item = makeItem('Aged Brie', 2, 0);
    updateQuality(item);
    assert(
      isExpected(item, 1, 1),
      `${title}: quality ${item.quality} didn't increase`
    );
  };
  test04();

  const test05 = () => {
    const title = 'Quality never exceeds 50';
    const item = makeItem('Aged Brie', 2, 50);
    updateQuality(item);
    assert(
      isExpected(item, 1, 50),
      `${title}: quality ${item.quality} exceeds maximum`
    );
  };
  test05();

  const test05A = () => {
    const title = 'Aged Brie quality increase doubles past sellIn';
    const item = makeItem('Aged Brie', 0, 20);
    updateQuality(item);
    assert(
      isExpected(item, -1, 22),
      `${title}: quality ${item.quality} doesn't match double increase`
    );
  };
  test05A();

  const test06 = () => {
    const title = `Sulfaras doesn't change`;
    const item = makeItem('Sulfuras, Hand of Ragnaros', -1, 80);
    updateQuality(item);
    assert(isExpected(item, -1, 80), `${title}: item unexpectedly changed`);
  };
  test06();

  const test07 = () => {
    const title = 'Backstages passes increase in quality (> 10 days)';
    const item = makeItem('Backstage passes to a TAFKAL80ETC concert', 11, 20);
    updateQuality(item);
    assert(
      isExpected(item, 10, 21),
      `${title}: quality ${item.quality} didn't increase`
    );
  };
  test07();

  const test08 = () => {
    const title = 'Backstages passes increase by 2 in quality (11 > days > 5)';
    const item1 = makeItem('Backstage passes to a TAFKAL80ETC concert', 10, 20);
    const item2 = makeItem('Backstage passes to a TAFKAL80ETC concert', 6, 30);
    updateQuality(item1);
    updateQuality(item2);
    assert(
      isExpected(item1, 9, 22),
      `${title}: quality ${item1.quality} didn't increase by 2`
    );
    assert(
      isExpected(item2, 5, 32),
      `${title}: quality ${item2.quality} didn't increase by 2`
    );
  };
  test08();

  const test09 = () => {
    const title = 'Backstages passes increase by 3 in quality (6 > days > -1)';
    const item1 = makeItem('Backstage passes to a TAFKAL80ETC concert', 5, 20);
    const item2 = makeItem('Backstage passes to a TAFKAL80ETC concert', 1, 30);
    updateQuality(item1);
    updateQuality(item2);
    assert(
      isExpected(item1, 4, 23),
      `${title}: quality ${item1.quality} didn't increase by 3`
    );
    assert(
      isExpected(item2, 0, 33),
      `${title}: quality ${item2.quality} didn't increase by 3`
    );
  };
  test09();

  const test10 = () => {
    const title = 'Backstages passes quality drops to zero';
    const item = makeItem('Backstage passes to a TAFKAL80ETC concert', 0, 30);
    updateQuality(item);
    assert(
      isExpected(item, -1, 0),
      `${title}: quality ${item.quality} didn't drop to zero`
    );
  };
  test10();

  if (updateQuality === updateQualityAfter) {
    const test11 = () => {
      const title = 'Conjured quality degrades twice as fast BEFORE sellIn';
      const item = makeItem('Conjured Mana Cake', 3, 6);
      updateQuality(item);
      assert(
        isExpected(item, 2, 4),
        `${title}: quality ${item.quality} doesn't match twice degraded value`
      );
    };
    test11();

    const test12 = () => {
      const title = 'Conjured quality degrades twice as fast AFTER sellIn';
      const item = makeItem('Conjured Mana Cake', 0, 6);
      updateQuality(item);
      assert(
        isExpected(item, -1, 2),
        `${title}: quality ${item.quality} doesn't match twice degraded value`
      );
    };
    test12();
  }

  console.log('tests DONE');
}

/*
 * DEMO
 *
 * Original:
 * https://github.com/emilybache/GildedRose-Refactoring-Kata/blob/main/TypeScript/test/golden-master-text-test.ts
 */
function demo(updateQuality: UpdateQuality) {
  const data: [string, number, number][] = [
    ['+5 Dexterity Vest', 10, 20],
    ['Aged Brie', 2, 0],
    ['Elixir of the Mongoose', 5, 7],
    ['Sulfuras, Hand of Ragnaros', 0, 80],
    ['Sulfuras, Hand of Ragnaros', -1, 80],
    ['Backstage passes to a TAFKAL80ETC concert', 15, 20],
    ['Backstage passes to a TAFKAL80ETC concert', 10, 49],
    ['Backstage passes to a TAFKAL80ETC concert', 5, 49],
  ];

  if (updateQuality === updateQualityAfter) {
    data.push(['Conjured Mana Cake', 3, 6]);
  }

  const items = data.map(([name, sellIn, quality]) =>
    makeItem(name, sellIn, quality)
  );

  const log = console.log;
  const days = 2;
  const displayItem = ({ name, sellIn, quality }: Item) =>
    log(`${name} ${sellIn} ${quality}`);

  for (let i = days; i > 0; i -= 1) {
    log(`-------- day ${days - i} --------`);
    log(`name, sellIn, quality`);
    items.forEach(displayItem);
    log();
    items.forEach(updateQuality);
  }
}

/*
 * RUN Script
 */
// tests(updateQualityBefore);
tests(updateQualityAfter);

// demo(updateQualityBefore);
// demo(updateQualityAfter);