koenbrouwer/gilded-rose-solution

My solution to the Gilded Rose Kata. Original repo via: https://github.com/emilybache/GildedRose-Refactoring-Kata.

My solution to the Gilded Rose Kata

My answer to the Gilded Rose Kata by EmilyBache in Javascript. (Started off in /js-mocha)

Changes and thoughts

I've done quite some modifications, some of which I have summarized below, with some of my thoughts, so that you understand why I made that change.

• Moved the Item class to a seperate file.

Because that's how it should be in EVERY project that I lead.

• Created a new Product class, which extends/augments the Item class .

I felt like a lot of logic should actually be part of the Item, but since we're not allowed to make any modifications to the Item class, I just decided to create a new Product class based on the original, unmodified Item class.

• Created a sampleData.json file in which all the data regarding products/items is stored.

This could of course be turned into a database of choice.

• Completely removed the whole logic of updateQuality().

I wanted to do something completely different, so I just removed it all, and completely redesigned the whole logic of aging and updating the quality of Items.

• Added defaultOptions as a base configuration for Products.

The goal here is to have a Product to be responsible for its own properties. We'll just pass in some properties and some basic configuration, and let the Product class handle the aging based on the specific configuration.

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It would be nice if we could just have a shop and call an age method on it, and the Shop will take care of all the things that need to happen to update the quality of its Products.

• Introduced an age property on the Product. This value represents the number of days that the Product has been in the Shop.

By age++'ing on every update, we can simulate the aging of Products.

• Introduced a degrationRate, which will represent the rate at which a Product will lose quality over time. Defaults to -1.

I know, it should be degradationRate, I was just too lazy to refactor it afterwards. In production I would totally take the time to find the correct term and refactor if required.

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The idea here is to have a per product configurable value, so that the update method in the Product class isn't responsible for the way it updates, just that it updates. And also it doesn't have to be overly filled with if/else statements that determine how the product should degrade.

• Added a seperate validate method, which will ensure that (according to the requirements) the quality property is never negative, and never goes above 50.

Now that validate is a seperate method, we can decide if it should be called, if in the future, there are products that have different "rules".

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Hey, what a coincidence, there's this Backstage Pass to a concert product, that has different rules!

• Added the ability to configure a different agingBehaviour for products that age in a different way.

Aging behaviour is also a configurable option, and the string value of it will be used to find a file with custom logic that is used as the doAge method.

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Totally overkill for this one Backstage Pass to a concert product, but very future proof if more products are added later.

• Added the option legendary which defaults to false.

Legendary Products will age++, but that will not have any effect on any property of it, because we'll just break after this check.

• With all my previous thoughts already implemented, finding a solution for conjured items, is now obsolete. We'll just change the value of qualityDegrationRate.
• Shop has a property age that keeps track of the number of times it has been updated (aged). Just for the sake of printing some stats as result of the test.
• Using console.table to print a nice summary of the current state of the Shop and its Products.

Instructions

To test or run this project:

1. Clone project
2. Run $ npm install
3. Run $ npm test

I've attached a log file, in case you are not able to run the script by yourself.

If you want to create a new log file, just run $ npm test > log.

Remarks

Feel free to submit a pull request or post an issue if you have any suggestions or questions.