Cartfidential

Within the current landscape of digital commerce, there is no such progress and there are still the same problems of scalability and performance with high traffic than some years ago. For this reason, we have decided to implement a new type of ecommerce based on the Blockchain technology, creating a decentralized network to execute and store, in a decentralized way, the different processes of an ecommerce.

That's why you will be in charge of creating a very important part of it, the shopping cart.

How it works?

The aim of this API is to manage a shopping cart of our ecommerce website. So, through it, the Frontend Team will be able to request and create, update or delete any item in the current cart.

Every action of the API will generate a new Block on the Blockchain in order to create a history and persist the information, so we can retrieve it later, but also keeps a history of which items have the user added to the cart.

You could find the API description on the OpenAPI description file.

Workflow

The workflow of this API is as follows:

• Create

1. Create request is received
2. Check if the id for a Cart is not already used
   1. If it has been used we return error
   2. If it has not been used, we create the cart with the given item and generates a new Block to add to the Blockchain
3. Add the new Block to the Blockchain with the current information of this Cart

• Update

1. Update request is received
2. Check if the id for a Cart exists
   1. If not exists return error
   2. If exist retrieve it
3. Update the items in the cart and generate a new Block with the information
4. Add the new Block to the Blockchain

• Delete

1. Delete request is received
2. Check if the id for a Cart exists
   1. If not exists return error
   2. If exist retrieve it
3. Remove cart information and create a new Block
4. Add the new Block to the Blockchain

Technical Considerations

Keep in mind the following:

1. Related with the Blockchain:
   1. The blockchain have a first block called 'genesis block', these block doesn't contain a reference of the previous block, usually is hardcoded on the software
   2. Every Block has multiple properties:
      1. timestamp: the timestamp for the moment when the block was created
      2. lastHash: hash of the previous block on the blockchain
      3. data: information we want to store in the block (in our case the votes)
      4. nonce: a unique number
      5. hash: a SHA256 string for the block, calculated concatenating the timestamp, lastHash, data and nonce.
   3. The implementation of the Blockchain must follow these contract:

       Blockchain
         /** Adds new block to blockchain */
         addBlock(block: Block): Block
         /** The new blockchain that is a candidate for replacing the current blockchain */
         replace(blockchain: Blockchain): boolean
         /**
          * Validates the chain by checking if:
          * - Genesis Block hash match given blockchain genesis block hash
          * - every element's last hash value matches previous block's hash
          * - data hasn't been tampered (which will produce a different hash value)
          */
         isValid(blockchain: Blockchain): boolean
      
       Block
         /** Generate the first block for the chain */
         static getGenesisBlock(): Block
         /** Generate the hash for the given block */
         static generateHashFromBlock(block: Block): string
      

Technical requirements

• Create a clean, maintainable and well-designed code. We expect to see a good and clear architecture that allows to add or modify the solution without so much troubles.
• Test your code until you are comfortable with it. We don't expect a 100% of Code Coverage but some tests that helps to have a more stable and confident base code.

To understand how you take decisions during the implementation, please write a COMMENTS.md file explaining some of the most important parts of the application. You would also be able to defend your code through Rviewer, once you submit your solution.

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How to submit your solution

• Push your code to the devel branch - we encourage you to commit regularly to show your thinking process was.
• Create a new Pull Request to main branch & merge it.

Once merged you won't be able to change or add anything to your solution, so double-check that everything is as you expected!

Remember that there is no countdown, so take your time and implement a solution that you are proud!

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If you have any feedback or problem, let us know! 🤘

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