API Update or creation

What I want to do User flow: Step 1 – User go on the shop page to check the product. Step 2 – User will check with their postcode about the availability of the product. Each result will be connected with the machine number, so using the API it will check availability of the product and inform the user if the code is available or not. Step 3 – Once the availability is confirmed, the user can add the product to the cart and make a purchase. Step 4 – After purchase the user will receive a code (which we already talked about yesterday) on an email, SMS and on the order success page. Step 5 – Once the code is used on the machine it should be deleted from the API and can’t be used on the Machine ever again. Here are the details about the API: This is what the previous developer was asked to do: The machines will connect to your website for: • uploading the stock level • downloading the reservations • uploading the reservation delivered you will arrange 3 web services on your side. This is the work he has done: 1) To add product uri is --- [login to view URL] pass json object specified in document format 2) To view orders on machine serial number --- a) [login to view URL] pass json object specified in document format. [POST] b)[login to view URL] [GET] 3) To confirm order and insert a) [login to view URL] Pass json object specified in document format. [POST]