Auto Add to Cart for shopify site

I need an application that automatically add a product to cart and complete checkout steps on shopify based website. Specifically, the website for the product auto purchase is [login to view URL] and a perfect example of how I would like it to function is here: [login to view URL] Key features: • Choose Item By Keyword • Supports Multiple Items • Supports Multiple Profiles • Select Color & Size • Fills Out Form With Javascript For Faster Performance • Auto Refreshes Until Finds Item • Completes Whole Process In Matter Of Seconds • Saves Personal Information For Later Uses. Only Have To Enter It Once. Details: GUI - Enter product keyword, size,  action options, shipping and billing info (with ability to save profiles), time intervals (e.g. 1 second) Program should have start and stop buttons. When start is activated, program should search the website for the keyword input. Once the keyword input is found, program should open the product, select the size input, and add to cart. It should proceed to checkout and fill out form with shipping and billing info. If it receives an out of stock error message, it should begin a loop where it goes back to the previous page and clicks the checkout button again until the product is secured in the cart. Action options: Add to cart only, Add to cart + fill out form, Add to cart + fill out form + submit, view full screen option (vs. pictureless condensed view to increase speed), if a size is sold out  or unavailable then include option to pick the next biggest size I need complete access to the source code because sometimes the website will change the name of buttons and I will need to be able to adjust the program accordingly.