SHOPIFY: convert 3rd partyXML products to standard CSV

I have a shopify e-commerce platform and my supplier provide xml file with product description. I need to fully automate the process of downloading the XMLs ,converting them to shopify standard CSV. code will be thoroughly reviewed for software best practice such as checking for errors and maintainability. Issue such as fatal error should be handled to avoid sending partial data. source files: [login to view URL] [login to view URL] [login to view URL] expected output format: [login to view URL]:Products#Preparing_the_CSV_file Looking for clean, professional and simple code.