Its more than 5 years , i am working as a Integration Programmer of PeopleHR Software (https://www.peoplehr.com/) . I have developed many integrations between People HR software & other 3rd party software / tools like Freshbooks; Greenhouse; Indeed; WhenIWork; Workable (and many more).
Xero API Integration (https://developer.xero.com/documentation/api/api-overview/) I have build a sample prototype to export (in CSV format) your Xero Invoice , contacts , accounts in one click. This prototype application using Xero Public application. You can easily convert your Xero public application