Migrate help desk tickets from Assembla to Jira

We have been using Assembla ([login to view URL]) for our help desk, and have two projects with in total nearly 5000 tickets. We wish to migrate to Jira ([login to view URL]) . Because Assembla has very few exporting options we need someone to either: a) Export the tickets using the JSON format from Assemble, then write a program to manipulate that data into a format that Jira will import, or: b) Write a script that calls the Assembla API, gets a the ticket's details, then calls the JIRA API and creates an identical ticket in Jira. This would then step through all tickets in the project. Important is the ability to pull the ticket, it's history AND any attachments out of Assembla and create these in Jira. We need this to be written as an automated tool so that we can do a trial migration, test and prove the data is correct, then clean out the Jira database and do a full migration again.