To make RubyGems Lister we need the following -
List of all the packages.
Source code URL and metadata for each package
To get the list of all the packages.
There is no public API endpoint available to list all the packages. Although there is an inbuilt API which can be used to list the packages and all the version present for a particular package.
$ gem list -r --all
This will list all the package and all versions available for a particular package. Here is a sample of the output from the inbuilt API https://forge.softwareheritage.org/P413
To get source code URL and metadata for a particular package
API provided by rubygem can be used to complete the task-
Here is the URL pattern which will be used to call the API
Here is the documentation for the API https://guides.rubygems.org/rubygems-org-api-v2/