SVG Favicon to PNG Conversion

Tasks

Task 1: Add mini_magick dependency

Add mini_magick gem to the gemspec as a runtime dependency (or development dependency if it should be optional).

Files:

• Modify: source_monitor.gemspec — add spec.add_dependency "mini_magick"

Details:

• MiniMagick is lightweight and widely used for image processing in Rails
• Requires ImageMagick installed on the host system
• Consider making it optional with a defined?(MiniMagick) guard

Task 2: Add SVG-to-PNG conversion in favicon pipeline

After the Discoverer downloads a favicon, detect if it's SVG and convert to PNG before returning the Result.

Files:

• Modify: lib/source_monitor/favicons/discoverer.rb — add conversion step in download_favicon method
• Create: lib/source_monitor/favicons/svg_converter.rb — isolated conversion class
• Create: test/lib/source_monitor/favicons/svg_converter_test.rb

Details:

• In download_favicon, after validating content_type, check if content_type == "image/svg+xml"
• If SVG: pass the body through SvgConverter.call(io) which uses MiniMagick to convert to PNG
• SvgConverter returns a new Result with content_type: "image/png", updated filename, and PNG io
• If conversion fails: log warning, return nil (skip this favicon, try next candidate)
• Keep image/svg+xml in allowed_content_types so SVGs are downloaded, but always convert before returning

Task 3: Test SVG favicon flow end-to-end

Write tests covering the SVG detection and conversion path.

Files:

• Create: test/lib/source_monitor/favicons/svg_converter_test.rb
• Modify: test/lib/source_monitor/favicons/discoverer_test.rb — add SVG scenario

Acceptance:

• SVG favicon downloaded from a site is converted to PNG before attachment
• If MiniMagick/ImageMagick unavailable, fails gracefully (returns nil)
• Non-SVG favicons pass through unchanged
• Converted PNG has correct content_type and filename