Image Metadata API

Project roadmap

1. 01

   Define the API and metadata

   ~1.5h

   Write API.md: POST /images (upload or path), GET /images/:id, DELETE /images/:id and GET /images?format=&camera=&orientation=&taken_from=&taken_to=&min_width=&has_gps=&sort=&page=. List the metadata fields, which ones can be filtered, and the error format. Create a Sinatra app with a Gemfile (sinatra, redis and an EXIF gem such as exifr or mini_exiftool). Done when: API.md defines every endpoint and field.

2. 02

   Extract metadata

   ~2h

   Write a MetadataExtractor that reads the format and dimensions from the file itself (for example with the fastimage gem or by checking file signatures), and EXIF fields (camera, date taken, orientation and GPS) for JPEG and TIFF files, converting GPS values to decimal degrees. Handle images without EXIF and corrupted files with clear results. Done when: tests extract correct metadata from sample images, with and without EXIF.

3. 03

   Store and index in Redis

   ~2.5h

   Store each image's metadata in a hash, and maintain indexes: sets for exact filters (format, camera, orientation and has GPS) and sorted sets for ranges (date taken, width and file size). Add and remove an image's index entries in one MULTI transaction, so indexes never point to missing images. Detect duplicates by a SHA-256 checksum. Done when: registering and deleting images keeps all indexes consistent.

4. 04

   Search with filters

   ~2.5h

   Implement GET /images: build the result by intersecting the sets for exact filters with ranges from the sorted sets (using ZRANGESTORE with BYSCORE into temporary keys with a short expiry, then ZINTERSTORE), sort by date or size, and page through the results. Validate every query parameter. Done when: combined filters return exactly the matching images in the right order.

5. 05

   Harden the API

   ~1.5h

   Limit upload size and accept only real images (checking the content), strip the GPS location from responses unless requested (it can reveal where someone lives), return 404, 409 and 422 correctly, and handle Redis being unavailable with a 503. Add a task to rebuild all indexes from the stored hashes. Done when: bad uploads and outages are handled clearly, and indexes can be rebuilt.

6. 06

   Test it

   ~2h

   Write RSpec tests with Rack::Test against a test Redis database: metadata extraction, registration and duplicates, each filter alone and combined, sorting and paging, deletion cleaning up indexes, and invalid parameters. Done when: all tests pass.

Resources

• DocsSinatra documentation
• DocsRedis sets
• DocsRedis sorted sets
• Docsexifr gem
• ArticleExif (Wikipedia)