replayio / delta

Replay Delta

Contributing

# Install dependencies
yarn install

# If you want to generate diffs locally, you'll also need
brew install graphicsmagick
brew install imagemagick

# Run dev server on port 3000
yarn dev

Resources

• Supabase - Database, file storage, authentication
• GitHub webhooks - Primary source of app data
• GitHub REST API - Used to update PR (status checks, comments)
• Next.js - Hosts front end
• LogTail - Error logging

How does the Delta GitHub app work?

Currently the only app integrated with Delta is the Replay devtools.

For a GitHub repository to integrate with Delta, it must:

1. Create a Project in the Delta Supabase projects table (requires admin access)
2. Install the GitHub “Delta” app
3. Setup a GitHub Workflow should be setup like this one to
   • Use Playwright to generate screenshots of UI
   • Upload screenshots to delta (as base64 images)

When a commit is pushed to the primary branch (typically main) or a when a PR is opened against that branch:

• GitHub webhook will notify Delta by posting to https://delta.replay.io/api/handleGithubEvents
• Delta cares specifically about the following events:
  • “pull_request”
    • “opened” (or “reopened”): Creates or updates branches record in Supabase
    • "closed": Update branches record in Supabase
  • "workflow_run" when run for the workflow named “Delta” (other workflows are ignored)
    • “in_progress”: Insert runs record in Supabase and use GitHub API to create a check on the PR
    • "completed": Compares Snapshots from the just-finished Run to those from the most recent run of the Primary branch and uses the GitHub API to update the check on PR (and to add/update a comment if images have changed)

At any point, users can view open PRs at delta.replay.io:

• This app is auto-deployed to Vercel from main
• The app fetches GH actions and screenshot data from Supabase
• Branches (and GitHub Workflow runs) can be selected from drop-down menus at the top