Fix SSE event parsing preventing progress bar updates and download functionality

[Copilot]

The compilation progress bar and download functionality appeared broken because SSE events were silently ignored due to incorrect parsing logic.

Root Cause

Client-side code attempted to extract both event: and data: from the same line, but SSE format specifies them on separate lines:

// Before: tried to parse both from one line
const data = JSON.parse(line.slice(6));
const eventType = line.match(/event: (\w+[\w:]*)/)?.[1]; // always undefined

// After: track event type across lines
let currentEventType = '';
if (line.startsWith('event: ')) {
    currentEventType = line.slice(7).trim();
} else if (line.startsWith('data: ')) {
    const data = JSON.parse(line.slice(6));
    handleEvent(currentEventType, data);
}

Changes

Client (public/index.html)

• Fixed SSE parser to handle multi-line event format
• Added handlers for transformation:complete and compilation:complete events
• Corrected field reference from data.transformation to data.name

Server (worker/worker.ts)

• Added cache lookup before streaming compilation for diff comparison support
• Store compilation results in gzip-compressed cache after successful compilation
• Include previousVersion data in result events

Result

Progress bar now updates in real-time, all transformation events display correctly, and download functionality works.

Before: Events ignored, UI appeared frozen

After: Full event pipeline with transformation completion feedback

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• sparrow.cloudflare.com
  • Triggering command: /usr/local/bin/node /usr/local/bin/node --no-warnings --experimental-vm-modules /home/REDACTED/work/adblock-compiler/adblock-compiler/node_modules/wrangler/wrangler-dist/cli.js dev --port 8787 (dns block)
• workers.cloudflare.com
  • Triggering command: /usr/local/bin/node /usr/local/bin/node --no-warnings --experimental-vm-modules /home/REDACTED/work/adblock-compiler/adblock-compiler/node_modules/wrangler/wrangler-dist/cli.js dev --port 8787 (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

After compiling a list on the website, how does a user get their list? When you click compile filter list, nothing happens. Shouldn't the progress bar show realtime compilation, and then present the user with a compiled list to download?

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Status	Name	Latest Commit	Updated (UTC)
✅ Deployment successful! View logs	adblock-compiler	24de342	Jan 04 2026, 02:44 AM