feat: add live re-audit workflow with pricing change detection

[eshwarrao123]

What this PR does

This PR adds a complete live re-audit workflow to StackAudit. Audits are now persisted with pricing snapshots, monitored for pricing drift, and automatically re-evaluated when tool pricing changes. Affected users receive a consolidated email notification with a one-click re-audit link that opens a visual diff between the old and updated audit.

The feature turns StackAudit from a one-time calculator into a continuously updated audit system.

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Why

AI tooling pricing changes frequently, especially across products like Cursor, Claude, ChatGPT, and Copilot. A static audit becomes stale quickly and can produce outdated recommendations or inaccurate savings estimates.

This feature assumes users care less about a snapshot score and more about staying continuously optimized as the tooling market evolves.

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How it works

Persistent Storage

Each generated audit now stores:

• audit id
• user email
• input stack JSON
• audit result JSON
• pricing snapshot JSON
• pricing version
• timestamp

These are persisted in Supabase and linked to the public report URL.

Pricing Change Detection

A deterministic backend engine compares historic pricing snapshots against the current pricing source of truth.

When pricing changes:

• the original audit is re-run
• recommendations are diffed
• score delta + savings delta are calculated
• unchanged audits are ignored to prevent spam

Notification Flow

Affected audits are grouped by user email.

One consolidated email per user is sent through Resend containing:

• what pricing changed
• affected recommendations
• updated savings impact
• a direct re-audit link

Re-Audit Diff View

The /re-audit/[id] route dynamically compares:

• original audit
• newly generated audit

The UI highlights:

• added recommendations
• removed recommendations
• changed savings
• score delta
• total savings delta

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What I cut

• I did not add unsubscribe links because the value/effort ratio under the 36h constraint favored shipping the complete diff workflow first.
• I skipped scheduled cron automation and used a manual trigger endpoint (/api/detect-changes) because it was faster to verify end-to-end reliably during development.
• I did not build a full admin dashboard for pricing-change analytics or email metrics.
• I skipped persistent storage of re-audit versions to avoid duplicating large audit payloads unnecessarily during the time window.
• I did not add CSV import support for audit inputs because the assignment emphasized the pricing-change lifecycle more than ingestion UX.

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How to test it manually

1. Run the application locally or open the deployed URL.
2. Generate a new audit report.
3. Submit an email using the lead capture form.
4. Verify the audit row is persisted in Supabase with:
   • pricing snapshot
   • audit result
   • user email
5. Modify a value in:
   lib/pricing/current-pricing.ts
6. Trigger:
   POST /api/detect-changes
7. Verify:
   • affected audit count increases
   • email is received
8. Click the re-audit link from the email.
9. Verify the diff page displays:
   • old vs new recommendations
   • score delta
   • savings delta
   • pricing changes

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What's tested

Automated tests included:

• pricing snapshot diff detection
• recommendation diff generation
• grouped notification batching
• re-audit generation logic
• detect-invalidated-audits orchestration
• detect-changes API endpoint
• resend email workflow

All tests pass successfully along with:

• npm run lint
• npm test
• npx tsc --noEmit

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Open questions / risks

• Pricing data is currently maintained manually in a centralized pricing file. A production system would likely require automated vendor scraping or admin tooling.
• Large-scale re-audits could create spikes in email volume without batching/rate-limiting infrastructure.
• The diff engine currently assumes recommendation IDs remain stable across audit-engine versions.

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Project	Deployment	Actions	Updated (UTC)
stackaudit	Ready	Preview, Comment	May 21, 2026 1:41pm
stackaudit-q1nu	Ready	Preview, Comment	May 21, 2026 1:41pm