Add Google Flights price tracking with SerpApi and GitHub Actions

[hoangsvit]

Summary

Adds Google Flights price tracking through SerpApi + GitHub Actions, without Cloudflare or a separate backend.

What this PR adds

• flights.html — mobile-friendly Google Flights price dashboard
• scripts/fetch-flights.mjs — SerpApi Google Flights search/normalisation
• .github/workflows/update-flight-prices.yml — scheduled GitHub Actions refresh
• data/flights.json — latest snapshot consumed by the static site
• data/flight-history.json — saved cheapest-price history
• PR web preview links
• PWA cache support for the flight page

Search configuration

• 6 adults + 1 infant under 2 on lap
• Economy
• Direct or maximum 1 stop
• SGN → Shanghai on 20 Oct 2026
• Beijing → SGN on 25 Oct 2026, evening preferred
• Beijing → SGN on 26 Oct 2026, morning preferred
• Currency: VND

Google Flights / SerpApi flow

SerpApi multi-city selection is sequential. For each return-date scenario the fetcher:

1. runs the initial multi-city search,
2. selects a first-leg result with its departure_token,
3. runs the next-leg search with that token,
4. normalises the complete itinerary price and flight segments.

There are two return-date scenarios, therefore one refresh uses 4 SerpApi searches.

Flight dashboard features

• direct comparison: return 25 Oct vs 26 Oct
• Cheapest / Fastest sorting
• Direct only / 1 stop filtering
• airline filter
• current total for the selected 7 travellers
• rough total ÷ 7 reference value
• change from previous check
• lowest / highest saved prices
• saved price trend chart
• stale/fresh data indicator
• browser-local target price
• manual “Check now” shortcut to GitHub Actions
• optional GitHub Issue price alert
• Verify link back to Google Flights

API setup

Add this repository Actions secret after merge:

SERPAPI_API_KEY=<your private SerpApi key>

The key is only read by GitHub Actions and is never written to the generated JSON or browser code.

Optional automatic price alert

Repository Actions variables:

• FLIGHT_ALERT_AMOUNT — e.g. 30000000
• FLIGHT_ALERT_CURRENCY — e.g. VND (optional)

When the current cheapest total is at or below the target, the workflow opens/updates a GitHub Issue named ✈️ Flight price alert · China 2026. When the price moves back above the target, that issue is closed.

Refresh schedule

Automatically at approximately 07:17 Asia/Ho_Chi_Minh once per day, plus manual workflow_dispatch.

With 4 searches per refresh, 30 scheduled days use about 120 SerpApi searches, leaving room for manual checks within the current 250-search free plan.

Preview

The PR preview workflow posts browser links for both the travel dashboard and flights.html and updates them on every commit.

Until SERPAPI_API_KEY is configured and the workflow is run from main, the preview intentionally displays the setup-required state rather than fake prices.

Price note

These are Google Flights search snapshots, not locked fares. Baggage, card or other optional fees may apply, and the final itinerary/price should be verified before payment.

[github-actions]

🌍 Web preview

• Open travel dashboard
• Open live flight prices

Preview is pinned to commit c35b518 and updates automatically when the PR changes.

[coderabbitai]

Important

• 🔍 Trigger review

This repository does not receive automatic reviews because it has fewer than 10 stars.

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 8913213a-2c9f-439d-9b23-ea664fed3089

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[hoangsvit]

✅ Fixed the PR merge conflict by syncing the latest main into agent/live-flight-prices while preserving the flight-price changes.

• Branch is now 0 commits behind main.
• GitHub reports the PR as mergeable.
• PR Preview reran successfully on commit df24228.
• Preview links were refreshed automatically.

No flight-price feature code was dropped during the sync.

[hoangsvit]

Switched the flight-price provider from Duffel to SerpApi Google Flights.

Validation completed:

• PR remains mergeable.
• PR Preview passed on c35b518.
• Secret is now SERPAPI_API_KEY.
• Search configuration remains 6 adults + 1 infant on lap, Economy, max 1 stop, return 25/26 Oct.
• Multi-city search follows SerpApi's departure_token flow.
• Auto refresh is now once daily at ~07:17 Asia/Ho_Chi_Minh to keep scheduled usage around 120 searches/month (4 searches per refresh).

No live/fake price is committed before the SerpApi key is configured and the workflow is run.