About ClassCast ☔

Inspiration

Students juggle back-to-back classes across campus, and rain or snow changes how long the walk takes. I wanted one link to answer: when do I leave, which route, and what do I bring?

What it does

Paste up to 5 calendar links (like LionPATH and Canvas), or drag in .ics files. ClassCast reads each event’s location, checks the weather, and gives you:

• Leave-by time

  When to head out so you arrive on time.

• Walking route

  Your path between buildings, on a map.

• Bring list

  Umbrella, boots, or nothing extra.

• Daily brief

  A short AI summary of your day.

• Due list

  Canvas assignments as bullet points, kept apart from your classes.

• Reality Check

  Busiest day, risky back-to-backs, rainy days, and free windows for the week.

• Save or share

  Save your plan as a PDF, or send it with Gmail or email.

How we built it

Stack

Next.js on Vercel, with code in GitHub.

UI

shadcn/ui on Base UI, Inter, and a red-orange and cyan theme. Works in light, dark, and print.

Data

The calendar link supplies the locations. Open-Meteo gives the forecast. OpenRouteService gives routes. OpenStreetMap gives geocoding and map tiles.

AI

Gemini, Groq or Claude writes the bring list and brief, whichever key works first. With no key, built-in rules write them instead. The code does the time math, so the AI can't invent leave times.

Leave-by formula

With a 5 minute buffer, plus 15% more travel time in rain and 25% in snow.

Challenges

• Security: The server fetches any calendar URL a user enters, which is an SSRF risk. We blocked internal IPs and checked every redirect.
• Prompt injection: Calendar text is untrusted, so we treat it that way before it reaches the AI.
• Map tiles blocked: Our privacy header stripped the Referer that OpenStreetMap requires. Sending only the site origin fixed it.
• Deploy error: Vercel built the empty main branch. Merging the PR fixed it.
• Canvas feeds: Canvas assignments are all-day or zero-length events, so they were dropped or showed up as fake classes. We split them into a Due list and matched all-day items by your own time zone.
• Blocked registry: The build sandbox couldn't reach the shadcn registry, so we recreated the preset's theme and components by hand.
• Live APIs: The build sandbox blocked the weather and map APIs, so we tested with mock data first.

What we learned

1. Keep API keys server-side.
2. Treat user URLs and calendar text as hostile input.
3. Let code do the math and AI do the language.
4. Real calendar feeds are messier than the spec: test with the shapes people actually use.