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Documentation Index

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Helios includes two Vercel serverless functions under /api/. These functions act as a server-side proxy so that API keys never appear in browser-side code. The app’s front-end (index_def.js) calls them using fetch() against the same origin — the browser never contacts third-party geocoding or timezone services directly.

Endpoints summary

EndpointMethodPurpose
/api/geocodeGETConvert city + country name to lat/lon coordinates
/api/timezoneGETReturn the UTC offset (in hours) for a lat/lon coordinate

Authentication

No authentication is required from the browser. The serverless functions authenticate outbound calls to third-party providers using server-side environment variables. These variables must be set under Settings → Environment Variables in the Vercel project dashboard before deploying:
VariableProviderUsed by
OPENCAGE_KEYOpenCage/api/geocode (fallback)
IPGEOLOCATION_KEYipgeolocation.io/api/timezone (primary)
TIMEZONEDB_KEYTimeZoneDB/api/timezone (fallback)

Error handling

Both endpoints return HTTP error status codes when a lookup fails. The front-end checks response.ok after every fetch() call and throws a descriptive Error if the response is not successful. That error propagates to the form submit handler, which stops the loading spinner and shows the message to the user via window.alert().

/api/geocode

Convert a city and country name to latitude and longitude coordinates.

/api/timezone

Return the UTC offset in hours for a given lat/lon coordinate.

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