Walletrac

Problem

A personal expense tracker should be quick to use, work without a connection, and keep data somewhere its owner controls, without paying for a server.

Solution

Built a Flutter app that reads and writes a Google Sheet through Google Apps Script, caches everything locally with Hive so it works offline, and adds an Android home-screen widget with quick-add presets.

System architecture

1. Flutter app with a local Hive cache as the first stop for every read and write.
2. Google Apps Script web app as a tiny API in front of a Google Sheet.
3. The cache syncs with the sheet whenever a connection is available.
4. Android home-screen widget with quick-add presets that writes through the same path.

Backend logic

• The Apps Script endpoint handles reads and writes to the sheet, so there is no server to host.
• Defensive parsing of API payloads, with tests for malformed responses and Apps Script redirect quirks.
• Tests for date-parsing edge cases.
• BDT currency formatting and localization.

Tech stack

Outcome / impact

• Runs at zero hosting cost.
• Data stays in a spreadsheet the owner controls.
• Logging an expense from the home screen takes seconds.

Result: A daily-use finance tracker with no hosting cost, and data that stays in the owner's own spreadsheet.