Auto Assistant (Авто-Ассистент) - Product Case Study

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A mobile app that turns the shoebox of fuel receipts and half-remembered service dates into a clean, offline-first car history logbook - every fill-up, repair, oil change and insurance renewal in one place, with reminders before the next one is due and a shareable PDF report of the whole history.

This is a product & architecture write-up of my own project. Source code is not published here.

The idea

Three layers, built outward from the driver:

1. For the owner - a car logbook (built). Log fuel, service, repairs, painting, insurance; track mileage and spending; get reminded before maintenance is due; export a full PDF history - useful on its own and when selling the car.
2. For auto services - a B2B side (planned). With the owner's consent, a shop sees the car's real state, spots upcoming maintenance (oil, timing belt, filters) from mileage and history, and reaches out at the right moment instead of waiting.
3. AI care tips (planned). Turn the car's history into personalized upkeep advice - what to check next, based on make, mileage and what has already been done.

What's built

A polished Android app (Expo / React Native) with a real backend:

• Garage - multiple cars, one active; rich add-car flow (brand, engine type, transmission, LPG, mileage, VIN, plate, tank).
• History - fuel and service records typed (fuel / service / repair / insurance / oil / wash / tuning / …), grouped by month, filterable, with running totals.
• Reminders - by mileage, date, fuel volume or combined; three priority levels; delivered as local push notifications.
• Analytics - spending breakdown, mileage trend, real fuel consumption and range estimation from full-tank intervals.
• Car profile - photo gallery by category (Supabase Storage), full spec sheet, PDF export, and owner-to-owner transfer.
• Offline-first - works fully as a guest on-device, then syncs to the cloud on sign-in.

Stack

React Native 0.81 · Expo ~54 · React 19 · TypeScript · expo-router · Zustand · Supabase (PostgreSQL + Auth + Storage + Row-Level Security) · expo-notifications · expo-print / expo-sharing · expo-image-picker · NativeWind / Tailwind · EAS Build (Android).

Architecture

Offline-first with a single storage seam: the UI and Zustand stores never know whether data lives on the device or in the cloud - a storageAdapter routes reads and writes, and a guest's local data is synced up on first sign-in.

flowchart TD
    UI[Screens · expo-router] --> Z[Zustand stores<br/>auth · cars · records · reminders]
    Z --> SA{storageAdapter}
    SA -->|guest| AS[(AsyncStorage · on device)]
    SA -->|signed in| SB[(Supabase PostgreSQL<br/>Row-Level Security)]
    AS -. sync on sign-in .-> SYNC[syncService] --> SB

    SB --- AUTH[Auth · Magic Link OTP]
    SB --- ST[Storage · car-photos bucket]

    Z --> NOTIF[expo-notifications<br/>local reminders]
    Z --> PDF[expo-print<br/>HTML → PDF report]

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Engineering highlights

• One storage seam, two backends. storageAdapter presents the same API over on-device AsyncStorage (guest) and Supabase (signed in); syncService migrates guest data up on sign-in. Users get value before creating an account, and lose nothing when they do.
• Per-user isolation in the database. PostgreSQL Row-Level Security scopes every row to its owner (auth.uid()), with separate SELECT/INSERT/UPDATE/DELETE policies - INSERT needs WITH CHECK, which a single FOR ALL policy silently misses.
• Reminders that actually fire. Mileage- and date-based reminders are scheduled as local notifications and re-armed whenever the app becomes active.
• Real consumption maths. Fuel economy and range are computed from full-tank intervals (two+ full-tank records), not naive per-fill averages.
• PDF from HTML, not a screenshot. The history report is built as an HTML document and rendered via expo-print, with a web fallback to the browser's print.

Data model

Seven tables in PostgreSQL, all under Row-Level Security; a trigger auto-creates a profile on sign-up, and car photos live in a Supabase Storage bucket.

erDiagram
    profiles ||--o{ cars : owns
    profiles ||--o{ service_records : logs
    cars ||--o{ service_records : has
    cars ||--o{ reminders : has
    cars ||--o{ car_photos : has
    cars ||--o{ car_ownership_history : "history of"
    service_records ||--o{ record_parts : includes

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• profiles - extends Supabase auth users (phone, name, push token).
• cars - make/model/year, engine & transmission, mileage, VIN, plate, tank, LPG.
• service_records - typed events (fuel/service/repair/insurance/…), cost, mileage, plus type-specific fields (litres, full-tank flag, oil volume, valid-until).
• record_parts - parts used in a service record (name, article, qty, cost).
• reminders - mileage/date/fuel-volume/combined, priority, notification toggle.
• car_photos - categorized gallery, stored in the car-photos bucket.
• car_ownership_history - ownership over time, with a pending → transferred flow.

Roadmap

• Server-side transfer completion - the new owner claims the car automatically on sign-in with the invited email.
• B2B auto-service side - consented shops see car state and due maintenance.
• AI care tips - personalized upkeep guidance from each car's history.

Screenshots

App screenshots (garage, add-car flow, history, analytics, PDF report) go in docs/screenshots/.