SpotPrice (Rust core + Kotlin Multiplatform UI)

A client-only sats price ticker and Sats ↔ fiat converter for Android and iOS. No backend — all logic runs on the device.

Architecture

• core/ — Rust workspace, the "compiled core":
  • price-sources/ — exchange/aggregator adapters (Coinbase, Kraken, Coingecko, Bitstamp)
  • aggregator/ — median + σ-rejection across sources
  • convert/ — sats ↔ fiat math (rust_decimal)
  • cache/ — in-memory + persisted last-known price
  • ffi/ — single UniFFI surface exposed to mobile
• app/ — KMP + Compose Multiplatform app, single composeApp module:
  • composeApp/src/commonMain/ — shared Kotlin business logic + Compose Multiplatform UI (target-agnostic)
  • composeApp/src/androidMain/ — Android shell: one Activity hosting the Compose UI and loading the UniFFI-generated bindings
  • iOS host: not yet wired up — see docs/PLAN-ios.md for the roadmap

Native libraries are produced by cargo-ndk (Android .so) today, and will be produced by cargo-swift (iOS .xcframework) once the iOS host lands. Both are wired to Kotlin/Swift through UniFFI-generated bindings.

Build prerequisites

Tool	Required version	Install
Rust	1.85+	rustup, pinned via rust-toolchain.toml
Android NDK	r28+ (for 16 KB pages)	Android Studio SDK Manager
JDK	21 (LTS)	Temurin / brew install --cask temurin@21
Xcode	16+ (full app, not CLT)	Mac App Store (~10 GB)
cargo-ndk	4.1+	cargo install cargo-ndk
cargo-swift	0.11+	cargo install cargo-swift
just	any	cargo install just

Quick start

just install-tools     # one-time toolchain bootstrap
just test              # run all Rust tests
just build-android     # cross-compile core for all 4 Android ABIs
just build-ios         # build .xcframework (Mac + full Xcode required)
just run-android       # install + launch on connected device/emulator

Installing

Three install paths, all directly from this repo's GitHub Releases — no intermediate store, no account, no telemetry:

• Obtainium (auto-updating sideload): add the app by pasting https://github.com/PeterXMR/spotprice into Obtainium's "Add app" field. It will track new releases as they're tagged and offer updates.
• F-Droid: planned. The repo ships Fastlane metadata and is set up for reproducible builds; the inclusion request will be filed once a signed release lands.
• Manual sideload: download the latest SpotPrice-vX.Y.Z.apk from Releases and install it with your file manager (you may need to enable "Install unknown apps" for the source app).

Releasing

Tag pushes (vX.Y.Z or vX.Y.Z-suffix) auto-publish a GitHub Release with the APK attached. See docs/RELEASING.md for the full release flow, pre-release vs. release semantics, and the roadmap to signed/minified production builds.

License

GPL-3.0-or-later. See LICENSE.