Rounds

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App Store Link

A Kotlin Multiplatform HIIT / interval timer app, built with Compose Multiplatform, Room, and a unidirectional-data-flow ViewModel base class.

Build & Run

First time in a fresh clone:

./scripts/install_hooks.sh   # enables the Conventional Commits commit-msg hook

Then:

# Android
./gradlew :apps:compose:assembleDebug

# iOS - compile Kotlin framework
./gradlew :apps:compose:compileKotlinIosSimulatorArm64

# iOS - or open in Xcode
open apps/ios/iosApp.xcodeproj

The first Gradle build will fail with a remediation message if you skip the hook install.

Project Structure

apps/compose/          # KMP entry point (Android + iOS)
apps/ios/              # Swift/Xcode wrapper
features/<name>/       # Routes and public API
features/<name>/impl/  # Screens and ViewModels
libraries/<name>/      # Interfaces
libraries/<name>/impl/ # Implementations

Architecture Rules

• api / impl split: features/<x> holds routes + public interfaces; features/<x>/impl holds screens, ViewModels, wiring.
• Cross-feature talk goes api → impl: features/<x>/impl can depend on features/<y> (api). Never on features/<y>/impl.
• No api-to-api edges: features/<x> must not depend on another feature's api. That path leads to cycles the first time someone adds the reverse.
• Only apps/compose depends on impls — it's the DI glue. Anything else reaching into an impl breaks the interface contract.
• Libraries follow the same rules. Shared code lives in libraries, not in feature apis.

Creating New Modules

./scripts/create_module

Plugin	Use Case
hiittimer.kotlin.multiplatform	Pure Kotlin modules
hiittimer.compose.multiplatform	Kotlin + Compose UI
hiittimer.feature	Feature modules

Architecture Patterns

ViewModel (Unidirectional Data Flow)

ViewModels extend SEAViewModel which enforces State-Event-Action unidirectional data flow:

class MyViewModel : SEAViewModel<State, Event, Action>(initialStateArg = State()) {
    override suspend fun handleAction(action: Action) {
        when (action) {
            is Action.Load -> action.updateState { it.copy(loading = true) }
            is Action.Submit -> {
                // Do work, then send one-shot event
                sendEvent(Event.NavigateBack)
            }
        }
    }
}

• State: Immutable data class representing UI state
• Event: One-shot side effects (navigation, toasts, etc.)
• Action: The only way to mutate state via action.updateState { }

Dependency Injection

Uses kotlin-inject-anvil:

// Bind implementation to interface
@ContributesBinding(AppScope::class)
@SingleIn(AppScope::class)
@Inject
class MyRepositoryImpl : MyRepository

// Multibinding for feature entry points
@ContributesBinding(AppScope::class, multibinding = true)
class MyFeatureEntryPoint : FeatureEntryPoint

Navigation

Routes are @Serializable data classes extending Route:

@Serializable
data class ProfileRoute(val userId: String) : Route

// Register in FeatureEntryPoint.buildNavGraph()
screen<ProfileRoute> { backStackEntry -> 
    ProfileScreen(userId = backStackEntry.toRoute<ProfileRoute>().userId)
}

Supports screen, bottomSheet, and dialog destinations.

iOS Integration

The iOS app embeds a Kotlin framework compiled from apps/compose. Swift types can be passed into Kotlin's DI graph via IosAppComponentFactory.create(...).

When exposing Kotlin types to Swift, use @ObjCName for stable naming:

@ObjCName("MyType", exact = true)
interface MyType { ... }

See Swift-Kotlin Communication Patterns for detailed guidance.

Coding Guidelines

• Use Catching { } from libraries/core instead of runCatching
• Custom UI components go in libraries/ui—avoid using Material components directly

Releases

Cutting a release is merging one PR. release-please maintains an open chore(main): release vX.Y.Z PR with the version bump + changelog; merging it tags, builds both platforms, and submits to the stores. PR titles must be conventional commits (fix:, feat:, feat!:) — the type picks the version bump.

See docs/release-automation.md for the full pipeline (CI, Sentry triage, secrets) and AGENTS.md for the commit convention.

Key Files

Purpose	Path
App DI Component	apps/compose/src/.../AppComponent.kt
Base ViewModel	libraries/flowroutines/src/.../SEAViewModel.kt
iOS Entry Point	apps/ios/iosApp/iOSApp.swift

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