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A graceful multiplatform bluesky client

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# Heron

Heron is a Jetpack Compose adaptive, reactive and offline-first Bluesky client.

## Download
<div>
 <a href="https://play.google.com/store/apps/details?id=com.tunjid.heron&referrer=utm_campaign%3Dandroid_metadata%26utm_medium%3Dweb%26utm_source%3Dgithub.com%26utm_content%3Dbadge" target="_blank"><img src="https://upload.wikimedia.org/wikipedia/commons/7/78/Google_Play_Store_badge_EN.svg" alt="Get it on Google Play" height="48"></a>
 <a href="http://apps.obtainium.imranr.dev/redirect.html?r=obtainium://add/https://github.com/tunjid/heron/releases" target="_blank"><img src="https://raw.githubusercontent.com/ImranR98/Obtainium/main/assets/graphics/badge_obtainium.png" alt="Get it on Obtainium" height="48"></a>
</div>

## Screenshots

| ![Scroll animations](https://raw.githubusercontent.com/tunjid/heron/main/docs/images/1.gif) | ![Screen transitions](https://raw.githubusercontent.com/tunjid/heron/main/docs/images/2.gif) | ![Thread diving](https://raw.githubusercontent.com/tunjid/heron/main/docs/images/3.gif) |
|-------------------------------------------|--------------------------------------------|---------------------------------------|

## UI/UX and App Design

Heron uses [Material design and motion](https://m3.material.io/) and is heavily inspired by the
[Crane](https://m2.material.io/design/material-studies/crane.html) material study.

Libraries:

1. Geometric shapes are created with
   the [Jetpack shapes](https://developer.android.com/jetpack/androidx/releases/graphics) graphics
   library.
2. UX patterns like pinch to zoom, drag to dismiss, collapsing headers, multipane layouts, and
   and so on are implemented with the [Composables](https://github.com/tunjid/composables) library.

## Architecture

This is a
multi-module [Kotlin Multiplatform](https://www.jetbrains.com/help/kotlin-multiplatform-dev/get-started.html)
project targeting Android, iOS and Desktop that follows
the [Android architecture guide](https://developer.android.com/topic/architecture).

For more details about this kind of architecture, take a look at
the [Now in Android sample](https://github.com/android/nowinandroid) repository,
this app follows the same architecture principles it does, and the architecture decisions are very
similar.

There are 5 kinds of modules:

1. `data-*` is the [data layer](https://developer.android.com/topic/architecture/data-layer) of the
   app containing models data and repository implementations for reading and writing that data.
   Data reads should never error, while writes are queued with a `WriteQueue`.
    - [Jetpack Room](https://developer.android.com/jetpack/androidx/releases/room)
      is used for persisting data with SQLite.
        - Given the highly relational nature of the app, a class called a `MultipleEntitySaver` is
          used to save bluesky
          network models.
    - [Jetpack DataStore](https://developer.android.com/jetpack/androidx/releases/datastore)
      is used for blob storage of arbitrary data with protobufs.
    - [Ktor](https://ktor.io/) is used for network connections via the
      [Ozone at-proto bindings](https://github.com/christiandeange/ozone).
2. `ui-*` contains standalone and reusable UI components and Jetpack Compose effects for the app
   ranging from basic layout to multimedia components for displaying photos and video playback.
    - Higher level, aggregated abstractions also live here, most notably `ui-timeline` which holds
      the `TimelineState` and `timelineStateHolder` that drive timeline data production with the
      [Tiling library](https://github.com/tunjid/Tiler).
    - `ui-sheets` holds the app's bottom sheets. Unusually for a `ui-*` module it depends on
      `ui-scaffold`, so the sheets can drive their own navigation.
3. `ui-scaffold` (a `ui-*` module) contains the application state in the `AppState` class, and
   coordinates app level UI logic like pane display, drag to dismiss, back previews and so on. It
   is the entry point to the multiplatform application
4. `feature-*` contains navigation destinations or screens in the app. Multiple features can
   run side by side in app panes depending on the navigation configuration and device screen size.
5. `/composeApp` is the module that assembles the fully wired app and depends on all other modules.
   It is consumed by each platform's launcher (see [Platform entry points](#platform-entry-points)).
   It contains several source sets:
    - `commonMain` is for code that’s common for all targets, including the shared `createAppState`
      builder that wires the whole DI graph.
    - The `androidMain`, `desktopMain` and `iosMain` folders hold Kotlin code compiled for only the
      platform indicated by the folder name, mostly each platform's `createAppState` overload.

### Dependency Injection

Dependency injection is implemented with the [Metro](https://github.com/ZacSweers/metro)
library which constructs the dependency graph at build time
and therefore is compile time safe. Assisted injection is used for feature screens to pass
navigation arguments information to the feature.

#### Graph levels

The DI graph is layered. Conceptually the data layer is the root of the app at the top, and each
level below it is built on the levels above. The fully assembled `composeApp` sits at the leaf:

* **Data** (`data-*`) — the top of the graph, the root of the app. Repository implementations,
  the Room database, the Ktor network stack and the `WriteQueue`. Depends on no other layer.
  Contributed to the graph via `DataBindings`.
* **UI** (`ui-*`) — depends on data. Reusable Compose components and effects. It can also host
  ViewModels that have access to the data layer, for example the sheet ViewModels in `ui-sheets`,
  each contributed via `SheetBindings` into a `Map` keyed by ViewModel type that `AppState` exposes
  through `PaneScaffoldState`.
* **Scaffold** (`ui-scaffold`) — depends on data and ui. Navigation lives here. It manages global app
  logic in discrete states — `IdentityState`, `NotificationState` and `NavigationState` — that are
  coordinated by `AppState`, the app level state holding app level concerns. `PaneScaffoldState` is
  a slice into `AppState` that feature modules can see. Contributed via `ScaffoldBindings`.
* **Sheets** (`ui-sheets`) — depends on `ui-scaffold` and `ui-timeline`. Holds the app's bottom
  sheets and their ViewModels; because it can see `PaneScaffoldState`, the sheets navigate
  themselves. Contributed via `SheetBindings`.
* **Feature** (`feature-*`) — navigation destinations. Depends on data and scaffold. Its ViewModels
  have access to the data layer and to navigation semantics, and it uses `PaneScaffoldState` to glean
  app level scope from the scaffold. Each feature contributes a `*NavigationBindings` (route matchers)
  and a feature `Bindings` (its screen entry and ViewModel access).
* **Compose App** (`composeApp`) — the fully assembled app, the lowest level of the tree. `AppGraph`
  `@Includes` every layer's bindings and exposes the assembled `entryMap` and `appState`, and each
  platform's entry point creates the `AppState` and renders `App()`.

```mermaid
graph TD
 Data["Data · data-* repositories, database, network, WriteQueue (root — depends on nothing)"]
 UI["UI · ui-* reusable Compose components + ViewModels"]
 Scaffold["Scaffold · ui-scaffold navigation + AppState (IdentityState, NotificationState, NavigationState) exposes PaneScaffoldState"]
 Sheets["Sheets · ui-sheets app bottom sheets (depends on scaffold to self-navigate)"]
 Feature["Feature · feature-* navigation destinations; ViewModels with data + navigation; read scope via PaneScaffoldState"]
 App["Compose App · composeApp AppGraph assembles all layers · per-platform entry points"]

Data --> UI
    Data --> Scaffold
    Data --> Feature
    UI --> Scaffold
    Scaffold --> Sheets
    Scaffold --> Feature
    Sheets --> Feature
    UI --> App
    Scaffold --> App
    Sheets --> App
    Feature --> App
```

> Arrows point from a layer to the layers built on top of it; the compile-time dependencies run the
> opposite way (e.g. every feature depends on data and scaffold).

#### Graph items

The items in the dependency graph are:

* `*NavigationBindings` from feature modules contributing `RouteMatcher` instances (`@IntoMap`) into
  the `AppNavigationGraph`'s `routeMatcherMap`.
* Feature `Bindings` from feature modules contributing the per-feature `PaneEntry` screen factory
  (`@IntoMap`) into the `AppGraph`'s `entryMap`, plus access to the data layer and app scaffold.
* `ScaffoldBindings` providing the `PaneScaffoldState` for building a multi-pane app and the global
  state holders.
* `DataBindings` for the data layer.
* An `AppNavigationGraph` for resolving navigation routes.
* An `AppGraph` containing the entire app DI graph.

### Platform entry points

`composeApp` produces the assembled app for every target — an Android library, an iOS framework and the
desktop application — but the OS-level launcher for each platform lives outside it. Every platform follows
the same two steps: build an `AppState` once, then hand it to the single shared root composable,
`ui-scaffold`'s `App(appState, modifier)`.

The wiring lives in the `EntryPoint*.kt` files in `composeApp`:

* **Common** — [`EntryPoint.kt`](apps/composeApp/src/commonMain/kotlin/com/tunjid/heron/EntryPoint.kt)
  exposes `createAppState(...)`. It creates the app-wide `CoroutineScope`, builds the `AppNavigationGraph`
  and `AppGraph` from every module's bindings via Metro's `createGraphFactory`, and returns
  `appGraph.appState`. It is platform-agnostic: the platform-specific pieces — `imageLoader`, `notifier`,
  `logger`, `videoPlayerController` and the data layer `args` (`DataBindingArgs`) — are passed in as
  factory lambdas.
* **Android** — [`EntryPoint.android.kt`](apps/composeApp/src/androidMain/kotlin/com/tunjid/heron/EntryPoint.android.kt)
  adds a `createAppState(context)` overload that supplies the Android implementations of those factories
  (e.g. the saved-state path under app storage) and delegates to the common builder. The OS launcher is
  the separate `androidApp` module: `HeronApplication` calls `createAppState(this)` on startup and holds
  the `AppState`, and `MainActivity` reads it and calls `setContent { App(appState, …) }`, also wiring the
  splash screen, FCM token registration and deep links.
* **Desktop (JVM)** — [`EntryPoint.jvm.kt`](apps/composeApp/src/desktopMain/kotlin/com/tunjid/heron/EntryPoint.jvm.kt)
  provides a no-arg `createAppState()` that resolves the per-OS app data directory and encrypts saved
  state with Tink. The launcher is [`main.kt`](apps/composeApp/src/desktopMain/kotlin/com/tunjid/heron/main.kt):
  a `fun main()` that opens a Compose `Window { App(appState = remember { createAppState() }, …) }`.
* **iOS** — [`EntryPoint.ios.kt`](apps/composeApp/src/iosMain/kotlin/com/tunjid/heron/EntryPoint.ios.kt) provides
  the iOS `createAppState()` plus bridge functions for FCM tokens and push notifications, and
  [`MainViewController.kt`](apps/composeApp/src/iosMain/kotlin/com/tunjid/heron/MainViewController.kt) wraps the
  root composable in a `ComposeUIViewController`. The OS launcher is the `iosApp` Xcode/SwiftUI project:
  `iOSApp.swift`'s `AppDelegate` calls `EntryPoint_iosKt.createAppState()` and holds the `AppState`, and
  `ContentView.swift` embeds `MainViewController(appState:)` in a SwiftUI `UIViewControllerRepresentable`.

### Navigation

Navigation uses the [treenav experiment](https://github.com/tunjid/treeNav) to implement
Android [adaptive navigation](https://developer.android.com/develop/ui/compose/layouts/adaptive).
Specifically it uses a `ThreePane` configuration, where up to 3 navigation panes may be shown, with
one reserved for back previews and another for modals. Navigation state is also saved to disk and
persisted across app restarts.

### State production

* State production follows
  the [Android guide to UI State Production](https://developer.android.com/topic/architecture/ui-layer/state-production).
* Each feature uses a
  single [Jetpack ViewModel](https://developer.android.com/topic/libraries/architecture/viewmodel)
  as
  the [business logic state holder](https://developer.android.com/topic/architecture/ui-layer/stateholders).
* State is produced in a lifecycle aware way using
  the [Jetpack Lifecyle](https://developer.android.com/jetpack/androidx/releases/lifecycle) APIs.
    * The `CoroutineScope` for each `ViewModel` is obtained using `viewModelCoroutineScope()`
      with special coroutine elements for UI state production.
* The specifics of producing state over time is implemented with
  the [Mutator library](https://github.com/tunjid/Mutator).
    * Inputs to the state production pipeline are passed to the mutator using an `Action` sealed
      class hierarchy.
    * Every coroutine launched is limited to running when the lifecycle of the component displaying
      it is resumed. When the lifecyle
      is paused, the coroutines are cancelled after 2 seconds:
      `SharingStarted.WhileSubscribed(FeatureWhileSubscribed)`.
    * Each user `Action` is in a sealed hierarchy, and action parallelism is defined by the
      `Action.key`. Actions with different keys run in parallel
      while those in the same key are processed sequentially. Each distinct subtype of an `Action`
      hierarchy typically has it's own
      key unless sequential processing is required for example:
        * All subtypes of `Action.Navigation` typically share the same key.
        * All subtypes of pagination actions, also share the same key and are processed with
          the [Tiling library](https://github.com/tunjid/Tiler).

## Building

### iOS Push Notifications

iOS push notifications are powered by Firebase Cloud Messaging (FCM) via Apple Push Notification
service (APNs). The following setup is required:

1. **Firebase iOS SDK** - Added via Swift Package Manager in `apps/iosApp/iosApp.xcodeproj`.
   The `FirebaseMessaging` package is required.

2. **`GoogleService-Info.plist`** - Download from Firebase Console > Project Settings > your iOS app
   and place at `apps/iosApp/iosApp/GoogleService-Info.plist`. This file is `.gitignore`d; in CI, decode
   it from the `FIREBASE_IOS_PLIST` base64 secret:
   ```bash
   echo "$FIREBASE_IOS_PLIST" | base64 -d > apps/iosApp/iosApp/GoogleService-Info.plist
   ```

3. **Push Notifications capability** - Enabled in Xcode under Signing & Capabilities. This adds
   `aps-environment` to `iosApp.entitlements`.

4. **Background Modes capability** - Enabled in Xcode with **Remote notifications** checked. This
   adds `remote-notification` to `UIBackgroundModes` in `Info.plist`, which is required for
   data-only/silent push delivery.

5. **APNs Authentication Key** - Create a `.p8` key in the
   [Apple Developer Portal](https://developer.apple.com/account/resources/authkeys/list)
   under Keys with Apple Push Notifications enabled. Note the Key ID and Team ID.

6. **Upload APNs key to Firebase** - In Firebase Console > Project Settings > Cloud Messaging >
   iOS app, upload the `.p8` key along with the Key ID and Team ID.

7. **Backend payload format** - FCM payloads targeting iOS must include `content-available: 1`
   in `apns.payload.aps` for data-only push delivery. Without this, iOS silently drops the
   notification. Note that iOS throttles silent pushes and does not deliver them to
   force-quit apps.

### Gradle Properties

The following properties can be set in `~/.gradle/gradle.properties` or passed via `-P` flags.
None are required for basic development builds.

| Property | Description                                                                                                                                                           |
|---|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| `heron.versionCode` | Integer version code. Managed by CI via `github.run_number`.                                                                                                          |
| `heron.endpoint` | Backend endpoint URL for the app.                                                                                                                                     |
| `heron.isRelease` | Set to `true` when building release artifacts.                                                                                                                        |
| `heron.releaseBranch` | Branch prefix (`bugfix/`, `feature/`, `release/`) controlling version increments.                                                                                     |
| `heron.macOS.signing.identity` | Name of the Developer ID Application certificate in your Keychain (e.g. `Developer ID Application: Name (TEAM_ID)`). When present, the macOS DMG will be code signed. |
macOS signing is only configured when `heron.macOS.signing.identity` is present,
so contributors without an Apple Developer account can still build unsigned DMGs with
`./gradlew packageReleaseDmg`.

Notarization is handled externally via `xcrun notarytool` (not a Gradle task) to maintain
compatibility with the Gradle configuration cache. To notarize locally after building a signed DMG:

```bash
./gradlew packageReleaseDmg
xcrun notarytool submit <path-to-dmg> \
 --apple-id <your-apple-id> \
 --password <app-specific-password> \
 --team-id <team-id> \
 --wait
xcrun stapler staple <path-to-dmg>
```

### Publishing

Publishing is triggered manually via the `Publish` GitHub Actions workflow (`workflow_dispatch`).
A `platform` input selects which jobs run — `all` (default), `android`, `ios`, or `mac` — so
you can push a single platform without burning CI minutes on the others.

**Android** (`publish-android-app`) builds a release AAB, signs it, uploads to the Play Store
internal track, extracts a universal APK, and attaches it to a draft GitHub Release.

**iOS** (`publish-ios-app`) imports the distribution certificate, downloads the provisioning
profile via the App Store Connect API, patches `iosApp.xcodeproj` for manual signing, stamps
the version and build number into `Info.plist`, archives and exports a signed `.ipa`, and
uploads it to App Store Connect for TestFlight. See [iOS publishing notes](#ios-publishing-notes)
below for the tricky bits.

**macOS** (`publish-mac-app`) imports a signing certificate, builds a signed DMG
via `packageReleaseDmg`, notarizes it with `xcrun notarytool`, staples the ticket,
and attaches it to the same draft GitHub Release.

The following repository secrets are required for CI publishing:

| Secret | Used by |
|---|---|
| `HERON_ENDPOINT` | All jobs |
| `GOOGLE_SERVICES_BASE_64` | Android |
| `SIGNING_KEY_BASE_64` | Android |
| `ALIAS` | Android |
| `KEY_STORE_PASSWORD` | Android |
| `KEY_PASSWORD` | Android |
| `MACOS_SIGNING_CERTIFICATE_P12_DATA` | macOS - base64-encoded Developer ID Application `.p12` file |
| `MACOS_SIGNING_CERTIFICATE_PASSWORD` | macOS - password for the `.p12` file |
| `MACOS_SIGNING_IDENTITY` | macOS - certificate identity string (e.g. `Developer ID Application: Name (TEAM_ID)`) |
| `MACOS_NOTARIZATION_APPLE_ID` | macOS - Apple ID email |
| `MACOS_NOTARIZATION_PASSWORD` | macOS - app-specific password |
| `MACOS_NOTARIZATION_TEAM_ID` | macOS - Apple Developer Team ID |
| `IOS_CERTIFICATES_P12` | iOS - base64-encoded Apple Distribution `.p12` file (must contain the private key) |
| `IOS_CERTIFICATES_PASSWORD` | iOS - password for the `.p12` file |
| `IOS_DIST_PROVISIONING_PROFILE_NAME` | iOS - exact display name of the App Store Connect provisioning profile |
| `APPSTORE_ISSUER_ID` | iOS - App Store Connect API issuer ID |
| `APPSTORE_KEY_ID` | iOS - App Store Connect API key ID |
| `APPSTORE_PRIVATE_KEY` | iOS - raw contents of the `.p8` private key (PEM text, **not** base64) |
| `APPSTORE_TEAM_ID` | iOS - Apple Developer Team ID |
| `FIREBASE_IOS_PLIST` | iOS - base64-encoded `GoogleService-Info.plist` |

### iOS publishing notes

Getting a Kotlin Multiplatform iOS build onto TestFlight via GitHub Actions has several
non-obvious failure modes. The fixes are already in the workflow and `apps/composeApp/build.gradle.kts`,
but the reasoning is worth preserving.

**Signing must be patched into `project.pbxproj`, not passed via `xcodebuild` overrides.**
The Xcode project uses `CODE_SIGN_STYLE = Automatic` with `CODE_SIGN_IDENTITY = "Apple Development"`
for local development. `xcodebuild`'s pre-flight signing check validates the project's
baked-in settings *before* applying command-line build-setting overrides, so passing
`CODE_SIGN_STYLE=Manual CODE_SIGN_IDENTITY="Apple Distribution" PROVISIONING_PROFILE_SPECIFIER=...`
positionally fails with `No "iOS Development" signing certificate found`. Using the `-xcconfig`
flag (which wins over positional args) fixes signing for the main target, but then cascades to
SPM dependencies (Firebase, GoogleUtilities, etc.) that don't support provisioning profiles and
error out. The CI uses `sed` on `project.pbxproj` to switch only the iosApp target's settings
(`CODE_SIGN_STYLE`, `CODE_SIGN_IDENTITY`, `PROVISIONING_PROFILE_SPECIFIER`), leaving SPM targets
untouched. This only affects CI's checked-out copy of the project file.

**Kotlin/Native devirtualization is disabled for release iOS framework builds.**
See the `freeCompilerArgs += "-Xdisable-phases=DevirtualizationAnalysis,Devirtualization"` block
in `apps/composeApp/build.gradle.kts`. At ~115k LOC, the K/N linker's `DevirtualizationAnalysis` phase
OOMs on GitHub's `macos-latest` runner (14 GB RAM) regardless of how high `org.gradle.jvmargs` is
set — the memory consumed by `ConstraintGraphBuilder` scales past the runner's physical RAM
ceiling. Two gotchas to know if you ever need to touch this:
- The flag name is `-Xdisable-phases=<PhaseName>`, not `-Xbinary=...`. Phase names come from
 the `name =` parameter of `createSimpleNamedCompilerPhase` in Kotlin/Native's `LTO.kt`. Unknown
 phase names are silently ignored (no error, no warning — the flag just does nothing).
- Don't disable `BuildDFG`. Other phases (`EscapeAnalysis`, `DCEPhase`, etc.) read from the
 symbol table it populates and crash with `IllegalArgumentException: The symbol table has been
 sealed` if it's skipped. Disable only `DevirtualizationAnalysis` (the memory hog) and
 `Devirtualization` (the downstream phase that applies its results).
- Revisit once Kotlin 2.4.0 stable ships with [KT-80367](https://youtrack.jetbrains.com/issue/KT-80367)
 (memory reduction for DevirtualizationAnalysis) and a Compose Multiplatform release targets it.

**Version string parsing.** The workflow reads the user-facing version from Axion Release's
`currentVersion` task, same source Android and macOS use. That task prints
`Project version: X.Y.Z`, not just `X.Y.Z`, so the workflow runs it through a regex
(`grep -oE '[0-9]+\.[0-9]+(\.[0-9]+)?'`) before writing it to `CFBundleShortVersionString`.
Apple rejects the upload with `-19239` if the value isn't one to three period-separated integers.

**APNs environment is flipped for CI builds.** `apps/iosApp/iosApp/iosApp.entitlements` has
`aps-environment = development` so local Xcode builds against a connected iPhone use the
sandbox APNs gateway (which is what development provisioning profiles require). TestFlight
and App Store builds need `production`, so CI runs `PlistBuddy` on the entitlements file
to flip the value before archiving. The committed entitlements file stays on `development`
so dev workflow is unaffected. Without this patch, Firebase-sent push notifications won't
arrive on TestFlight devices — iOS rejects the registration token mismatch silently.

**Apple-side prerequisites** (one-time setup, not done by CI):
1. Register an App ID for `com.tunjid.heron` at developer.apple.com with the capabilities
   listed in `apps/iosApp/iosApp/iosApp.entitlements` (currently Push Notifications, Associated Domains).
2. Create an **Apple Distribution** certificate, export the cert + private key from Keychain
   as a `.p12` file, and base64-encode it for `IOS_CERTIFICATES_P12`.
3. Create an **App Store Connect**-type provisioning profile tied to the App ID and that cert.
   Its display name goes into `IOS_DIST_PROVISIONING_PROFILE_NAME`. No device registration
   is required since distribution profiles have no device list.
4. Create an App Store Connect API key with **App Manager** role. The issuer ID, key ID, and
   `.p8` private key contents go into the three `APPSTORE_*` secrets. The `.p8` is PEM text —
   copy it verbatim, do **not** base64-encode.
5. Create the app record in App Store Connect (My Apps > + > New App) with bundle ID
   `com.tunjid.heron` before the first CI upload.

After upload, the build appears in App Store Connect > TestFlight within ~15 minutes. Internal
testing (up to 100 team members, no review) can be enabled immediately. External testing
requires a brief Beta App Review.

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