simplex-chat/apps/multiplatform/spec

SimpleX Chat -- Kotlin Multiplatform Specification

Table of Contents

1. Executive Summary
2. Dependency Graph
3. Specification Documents
4. Product Documents
5. Source Entry Points

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Executive Summary

SimpleX Chat is a Kotlin Multiplatform application targeting Android and Desktop (JVM) platforms. The UI layer is built entirely with Jetpack Compose. The application communicates with a Haskell-based cryptographic core (simplex-chat) through a JNI bridge -- native functions declared in Kotlin and linked at runtime to a shared library (libapp-lib). Platform-specific behavior (notifications, file system paths, services, audio/video) is abstracted using the expect/actual pattern and a runtime-assignable PlatformInterface callback object.

The Gradle project is structured as three modules:

Module	Purpose
:common	Shared Compose UI, models, platform abstractions (commonMain, androidMain, desktopMain)
:android	Android application entry point (SimplexApp, MainActivity)
:desktop	Desktop application entry point (Main.kt, showApp())

All meaningful application logic resides in :common/commonMain. Platform source sets (androidMain, desktopMain) provide actual implementations for expect declarations and host platform-specific integration code.

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Dependency Graph

App Entry Points
+-- Android: SimplexApp.onCreate -> initHaskell -> initMultiplatform -> initChatControllerOnStart
|            MainActivity.onCreate -> setContent { AppScreen() }
+-- Desktop: main() -> initHaskell -> runMigrations -> initApp -> showApp -> AppWindow -> AppScreen()
    |
    v
Common Module (commonMain)
+-- ChatModel (Compose state singleton) <-> ChatController/SimpleXAPI (JNI bridge) <-> Haskell Core (chat_ctrl)
+-- Views (Compose)
|   +-- App.kt: AppScreen -> MainScreen
|   +-- ChatListView -> ChatView -> ComposeView -> SendMsgView
|   +-- ChatItemView (message rendering: text, image, video, voice, file, call, events)
|   +-- Settings: SettingsView, UserProfileView, UserProfilesView
|   +-- Onboarding: OnboardingView, WhatsNewView, CreateFirstProfile
|   +-- Call: CallView, IncomingCallAlertView
|   +-- Database: DatabaseView, DatabaseEncryptionView, DatabaseErrorView
|   +-- Groups: GroupChatInfoView, AddGroupMembersView, GroupMemberInfoView
|   +-- Contacts: ContactListNavView
|   +-- Remote: ConnectDesktopView, ConnectMobileView
|   +-- Terminal: TerminalView
+-- Models
|   +-- ChatModel       -- global app state (Compose MutableState singleton)
|   +-- ChatsContext     -- per-context chat list state (primary + optional secondary)
|   +-- Chat             -- per-conversation state (chatInfo, chatItems, chatStats)
|   +-- ChatController   -- API command dispatch, event receiver, preferences
|   +-- AppPreferences   -- 150+ SharedPreferences keys
+-- Services
|   +-- NtfManager       -- abstract notification coordinator (Android/Desktop implementations)
|   +-- SimplexService   -- Android foreground service for background messaging
|   +-- ThemeManager     -- theme resolution (system/light/dark/simplex/black + per-user overrides)
|   +-- CallManager      -- WebRTC call lifecycle
+-- Platform (expect/actual)
    +-- Core.kt          -- JNI declarations (external fun), initChatController, chatInitTemporaryDatabase
    +-- AppCommon.kt     -- runMigrations, AppPlatform enum
    +-- Files.kt         -- dataDir, tmpDir, filesDir, dbAbsolutePrefixPath (expect)
    +-- Share.kt         -- shareText, shareFile, openFile (expect)
    +-- VideoPlayer.kt   -- VideoPlayerInterface, VideoPlayer (expect class)
    +-- RecAndPlay.kt    -- RecorderInterface, AudioPlayerInterface (expect)
    +-- UI.kt            -- showToast, hideKeyboard, getKeyboardState (expect)
    +-- Notifications.kt -- allowedToShowNotification (expect)
    +-- NtfManager.kt    -- abstract NtfManager class
    +-- Platform.kt      -- PlatformInterface (runtime callback object)
    +-- Cryptor.kt       -- CryptorInterface (expect)
    +-- Images.kt        -- bitmap utilities (expect)
    +-- SimplexService.kt-- getWakeLock (expect)
    +-- Log.kt, Modifier.kt, Back.kt, ScrollableColumn.kt, PlatformTextField.kt, Resources.kt

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Specification Documents

Document	Path	Description
Architecture	spec/architecture.md	System layers, module structure, JNI bridge, app lifecycle, event streaming, platform abstraction
State Management	spec/state.md	ChatModel singleton, ChatsContext, Chat data class, AppPreferences, ActiveChatState
API	spec/api.md	ChatController command dispatch, ~150 API functions in 11 categories, CC/CR/API types
Database	spec/database.md	SQLite database files, migrations, encryption, backup/restore
Impact	spec/impact.md	Source file → product concept mapping for change impact analysis
Chat View	spec/client/chat-view.md	ChatView, ChatItemView, message rendering, item interactions, terminal layout (TerminalItemView)
Chat List	spec/client/chat-list.md	ChatListView, ChatPreviewView, filtering, search, tags
Compose	spec/client/compose.md	ComposeView, SendMsgView, ComposeState, attachments, mentions
Navigation	spec/client/navigation.md	App screen routing, onboarding, settings, new chat flows
Calls	spec/services/calls.md	WebRTC call lifecycle, signaling, platform-specific call views
Files	spec/services/files.md	File transfer (SMP inline / XFTP), CryptoFile encryption, platform file paths
Notifications	spec/services/notifications.md	NtfManager, SimplexService, notification channels, background delivery
Theme	spec/services/theme.md	ThemeManager, color system, wallpapers, per-user overrides

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Product Documents

Category	Path	Topic
Overview	product/README.md	Product overview, capability map, navigation map
Concepts	product/concepts.md	32 product concepts (PC1-PC32) mapped to docs + source
Glossary	product/glossary.md	Domain term definitions (9 sections)
Rules	product/rules.md	18 business rules in 6 categories
Gaps	product/gaps.md	8 known gaps with recommendations
Flows	product/flows/	onboarding, messaging, connection, calling, file-transfer, group-lifecycle
Views	product/views/	chat-list, chat, settings, onboarding, call, new-chat, contact-info, group-info, user-profiles

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Source Entry Points

Component	File	Key Symbol	Line
Android Application	SimplexApp.kt	class SimplexApp	41
Android Activity	MainActivity.kt	class MainActivity	27
Desktop Entry	Main.kt	fun main(args: Array<String>)	26
Desktop App Window	DesktopApp.kt	fun showApp()	33
Desktop Init	AppCommon.desktop.kt	fun initApp()	21
Common App Screen	App.kt	fun AppScreen()	47
JNI Bridge	Core.kt	external fun initHS()	18
Chat Controller	SimpleXAPI.kt	object ChatController	525
Chat Model	ChatModel.kt	object ChatModel	86
App Preferences	SimpleXAPI.kt	class AppPreferences	102
Platform Interface	Platform.kt	interface PlatformInterface	15
Notification Manager	NtfManager.kt	abstract class NtfManager	20
Theme Manager	ThemeManager.kt	object ThemeManager	18
Android Haskell Init	AppCommon.android.kt	fun initHaskell(packageName: String)	36
Common Migrations	AppCommon.kt	fun runMigrations()	48
Android Service	SimplexService.kt	class SimplexService	41
Gradle Root	settings.gradle.kts	include(":android", ":desktop", ":common")	22
Common Build	build.gradle.kts	kotlin { androidTarget(); jvm("desktop") }	14