Architecture & Data Flow - CometChat Docs

The UI Kit is split into three modules that follow Clean Architecture principles. chatuikit-core holds all business logic, data access, and state management. The UI modules (chatuikit-jetpack and chatuikit-kotlin) provide platform-specific rendering on top of the shared core.

Module Structure

4-Layer Architecture

Every feature follows the same layered flow: View → ViewModel → Repository → DataSource. The ViewModel lives in chatuikit-core and is shared by both UI modules. This means the same CometChatConversationsViewModel drives both the XML View and the Composable — only the rendering layer differs.

Clean Architecture Layers (chatuikit-core)

Data Layer

The data layer wraps the CometChat SDK behind interfaces, making it swappable and testable. DataSource — defines the contract for raw SDK operations:

// Interface (contract)
interface ConversationsDataSource {
    suspend fun fetchConversations(request: ConversationsRequest): List<Conversation>
    suspend fun deleteConversation(conversationWith: String, conversationType: String): String
    suspend fun markAsDelivered(message: BaseMessage)
}

// Implementation (calls CometChat SDK)
class ConversationsDataSourceImpl : ConversationsDataSource {
    override suspend fun fetchConversations(request: ConversationsRequest): List<Conversation> {
        // Wraps CometChat.fetchConversations() in a coroutine
    }
}

Every feature has a DataSource pair: ConversationsDataSource / ConversationsDataSourceImpl, UsersDataSource / UsersDataSourceImpl, etc. Repository Implementation — coordinates data sources and handles error wrapping:

class ConversationsRepositoryImpl(
    private val dataSource: ConversationsDataSource
) : ConversationsRepository {

    private var hasMore = true

    override suspend fun getConversations(
        request: ConversationsRequest
    ): Result<List<Conversation>> {
        return try {
            val conversations = dataSource.fetchConversations(request)
            hasMore = conversations.isNotEmpty()
            Result.success(conversations)
        } catch (e: CometChatException) {
            Result.failure(e)
        }
    }
}

Repositories wrap raw SDK exceptions into Kotlin Result types, track pagination state, and coordinate between data sources.

Domain Layer

The domain layer defines contracts and single-purpose use cases. It has no dependency on the SDK or Android framework. Repository Interfaces — contracts that the data layer implements:

interface ConversationsRepository {
    suspend fun getConversations(request: ConversationsRequest): Result<List<Conversation>>
    suspend fun deleteConversation(conversationWith: String, conversationType: String): Result<Unit>
    suspend fun markAsDelivered(conversation: Conversation): Result<Unit>
    fun hasMoreConversations(): Boolean
}

Use Cases — encapsulate a single business action:

open class GetConversationsUseCase(
    private val repository: ConversationsRepository
) {
    open suspend operator fun invoke(
        request: ConversationsRequest
    ): Result<List<Conversation>> {
        return repository.getConversations(request)
    }

    open fun hasMore(): Boolean = repository.hasMoreConversations()
}

Use cases are open so they can be overridden for testing or custom behavior. Each use case does one thing:

Use Case	Action
`GetConversationsUseCase`	Fetch paginated conversations
`DeleteConversationUseCase`	Delete a conversation
`RefreshConversationsUseCase`	Clear and re-fetch
`FetchUsersUseCase` / `SearchUsersUseCase`	Fetch or search users
`FetchGroupsUseCase`	Fetch groups
`FetchGroupMembersUseCase` / `SearchGroupMembersUseCase`	Fetch or search group members
`BanGroupMemberUseCase` / `KickGroupMemberUseCase`	Member moderation
`ChangeMemberScopeUseCase`	Change member role
`SendTextMessageUseCase` / `SendMediaMessageUseCase` / `SendCustomMessageUseCase`	Send messages
`EditMessageUseCase`	Edit a sent message
`FetchCallLogsUseCase`	Fetch call history
`InitiateCallUseCase` / `InitiateUserCallUseCase` / `StartGroupCallUseCase`	Start calls
`FetchReactionsUseCase` / `RemoveReactionUseCase`	Reaction management
`CreatePollUseCase`	Create a poll
`GetStickersUseCase`	Fetch sticker sets
`JoinGroupUseCase` / `GetGroupUseCase` / `GetUserUseCase`	Entity lookups

ViewModel Layer

ViewModels receive use cases via constructor injection and expose StateFlow / sealed UIState classes to the UI:

class CometChatConversationsViewModel(
    private val getConversationsUseCase: GetConversationsUseCase,
    private val deleteConversationUseCase: DeleteConversationUseCase,
    private val refreshConversationsUseCase: RefreshConversationsUseCase,
    private val enableListeners: Boolean = true
) : ViewModel() {

    // UI observes this sealed state
    private val _uiState = MutableStateFlow<UIState>(UIState.Loading)
    val uiState: StateFlow<UIState> = _uiState

    fun fetchConversations() {
        viewModelScope.launch {
            getConversationsUseCase(request)
                .onSuccess { conversations ->
                    _uiState.value = if (conversations.isEmpty()) UIState.Empty
                                     else UIState.Content(conversations)
                }
                .onFailure { _uiState.value = UIState.Error(it) }
        }
    }
}

State Management (StateFlow + Sealed Classes)

Each feature has a dedicated sealed UIState class. All state is exposed via StateFlow — not LiveData:

sealed class UIState {
    object Loading : UIState()
    object Empty : UIState()
    data class Error(val exception: CometChatException) : UIState()
    data class Content(val conversations: List<Conversation>) : UIState()
}

Feature-specific states include additional fields:

State Class	Feature	Extra Fields
`ConversationStarterUIState`	Conversation list	—
`MessageListUIState`	Message list	scroll position, reply state
`MessageComposerUIState`	Composer	attachment state, edit mode
`MessageHeaderUIState`	Header	typing indicator, user status
`GroupsUIState`	Groups	—
`UsersUIState`	Users	—
`GroupMembersUIState`	Group members	scope change state
`CallLogsUIState`	Call logs	—
`CallButtonsUIState`	Call buttons	call initiation state
`IncomingCallUIState` / `OutgoingCallUIState` / `OngoingCallUIState`	Calls	call session state
`ReactionListUIState`	Reactions	—
`CreatePollUIState`	Polls	form validation state
`StickerKeyboardUIState`	Stickers	sticker sets

ListOperations Interface

List-based ViewModels implement the ListOperations interface, which provides a standard contract for manipulating list data:

interface ListOperations<T> {
    fun addAtIndex(index: Int, item: T)
    fun updateAtIndex(index: Int, item: T)
    fun removeAtIndex(index: Int)
    fun moveToTop(item: T)
}

This ensures consistent list manipulation across Conversations, Users, Groups, Group Members, and Call Logs.

Dependency Injection via Factories

ViewModels are created through ViewModelProvider.Factory classes that wire up the dependency chain:

class CometChatConversationsViewModelFactory(
    private val repository: ConversationsRepository = ConversationsRepositoryImpl(
        ConversationsDataSourceImpl()
    ),
    private val enableListeners: Boolean = true
) : ViewModelProvider.Factory {

    override fun <T : ViewModel> create(modelClass: Class<T>): T {
        val getUseCase = GetConversationsUseCase(repository)
        val deleteUseCase = DeleteConversationUseCase(repository)
        val refreshUseCase = RefreshConversationsUseCase(repository)

        return CometChatConversationsViewModel(
            getConversationsUseCase = getUseCase,
            deleteConversationUseCase = deleteUseCase,
            refreshConversationsUseCase = refreshUseCase,
            enableListeners = enableListeners
        ) as T
    }
}

Default implementations are provided, but you can inject custom repositories:

// Custom repository for testing or caching
val factory = CometChatConversationsViewModelFactory(
    repository = MyCustomConversationRepository(),
    enableListeners = false  // disable for previews
)

Data Flow: End to End

Fetching Conversations

Real-Time Updates

User Action (Delete Conversation)

Component ↔ Core Mapping

UI Component	Core ViewModel	Use Cases	Repository	DataSource
Conversation List	`CometChatConversationsViewModel`	Get, Delete, Refresh	`ConversationsRepository`	`ConversationsDataSource`
Message List	`CometChatMessageListViewModel`	(message fetching)	`MessageListRepository`	`MessageListDataSource`
Message Composer	`CometChatMessageComposerViewModel`	SendText, SendMedia, SendCustom, Edit	`MessageComposerRepository`	`MessageComposerDataSource`
Message Header	`CometChatMessageHeaderViewModel`	—	`MessageHeaderRepository`	`MessageHeaderDataSource`
Users	`CometChatUsersViewModel`	FetchUsers, SearchUsers	`UsersRepository`	`UsersDataSource`
Groups	`CometChatGroupsViewModel`	FetchGroups, JoinGroup	`GroupsRepository`	`GroupsDataSource`
Group Members	`CometChatGroupMembersViewModel`	FetchMembers, Search, Ban, Kick, ChangeScope	`GroupMembersRepository`	`GroupMembersDataSource`
Call Logs	`CometChatCallLogsViewModel`	FetchCallLogs	`CallLogsRepository`	`CallLogsDataSource`
Call Buttons	`CometChatCallButtonsViewModel`	InitiateCall, StartGroupCall	`CallButtonsRepository`	`CallButtonsDataSource`
Reactions	`CometChatReactionListViewModel`	FetchReactions, RemoveReaction	`ReactionListRepository`	`ReactionListDataSource`
Message Info	`CometChatMessageInformationViewModel`	—	`MessageInformationRepository`	`MessageInformationDataSource`

Events (Cross-Component Communication)

The CometChatEvents singleton in chatuikit-core provides a typed event bus using Kotlin SharedFlow for communication between components that don’t share a ViewModel:

Event Flow	Emitted When
`CometChatEvents.messageEvents`	Message sent, edited, deleted, reacted
`CometChatEvents.conversationEvents`	Conversation deleted
`CometChatEvents.groupEvents`	Group created, member added/removed/banned
`CometChatEvents.userEvents`	User blocked/unblocked
`CometChatEvents.callEvents`	Call initiated, accepted, rejected
`CometChatEvents.uiEvents`	UI-level events (show dialog, navigate)

See the Events reference for sealed class types and subscription examples.

Component-Level Overrides

Every layer in the architecture is designed to be replaceable. You can override at the level that makes sense for your use case — from swapping the entire data source to just tweaking a single use case.

Override Points

1. Custom Repository

The most common override. Implement the repository interface and pass it to the factory.

class OfflineUsersRepository : UsersRepository {

    private val cachedUsers = listOf(/* local data */)

    override suspend fun getUsers(request: UsersRequest): Result<List<User>> {
        return Result.success(cachedUsers)
    }

    override fun hasMoreUsers(): Boolean = false
}

Wire it in:

Kotlin (XML Views)
Jetpack Compose

val factory = CometChatUsersViewModelFactory(
    repository = OfflineUsersRepository(),
    enableListeners = false
)
val viewModel = ViewModelProvider(this, factory)[CometChatUsersViewModel::class.java]

val usersView = findViewById<CometChatUsers>(R.id.users)
usersView.setViewModel(viewModel)

val factory = CometChatUsersViewModelFactory(
    repository = OfflineUsersRepository(),
    enableListeners = false
)
val viewModel: CometChatUsersViewModel = viewModel(factory = factory)

CometChatUsers(
    usersViewModel = viewModel
)

2. Custom DataSource

Override at the lowest level to change how SDK calls are made — useful for caching, offline support, or wrapping a different backend.

class CachedUsersDataSource(
    private val sdkDataSource: UsersDataSourceImpl = UsersDataSourceImpl(),
    private val cache: UserCache
) : UsersDataSource {

    override suspend fun fetchUsers(request: UsersRequest): List<User> {
        val cached = cache.get(request)
        if (cached != null) return cached

        val users = sdkDataSource.fetchUsers(request)
        cache.put(request, users)
        return users
    }
}

Then wrap it in the default repository implementation:

val dataSource = CachedUsersDataSource(cache = myCache)
val repository = UsersRepositoryImpl(dataSource)
val factory = CometChatUsersViewModelFactory(repository = repository)

3. Custom Use Cases

Use cases are open classes, so you can subclass them to add validation, logging, or transformation:

class LoggingGetConversationsUseCase(
    repository: ConversationsRepository
) : GetConversationsUseCase(repository) {

    override suspend operator fun invoke(
        request: ConversationsRequest
    ): Result<List<Conversation>> {
        Log.d("Conversations", "Fetching conversations...")
        val result = super.invoke(request)
        result.onSuccess { Log.d("Conversations", "Fetched ${it.size} items") }
        result.onFailure { Log.e("Conversations", "Fetch failed", it) }
        return result
    }
}

4. Passing a Custom ViewModel to the UI Component

Both chatuikit-jetpack (Compose) and chatuikit-kotlin (XML Views) accept a pre-built ViewModel. This is the entry point for all overrides.

Kotlin (XML Views)
Jetpack Compose

class MyUsersActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_users)

        val factory = CometChatUsersViewModelFactory(
            repository = MyCustomUsersRepository()
        )
        val viewModel = ViewModelProvider(this, factory)[CometChatUsersViewModel::class.java]

        val usersView = findViewById<CometChatUsers>(R.id.users)
        usersView.setViewModel(viewModel)
    }
}

@Composable
fun MyUsersScreen() {
    val factory = CometChatUsersViewModelFactory(
        repository = MyCustomUsersRepository(),
        enableListeners = true
    )
    val viewModel: CometChatUsersViewModel = viewModel(factory = factory)

    CometChatUsers(
        usersViewModel = viewModel,
        style = CometChatUsersStyle.default(),
        hideToolbar = false,
        hideSearchBox = false
    )
}

5. Disabling Listeners for Previews and Testing

Every factory accepts enableListeners = false. When disabled, the ViewModel won’t register SDK listeners or UIKit event subscriptions — useful for Compose previews, unit tests, or showcase screens:

val factory = CometChatConversationsViewModelFactory(
    repository = FakeConversationRepository(),
    enableListeners = false  // No WebSocket listeners, no event subscriptions
)

Override Summary by Component

Component	Factory Class	Repository Interface	Key Use Cases
Conversation List	`CometChatConversationsViewModelFactory`	`ConversationsRepository`	Get, Delete, Refresh
Users	`CometChatUsersViewModelFactory`	`UsersRepository`	FetchUsers, SearchUsers
Groups	`CometChatGroupsViewModelFactory`	`GroupsRepository`	FetchGroups, JoinGroup
Group Members	`CometChatGroupMembersViewModelFactory`	`GroupMembersRepository`	FetchMembers, Search, Ban, Kick, ChangeScope
Message List	`CometChatMessageListViewModelFactory`	`MessageListRepository`	(message fetching)
Message Composer	`CometChatMessageComposerViewModelFactory`	`MessageComposerRepository`	SendText, SendMedia, SendCustom, Edit
Call Logs	`CometChatCallLogsViewModelFactory`	`CallLogsRepository`	FetchCallLogs
Call Buttons	`CometChatCallButtonsViewModelFactory`	`CallButtonsRepository`	InitiateCall, StartGroupCall
Reactions	`CometChatReactionListViewModelFactory`	`ReactionListRepository`	FetchReactions, RemoveReaction

Events — Cross-component communication via CometChatEvents SharedFlow
Methods — UI Kit wrapper methods for init, auth, and messaging

​Module Structure

​4-Layer Architecture

​Clean Architecture Layers (chatuikit-core)

​Data Layer

​Domain Layer

​ViewModel Layer

​State Management (StateFlow + Sealed Classes)

​ListOperations Interface

​Dependency Injection via Factories

​Data Flow: End to End

​Fetching Conversations

​Real-Time Updates

​User Action (Delete Conversation)

​Component ↔ Core Mapping

​Events (Cross-Component Communication)

​Component-Level Overrides

​Override Points

​1. Custom Repository

​2. Custom DataSource

​3. Custom Use Cases

​4. Passing a Custom ViewModel to the UI Component

​5. Disabling Listeners for Previews and Testing

​Override Summary by Component

​Related