WIP sagas

16 files changed, 453 insertions, 21 deletions

diff --git a/build.gradle.kts b/build.gradle.kts
index dc9c46be..af286b54 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -17,4 +17,8 @@ subprojects {
     tasks.withType<org.jetbrains.kotlin.gradle.tasks.KotlinCompile> {
         kotlinOptions.jvmTarget = "1.8"
     }
+
+    tasks.withType<org.jetbrains.kotlin.gradle.tasks.Kotlin2JsCompile> {
+        kotlinOptions.freeCompilerArgs = listOf("-Xuse-experimental=kotlin.Experimental")
+    }
 }
diff --git a/sw-client/src/commonMain/kotlin/org/luxons/sevenwonders/client/SevenWondersClient.kt b/sw-client/src/commonMain/kotlin/org/luxons/sevenwonders/client/SevenWondersClient.kt
index 544c870b..70cefbcc 100644
--- a/sw-client/src/commonMain/kotlin/org/luxons/sevenwonders/client/SevenWondersClient.kt
+++ b/sw-client/src/commonMain/kotlin/org/luxons/sevenwonders/client/SevenWondersClient.kt
@@ -94,10 +94,8 @@ class SevenWondersSession(private val stompSession: KrossbowSession) {
     suspend fun watchGameStart(gameId: Long): SevenWondersSubscription<Unit> =
         stompSession.subscribe<Unit>("/topic/lobby/$gameId/started").ignoreHeaders()
 
-    suspend fun startGame(gameId: Long) {
-        val sendDestination = "/app/lobby/startGame"
-        val receiveDestination = "/topic/lobby/$gameId/started"
-        stompSession.request<Unit>(sendDestination, receiveDestination)
+    suspend fun startGame() {
+        stompSession.send("/app/lobby/startGame")
     }
 
     suspend fun watchPlayerReady(gameId: Long): SevenWondersSubscription<String> =
diff --git a/sw-server/src/test/kotlin/org/luxons/sevenwonders/server/SevenWondersTest.kt b/sw-server/src/test/kotlin/org/luxons/sevenwonders/server/SevenWondersTest.kt
index 4771076d..7b996680 100644
--- a/sw-server/src/test/kotlin/org/luxons/sevenwonders/server/SevenWondersTest.kt
+++ b/sw-server/src/test/kotlin/org/luxons/sevenwonders/server/SevenWondersTest.kt
@@ -69,7 +69,7 @@ class SevenWondersTest {
             val outsiderSession = newPlayer("Outsider")
             val (started) = outsiderSession.watchGameStart(lobby.id)
 
-            ownerSession.startGame(lobby.id)
+            ownerSession.startGame()
             val nothing = withTimeoutOrNull(30) { started.receive() }
             assertNull(nothing)
             disconnect(ownerSession, session1, session2, outsiderSession)
@@ -126,7 +126,14 @@ class SevenWondersTest {
         val session3 = newPlayer("Player3")
         session3.joinGame(lobby.id)
 
-        session1.startGame(lobby.id)
+        val (gameStart1) = session1.watchGameStart(lobby.id)
+        val (gameStart2) = session2.watchGameStart(lobby.id)
+        val (gameStart3) = session3.watchGameStart(lobby.id)
+        session1.startGame()
+
+        withTimeout(500) { gameStart1.receive() }
+        withTimeout(500) { gameStart2.receive() }
+        withTimeout(500) { gameStart3.receive() }
 
         val (turns1) = session1.watchTurns()
         val (turns2) = session2.watchTurns()
@@ -134,9 +141,9 @@ class SevenWondersTest {
         session1.sayReady()
         session2.sayReady()
         session3.sayReady()
-        val turn1 = turns1.receive()
-        val turn2 = turns2.receive()
-        val turn3 = turns3.receive()
+        val turn1 = withTimeout(500) { turns1.receive() }
+        val turn2 = withTimeout(500) { turns2.receive() }
+        val turn3 = withTimeout(500) { turns3.receive() }
         assertNotNull(turn1)
         assertNotNull(turn2)
         assertNotNull(turn3)
diff --git a/sw-ui-kt/build.gradle.kts b/sw-ui-kt/build.gradle.kts
index 04bf8cf8..d2467ef7 100644
--- a/sw-ui-kt/build.gradle.kts
+++ b/sw-ui-kt/build.gradle.kts
@@ -43,7 +43,12 @@ kotlin {
                 // seems to be required by "kotlin-extensions" JS lib
                 implementation(npm("core-js", "3.1.4"))
 
-                // implementation(npm("@blueprintjs/core", "3.15.1"))
+                implementation(npm("@blueprintjs/core", "3.15.1"))
+            }
+        }
+        test {
+            dependencies {
+                implementation(kotlin("test-js"))
             }
         }
     }
diff --git a/sw-ui-kt/src/main/kotlin/org/luxons/sevenwonders/ui/SevenWondersUi.kt b/sw-ui-kt/src/main/kotlin/org/luxons/sevenwonders/ui/SevenWondersUi.kt
index 2a075ba9..fafa2333 100644
--- a/sw-ui-kt/src/main/kotlin/org/luxons/sevenwonders/ui/SevenWondersUi.kt
+++ b/sw-ui-kt/src/main/kotlin/org/luxons/sevenwonders/ui/SevenWondersUi.kt
@@ -1,11 +1,16 @@
 package org.luxons.sevenwonders.ui
 
 import org.luxons.sevenwonders.ui.components.application
+import org.luxons.sevenwonders.ui.redux.SwState
 import org.luxons.sevenwonders.ui.redux.configureStore
+import org.luxons.sevenwonders.ui.redux.sagas.SagaManager
+import org.luxons.sevenwonders.ui.redux.sagas.rootSaga
 import org.w3c.dom.Element
-import react.RBuilder
 import react.dom.*
 import react.redux.provider
+import redux.RAction
+import redux.Store
+import redux.WrapperAction
 import kotlin.browser.document
 import kotlin.browser.window
 
@@ -21,10 +26,18 @@ fun main() {
 }
 
 private fun initializeAndRender(rootElement: Element) {
-    val store = configureStore()
+    val store = initRedux()
+
     render(rootElement) {
         provider(store) {
             application()
         }
     }
 }
+
+private fun initRedux(): Store<SwState, RAction, WrapperAction> {
+    val sagaManager = SagaManager<SwState, RAction, WrapperAction>()
+    val store = configureStore(sagaManager = sagaManager)
+    sagaManager.startSaga(rootSaga())
+    return store
+}
diff --git a/sw-ui-kt/src/main/kotlin/org/luxons/sevenwonders/ui/components/home/ChooseNameForm.kt b/sw-ui-kt/src/main/kotlin/org/luxons/sevenwonders/ui/components/home/ChooseNameForm.kt
index 8bf43f1d..30a0883a 100644
--- a/sw-ui-kt/src/main/kotlin/org/luxons/sevenwonders/ui/components/home/ChooseNameForm.kt
+++ b/sw-ui-kt/src/main/kotlin/org/luxons/sevenwonders/ui/components/home/ChooseNameForm.kt
@@ -3,7 +3,7 @@ package org.luxons.sevenwonders.ui.components.home
 import kotlinx.html.InputType
 import kotlinx.html.js.onChangeFunction
 import kotlinx.html.js.onSubmitFunction
-import org.luxons.sevenwonders.ui.redux.ChooseUserName
+import org.luxons.sevenwonders.ui.redux.RequestChooseName
 import org.luxons.sevenwonders.ui.redux.connectDispatch
 import react.RBuilder
 import react.RClass
@@ -37,5 +37,5 @@ private class ChooseNameForm(props: ChooseNameFormProps): RComponent<ChooseNameF
 }
 
 val chooseNameForm: RClass<RProps> = connectDispatch(ChooseNameForm::class) { dispatch, _ ->
-    chooseUsername = { name -> dispatch(ChooseUserName(name)) }
+    chooseUsername = { name -> dispatch(RequestChooseName(name)) }
 }
diff --git a/sw-ui-kt/src/main/kotlin/org/luxons/sevenwonders/ui/redux/Actions.kt b/sw-ui-kt/src/main/kotlin/org/luxons/sevenwonders/ui/redux/Actions.kt
index 3fc51d6e..27c451be 100644
--- a/sw-ui-kt/src/main/kotlin/org/luxons/sevenwonders/ui/redux/Actions.kt
+++ b/sw-ui-kt/src/main/kotlin/org/luxons/sevenwonders/ui/redux/Actions.kt
@@ -1,5 +1,30 @@
 package org.luxons.sevenwonders.ui.redux
 
+import org.luxons.sevenwonders.model.GameState
+import org.luxons.sevenwonders.model.PlayerMove
+import org.luxons.sevenwonders.model.api.LobbyDTO
+import org.luxons.sevenwonders.model.api.PlayerDTO
+import org.luxons.sevenwonders.model.cards.PreparedCard
 import redux.RAction
 
-class ChooseUserName(val newUsername: String): RAction
+data class SetCurrentPlayerAction(val player: PlayerDTO): RAction
+
+data class UpdateGameListAction(val games: List<LobbyDTO>): RAction
+
+data class UpdateLobbyAction(val lobby: LobbyDTO): RAction
+
+data class EnterLobbyAction(val gameId: Long): RAction
+
+data class UpdatePlayers(val players: Map<String, PlayerDTO>): RAction
+
+data class EnterGameAction(val gameId: Long): RAction
+
+data class TurnInfoEvent(val players: Map<String, PlayerDTO>): RAction
+
+data class PrepareMoveAction(val move: PlayerMove): RAction
+
+data class PreparedCardEvent(val card: PreparedCard): RAction
+
+data class PlayerReadyEvent(val username: String): RAction
+
+data class TableUpdateEvent(val table: GameState): RAction
diff --git a/sw-ui-kt/src/main/kotlin/org/luxons/sevenwonders/ui/redux/ApiActions.kt b/sw-ui-kt/src/main/kotlin/org/luxons/sevenwonders/ui/redux/ApiActions.kt
new file mode 100644
index 00000000..dc959a2f
--- /dev/null
+++ b/sw-ui-kt/src/main/kotlin/org/luxons/sevenwonders/ui/redux/ApiActions.kt
@@ -0,0 +1,19 @@
+package org.luxons.sevenwonders.ui.redux
+
+import org.luxons.sevenwonders.model.CustomizableSettings
+import org.luxons.sevenwonders.model.PlayerMove
+import redux.RAction
+
+data class RequestChooseName(val playerName: String): RAction
+
+data class RequestCreateGameAction(val gameName: String): RAction
+
+data class RequestJoinGameAction(val gameId: Long): RAction
+
+data class RequestReorderPlayers(val orderedPlayers: List<String>): RAction
+
+data class RequestUpdateSettings(val settings: CustomizableSettings): RAction
+
+class RequestStartGameAction: RAction
+
+data class PrepareMove(val move: PlayerMove): RAction
diff --git a/sw-ui-kt/src/main/kotlin/org/luxons/sevenwonders/ui/redux/Reducers.kt b/sw-ui-kt/src/main/kotlin/org/luxons/sevenwonders/ui/redux/Reducers.kt
index d811d32e..f9f5a26d 100644
--- a/sw-ui-kt/src/main/kotlin/org/luxons/sevenwonders/ui/redux/Reducers.kt
+++ b/sw-ui-kt/src/main/kotlin/org/luxons/sevenwonders/ui/redux/Reducers.kt
@@ -3,6 +3,6 @@ package org.luxons.sevenwonders.ui.redux
 import redux.RAction
 
 fun rootReducer(state: SwState, action: RAction) = when (action) {
-    is ChooseUserName -> state.copy(playerName = action.newUsername)
+    is RequestChooseName -> state.copy(playerName = action.playerName)
     else -> state
 }
diff --git a/sw-ui-kt/src/main/kotlin/org/luxons/sevenwonders/ui/redux/Store.kt b/sw-ui-kt/src/main/kotlin/org/luxons/sevenwonders/ui/redux/Store.kt
index 75f7e8a8..fea13f04 100644
--- a/sw-ui-kt/src/main/kotlin/org/luxons/sevenwonders/ui/redux/Store.kt
+++ b/sw-ui-kt/src/main/kotlin/org/luxons/sevenwonders/ui/redux/Store.kt
@@ -1,8 +1,11 @@
 package org.luxons.sevenwonders.ui.redux
 
+import org.luxons.sevenwonders.ui.redux.sagas.SagaManager
 import redux.RAction
 import redux.Store
 import redux.WrapperAction
+import redux.applyMiddleware
+import redux.compose
 import redux.createStore
 import redux.rEnhancer
 
@@ -12,9 +15,10 @@ data class SwState(
 
 val INITIAL_STATE = SwState("Bob")
 
-fun configureStore(initialState: SwState = INITIAL_STATE): Store<SwState, RAction, WrapperAction> {
-
-    // TODO configure middlewares
-
-    return createStore(::rootReducer, initialState, rEnhancer())
+fun configureStore(
+    sagaManager: SagaManager<SwState, RAction, WrapperAction>,
+    initialState: SwState = INITIAL_STATE
+): Store<SwState, RAction, WrapperAction> {
+    val sagaEnhancer = applyMiddleware(sagaManager.createMiddleware())
+    return createStore(::rootReducer, initialState, compose(sagaEnhancer, rEnhancer()))
 }
diff --git a/sw-ui-kt/src/main/kotlin/org/luxons/sevenwonders/ui/redux/sagas/GameBrowserSagas.kt b/sw-ui-kt/src/main/kotlin/org/luxons/sevenwonders/ui/redux/sagas/GameBrowserSagas.kt
new file mode 100644
index 00000000..cd9e0cf8
--- /dev/null
+++ b/sw-ui-kt/src/main/kotlin/org/luxons/sevenwonders/ui/redux/sagas/GameBrowserSagas.kt
@@ -0,0 +1,52 @@
+package org.luxons.sevenwonders.ui.redux.sagas
+
+import kotlinx.coroutines.flow.collect
+import kotlinx.coroutines.isActive
+import org.luxons.sevenwonders.client.SevenWondersSession
+import org.luxons.sevenwonders.model.api.LobbyDTO
+import org.luxons.sevenwonders.ui.redux.EnterLobbyAction
+import org.luxons.sevenwonders.ui.redux.RequestCreateGameAction
+import org.luxons.sevenwonders.ui.redux.RequestJoinGameAction
+import org.luxons.sevenwonders.ui.redux.SwState
+import org.luxons.sevenwonders.ui.redux.UpdateGameListAction
+import org.luxons.sevenwonders.ui.redux.UpdateLobbyAction
+import redux.RAction
+import redux.WrapperAction
+
+fun gameBrowserSaga(session: SevenWondersSession) = saga<SwState, RAction, WrapperAction> {
+    val watchGamesJob = fork(watchGames(session))
+    val watchCreateGameJob = fork(watchCreateGame(session))
+    val watchJoinGameJob = fork(watchJoinGame(session))
+}
+
+private fun watchGames(session: SevenWondersSession) = saga<SwState, RAction, WrapperAction> {
+    val gamesSubscription = session.watchGames()
+    for (lobbies in gamesSubscription.messages) {
+        if (!isActive) {
+            gamesSubscription.unsubscribe()
+            break
+        }
+        dispatch(UpdateGameListAction(lobbies.toList()))
+    }
+}
+
+private fun watchCreateGame(session: SevenWondersSession) =
+        actionHandlerSaga<SwState, RAction, WrapperAction, RequestCreateGameAction> {
+            val lobby = session.createGame(it.gameName)
+            handleGameJoined(session, lobby)
+        }
+
+private fun watchJoinGame(session: SevenWondersSession) = actionHandlerSaga<SwState, RAction, WrapperAction, RequestJoinGameAction> {
+    val lobby = session.joinGame(it.gameId)
+    handleGameJoined(session, lobby)
+}
+
+private fun SagaContext<SwState, RAction, WrapperAction>.handleGameJoined(
+    session: SevenWondersSession,
+    lobby: LobbyDTO
+) {
+    dispatch(UpdateLobbyAction(lobby))
+    dispatch(EnterLobbyAction(lobby.id))
+    fork(lobbySaga(session, lobby.id))
+    // TODO push /lobby/{lobby.id}
+}
diff --git a/sw-ui-kt/src/main/kotlin/org/luxons/sevenwonders/ui/redux/sagas/GameSagas.kt b/sw-ui-kt/src/main/kotlin/org/luxons/sevenwonders/ui/redux/sagas/GameSagas.kt
new file mode 100644
index 00000000..24a9e1b4
--- /dev/null
+++ b/sw-ui-kt/src/main/kotlin/org/luxons/sevenwonders/ui/redux/sagas/GameSagas.kt
@@ -0,0 +1,15 @@
+package org.luxons.sevenwonders.ui.redux.sagas
+
+import org.luxons.sevenwonders.client.SevenWondersSession
+import org.luxons.sevenwonders.ui.redux.SwState
+import redux.RAction
+import redux.WrapperAction
+
+fun gameSaga(session: SevenWondersSession, gameId: Long) = saga<SwState, RAction, WrapperAction> {
+    fork(watchPlayerReady(session, gameId))
+}
+
+fun watchPlayerReady(session: SevenWondersSession, gameId: Long) = saga<SwState, RAction, WrapperAction> {
+    session.watchPlayerReady(gameId)
+}
+
diff --git a/sw-ui-kt/src/main/kotlin/org/luxons/sevenwonders/ui/redux/sagas/LobbySagas.kt b/sw-ui-kt/src/main/kotlin/org/luxons/sevenwonders/ui/redux/sagas/LobbySagas.kt
new file mode 100644
index 00000000..89e8e890
--- /dev/null
+++ b/sw-ui-kt/src/main/kotlin/org/luxons/sevenwonders/ui/redux/sagas/LobbySagas.kt
@@ -0,0 +1,33 @@
+package org.luxons.sevenwonders.ui.redux.sagas
+
+import org.luxons.sevenwonders.client.SevenWondersSession
+import org.luxons.sevenwonders.ui.redux.EnterGameAction
+import org.luxons.sevenwonders.ui.redux.RequestStartGameAction
+import org.luxons.sevenwonders.ui.redux.SwState
+import org.luxons.sevenwonders.ui.redux.UpdateLobbyAction
+import redux.RAction
+import redux.WrapperAction
+
+fun lobbySaga(session: SevenWondersSession, lobbyId: Long) = saga<SwState, RAction, WrapperAction> {
+    fork(watchLobbyUpdates(session, lobbyId))
+    fork(watchGameStart(session, lobbyId))
+    fork(startGame(session))
+}
+
+private fun watchLobbyUpdates(session: SevenWondersSession, lobbyId: Long) = saga<SwState, RAction, WrapperAction> {
+    val lobbyUpdates = session.watchLobbyUpdates(lobbyId)
+    for (lobby in lobbyUpdates.messages) {
+        dispatch(UpdateLobbyAction(lobby))
+    }
+}
+
+private fun watchGameStart(session: SevenWondersSession, lobbyId: Long) = saga<SwState, RAction, WrapperAction> {
+    val gameStartSubscription = session.watchGameStart(lobbyId)
+    gameStartSubscription.messages.receive()
+    dispatch(EnterGameAction(lobbyId))
+    // TODO push /game/{lobby.id}
+}
+
+private fun startGame(session: SevenWondersSession) = actionHandlerSaga<SwState, RAction, WrapperAction, RequestStartGameAction> {
+    session.startGame()
+}
diff --git a/sw-ui-kt/src/main/kotlin/org/luxons/sevenwonders/ui/redux/sagas/Sagas.kt b/sw-ui-kt/src/main/kotlin/org/luxons/sevenwonders/ui/redux/sagas/Sagas.kt
new file mode 100644
index 00000000..96311f98
--- /dev/null
+++ b/sw-ui-kt/src/main/kotlin/org/luxons/sevenwonders/ui/redux/sagas/Sagas.kt
@@ -0,0 +1,20 @@
+package org.luxons.sevenwonders.ui.redux.sagas
+
+import org.luxons.sevenwonders.client.SevenWondersClient
+import org.luxons.sevenwonders.model.api.SEVEN_WONDERS_WS_ENDPOINT
+import org.luxons.sevenwonders.ui.redux.RequestChooseName
+import org.luxons.sevenwonders.ui.redux.SetCurrentPlayerAction
+import org.luxons.sevenwonders.ui.redux.SwState
+import redux.RAction
+import redux.WrapperAction
+
+fun rootSaga() = saga<SwState, RAction, WrapperAction> {
+    val action = next<RequestChooseName>()
+    val session = SevenWondersClient().connect(SEVEN_WONDERS_WS_ENDPOINT)
+
+    fork(gameBrowserSaga(session))
+
+    val player = session.chooseName(action.playerName)
+    dispatch(SetCurrentPlayerAction(player))
+    // push /games
+}
diff --git a/sw-ui-kt/src/main/kotlin/org/luxons/sevenwonders/ui/redux/sagas/SagasFramework.kt b/sw-ui-kt/src/main/kotlin/org/luxons/sevenwonders/ui/redux/sagas/SagasFramework.kt
new file mode 100644
index 00000000..2aa677fe
--- /dev/null
+++ b/sw-ui-kt/src/main/kotlin/org/luxons/sevenwonders/ui/redux/sagas/SagasFramework.kt
@@ -0,0 +1,143 @@
+package org.luxons.sevenwonders.ui.redux.sagas
+
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.FlowPreview
+import kotlinx.coroutines.GlobalScope
+import kotlinx.coroutines.Job
+import kotlinx.coroutines.channels.BroadcastChannel
+import kotlinx.coroutines.isActive
+import kotlinx.coroutines.launch
+import kotlinx.coroutines.promise
+import redux.Middleware
+import redux.MiddlewareApi
+import redux.RAction
+import kotlin.coroutines.CoroutineContext
+
+@UseExperimental(ExperimentalCoroutinesApi::class)
+class SagaManager<S, A : RAction, R>(
+    private val monitor: ((A) -> Unit)? = null
+) {
+    private lateinit var context: SagaContext<S, A, R>
+
+    private val actions = BroadcastChannel<A>(16)
+
+    fun createMiddleware(): Middleware<S, A, R, A, R> = ::sagasMiddleware
+
+    private fun sagasMiddleware(api: MiddlewareApi<S, A, R>): ((A) -> R) -> (A) -> R {
+        context = SagaContext(api, actions)
+        return { nextDispatch ->
+            { action ->
+                onActionDispatched(action)
+                val result = nextDispatch(action)
+                handleAction(action)
+                result
+            }
+        }
+    }
+
+    private fun onActionDispatched(action: A) {
+        monitor?.invoke(action)
+    }
+
+    private fun handleAction(action: A) {
+        GlobalScope.promise { actions.send(action) }
+    }
+
+    fun startSaga(saga: Saga<S, A, R>): Job {
+        check(::context.isInitialized) {
+            "Before running a Saga, you must mount the Saga middleware on the Store using applyMiddleware"
+        }
+        return context.launch {
+            saga.execute(context)
+        }
+    }
+
+    suspend fun runSaga(saga: Saga<S, A, R>) {
+        check(::context.isInitialized) {
+            "Before running a Saga, you must mount the Saga middleware on the Store using applyMiddleware"
+        }
+        saga.execute(context)
+    }
+}
+
+fun <S, A : RAction, R> saga(block: suspend SagaContext<S, A, R>.() -> Unit) = Saga(block)
+
+inline fun <S, A : RAction, R, reified AT : A> actionHandlerSaga(
+    noinline block: suspend SagaContext<S, A, R>.(AT) -> Unit
+) = saga<S, A, R> {
+    onEach<AT> {
+        block(it)
+    }
+}
+
+class Saga<S, A : RAction, R>(private val body: suspend SagaContext<S, A, R>.() -> Unit) {
+
+    internal suspend fun execute(context: SagaContext<S, A, R>) = context.body()
+}
+
+@UseExperimental(FlowPreview::class, ExperimentalCoroutinesApi::class)
+class SagaContext<S, A : RAction, R>(
+    private val reduxApi: MiddlewareApi<S, A, R>,
+    private val actions: BroadcastChannel<A>
+): CoroutineScope {
+
+    private val job = Job()
+
+    override val coroutineContext: CoroutineContext
+        get() = job
+
+    fun dispatch(action: A) {
+        reduxApi.dispatch(action)
+    }
+
+    /**
+     * Starts a concurrent coroutine that executes [handle] on every action dispatched.
+     * Returns an "unsubscribe" function.
+     */
+    suspend fun onEach(handle: suspend SagaContext<S, A, R>.(A) -> Unit) {
+        val channel = actions.openSubscription()
+        for (a in channel) {
+            if (!isActive) {
+                channel.cancel()
+                break
+            }
+            handle(a)
+        }
+    }
+
+    /**
+     * Starts a concurrent coroutine that executes [handle] on every action dispatched of the given type.
+     * Returns an "unsubscribe" function.
+     */
+    suspend inline fun <reified AT : A> onEach(
+        crossinline handle: suspend SagaContext<S, A, R>.(AT) -> Unit
+    ) = onEach {
+        if (it is AT) {
+            handle(it)
+        }
+    }
+
+    /**
+     * Suspends until the next action matching the given [predicate] is dispatched, and returns that action.
+     */
+    suspend fun next(predicate: (A) -> Boolean): A {
+        val channel = actions.openSubscription()
+        for (a in channel) {
+            if (predicate(a)) {
+                channel.cancel()
+                return a
+            }
+        }
+        throw IllegalStateException("Actions channel closed before receiving a matching action")
+    }
+
+    /**
+     * Suspends until the next action of type [T] is dispatched, and returns that action.
+     */
+    suspend inline fun <reified T : A> next(): T = next { it is T } as T
+
+    fun fork(saga: Saga<S, A, R>) = SagaContext(reduxApi, actions).launch {
+        saga.execute(this@SagaContext)
+    }
+}
diff --git a/sw-ui-kt/src/test/kotlin/org/luxons/sevenwonders/ui/redux/sagas/SagasFrameworkTest.kt b/sw-ui-kt/src/test/kotlin/org/luxons/sevenwonders/ui/redux/sagas/SagasFrameworkTest.kt
new file mode 100644
index 00000000..d8efcc3a
--- /dev/null
+++ b/sw-ui-kt/src/test/kotlin/org/luxons/sevenwonders/ui/redux/sagas/SagasFrameworkTest.kt
@@ -0,0 +1,94 @@
+package org.luxons.sevenwonders.ui.redux.sagas
+
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.GlobalScope
+import kotlinx.coroutines.delay
+import kotlinx.coroutines.promise
+import redux.RAction
+import redux.Store
+import redux.WrapperAction
+import redux.applyMiddleware
+import redux.compose
+import redux.createStore
+import redux.rEnhancer
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+private data class State(val data: String)
+
+private data class UpdateData(val newData: String): RAction
+private class DuplicateData: RAction
+private class SideEffectAction(val data: String): RAction
+
+private fun reduce(state: State, action: RAction): State = when (action) {
+    is UpdateData -> State(action.newData)
+    is DuplicateData -> State(state.data + state.data)
+    else -> state
+}
+
+private fun configureTestStore(initialState: State): TestRedux {
+    val sagaMiddlewareFactory = SagaManager<State, RAction, WrapperAction>()
+    val sagaMiddleware = sagaMiddlewareFactory.createMiddleware()
+    val enhancers = compose(applyMiddleware(sagaMiddleware), rEnhancer())
+    val store = createStore(::reduce, initialState, enhancers)
+    return TestRedux(store, sagaMiddlewareFactory)
+}
+
+private data class TestRedux(
+    val store: Store<State, RAction, WrapperAction>,
+    val sagas: SagaManager<State, RAction, WrapperAction>
+)
+
+@UseExperimental(ExperimentalCoroutinesApi::class)
+class SagaContextTest {
+
+    @Test
+    fun dispatch(): dynamic = GlobalScope.promise {
+
+        val redux = configureTestStore(State("initial"))
+
+        val saga = saga<State, RAction, WrapperAction> {
+            dispatch(UpdateData("Bob"))
+        }
+        redux.sagas.runSaga(saga)
+
+        assertEquals(State("Bob"), redux.store.getState(), "state is not as expected")
+    }
+
+    @Test
+    fun next(): dynamic = GlobalScope.promise {
+        val redux = configureTestStore(State("initial"))
+
+        val saga = saga<State, RAction, WrapperAction> {
+            val action = next<SideEffectAction>()
+            dispatch(UpdateData("effect-${action.data}"))
+        }
+        redux.sagas.startSaga(saga)
+
+        assertEquals(State("initial"), redux.store.getState())
+
+        redux.store.dispatch(SideEffectAction("data"))
+        delay(50)
+        assertEquals(State("effect-data"), redux.store.getState())
+    }
+
+    @Test
+    fun onEach(): dynamic = GlobalScope.promise {
+
+        val redux = configureTestStore(State("initial"))
+
+        val saga = saga<State, RAction, WrapperAction> {
+            onEach<SideEffectAction> {
+                dispatch(UpdateData("effect-${it.data}"))
+            }
+        }
+        val job = redux.sagas.startSaga(saga)
+
+        assertEquals(State("initial"), redux.store.getState())
+
+        redux.store.dispatch(SideEffectAction("data"))
+        delay(50)
+        assertEquals(State("effect-data"), redux.store.getState())
+        job.cancel()
+    }
+}