From ced1bdf962c713b889267c7242a8afbafb79259d Mon Sep 17 00:00:00 2001
From: Wojciech M <combaine@gmail.com>
Date: Wed, 3 Jun 2020 13:48:36 +0200
Subject: [PATCH 1/3] add a test for a state machine with split state
 definitions

---
 .../kotlin/com/tinder/StateMachineTest.kt     | 78 ++++++++++++++++++-
 1 file changed, 77 insertions(+), 1 deletion(-)

diff --git a/src/test/kotlin/com/tinder/StateMachineTest.kt b/src/test/kotlin/com/tinder/StateMachineTest.kt
index 5d6e579..67199a3 100644
--- a/src/test/kotlin/com/tinder/StateMachineTest.kt
+++ b/src/test/kotlin/com/tinder/StateMachineTest.kt
@@ -719,6 +719,83 @@ internal class StateMachineTest {
             }
         }
 
+        class WithSplitStateDefinition {
+            private val firstDefinitionOnEnterListener = mock<String.(Int) -> Unit>()
+            private val secondDefinitionOnEnterListener = mock<String.(Int) -> Unit>()
+            private val firstDefinitionOnExitListener = mock<String.(Int) -> Unit>()
+            private val secondDefinitionOnExitListener = mock<String.(Int) -> Unit>()
+
+            private val stateMachine = StateMachine.create<String, Int, Nothing> {
+                initialState(STATE_A)
+
+                state(STATE_A) {
+                    on(EVENT_1) {
+                        transitionTo(STATE_B)
+                    }
+
+                    onExit(firstDefinitionOnExitListener)
+                }
+
+                state(STATE_A) {
+                    on(EVENT_2) {
+                        transitionTo(STATE_B)
+                    }
+
+                    onExit(secondDefinitionOnExitListener)
+                }
+
+                state(STATE_B) {
+                    onEnter(firstDefinitionOnEnterListener)
+                }
+
+                state(STATE_B) {
+                    onEnter(secondDefinitionOnEnterListener)
+                }
+            }
+
+            @Test
+            fun transition_givenFirstDefinitionEvent_shouldReturnValidTransition() {
+                // When
+                val transition = stateMachine.transition(EVENT_1)
+
+                // Then
+                assertThat(transition).isEqualTo(
+                    StateMachine.Transition.Valid<String, Int, String>(STATE_A, EVENT_1, STATE_B, null)
+                )
+            }
+
+            @Test
+            fun transition_givenSecondDefinitionEvent_shouldReturnValidTransition() {
+                // When
+                val transition = stateMachine.transition(EVENT_2)
+
+                // Then
+                assertThat(transition).isEqualTo(
+                    StateMachine.Transition.Valid<String, Int, String>(STATE_A, EVENT_2, STATE_B, null)
+                )
+            }
+
+            @Test
+            fun transition_givenValidEvent_shouldTriggerOnExitListeners() {
+                // When
+                stateMachine.transition(EVENT_1)
+
+                // Then
+                then(firstDefinitionOnExitListener).should().invoke(STATE_A, EVENT_1)
+                then(secondDefinitionOnExitListener).should().invoke(STATE_A, EVENT_1)
+            }
+
+            @Test
+            fun transition_givenValidEvent_shouldTriggerOnEnterListeners() {
+                // When
+                stateMachine.transition(EVENT_1)
+
+                // Then
+                then(firstDefinitionOnEnterListener).should().invoke(STATE_B, EVENT_1)
+                then(secondDefinitionOnEnterListener).should().invoke(STATE_B, EVENT_1)
+            }
+        }
+
         private companion object {
             private const val STATE_A = "a"
             private const val STATE_B = "b"
@@ -733,5 +810,4 @@ internal class StateMachineTest {
             private const val SIDE_EFFECT_1 = "alpha"
         }
     }
-
 }

From 81156c1c0f06fa176e1d68c4781defaf696cd7ce Mon Sep 17 00:00:00 2001
From: Wojciech M <combaine@gmail.com>
Date: Wed, 3 Jun 2020 13:48:43 +0200
Subject: [PATCH 2/3] honor all state definitions instead of only the first one

---
 src/main/kotlin/com/tinder/StateMachine.kt | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/main/kotlin/com/tinder/StateMachine.kt b/src/main/kotlin/com/tinder/StateMachine.kt
index 4b785c7..8277a9b 100644
--- a/src/main/kotlin/com/tinder/StateMachine.kt
+++ b/src/main/kotlin/com/tinder/StateMachine.kt
@@ -51,7 +51,13 @@ class StateMachine<STATE : Any, EVENT : Any, SIDE_EFFECT : Any> private construc
     private fun STATE.getDefinition() = graph.stateDefinitions
         .filter { it.key.matches(this) }
         .map { it.value }
-        .firstOrNull() ?: error("Missing definition for state ${this.javaClass.simpleName}!")
+        .fold(Graph.State<STATE, EVENT, SIDE_EFFECT>()) { acc, state ->
+            acc.apply {
+                onEnterListeners.addAll(state.onEnterListeners)
+                onExitListeners.addAll(state.onExitListeners)
+                transitions.putAll(state.transitions)
+            }
+        }
 
     private fun STATE.notifyOnEnter(cause: EVENT) {
         getDefinition().onEnterListeners.forEach { it(this, cause) }

From faee9b0101331922f4f455a45379ab141817bded Mon Sep 17 00:00:00 2001
From: Wojciech M <combaine@gmail.com>
Date: Wed, 3 Jun 2020 14:14:57 +0200
Subject: [PATCH 3/3] reintroduce an error when no valid state definitions were
 found

---
 src/main/kotlin/com/tinder/StateMachine.kt | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/main/kotlin/com/tinder/StateMachine.kt b/src/main/kotlin/com/tinder/StateMachine.kt
index 8277a9b..6a316af 100644
--- a/src/main/kotlin/com/tinder/StateMachine.kt
+++ b/src/main/kotlin/com/tinder/StateMachine.kt
@@ -51,6 +51,7 @@ class StateMachine<STATE : Any, EVENT : Any, SIDE_EFFECT : Any> private construc
     private fun STATE.getDefinition() = graph.stateDefinitions
         .filter { it.key.matches(this) }
         .map { it.value }
+        .also { if (it.isEmpty()) error("Missing definition for state ${this.javaClass.simpleName}!") }
         .fold(Graph.State<STATE, EVENT, SIDE_EFFECT>()) { acc, state ->
             acc.apply {
                 onEnterListeners.addAll(state.onEnterListeners)