Add StateSource (#221)

README.md

@@ -173,19 +173,71 @@ in order to create the `ViewState`.
 
 There are several implementations provided by VICE that cover common use cases.
 
+### StateSource
+
+`StateSource` simply makes `ViceSource` implement Compose's `State` type, and by default provides [currentState]
+with its value.
+
+`StateSource` can be used instead of the other `State` based sources if the stricter rules of an `abstract class` aren't needed.
+
+```kotlin
+internal sealed interface MyFeatureDialogState {
+  data object None : MyFeatureDialogState
+  data class Error(val message: String) : MyFeatureDialogState
+}
+
+internal class MyFeatureDialogSource : StateSource<MyFeatureDialogState> {
+  override var value: MyFeatureDialogState by mutableStateOf(MyFeatureDialogState.None)
+    private set
+
+  fun clearError() {
+    value = MyFeatureDialogState.None
+  }
+
+  fun showError(message: String) {
+    value = MyFeatureDialogState.Error(message)
+  }
+}
+```
+
+`StateSource` can also be used to define a custom interface, and abstract 
+implementors of it (e.g. `MutableStateSource`, etc...) can be used to provide the implementation.
+
+```kotlin
+internal sealed interface MyFeatureDialogState {
+  data object None : MyFeatureDialogState
+  data class Error(val message: String) : MyFeatureDialogState
+}
+
+internal interface MyFeatureDialogSource : StateSource<MyFeatureDialogState>
+
+internal class RealMyFeatureDialogSource : MyFeatureDialogSource, MutableStateSource<MyFeatureDialogState>() {
+  override val initial = MyFeatureDialogState.None
+
+  fun clearError() {
+    update(MyFeatureDialogState.None)
+  }
+
+  fun showError(message: String) {
+    update(
+      MyFeatureDialogState.Error(message)
+    )
+  }
+}
+```
+
 ### MutableStateSource
 
 `MutableStateSource` wraps a `MutableState`, and provides an `update` function for implementations to
 mutate it. Useful for encapsulating behavior around the `MutableState` instead of managing it in the `ViceCompositor`.
 
-
 ```kotlin
 internal sealed interface MyFeatureDialogState {
   data object None : MyFeatureDialogState
   data class Error(val message: String) : MyFeatureDialogState
 }
 
-internal class MyFeatureDialogSource : MutableStateSource<MyFeatureDialogState> {
+internal class MyFeatureDialogSource : MutableStateSource<MyFeatureDialogState>() {
   override val initial = MyFeatureDialogState.None
 
   fun clearError() {
@@ -207,7 +259,7 @@ internal class MyFeatureDialogSource : MutableStateSource<MyFeatureDialogState>
 
 
 ```kotlin
-internal class MyCounterSource : SaveableMutableStateSource<Int> {
+internal class MyCounterSource : SaveableMutableStateSource<Int>() {
   override val initial = 0
 
   fun reset() {
@@ -227,7 +279,7 @@ internal class MyCounterSource : SaveableMutableStateSource<Int> {
 ```kotlin
 internal class MyDerivedStateSource(
   private val fastChangingStateSource: FastChangingStateSource,
-) : DerivedStateSource<MyDerivedState> {
+) : DerivedStateSource<MyDerivedState>() {
   override fun deriveState(): MyDerivedState {
     val fastChangingState by fastChangingStateSource
 
@@ -247,7 +299,7 @@ internal class MyDerivedStateSource(
 ```kotlin
 internal class MyFlowSource(
   private val featureRepo: MyFeatureRepository,
-) : FlowSource<List<MyFeatureData>> {
+) : FlowSource<List<MyFeatureData>>() {
   override val initial = emptyList()
 
   override val flow = featureRepo
@@ -323,7 +375,7 @@ fun TodoListView(
 allows you to modify the `StateFlow` (which is usually implemented as a `MutableStateFlow`).
 
 ```kotlin
-internal class TimerFlowSource : StateFlowSource<Int> {
+internal class TimerFlowSource : StateFlowSource<Int>() {
   override val flow = MutableStateFlow(0)
 
   override suspend fun onAttached(scope: CoroutineScope) {

vice-sources/src/commonMain/kotlin/com/eygraber/vice/sources/DerivedStateSource.kt

@@ -2,13 +2,11 @@ package com.eygraber.vice.sources
 
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.ReadOnlyComposable
-import androidx.compose.runtime.State
 import androidx.compose.runtime.derivedStateOf
 import androidx.compose.runtime.snapshotFlow
-import com.eygraber.vice.ViceSource
 import kotlinx.coroutines.flow.Flow
 
-public abstract class DerivedStateSource<T> : ViceSource<T>, State<T> {
+public abstract class DerivedStateSource<T> : StateSource<T> {
   protected abstract fun deriveState(): T
 
   private val state by lazy {

vice-sources/src/commonMain/kotlin/com/eygraber/vice/sources/MutableStateSource.kt

@@ -2,13 +2,11 @@ package com.eygraber.vice.sources
 
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.ReadOnlyComposable
-import androidx.compose.runtime.State
 import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.snapshotFlow
-import com.eygraber.vice.ViceSource
 import kotlinx.coroutines.flow.Flow
 
-public abstract class MutableStateSource<T> : ViceSource<T>, State<T> {
+public abstract class MutableStateSource<T> : StateSource<T> {
   private val state by lazy {
     mutableStateOf(initial)
   }

vice-sources/src/commonMain/kotlin/com/eygraber/vice/sources/SaveableMutableStateSource.kt

@@ -1,17 +1,15 @@
 package com.eygraber.vice.sources
 
 import androidx.compose.runtime.Composable
-import androidx.compose.runtime.State
 import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.saveable.Saver
 import androidx.compose.runtime.saveable.rememberSaveable
 import androidx.compose.runtime.snapshotFlow
-import com.eygraber.vice.ViceSource
 import kotlinx.coroutines.flow.Flow
 
 public abstract class SaveableMutableStateSource<T : Any>(
   private val saver: Saver<T, out Any>? = null,
-) : ViceSource<T>, State<T> {
+) : StateSource<T> {
   private val state by lazy {
     mutableStateOf(initial)
   }

vice-sources/src/commonMain/kotlin/com/eygraber/vice/sources/StateSource.kt

@@ -0,0 +1,12 @@
+package com.eygraber.vice.sources
+
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.ReadOnlyComposable
+import androidx.compose.runtime.State
+import com.eygraber.vice.ViceSource
+
+public interface StateSource<T> : ViceSource<T>, State<T> {
+  @Composable
+  @ReadOnlyComposable
+  override fun currentState(): T = value
+}