From d3977a461c228632d0c62717304d237e52a07227 Mon Sep 17 00:00:00 2001
From: takahirom <takam.dev@gmail.com>
Date: Wed, 4 May 2022 18:13:48 +0900
Subject: [PATCH] Add compose state molecule function

---
 .../kotlin/app/cash/molecule/molecule.kt      | 30 +++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/molecule/molecule-runtime/src/commonMain/kotlin/app/cash/molecule/molecule.kt b/molecule/molecule-runtime/src/commonMain/kotlin/app/cash/molecule/molecule.kt
index 57696005..38093af0 100644
--- a/molecule/molecule-runtime/src/commonMain/kotlin/app/cash/molecule/molecule.kt
+++ b/molecule/molecule-runtime/src/commonMain/kotlin/app/cash/molecule/molecule.kt
@@ -19,7 +19,10 @@ import androidx.compose.runtime.AbstractApplier
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.Composition
 import androidx.compose.runtime.MonotonicFrameClock
+import androidx.compose.runtime.MutableState
 import androidx.compose.runtime.Recomposer
+import androidx.compose.runtime.State
+import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.snapshots.Snapshot
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.CoroutineStart.UNDISPATCHED
@@ -77,6 +80,33 @@ fun <T> CoroutineScope.launchMolecule(
   return flow!!
 }
 
+/**
+ * Launch a coroutine into this [CoroutineScope] which will continually recompose `body`
+ * to produce a [State] stream of [T] values.
+ *
+ * The [CoroutineScope] in which this [State] is created must contain a
+ * [MonotonicFrameClock] key which controls when recomposition occurs.
+ */
+fun <T> CoroutineScope.moleculeComposeState(
+  body: @Composable () -> T,
+): State<T> {
+  var mutableState: MutableState<T>? = null
+
+  launchMolecule(
+    emitter = { value ->
+      val outputFlow = mutableState
+      if (outputFlow != null) {
+        outputFlow.value = value
+      } else {
+        mutableState = mutableStateOf(value)
+      }
+    },
+    body = body,
+  )
+
+  return mutableState!!
+}
+
 /**
  * Launch a coroutine into this [CoroutineScope] which will continually recompose `body`
  * to invoke [emitter] with each returned [T] value.