add PreferencesFlow

core/src/main/kotlin/com/kroegerama/kaiteki/architecture/PreferencesFlow.kt

@@ -0,0 +1,37 @@
+package com.kroegerama.kaiteki.architecture
+
+import android.content.SharedPreferences
+import android.util.Log
+import kotlinx.coroutines.channels.awaitClose
+import kotlinx.coroutines.channels.trySendBlocking
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.callbackFlow
+
+private fun <T> SharedPreferences.flow(
+    key: String,
+    getter: () -> T
+): Flow<T?> = callbackFlow {
+    fun getOrNull() = if (contains(key)) getter() else null
+
+    val listener = SharedPreferences.OnSharedPreferenceChangeListener { _, callbackKey ->
+        Log.d("PrefsFlow", "KEY $callbackKey")
+        if (callbackKey == key) {
+            trySendBlocking(getOrNull())
+        }
+    }
+    trySend(getOrNull())
+    registerOnSharedPreferenceChangeListener(listener)
+    awaitClose {
+        unregisterOnSharedPreferenceChangeListener(listener)
+    }
+}
+
+fun SharedPreferences.intFlow(key: String) = flow(key) { getInt(key, 0) }
+
+fun SharedPreferences.longFlow(key: String) = flow(key) { getLong(key, 0L) }
+
+fun SharedPreferences.floatFlow(key: String) = flow(key) { getFloat(key, 0f) }
+
+fun SharedPreferences.booleanFlow(key: String) = flow(key) { getBoolean(key, false) }
+
+fun SharedPreferences.stringFlow(key: String) = flow(key) { getString(key, null) }