Let the user choose theme (#1499)

libraries/preferences/api/src/main/kotlin/io/element/android/features/preferences/api/store/PreferencesStore.kt

@@ -28,5 +28,8 @@ interface PreferencesStore {
     suspend fun setCustomElementCallBaseUrl(string: String?)
     fun getCustomElementCallBaseUrlFlow(): Flow<String?>
 
+    suspend fun setTheme(theme: String)
+    fun getThemeFlow(): Flow<String?>
+
     suspend fun reset()
 }

libraries/preferences/impl/src/main/kotlin/io/element/android/libraries/preferences/impl/store/DefaultPreferencesStore.kt

@@ -39,6 +39,7 @@ private val Context.dataStore: DataStore<Preferences> by preferencesDataStore(na
 private val richTextEditorKey = booleanPreferencesKey("richTextEditor")
 private val developerModeKey = booleanPreferencesKey("developerMode")
 private val customElementCallBaseUrlKey = stringPreferencesKey("elementCallBaseUrl")
+private val themeKey = stringPreferencesKey("theme")
 
 @ContributesBinding(AppScope::class)
 class DefaultPreferencesStore @Inject constructor(
@@ -89,6 +90,18 @@ class DefaultPreferencesStore @Inject constructor(
         }
     }
 
+    override suspend fun setTheme(theme: String) {
+        store.edit { prefs ->
+            prefs[themeKey] = theme
+        }
+    }
+
+    override fun getThemeFlow(): Flow<String?> {
+        return store.data.map { prefs ->
+            prefs[themeKey]
+        }
+    }
+
     override suspend fun reset() {
         store.edit { it.clear() }
     }

libraries/preferences/test/src/main/kotlin/io/element/android/libraries/featureflag/test/InMemoryPreferencesStore.kt

@@ -24,10 +24,12 @@ class InMemoryPreferencesStore(
     isRichTextEditorEnabled: Boolean = false,
     isDeveloperModeEnabled: Boolean = false,
     customElementCallBaseUrl: String? = null,
+    theme: String? = null,
 ) : PreferencesStore {
     private var _isRichTextEditorEnabled = MutableStateFlow(isRichTextEditorEnabled)
     private var _isDeveloperModeEnabled = MutableStateFlow(isDeveloperModeEnabled)
     private var _customElementCallBaseUrl = MutableStateFlow(customElementCallBaseUrl)
+    private var _theme = MutableStateFlow(theme)
 
     override suspend fun setRichTextEditorEnabled(enabled: Boolean) {
         _isRichTextEditorEnabled.value = enabled
@@ -53,6 +55,14 @@ class InMemoryPreferencesStore(
         return _customElementCallBaseUrl
     }
 
+    override suspend fun setTheme(theme: String) {
+        _theme.value = theme
+    }
+
+    override fun getThemeFlow(): Flow<String?> {
+        return _theme
+    }
+
     override suspend fun reset() {
         // No op
     }

libraries/theme/src/main/kotlin/io/element/android/libraries/theme/theme/Theme.kt

@@ -0,0 +1,46 @@
+/*
+ * Copyright (c) 2023 New Vector Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.element.android.libraries.theme.theme
+
+import androidx.compose.foundation.isSystemInDarkTheme
+import androidx.compose.runtime.Composable
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.map
+
+enum class Theme {
+    System,
+    Dark,
+    Light;
+}
+
+val themes = listOf(Theme.System, Theme.Dark, Theme.Light)
+
+@Composable
+fun Theme.isDark(): Boolean {
+    return when (this) {
+        Theme.System -> isSystemInDarkTheme()
+        Theme.Dark -> true
+        Theme.Light -> false
+    }
+}
+
+fun Flow<String?>.mapToTheme(): Flow<Theme> = map {
+    when (it) {
+        null -> Theme.System
+        else -> Theme.valueOf(it)
+    }
+}