allow user to select a theme preference over light/dark/system (#318)

app/src/main/java/com/bitchat/android/BitchatApplication.kt

@@ -2,6 +2,7 @@ package com.bitchat.android
 
 import android.app.Application
 import com.bitchat.android.nostr.RelayDirectory
+import com.bitchat.android.ui.theme.ThemePreferenceManager
 
 /**
  * Main application class for bitchat Android
@@ -23,5 +24,8 @@ class BitchatApplication : Application() {
         try {
             com.bitchat.android.nostr.NostrIdentityBridge.getCurrentNostrIdentity(this)
         } catch (_: Exception) { }
+
+        // Initialize theme preference
+        ThemePreferenceManager.init(this)
     }
 }

app/src/main/java/com/bitchat/android/MainActivity.kt

@@ -10,13 +10,11 @@ import androidx.activity.compose.setContent
 import androidx.activity.enableEdgeToEdge
 import androidx.activity.viewModels
 import androidx.core.view.WindowCompat
+import androidx.compose.foundation.isSystemInDarkTheme
 import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.Surface
-import androidx.compose.runtime.Composable
-import androidx.compose.runtime.DisposableEffect
-import androidx.compose.runtime.collectAsState
-import androidx.compose.runtime.getValue
+import androidx.compose.runtime.*
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.platform.LocalContext
 import androidx.lifecycle.lifecycleScope
@@ -42,6 +40,8 @@ import com.bitchat.android.onboarding.PermissionManager
 import com.bitchat.android.ui.ChatScreen
 import com.bitchat.android.ui.ChatViewModel
 import com.bitchat.android.ui.theme.BitchatTheme
+import com.bitchat.android.ui.theme.ThemePreference
+import com.bitchat.android.ui.theme.ThemePreferenceManager
 import kotlinx.coroutines.delay
 import kotlinx.coroutines.launch
 

app/src/main/java/com/bitchat/android/ui/AboutSheet.kt

@@ -160,6 +160,40 @@ fun AboutSheet(
                         }
                     }
                 }
+
+                // Appearance section (theme toggle)
+                item {
+                    val themePref by com.bitchat.android.ui.theme.ThemePreferenceManager.themeFlow.collectAsState()
+                    Column(
+                        modifier = Modifier.fillMaxWidth(),
+                        verticalArrangement = Arrangement.spacedBy(8.dp)
+                    ) {
+                        Text(
+                            text = "appearance",
+                            fontSize = 12.sp,
+                            fontFamily = FontFamily.Monospace,
+                            fontWeight = FontWeight.Medium,
+                            color = colorScheme.onSurface.copy(alpha = 0.8f)
+                        )
+                        Row(horizontalArrangement = Arrangement.spacedBy(8.dp)) {
+                            FilterChip(
+                                selected = themePref == com.bitchat.android.ui.theme.ThemePreference.System,
+                                onClick = { com.bitchat.android.ui.theme.ThemePreferenceManager.set(context, com.bitchat.android.ui.theme.ThemePreference.System) },
+                                label = { Text("system", fontFamily = FontFamily.Monospace) }
+                            )
+                            FilterChip(
+                                selected = themePref == com.bitchat.android.ui.theme.ThemePreference.Light,
+                                onClick = { com.bitchat.android.ui.theme.ThemePreferenceManager.set(context, com.bitchat.android.ui.theme.ThemePreference.Light) },
+                                label = { Text("light", fontFamily = FontFamily.Monospace) }
+                            )
+                            FilterChip(
+                                selected = themePref == com.bitchat.android.ui.theme.ThemePreference.Dark,
+                                onClick = { com.bitchat.android.ui.theme.ThemePreferenceManager.set(context, com.bitchat.android.ui.theme.ThemePreference.Dark) },
+                                label = { Text("dark", fontFamily = FontFamily.Monospace) }
+                            )
+                        }
+                    }
+                }
                 
                 // Emergency warning
                 item {

app/src/main/java/com/bitchat/android/ui/InputComponents.kt

@@ -35,6 +35,7 @@ import com.bitchat.android.R
 import androidx.compose.ui.focus.onFocusChanged
 import androidx.compose.ui.text.withStyle
 import com.bitchat.android.ui.theme.BASE_FONT_SIZE
+import androidx.compose.foundation.isSystemInDarkTheme
 
 /**
  * Input components for ChatScreen

app/src/main/java/com/bitchat/android/ui/theme/Theme.kt

@@ -5,6 +5,8 @@ import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.darkColorScheme
 import androidx.compose.material3.lightColorScheme
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.collectAsState
+import androidx.compose.runtime.getValue
 import androidx.compose.ui.graphics.Color
 
 // Colors that match the iOS bitchat theme
@@ -36,14 +38,23 @@ private val LightColorScheme = lightColorScheme(
 
 @Composable
 fun BitchatTheme(
-    darkTheme: Boolean = isSystemInDarkTheme(),
+    darkTheme: Boolean? = null,
     content: @Composable () -> Unit
 ) {
-    val colorScheme = when {
-        darkTheme -> DarkColorScheme
-        else -> LightColorScheme
+    // App-level override from ThemePreferenceManager
+    val themePref by ThemePreferenceManager.themeFlow.collectAsState(initial = ThemePreference.System)
+    val shouldUseDark = when (darkTheme) {
+        true -> true
+        false -> false
+        null -> when (themePref) {
+            ThemePreference.Dark -> true
+            ThemePreference.Light -> false
+            ThemePreference.System -> isSystemInDarkTheme()
+        }
     }
 
+    val colorScheme = if (shouldUseDark) DarkColorScheme else LightColorScheme
+
     MaterialTheme(
         colorScheme = colorScheme,
         typography = Typography,

app/src/main/java/com/bitchat/android/ui/theme/ThemePreference.kt

@@ -0,0 +1,36 @@
+package com.bitchat.android.ui.theme
+
+import android.content.Context
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.StateFlow
+
+/**
+ * App theme preference: System default, Light, or Dark.
+ */
+enum class ThemePreference {
+    System, Light, Dark
+}
+
+/**
+ * Simple SharedPreferences-backed manager for theme preference with a StateFlow.
+ * Avoids adding DataStore dependency for now.
+ */
+object ThemePreferenceManager {
+    private const val PREFS_NAME = "bitchat_settings"
+    private const val KEY_THEME = "theme_preference"
+
+    private val _themeFlow = MutableStateFlow(ThemePreference.System)
+    val themeFlow: StateFlow<ThemePreference> = _themeFlow
+
+    fun init(context: Context) {
+        val prefs = context.getSharedPreferences(PREFS_NAME, Context.MODE_PRIVATE)
+        val saved = prefs.getString(KEY_THEME, ThemePreference.System.name)
+        _themeFlow.value = runCatching { ThemePreference.valueOf(saved!!) }.getOrDefault(ThemePreference.System)
+    }
+
+    fun set(context: Context, preference: ThemePreference) {
+        val prefs = context.getSharedPreferences(PREFS_NAME, Context.MODE_PRIVATE)
+        prefs.edit().putString(KEY_THEME, preference.name).apply()
+        _themeFlow.value = preference
+    }
+}