DarkTheme.kt: Add utils to check whether dark theme should be applied

* Add for existing `DarkThemeValue.Version2`
* And `DarkModeSetting` from the ProtoBuf message

Author: EdricChan03

ui/theming/common/src/main/kotlin/com/edricchan/studybuddy/ui/theming/common/night/DarkTheme.kt

@@ -3,6 +3,8 @@ package com.edricchan.studybuddy.ui.theming.common.night
 import android.content.Context
 import android.content.res.Configuration
 import android.content.res.Resources
+import com.edricchan.studybuddy.core.settings.appearance.DarkThemeValue
+import com.edricchan.studybuddy.core.settings.appearance.proto.DarkModeSetting
 
 /** Checks if the receiver [Resources] has dark theme enabled. */
 val Resources.isDarkThemeEnabled: Boolean
@@ -14,3 +16,33 @@ val Resources.isDarkThemeEnabled: Boolean
  * @see [Resources.isDarkThemeEnabled]
  */
 val Context.isDarkThemeEnabled: Boolean get() = resources.isDarkThemeEnabled
+
+/**
+ * Whether dark theme should be applied based on the value of [themeValue].
+ * @param themeValue The current [DarkThemeValue.Version2].
+ * @param isSystemInDarkTheme Whether the system is using dark theme.
+ */
+@Suppress("DEPRECATION")
+fun Context.shouldApplyDarkTheme(
+    themeValue: DarkThemeValue.Version2,
+    isSystemInDarkTheme: Boolean = isDarkThemeEnabled
+): Boolean = when (themeValue) {
+    DarkThemeValue.V2Never -> false
+    DarkThemeValue.V2Always -> true
+    DarkThemeValue.V2FollowSystem -> isSystemInDarkTheme
+}
+
+/**
+ * Whether dark theme should be applied based on the value of [themeSetting].
+ * @param themeSetting The current [DarkModeSetting].
+ * @param isSystemInDarkTheme Whether the system is using dark theme.
+ */
+fun shouldApplyDarkTheme(
+    themeSetting: DarkModeSetting,
+    isSystemInDarkTheme: Boolean
+): Boolean = when (themeSetting) {
+    DarkModeSetting.AlwaysOff -> false
+    DarkModeSetting.AlwaysOn -> true
+    DarkModeSetting.FollowSystem -> isSystemInDarkTheme
+    else -> true
+}

ui/theming/compose/src/main/kotlin/com/edricchan/studybuddy/ui/theming/compose/night/DarkTheme.kt

@@ -0,0 +1,26 @@
+package com.edricchan.studybuddy.ui.theming.compose.night
+
+import android.content.Context
+import androidx.compose.foundation.isSystemInDarkTheme
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.platform.LocalContext
+import com.edricchan.studybuddy.core.settings.appearance.DarkThemeValue
+import com.edricchan.studybuddy.core.settings.appearance.proto.DarkModeSetting
+import com.edricchan.studybuddy.ui.theming.common.night.shouldApplyDarkTheme as commonShouldApplyDarkTheme
+
+@Composable
+fun shouldApplyDarkTheme(
+    context: Context = LocalContext.current,
+    themeValue: DarkThemeValue.Version2
+): Boolean = context.commonShouldApplyDarkTheme(
+    themeValue = themeValue,
+    isSystemInDarkTheme = isSystemInDarkTheme()
+)
+
+@Composable
+fun shouldApplyDarkTheme(
+    themeSetting: DarkModeSetting
+): Boolean = commonShouldApplyDarkTheme(
+    themeSetting = themeSetting,
+    isSystemInDarkTheme = isSystemInDarkTheme()
+)