Introduce persistent settings using SharedPreferences

This commit introduces `PrefsManager` to store and retrieve user preferences for real-time diffing and view type.

Key changes:
- Added `BaseApp.kt` to initialize `AppModule` and provide access to `PrefsManager`.
- Created `PrefsManager.kt` to handle SharedPreferences operations for `realTimeDiff` (Boolean) and `selectedViewType` (String).
- Defined preference keys in `Constant.kt`.
- Updated `AppModule.kt` to initialize and provide `PrefsManager`.
- Modified `DiffCheckerViewModel.kt`:
    - Reads initial values for `realTimeDiff` and `selectedViewType` from `PrefsManager`.
    - Saves changes to these settings back to `PrefsManager`.
- Registered `BaseApp` in `AndroidManifest.xml`.

Author: JahidHasanCO

app/src/main/AndroidManifest.xml

@@ -3,6 +3,7 @@
     xmlns:tools="http://schemas.android.com/tools">
 
     <application
+        android:name=".BaseApp"
         android:allowBackup="true"
         android:dataExtractionRules="@xml/data_extraction_rules"
         android:fullBackupContent="@xml/backup_rules"

app/src/main/java/dev/jahidhasanco/diffly/BaseApp.kt

@@ -0,0 +1,15 @@
+package dev.jahidhasanco.diffly
+
+import android.app.Application
+import dev.jahidhasanco.diffly.data.local.PrefsManager
+import dev.jahidhasanco.diffly.di.AppModule
+
+class BaseApp : Application() {
+    lateinit var settingsManager: PrefsManager
+        private set
+
+    override fun onCreate() {
+        super.onCreate()
+        AppModule.init(this)
+    }
+}

app/src/main/java/dev/jahidhasanco/diffly/data/local/PrefsManager.kt

@@ -0,0 +1,24 @@
+package dev.jahidhasanco.diffly.data.local
+import android.content.Context
+import android.content.SharedPreferences
+import androidx.core.content.edit
+import dev.jahidhasanco.diffly.util.Constant.KEY_REALTIME_DIFF
+import dev.jahidhasanco.diffly.util.Constant.KEY_VIEW_TYPE
+import dev.jahidhasanco.diffly.util.Constant.PREFS_NAME
+
+class PrefsManager(context: Context) {
+    private val prefs: SharedPreferences =
+        context.getSharedPreferences(PREFS_NAME, Context.MODE_PRIVATE)
+
+    var realTimeDiff: Boolean
+        get() = prefs.getBoolean(KEY_REALTIME_DIFF, false)
+        set(value) = prefs.edit { putBoolean(KEY_REALTIME_DIFF, value) }
+
+    var selectedViewType: String?
+        get() = prefs.getString(KEY_VIEW_TYPE, null)
+        set(value) = prefs.edit { putString(KEY_VIEW_TYPE, value) }
+
+    fun clearAll() {
+        prefs.edit { clear() }
+    }
+}

app/src/main/java/dev/jahidhasanco/diffly/di/AppModule.kt

@@ -1,13 +1,24 @@
 package dev.jahidhasanco.diffly.di
 
+import android.content.Context
+import dev.jahidhasanco.diffly.data.local.PrefsManager
 import dev.jahidhasanco.diffly.data.repository.DiffRepositoryImpl
 import dev.jahidhasanco.diffly.domain.repository.DiffRepository
 import dev.jahidhasanco.diffly.domain.usecase.CalculateDiffUseCase
-import dev.jahidhasanco.diffly.domain.util.CharLevelDiff
 import dev.jahidhasanco.diffly.domain.util.MyersDiff
 
 object AppModule {
+
+    private lateinit var _prefsManager: PrefsManager
+    val prefsManager: PrefsManager
+        get() = _prefsManager
+
+    fun init(context: Context) {
+        _prefsManager = PrefsManager(context)
+    }
+
     private val myersDiff = MyersDiff()
     private val repository: DiffRepository = DiffRepositoryImpl(myersDiff)
     val calculateDiffUseCase = CalculateDiffUseCase(repository)
+
 }

app/src/main/java/dev/jahidhasanco/diffly/presentation/viewmodel/DiffCheckerViewModel.kt

@@ -3,6 +3,7 @@ package dev.jahidhasanco.diffly.presentation.viewmodel
 import android.util.Log
 import androidx.lifecycle.ViewModel
 import androidx.lifecycle.viewModelScope
+import dev.jahidhasanco.diffly.di.AppModule
 import dev.jahidhasanco.diffly.domain.model.DiffEntry
 import dev.jahidhasanco.diffly.domain.model.DiffViewType
 import dev.jahidhasanco.diffly.domain.usecase.CalculateDiffUseCase
@@ -16,6 +17,8 @@ class DiffCheckerViewModel(
     private val router: NavigationRouter
 ) : ViewModel() {
 
+    private val prefs = AppModule.prefsManager
+
     private val _diffResult = MutableStateFlow<List<DiffEntry>>(emptyList())
     val diffResult: StateFlow<List<DiffEntry>> = _diffResult
 
@@ -25,13 +28,17 @@ class DiffCheckerViewModel(
     private val _newText = MutableStateFlow("")
     val newText: StateFlow<String> = _newText
 
-    private val _realTimeDiff = MutableStateFlow(false)
+    private val _realTimeDiff = MutableStateFlow(prefs.realTimeDiff)
     val realTimeDiff: StateFlow<Boolean> = _realTimeDiff
 
     private val _expanded = MutableStateFlow(false)
     val expanded: StateFlow<Boolean> = _expanded
 
-    private val _selectedViewType = MutableStateFlow(DiffViewType.TWO_SIDE)
+    private val _selectedViewType = MutableStateFlow(
+        DiffViewType.valueOf(
+            prefs.selectedViewType ?: DiffViewType.TWO_SIDE.name
+        )
+    )
     val selectedViewType: StateFlow<DiffViewType> = _selectedViewType
 
     fun updateOldText(value: String) {
@@ -46,6 +53,7 @@ class DiffCheckerViewModel(
 
     fun setRealTimeDiff(value: Boolean) {
         _realTimeDiff.value = value
+        prefs.realTimeDiff = value
         if (value) calculateDiff(_oldText.value, _newText.value)
     }
 
@@ -55,6 +63,7 @@ class DiffCheckerViewModel(
 
     fun selectViewType(type: DiffViewType) {
         _selectedViewType.value = type
+        prefs.selectedViewType = type.name
         _expanded.value = false
     }
 

app/src/main/java/dev/jahidhasanco/diffly/util/Constant.kt

@@ -0,0 +1,7 @@
+package dev.jahidhasanco.diffly.util
+
+object Constant {
+    const val PREFS_NAME = "diffly_prefs"
+    const val KEY_REALTIME_DIFF = "key_realtime_diff"
+    const val KEY_VIEW_TYPE = "key_view_type"
+}