feat: ActivityProvider

app/src/main/kotlin/com/aliucord/manager/ManagerApplication.kt

@@ -29,7 +29,11 @@ class ManagerApplication : Application() {
         super.onCreate()
 
         startKoin {
+            // Android activities & context
             androidContext(this@ManagerApplication)
+            modules(module(createdAtStart = true) {
+                singleOf(::ActivityProvider)
+            })
 
             // HTTP
             modules(module {

app/src/main/kotlin/com/aliucord/manager/di/ActivityProvider.kt

@@ -0,0 +1,34 @@
+package com.aliucord.manager.di
+
+import android.app.Activity
+import android.app.Application
+import android.os.Bundle
+import java.util.Objects
+
+class ActivityProvider(application: Application) {
+    private var activeActivity: Activity? = null
+
+    /**
+     * Gets the current active activity as a specific activity or errors otherwise.
+     */
+    @Suppress("UNCHECKED_CAST")
+    fun <T : Activity> get(): T = Objects.requireNonNull(activeActivity, "No active activity cached!") as T
+
+    init {
+        application.registerActivityLifecycleCallbacks(object : Application.ActivityLifecycleCallbacks {
+            override fun onActivityCreated(activity: Activity, savedInstanceState: Bundle?) {}
+            override fun onActivityPaused(activity: Activity) {}
+            override fun onActivitySaveInstanceState(activity: Activity, outState: Bundle) {}
+            override fun onActivityStarted(activity: Activity) {}
+            override fun onActivityStopped(activity: Activity) {}
+
+            override fun onActivityResumed(activity: Activity) {
+                activeActivity = activity
+            }
+
+            override fun onActivityDestroyed(activity: Activity) {
+                activeActivity = null
+            }
+        })
+    }
+}