Add UniqueLiveEvent

SingleLiveEvent wasn't unique if used with `observeForever`. UniqueLiveEvent provides a unique notification among both `observe` and `observeForever`.

Unfortunately I cannot simply update SingleLiveEvent because, right now, some SingleLiveEvent are used inside one or more MediatorLiveData which would break those usages

src/main/java/com/infomaniak/lib/core/utils/SingleLiveEvent.kt

@@ -36,16 +36,20 @@ import java.util.concurrent.atomic.AtomicBoolean
  *
  * Note that only one observer is going to be notified of changes.
  */
-class SingleLiveEvent<T> : MutableLiveData<T> {
+@Deprecated(
+    "SingleLiveEvent won't stop triggering if observed using observeForever(). UniqueLiveEvent solves this issue by making notifications truly unique among observe() and observeForever().",
+    replaceWith = ReplaceWith("UniqueLiveEvent"),
+)
+open class SingleLiveEvent<T> : MutableLiveData<T> {
 
-    private val pending = AtomicBoolean(false)
+    protected val pending = AtomicBoolean(false)
 
     constructor() : super()
     constructor(value: T) : super(value)
 
     @MainThread
     override fun observe(owner: LifecycleOwner, observer: Observer<in T>) {
-        if (hasActiveObservers()) Log.w(TAG, "Multiple observers registered but only one will be notified of changes.")
+        if (hasActiveObservers()) Log.w(TAG, MULTIPLE_OBSERVER_WARNING)
 
         // Observe the internal MutableLiveData
         super.observe(owner) { t -> if (pending.compareAndSet(true, false)) observer.onChanged(t) }
@@ -65,7 +69,8 @@ class SingleLiveEvent<T> : MutableLiveData<T> {
         value = null
     }
 
-    private companion object {
+    protected companion object {
         const val TAG = "SingleLiveEvent"
+        const val MULTIPLE_OBSERVER_WARNING = "Multiple observers registered but only one will be notified of changes."
     }
 }

src/main/java/com/infomaniak/lib/core/utils/UniqueLiveEvent.kt

@@ -0,0 +1,39 @@
+/*
+ * Infomaniak Core - Android
+ * Copyright (C) 2024 Infomaniak Network SA
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+package com.infomaniak.lib.core.utils
+
+import android.util.Log
+import androidx.lifecycle.MediatorLiveData
+import androidx.lifecycle.Observer
+
+/**
+ * "Now with 100% more uniqueness to it!".
+ *
+ * [UniqueLiveEvent] single notification is now shared between [observe] and [observeForever].
+ *
+ * This has for a side effect that [UniqueLiveEvent] will only trigger once even if used with [MediatorLiveData] which is not
+ * backward compatible with [SingleLiveEvent].
+ */
+class UniqueLiveEvent<T> : SingleLiveEvent<T>() {
+    override fun observeForever(observer: Observer<in T>) {
+        if (hasActiveObservers()) Log.w(TAG, MULTIPLE_OBSERVER_WARNING)
+
+        // Observe the internal MutableLiveData
+        super.observeForever { t -> if (pending.compareAndSet(true, false)) observer.onChanged(t) }
+    }
+}