feat(reminders): AddEditReminderDialog view model

GSoC 2025: Review Reminders

- Created a ViewModel for the AddEditReminderDialog. A specific view model is created because this allows the dialog's state to persist across redraws, ex. if the theme changes, if the device rotates, etc. It also centralizes the data of the review reminder being edited in a single source of truth.

Author: ericli3690

AnkiDroid/src/main/java/com/ichi2/anki/reviewreminders/AddEditReminderDialogViewModel.kt

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+/*
+ *  Copyright (c) 2025 Eric Li <[email protected]>
+ *
+ *  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.ichi2.anki.reviewreminders
+
+import androidx.lifecycle.LiveData
+import androidx.lifecycle.MutableLiveData
+import androidx.lifecycle.ViewModel
+import com.ichi2.anki.libanki.DeckId
+import timber.log.Timber
+
+/**
+ * Represents the state of an [AddEditReminderDialog]'s UI. Does not represent the [ReviewReminder] object itself.
+ * For example, instead of storing the card trigger threshold as a [ReviewReminderCardTriggerThreshold], we store an Int, since that's
+ * the input type the user is using to enter the threshold into the app. In other words, this class reflects the concrete
+ * EditText fields in the dialog, not abstract backend data representations.
+ */
+class AddEditReminderDialogViewModel(
+    initialTime: ReviewReminderTime,
+    initialDeckSelected: DeckId,
+    initialCardTriggerThreshold: Int,
+    initialAdvancedSettingsOpen: Boolean,
+) : ViewModel() {
+    private val _time = MutableLiveData(initialTime)
+    val time: LiveData<ReviewReminderTime> = _time
+
+    private val _deckSelected = MutableLiveData(initialDeckSelected)
+
+    /**
+     * [com.ichi2.anki.DeckSpinnerSelection.ALL_DECKS_ID] is used to represent All Decks
+     * (i.e. [ReviewReminderScope.Global]) being selected.
+     */
+    val deckSelected: LiveData<DeckId> = _deckSelected
+
+    private val _cardTriggerThreshold = MutableLiveData(initialCardTriggerThreshold)
+    val cardTriggerThreshold: LiveData<Int> = _cardTriggerThreshold
+
+    private val _advancedSettingsOpen = MutableLiveData(initialAdvancedSettingsOpen)
+    val advancedSettingsOpen: LiveData<Boolean> = _advancedSettingsOpen
+
+    fun setTime(time: ReviewReminderTime) {
+        Timber.d("Updated time to %s", time)
+        _time.value = time
+    }
+
+    fun setDeckSelected(deckId: DeckId) {
+        Timber.d("Updated deck selected to %s", deckId)
+        _deckSelected.value = deckId
+    }
+
+    fun setCardTriggerThreshold(threshold: Int) {
+        Timber.d("Updated card trigger threshold to %s", threshold)
+        _cardTriggerThreshold.value = threshold
+    }
+
+    fun toggleAdvancedSettingsOpen() {
+        Timber.d("Toggled advanced settings open from %s", _advancedSettingsOpen.value)
+        _advancedSettingsOpen.value = !(_advancedSettingsOpen.value ?: false)
+    }
+}