feat(set-due-date): display interval

Only for review 'type' cards: other types don't have an interval

Only when 1 card is selected

Fixes 16406

Author: theMr17

AnkiDroid/src/main/java/com/ichi2/anki/scheduling/SetDueDateDialog.kt

@@ -41,6 +41,7 @@ import com.google.android.material.snackbar.Snackbar
 import com.google.android.material.tabs.TabLayout
 import com.google.android.material.tabs.TabLayoutMediator
 import com.google.android.material.textfield.TextInputLayout
+import com.google.android.material.textview.MaterialTextView
 import com.ichi2.anki.AnkiActivity
 import com.ichi2.anki.CollectionManager
 import com.ichi2.anki.CollectionManager.TR
@@ -168,6 +169,25 @@ class SetDueDateDialog : DialogFragment() {
                         viewModel.updateIntervalToMatchDueDate = isChecked
                     }
                 }
+
+                lifecycleScope.launch {
+                    viewModel.currentInterval.collect { currentInterval ->
+                        findViewById<MaterialTextView>(R.id.current_interval_text)!!.also { tv ->
+                            // Current interval is set to null when multiple cards are selected
+                            if (currentInterval != null) {
+                                tv.isVisible = true
+                                tv.text =
+                                    resources.getQuantityString(
+                                        R.plurals.set_due_date_current_interval,
+                                        currentInterval,
+                                        currentInterval,
+                                    )
+                            } else {
+                                tv.isVisible = false
+                            }
+                        }
+                    }
+                }
             }
 
     override fun setupDialog(

AnkiDroid/src/main/java/com/ichi2/anki/scheduling/SetDueDateViewModel.kt

@@ -19,13 +19,16 @@ package com.ichi2.anki.scheduling
 import androidx.annotation.DrawableRes
 import androidx.lifecycle.ViewModel
 import androidx.lifecycle.viewModelScope
+import com.ichi2.anki.CollectionManager.withCol
 import com.ichi2.anki.R
 import com.ichi2.libanki.CardId
+import com.ichi2.libanki.CardType
 import com.ichi2.libanki.sched.SetDueDateDays
 import com.ichi2.libanki.undoableOp
 import kotlinx.coroutines.async
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.update
+import kotlinx.coroutines.launch
 import timber.log.Timber
 
 /**
@@ -34,6 +37,14 @@ import timber.log.Timber
  */
 typealias NumberOfDaysInFuture = Int
 
+/**
+ * Represents the interval between reviews in days.
+ *
+ * - A value of `0` means the next review is due today.
+ * - Indicates the number of days until a card's next review.
+ */
+typealias ReviewIntervalDays = Int
+
 /**
  * [ViewModel] for [SetDueDateDialog]
  */
@@ -112,12 +123,40 @@ class SetDueDateViewModel : ViewModel() {
             field = value
         }
 
+    /**
+     * The current interval of the card.
+     *
+     * The value represents the number of days.
+     * The value is not-null if exactly one card is selected, which is the only case
+     * in which the view should display the interval.
+     */
+    val currentInterval = MutableStateFlow<ReviewIntervalDays?>(null)
+
     fun init(
         cardIds: LongArray,
         fsrsEnabled: Boolean,
     ) {
         this.cardIds = cardIds.toList()
         this.fsrsEnabled = fsrsEnabled
+
+        initCurrentInterval(cardIds)
+    }
+
+    private fun initCurrentInterval(cardIds: LongArray) {
+        // Current interval cannot be shown if multiple cards are selected
+        if (cardCount > 1) {
+            return
+        }
+
+        viewModelScope.launch {
+            withCol {
+                getCard(cardIds.first()).let {
+                    // Only show interval if card is in the review state
+                    // New, learning, or relearning cards have an interval of 0 and should not display it
+                    currentInterval.value = if (it.type == CardType.Rev) it.ivl else null
+                }
+            }
+        }
     }
 
     fun setNextDateRangeStart(value: Int?) {

AnkiDroid/src/main/res/layout/dialog_set_due_date.xml

@@ -58,6 +58,11 @@
             android:layout_height="wrap_content"
             />
 
+        <com.google.android.material.textview.MaterialTextView
+            android:id="@+id/current_interval_text"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:layout_marginStart="16dp" />
 
         <com.google.android.material.checkbox.MaterialCheckBox
             android:id="@+id/change_interval"

AnkiDroid/src/main/res/values/03-dialogs.xml

@@ -240,6 +240,10 @@ also changes the interval of the card"
         <item quantity="one">day</item>
         <item quantity="other">days</item>
     </plurals>
+    <plurals name="set_due_date_current_interval">
+        <item quantity="one">Current interval: %d day</item>
+        <item quantity="other">Current interval: %d days</item>
+    </plurals>
     <string name="range_delimiter" comment="Placed between two input boxes to denote a range">–</string>
     <string name="set_due_date_range_start" comment="'Set Due Date' may change the due date of a card to a random number of days in the future. This labels the 'minimum' value of this range (inclusive)">From</string>
     <string name="set_due_date_range_end" comment="'Set Due Date' may change the due date of a card to a random number of days in the future. This labels the 'maximum' value of this range (inclusive)">To</string>

AnkiDroid/src/test/java/com/ichi2/anki/scheduling/SetDueDateViewModelTest.kt

@@ -159,6 +159,13 @@ class SetDueDateViewModelTest : JvmTest() {
         }
     }
 
+    @Test
+    fun `currentInterval is null when multiple cards are selected`() {
+        runViewModelTest(cardIds = listOf(1, 2)) {
+            assertThat("currentInterval should be null", currentInterval.value, equalTo(null))
+        }
+    }
+
     private fun runViewModelTest(
         cardIds: List<CardId> = listOf(1, 2, 3),
         fsrsEnabled: Boolean = false,