Speed up deck list by rendering it with the backend

This delegates to the backend to render the deck tree, instead of
calculating it in Java. On @Arthur-Milchior's large collection with the
daily limits turned up, the speed difference in an x86_64 sim is
dramatic: 2.4s with the old Java code, and 70ms with the new Rust code.

- Make deckDueList() private; switch callers to use deckDueTree()
The backend only provides a deckDueTree(), and switching the calls to
deckDueList() now will make migration easier in the future.

Squashed from ankidroid#11599

AnkiDroid/src/main/java/com/ichi2/anki/provider/CardContentProvider.kt

@@ -37,6 +37,7 @@ import com.ichi2.libanki.backend.exception.DeckRenameException
 import com.ichi2.libanki.exception.EmptyMediaException
 import com.ichi2.libanki.sched.AbstractSched
 import com.ichi2.libanki.sched.DeckDueTreeNode
+import com.ichi2.libanki.sched.TreeNode
 import com.ichi2.libanki.utils.TimeManager
 import com.ichi2.utils.FileUtil.internalizeUri
 import com.ichi2.utils.JSONArray
@@ -375,28 +376,44 @@ class CardContentProvider : ContentProvider() {
                 rv
             }
             DECKS -> {
-                val allDecks = col.sched.deckDueList()
                 val columns = projection ?: FlashCardsContract.Deck.DEFAULT_PROJECTION
-                val rv = MatrixCursor(columns, allDecks.size)
-                for (deck: DeckDueTreeNode? in allDecks) {
-                    val id = deck!!.did
-                    val name = deck.fullDeckName
-                    addDeckToCursor(id, name, getDeckCountsFromDueTreeNode(deck), rv, col, columns)
+                val allDecks = col.sched.deckDueTree()
+                val rv = MatrixCursor(columns, 1)
+                fun forEach(nodeList: List<TreeNode<DeckDueTreeNode>>, fn: (DeckDueTreeNode) -> Unit) {
+                    for (node in nodeList) {
+                        fn(node.value)
+                        forEach(node.children, fn)
+                    }
+                }
+                forEach(allDecks) {
+                    addDeckToCursor(
+                        it.did,
+                        it.fullDeckName,
+                        getDeckCountsFromDueTreeNode(it),
+                        rv,
+                        col,
+                        columns
+                    )
                 }
                 rv
             }
             DECKS_ID -> {
-
                 /* Direct access deck */
                 val columns = projection ?: FlashCardsContract.Deck.DEFAULT_PROJECTION
                 val rv = MatrixCursor(columns, 1)
-                val allDecks = col.sched.deckDueList()
-                val deckId = uri.pathSegments[1].toLong()
-                for (deck: DeckDueTreeNode? in allDecks) {
-                    if (deck!!.did == deckId) {
-                        addDeckToCursor(deckId, deck.fullDeckName, getDeckCountsFromDueTreeNode(deck), rv, col, columns)
-                        return rv
+                val allDecks = col.sched.deckDueTree()
+                val desiredDeckId = uri.pathSegments[1].toLong()
+                fun find(nodeList: List<TreeNode<DeckDueTreeNode>>, id: Long): DeckDueTreeNode? {
+                    for (node in nodeList) {
+                        if (node.value.did == id) {
+                            return node.value
+                        }
+                        return find(node.children, id)
                     }
+                    return null
+                }
+                find(allDecks, desiredDeckId)?.let {
+                    addDeckToCursor(it.did, it.fullDeckName, getDeckCountsFromDueTreeNode(it), rv, col, columns)
                 }
                 rv
             }
@@ -413,10 +430,9 @@ class CardContentProvider : ContentProvider() {
         }
     }
 
-    private fun getDeckCountsFromDueTreeNode(deck: DeckDueTreeNode?): JSONArray {
-        @KotlinCleanup("use a scope function")
+    private fun getDeckCountsFromDueTreeNode(deck: DeckDueTreeNode): JSONArray {
         val deckCounts = JSONArray()
-        deckCounts.put(deck!!.lrnCount)
+        deckCounts.put(deck.lrnCount)
         deckCounts.put(deck.revCount)
         deckCounts.put(deck.newCount)
         return deckCounts

AnkiDroid/src/main/java/com/ichi2/libanki/sched/AbstractSched.kt

@@ -178,26 +178,23 @@ abstract class AbstractSched {
      */
     abstract fun extendLimits(newc: Int, rev: Int)
 
-    /**
-     * @return [deckname, did, rev, lrn, new]
-     */
-    abstract fun deckDueList(): List<DeckDueTreeNode>
-
     /**
      * @param cancelListener A task that is potentially cancelled
-     * @return the due tree. null if task is cancelled
+     * @return the due tree. null only if task is cancelled
      */
     abstract fun deckDueTree(cancelListener: CancelListener?): List<TreeNode<DeckDueTreeNode>>?
 
     /**
-     * @return the due tree. null if task is cancelled.
+     * @return the due tree. Never null.
      */
-    abstract fun deckDueTree(): List<TreeNode<DeckDueTreeNode>>
+    fun deckDueTree(): List<TreeNode<DeckDueTreeNode>> {
+        return deckDueTree(null)!!
+    }
 
     /**
      * @return The tree of decks, without numbers
      */
-    abstract fun quickDeckDueTree(): List<TreeNode<DeckTreeNode>>
+    abstract fun<T : AbstractDeckTreeNode> quickDeckDueTree(): List<TreeNode<T>>
 
     /** New count for a single deck.
      * @param did The deck to consider (descendants and ancestors are ignored)

AnkiDroid/src/main/java/com/ichi2/libanki/sched/BackendSched.kt

@@ -0,0 +1,55 @@
+/***************************************************************************************
+ * Copyright (c) 2012 Ankitects Pty Ltd <http://apps.ankiweb.net>                       *
+ *                                                                                      *
+ * 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.libanki.sched
+
+import anki.decks.DeckTreeNode
+import com.ichi2.libanki.CollectionV16
+import com.ichi2.libanki.utils.TimeManager
+
+// The desktop code stores these routines in sched/base.py, and all schedulers inherit them.
+// The presence of AbstractSched is going to complicate the introduction of the v3 scheduler,
+// so for now these are stored in a separate file.
+
+fun CollectionV16.deckTree(includeCounts: Boolean): DeckTreeNode {
+    return backend.deckTree(if (includeCounts) TimeManager.time.intTime() else 0)
+}
+
+/**
+ * Mutate the backend reply into a format expected by legacy code. This is less efficient,
+ * and AnkiDroid may wish to use .deckTree() in the future instead.
+ */
+fun CollectionV16.deckTreeLegacy(includeCounts: Boolean): List<TreeNode<DeckDueTreeNode>> {
+    fun toLegacyNode(node: anki.decks.DeckTreeNode, parentName: String): TreeNode<DeckDueTreeNode> {
+        val thisName = if (parentName.isEmpty()) {
+            node.name
+        } else {
+            "$parentName::${node.name}"
+        }
+        val treeNode = TreeNode(
+            DeckDueTreeNode(
+                thisName,
+                node.deckId,
+                node.reviewCount,
+                node.learnCount,
+                node.newCount,
+            )
+        )
+        treeNode.children.addAll(node.childrenList.asSequence().map { toLegacyNode(it, thisName) })
+        return treeNode
+    }
+    return toLegacyNode(deckTree(includeCounts), "").children
+}

AnkiDroid/src/main/java/com/ichi2/libanki/sched/DeckDueTreeNode.kt

@@ -18,6 +18,7 @@ package com.ichi2.libanki.sched
 import com.ichi2.libanki.Collection
 import com.ichi2.libanki.Decks
 import com.ichi2.utils.KotlinCleanup
+import net.ankiweb.rsdroid.RustCleanup
 import java.util.*
 import kotlin.math.max
 import kotlin.math.min
@@ -34,6 +35,7 @@ import kotlin.math.min
  */
 @KotlinCleanup("maybe possible to remove gettres for revCount/lrnCount")
 @KotlinCleanup("rename name -> fullDeckName")
+@RustCleanup("after migration, consider dropping this and using backend tree structure directly")
 class DeckDueTreeNode(name: String, did: Long, override var revCount: Int, override var lrnCount: Int, override var newCount: Int) : AbstractDeckTreeNode(name, did) {
     override fun toString(): String {
         return String.format(

AnkiDroid/src/main/java/com/ichi2/libanki/sched/Sched.java

@@ -213,7 +213,7 @@ private void unburyCardsForDeck(@NonNull List<Long> allDecks) {
      * Returns [deckname, did, rev, lrn, new]
      */
     @Override
-    public @Nullable List<DeckDueTreeNode> deckDueList(@Nullable CancelListener cancelListener) {
+    protected @Nullable List<DeckDueTreeNode> deckDueList(@Nullable CancelListener cancelListener) {
         _checkDay();
         mCol.getDecks().checkIntegrity();
         List<Deck> allDecksSorted = mCol.getDecks().allSorted();

AnkiDroid/src/main/java/com/ichi2/libanki/sched/SchedV2.java

@@ -31,6 +31,7 @@
 import android.text.style.StyleSpan;
 import android.util.Pair;
 
+import com.ichi2.anki.AnkiDroidApp;
 import com.ichi2.anki.R;
 import com.ichi2.async.CancelListener;
 import com.ichi2.async.CollectionTask;
@@ -57,6 +58,7 @@
 import com.ichi2.utils.JSONObject;
 import com.ichi2.utils.SyncStatus;
 
+import net.ankiweb.rsdroid.BackendFactory;
 import net.ankiweb.rsdroid.RustCleanup;
 import net.ankiweb.rsdroid.RustV1Cleanup;
 
@@ -524,14 +526,14 @@ protected int _walkingCount(@NonNull LimitMethod limFn, @NonNull CountMethod cnt
      *
      * Return nulls when deck task is cancelled.
      */
-    public @NonNull List<DeckDueTreeNode> deckDueList() {
+    private @NonNull List<DeckDueTreeNode> deckDueList() {
         return deckDueList(null);
     }
 
     // Overridden
     /**
      * Return sorted list of all decks.*/
-    public @Nullable List<DeckDueTreeNode> deckDueList(@Nullable CancelListener collectionTask) {
+    protected @Nullable List<DeckDueTreeNode> deckDueList(@Nullable CancelListener collectionTask) {
         _checkDay();
         mCol.getDecks().checkIntegrity();
         List<Deck> allDecksSorted = mCol.getDecks().allSorted();
@@ -575,9 +577,11 @@ protected int _walkingCount(@NonNull LimitMethod limFn, @NonNull CountMethod cnt
      requires multiple database access by deck.  Ignoring this number
      lead to the creation of a tree more quickly.*/
     @Override
-    public @NonNull List<TreeNode<DeckTreeNode>> quickDeckDueTree() {
-        // Similar to deckDueTree, ignoring the numbers
-
+    public @NonNull
+    List<? extends TreeNode<? extends AbstractDeckTreeNode>> quickDeckDueTree() {
+        if (!BackendFactory.getDefaultLegacySchema()) {
+            return BackendSchedKt.deckTreeLegacy(mCol.getNewBackend(), false);
+        }
         // Similar to deckDueList
         ArrayList<DeckTreeNode> allDecksSorted = new ArrayList<>();
         for (JSONObject deck : mCol.getDecks().allSorted()) {
@@ -589,18 +593,19 @@ protected int _walkingCount(@NonNull LimitMethod limFn, @NonNull CountMethod cnt
         return _groupChildren(allDecksSorted, false);
     }
 
-
-    public @NonNull List<TreeNode<DeckDueTreeNode>> deckDueTree() {
-        return deckDueTree(null);
-    }
-
     @Nullable
+    @RustCleanup("enable for v2 once backend is updated to 2.1.41+")
+    @RustCleanup("once both v1 and v2 are using backend, cancelListener can be removed")
     public List<TreeNode<DeckDueTreeNode>> deckDueTree(@Nullable CancelListener cancelListener) {
-        List<DeckDueTreeNode> allDecksSorted = deckDueList(cancelListener);
-        if (allDecksSorted == null) {
-            return null;
+        if (!BackendFactory.getDefaultLegacySchema()) {
+            return BackendSchedKt.deckTreeLegacy(mCol.getNewBackend(), true);
+        } else {
+            List<DeckDueTreeNode> allDecksSorted = deckDueList(cancelListener);
+            if (allDecksSorted == null) {
+                return null;
+            }
+            return _groupChildren(allDecksSorted, true);
         }
-        return _groupChildren(allDecksSorted, true);
     }
 
     /**

AnkiDroid/src/main/java/com/ichi2/libanki/sync/Syncer.java

@@ -449,7 +449,7 @@ public JSONObject sanityCheck() {
                 mCol.getModels().save();
             }
             // check for missing parent decks
-            mCol.getSched().deckDueList();
+            mCol.getSched().quickDeckDueTree();
             // return summary of deck
             JSONArray check = new JSONArray();
             JSONArray counts = new JSONArray();

AnkiDroid/src/test/java/com/ichi2/libanki/sched/AbstractSchedTest.java

@@ -204,7 +204,7 @@ public void deckDueTreeInconsistentDecksPasses() {
         addDeckWithExactName(child);
 
         getCol().getDecks().checkIntegrity();
-        assertDoesNotThrow(() -> getCol().getSched().deckDueList());
+        assertDoesNotThrow(() -> getCol().getSched().deckDueTree());
     }
 
 

AnkiDroid/src/test/java/com/ichi2/libanki/sched/SchedV2Test.java

@@ -822,8 +822,12 @@ public void test_review_limits() throws Exception {
             c.flush();
         }
 
-        // position 0 is default deck. Different from upstream
-        TreeNode<DeckDueTreeNode> tree = col.getSched().deckDueTree().get(1);
+        int parentIndex = 0;
+        if (BackendFactory.getDefaultLegacySchema()) {
+            // position 0 is default deck. Different from upstream
+            parentIndex = 1;
+        }
+        TreeNode<DeckDueTreeNode> tree = col.getSched().deckDueTree().get(parentIndex);
         // (('parent', 1514457677462, 5, 0, 0, (('child', 1514457677463, 5, 0, 0, ()),)))
         assertEquals("parent", tree.getValue().getFullDeckName());
         assertEquals(5, tree.getValue().getRevCount());  // paren, tree.review_count)t
@@ -839,7 +843,7 @@ public void test_review_limits() throws Exception {
         col.getSched().answerCard(c, BUTTON_THREE);
         assertEquals(new Counts(0, 0, 9), col.getSched().counts());
 
-        tree = col.getSched().deckDueTree().get(1);
+        tree = col.getSched().deckDueTree().get(parentIndex);
         assertEquals(4, tree.getValue().getRevCount());
         assertEquals(9, tree.getChildren().get(0).getValue().getRevCount());
     }