Speed up deck list by rendering it with the backend

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/backend/DroidBackend.kt

@@ -15,6 +15,7 @@
  */
 package com.ichi2.libanki.backend
 
+import BackendProto.Backend
 import BackendProto.Backend.ExtractAVTagsOut
 import BackendProto.Backend.RenderCardOut
 import android.content.Context
@@ -26,6 +27,8 @@ import com.ichi2.libanki.Decks
 import com.ichi2.libanki.TemplateManager.TemplateRenderContext
 import com.ichi2.libanki.backend.exception.BackendNotSupportedException
 import com.ichi2.libanki.backend.model.SchedTimingToday
+import com.ichi2.libanki.sched.DeckDueTreeNode
+import com.ichi2.libanki.sched.TreeNode
 import com.ichi2.utils.KotlinCleanup
 import net.ankiweb.rsdroid.RustV1Cleanup
 
@@ -84,4 +87,9 @@ interface DroidBackend {
 
     @Throws(BackendNotSupportedException::class)
     fun renderCardForTemplateManager(templateRenderContext: TemplateRenderContext): RenderCardOut
+
+    fun deckDueTree(includeCounts: Boolean): Backend.DeckTreeNode
+
+    @KotlinCleanup("move to SchedV2 once it's converted to Kotlin")
+    fun legacyDeckDueTree(includeCounts: Boolean): List<TreeNode<DeckDueTreeNode>>
 }

AnkiDroid/src/main/java/com/ichi2/libanki/backend/RustDroidBackend.kt

@@ -16,6 +16,7 @@
 
 package com.ichi2.libanki.backend
 
+import BackendProto.Backend
 import BackendProto.Backend.ExtractAVTagsOut
 import BackendProto.Backend.RenderCardOut
 import android.content.Context
@@ -25,6 +26,8 @@ import com.ichi2.libanki.TemplateManager.TemplateRenderContext
 import com.ichi2.libanki.backend.exception.BackendNotSupportedException
 import com.ichi2.libanki.backend.model.SchedTimingToday
 import com.ichi2.libanki.backend.model.SchedTimingTodayProto
+import com.ichi2.libanki.sched.DeckDueTreeNode
+import com.ichi2.libanki.sched.TreeNode
 import net.ankiweb.rsdroid.BackendFactory
 import net.ankiweb.rsdroid.database.RustV11SQLiteOpenHelperFactory
 
@@ -94,6 +97,14 @@ open class RustDroidBackend(
         throw BackendNotSupportedException()
     }
 
+    override fun deckDueTree(includeCounts: Boolean): Backend.DeckTreeNode {
+        TODO("Not yet implemented")
+    }
+
+    override fun legacyDeckDueTree(includeCounts: Boolean): List<TreeNode<DeckDueTreeNode>> {
+        TODO("Not yet implemented")
+    }
+
     companion object {
         const val UNUSED_VALUE = 0
     }

AnkiDroid/src/main/java/com/ichi2/libanki/backend/RustDroidV16Backend.kt

@@ -23,6 +23,9 @@ import com.ichi2.libanki.DB
 import com.ichi2.libanki.TemplateManager
 import com.ichi2.libanki.backend.BackendUtils.to_json_bytes
 import com.ichi2.libanki.backend.model.to_backend_note
+import com.ichi2.libanki.sched.DeckDueTreeNode
+import com.ichi2.libanki.sched.TreeNode
+import com.ichi2.libanki.utils.TimeManager
 import com.ichi2.utils.JSONObject
 import net.ankiweb.rsdroid.BackendFactory
 import net.ankiweb.rsdroid.BackendV1
@@ -71,4 +74,36 @@ class RustDroidV16Backend(private val backendFactory: BackendFactory) : RustDroi
             backend.renderExistingCard(templateRenderContext._card.id, templateRenderContext._browser)
         }
     }
+
+    override fun deckDueTree(includeCounts: Boolean): Backend.DeckTreeNode {
+        val now = if (includeCounts) {
+            TimeManager.time.intTime()
+        } else {
+            0 // counts are skipped
+        }
+        return backend.deckTree(now, 0)
+    }
+
+    override fun legacyDeckDueTree(includeCounts: Boolean): List<TreeNode<DeckDueTreeNode>> {
+        fun toLegacyNode(node: Backend.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
+        }
+        val top = deckDueTree(includeCounts)
+        return toLegacyNode(top, "").children
+    }
 }

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

@@ -32,7 +32,6 @@ import java.util.*
  * [processChildren] should be called if the children of this node are modified.
  */
 abstract class AbstractDeckTreeNode(
-    val col: Collection,
     /**
      * @return The full deck name, e.g. "A::B::C"
      */
@@ -68,7 +67,7 @@ abstract class AbstractDeckTreeNode(
         )
     }
 
-    abstract fun processChildren(children: List<AbstractDeckTreeNode>, addRev: Boolean)
+    abstract fun processChildren(col: Collection, children: List<AbstractDeckTreeNode>, addRev: Boolean)
 
     override fun toString(): String {
         val buf = StringBuffer()

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

@@ -178,11 +178,6 @@ 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
@@ -197,7 +192,7 @@ abstract class AbstractSched {
     /**
      * @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/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
@@ -34,7 +35,8 @@ import kotlin.math.min
  */
 @KotlinCleanup("maybe possible to remove gettres for revCount/lrnCount")
 @KotlinCleanup("rename name -> fullDeckName")
-class DeckDueTreeNode(col: Collection, name: String, did: Long, override var revCount: Int, override var lrnCount: Int, override var newCount: Int) : AbstractDeckTreeNode(col, name, did) {
+@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(
             Locale.US, "%s, %d, %d, %d, %d",
@@ -50,7 +52,7 @@ class DeckDueTreeNode(col: Collection, name: String, did: Long, override var rev
         newCount = max(0, min(newCount, limit))
     }
 
-    override fun processChildren(children: List<AbstractDeckTreeNode>, addRev: Boolean) {
+    override fun processChildren(col: Collection, children: List<AbstractDeckTreeNode>, addRev: Boolean) {
         // tally up children counts
         for (ch in children) {
             lrnCount += ch.lrnCount

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

@@ -16,11 +16,11 @@
 package com.ichi2.libanki.sched
 
 import com.ichi2.libanki.Collection
-import com.ichi2.utils.KotlinCleanup
+import net.ankiweb.rsdroid.RustCleanup
 
-@KotlinCleanup("confusing nullability for col, verify real nullability after code related to scheduling is fully migrated to kotlin")
-class DeckTreeNode(col: Collection?, name: String, did: Long) : AbstractDeckTreeNode(col!!, name, did) {
-    override fun processChildren(children: List<AbstractDeckTreeNode>, addRev: Boolean) {
+@RustCleanup("processChildren() can be removed after migrating to backend implementation")
+class DeckTreeNode(name: String, did: Long) : AbstractDeckTreeNode(name, did) {
+    override fun processChildren(col: Collection, children: List<AbstractDeckTreeNode>, addRev: Boolean) {
         // intentionally blank
     }
 }

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();
@@ -242,7 +242,7 @@ private void unburyCardsForDeck(@NonNull List<Long> allDecks) {
             // reviews
             int rev = _revForDeck(deck.getLong("id"), rlim);
             // save to list
-            deckNodes.add(new DeckDueTreeNode(mCol, deck.getString("name"), deck.getLong("id"), rev, lrn, _new));
+            deckNodes.add(new DeckDueTreeNode(deck.getString("name"), deck.getLong("id"), rev, lrn, _new));
             // add deck as a parent
             lims.put(Decks.normalizeName(deck.getString("name")), new Integer[]{nlim, rlim});
         }

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;
@@ -522,14 +523,14 @@ 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();
@@ -560,7 +561,7 @@ protected int _walkingCount(@NonNull LimitMethod limFn, @NonNull CountMethod cnt
             int rlim = _deckRevLimitSingle(deck, plim, false);
             int rev = _revForDeck(deck.getLong("id"), rlim, childMap);
             // save to list
-            deckNodes.add(new DeckDueTreeNode(mCol, deck.getString("name"), deck.getLong("id"), rev, lrn, _new));
+            deckNodes.add(new DeckDueTreeNode(deck.getString("name"), deck.getLong("id"), rev, lrn, _new));
             // add deck as a parent
             lims.put(Decks.normalizeName(deck.getString("name")), new Integer[]{nlim, rlim});
         }
@@ -573,13 +574,16 @@ 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 (AnkiDroidApp.TESTING_USE_V16_BACKEND) {
+            return mCol.getBackend().legacyDeckDueTree(false);
+        }
 
         // Similar to deckDueList
         ArrayList<DeckTreeNode> allDecksSorted = new ArrayList<>();
         for (JSONObject deck : mCol.getDecks().allSorted()) {
-            DeckTreeNode g = new DeckTreeNode(mCol, deck.getString("name"), deck.getLong("id"));
+            DeckTreeNode g = new DeckTreeNode(deck.getString("name"), deck.getLong("id"));
             allDecksSorted.add(g);
         }
         // End of the similar part.
@@ -593,12 +597,18 @@ protected int _walkingCount(@NonNull LimitMethod limFn, @NonNull CountMethod cnt
     }
 
     @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 (AnkiDroidApp.TESTING_USE_V16_BACKEND) {
+            return mCol.getBackend().legacyDeckDueTree(true);
+        } else {
+            List<DeckDueTreeNode> allDecksSorted = deckDueList(cancelListener);
+            if (allDecksSorted == null) {
+                return null;
+            }
+            return _groupChildren(allDecksSorted, true);
         }
-        return _groupChildren(allDecksSorted, true);
     }
 
     /**
@@ -665,7 +675,7 @@ public List<TreeNode<DeckDueTreeNode>> deckDueTree(@Nullable CancelListener canc
             TreeNode<T> toAdd = new TreeNode<>(child);
             toAdd.getChildren().addAll(childrenNode);
             List<T> childValues = childrenNode.stream().map(TreeNode::getValue).collect(Collectors.toList());
-            child.processChildren(childValues, "std".equals(getName()));
+            child.processChildren(mCol, childValues, "std".equals(getName()));
 
             sortedChildren.add(toAdd);
         }

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());
     }