Add ChangeManager

AnkiDroid/src/main/java/com/ichi2/anki/BackendImporting.kt

@@ -28,16 +28,15 @@ fun DeckPicker.importApkg(apkgPath: String) {
     val deckPicker = this
     val col = CollectionHelper.getInstance().getCol(deckPicker.baseContext).newBackend
     catchingLifecycleScope(this) {
-        val report = runInBackgroundWithProgress(col, {
+        val report = col.opWithProgress({
             if (it.hasImporting()) {
                 // TODO: show progress in GUI
                 Timber.i("%s", it.importing)
             }
         }) {
-            col.importAnkiPackage(apkgPath)
+            importAnkiPackage(apkgPath)
         }
         showSimpleMessageDialog(summarizeReport(col.tr, report))
-        deckPicker.updateDeckList()
     }
 }
 

AnkiDroid/src/main/java/com/ichi2/anki/CoroutineHelpers.kt

@@ -21,6 +21,7 @@ import androidx.lifecycle.LifecycleOwner
 import androidx.lifecycle.coroutineScope
 import anki.collection.Progress
 import com.ichi2.anki.UIUtils.showSimpleSnackbar
+import com.ichi2.libanki.ChangeManager
 import com.ichi2.libanki.CollectionV16
 import kotlinx.coroutines.*
 import net.ankiweb.rsdroid.Backend
@@ -51,6 +52,18 @@ suspend fun <T> runInBackground(block: suspend CoroutineScope.() -> T): T {
     }
 }
 
+/**
+ * Run an operation and notify change subscribers.
+ * * See the docs in ChangeManager.kt
+ * */
+suspend fun <T> CollectionV16.op(handler: Any? = null, block: suspend CollectionV16.() -> T): T {
+    return runInBackground {
+        block()
+    }.also {
+        ChangeManager.notifySubscribers(it, handler)
+    }
+}
+
 suspend fun <T> Backend.withProgress(onProgress: (Progress) -> Unit, block: suspend CoroutineScope.() -> T): T {
     val backend = this
     return coroutineScope {
@@ -75,6 +88,23 @@ suspend fun <T> runInBackgroundWithProgress(
     }
 }
 
+/**
+ * Run an operation and notify change subscribers, and capture backend progress.
+ *
+ * See the docs in ChangeManager.kt
+ * */
+suspend fun <T> CollectionV16.opWithProgress(
+    onProgress: (Progress) -> Unit,
+    handler: Any? = null,
+    op: suspend CollectionV16.() -> T,
+): T = coroutineScope {
+    backend.withProgress(onProgress) {
+        this@opWithProgress.op(handler) {
+            op()
+        }
+    }
+}
+
 suspend fun monitorProgress(backend: Backend, op: (Progress) -> Unit) {
     while (true) {
         val progress = backend.latestProgress()

AnkiDroid/src/main/java/com/ichi2/anki/DeckPicker.kt

@@ -54,6 +54,7 @@ import androidx.recyclerview.widget.DividerItemDecoration
 import androidx.recyclerview.widget.LinearLayoutManager
 import androidx.recyclerview.widget.RecyclerView
 import androidx.swiperefreshlayout.widget.SwipeRefreshLayout
+import anki.collection.OpChanges
 import com.afollestad.materialdialogs.DialogAction
 import com.afollestad.materialdialogs.GravityEnum
 import com.afollestad.materialdialogs.MaterialDialog
@@ -92,6 +93,7 @@ import com.ichi2.async.CollectionTask.*
 import com.ichi2.async.Connection.CancellableTaskListener
 import com.ichi2.async.Connection.ConflictResolution
 import com.ichi2.compat.CompatHelper.Companion.sdkVersion
+import com.ichi2.libanki.ChangeManager
 import com.ichi2.libanki.Collection.CheckDatabaseResult
 import com.ichi2.libanki.Consts
 import com.ichi2.libanki.Decks
@@ -140,7 +142,15 @@ import kotlin.math.roundToLong
  * * A custom image as a background can be added: [applyDeckPickerBackground]
  */
 @KotlinCleanup("lots to do")
-open class DeckPicker : NavigationDrawerActivity(), StudyOptionsListener, SyncErrorDialogListener, ImportDialogListener, MediaCheckDialogListener, OnRequestPermissionsResultCallback, CustomStudyListener {
+open class DeckPicker :
+    NavigationDrawerActivity(),
+    StudyOptionsListener,
+    SyncErrorDialogListener,
+    ImportDialogListener,
+    MediaCheckDialogListener,
+    OnRequestPermissionsResultCallback,
+    CustomStudyListener,
+    ChangeManager.ChangeSubscriber {
     // Short animation duration from system
     private var mShortAnimDuration = 0
     private var mBackButtonPressedToExit = false
@@ -191,6 +201,10 @@ open class DeckPicker : NavigationDrawerActivity(), StudyOptionsListener, SyncEr
     private lateinit var mCustomStudyDialogFactory: CustomStudyDialogFactory
     private lateinit var mContextMenuFactory: DeckPickerContextMenu.Factory
 
+    init {
+        ChangeManager.subscribe(this)
+    }
+
     // ----------------------------------------------------------------------------
     // LISTENERS
     // ----------------------------------------------------------------------------
@@ -2573,4 +2587,10 @@ open class DeckPicker : NavigationDrawerActivity(), StudyOptionsListener, SyncEr
                 .withEndAction(endAction)
         }
     }
+
+    override fun opExecuted(changes: OpChanges, handler: Any?) {
+        if (changes.studyQueues && handler !== this) {
+            updateDeckList()
+        }
+    }
 }

AnkiDroid/src/main/java/com/ichi2/libanki/ChangeManager.kt

@@ -0,0 +1,81 @@
+/***************************************************************************************
+ * Copyright (c) 2022 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/>.                           *
+ ****************************************************************************************/
+
+/**
+ * With the Rust backend, operations that modify the collection return a description of changes (OpChanges).
+ * The UI can subscribe to these changes, so it can update itself when actions have been performed
+ * (eg, the deck list can check if studyQueues has been updated, and if so, it will redraw the list).
+ *
+ * The optional handler argument can be used so that the initiator of an action can tell when a
+ * OpChanges action was caused by itself. This can be useful when the default change behaviour
+ * should be ignored, in favour of specific handling (eg the UI wishes to directly update the
+ * displayed flag, without redrawing the entire review screen).
+ */
+
+// BackendFactory.defaultLegacySchema must be false to use this code.
+
+package com.ichi2.libanki
+
+import anki.collection.OpChanges
+import anki.collection.OpChangesAfterUndo
+import anki.collection.OpChangesWithCount
+import anki.collection.OpChangesWithId
+import anki.import_export.ImportAnkiPackageResponse
+import java.lang.ref.WeakReference
+
+object ChangeManager {
+    interface ChangeSubscriber {
+        /**
+         * Called after a backend method invoked via col.op() or col.opWithProgress()
+         * has modified the collection. Subscriber should inspect the changes, and update
+         * the UI if necessary.
+         */
+        fun opExecuted(changes: OpChanges, handler: Any?)
+    }
+
+    private val subscribers = mutableListOf<WeakReference<ChangeSubscriber>>()
+
+    fun subscribe(subscriber: ChangeSubscriber) {
+        subscribers.add(WeakReference(subscriber))
+    }
+
+    private fun notifySubscribers(changes: OpChanges, handler: Any?) {
+        val expired = mutableListOf<WeakReference<ChangeSubscriber>>()
+        for (subscriber in subscribers) {
+            val ref = subscriber.get()
+            if (ref == null) {
+                expired.add(subscriber)
+            } else {
+                ref.opExecuted(changes, handler)
+            }
+        }
+        for (item in expired) {
+            subscribers.remove(item)
+        }
+    }
+
+    fun<T> notifySubscribers(changes: T, initiator: Any?) {
+        val opChanges = when (changes) {
+            is OpChanges -> changes
+            is OpChangesWithCount -> changes.changes
+            is OpChangesWithId -> changes.changes
+            is OpChangesAfterUndo -> changes.changes
+            is ImportAnkiPackageResponse -> changes.changes
+            else -> TODO("unhandled change type")
+        }
+        notifySubscribers(opChanges, initiator)
+    }
+}