Add hierarchy operations to container transaction

Also add a way to query for child containers of a container.

Combined, these provide enough flexibility to re-arrange
containers to system-ui. For now, it is locked-down a bit so
it only provides children of TaskTiles and can only reparent
ActivityStacks. Eventually, this can be expanded for nested
tasks or display areas.

Bug: 133381284
Test: Added TaskTileTest#testHierarchyTransaction
Change-Id: Id0e89a4e4b9352d9392349c4e1fe7d69b4f9f212
diff --git a/core/java/android/app/ITaskOrganizerController.aidl b/core/java/android/app/ITaskOrganizerController.aidl
index bfc42ef..5d5956e 100644
--- a/core/java/android/app/ITaskOrganizerController.aidl
+++ b/core/java/android/app/ITaskOrganizerController.aidl
@@ -51,6 +51,9 @@
     /** Deletes a persistent root task in WM */
     boolean deleteRootTask(IWindowContainer task);
 
+    /** Gets direct child tasks (ordered from top-to-bottom) */
+    List<ActivityManager.RunningTaskInfo> getChildTasks(in IWindowContainer parent);
+
     /** Get the root task which contains the current ime target */
     IWindowContainer getImeTarget(int display);
 
diff --git a/core/java/android/view/WindowContainerTransaction.java b/core/java/android/view/WindowContainerTransaction.java
index 33f21f2..cf34b0b 100644
--- a/core/java/android/view/WindowContainerTransaction.java
+++ b/core/java/android/view/WindowContainerTransaction.java
@@ -16,6 +16,8 @@
 
 package android.view;
 
+import android.annotation.NonNull;
+import android.annotation.Nullable;
 import android.app.WindowConfiguration;
 import android.content.pm.ActivityInfo;
 import android.content.res.Configuration;
@@ -25,6 +27,8 @@
 import android.os.Parcelable;
 import android.util.ArrayMap;
 
+import java.util.ArrayList;
+import java.util.List;
 import java.util.Map;
 
 /**
@@ -36,10 +40,14 @@
 public class WindowContainerTransaction implements Parcelable {
     private final ArrayMap<IBinder, Change> mChanges = new ArrayMap<>();
 
+    // Flat list because re-order operations are order-dependent
+    private final ArrayList<HierarchyOp> mHierarchyOps = new ArrayList<>();
+
     public WindowContainerTransaction() {}
 
     protected WindowContainerTransaction(Parcel in) {
         in.readMap(mChanges, null /* loader */);
+        in.readList(mHierarchyOps, null /* loader */);
     }
 
     private Change getOrCreateChange(IBinder token) {
@@ -97,10 +105,39 @@
         return this;
     }
 
+    /**
+     * Reparents a container into another one. The effect of a {@code null} parent can vary. For
+     * example, reparenting a stack to {@code null} will reparent it to its display.
+     *
+     * @param onTop When {@code true}, the child goes to the top of parent; otherwise it goes to
+     *              the bottom.
+     */
+    public WindowContainerTransaction reparent(@NonNull IWindowContainer child,
+            @Nullable IWindowContainer parent, boolean onTop) {
+        mHierarchyOps.add(new HierarchyOp(child.asBinder(),
+                parent == null ? null : parent.asBinder(), onTop));
+        return this;
+    }
+
+    /**
+     * Reorders a container within its parent.
+     *
+     * @param onTop When {@code true}, the child goes to the top of parent; otherwise it goes to
+     *              the bottom.
+     */
+    public WindowContainerTransaction reorder(@NonNull IWindowContainer child, boolean onTop) {
+        mHierarchyOps.add(new HierarchyOp(child.asBinder(), onTop));
+        return this;
+    }
+
     public Map<IBinder, Change> getChanges() {
         return mChanges;
     }
 
+    public List<HierarchyOp> getHierarchyOps() {
+        return mHierarchyOps;
+    }
+
     @Override
     public String toString() {
         return "WindowContainerTransaction { changes = " + mChanges + " }";
@@ -109,6 +146,7 @@
     @Override
     public void writeToParcel(Parcel dest, int flags) {
         dest.writeMap(mChanges);
+        dest.writeList(mHierarchyOps);
     }
 
     @Override
@@ -249,4 +287,88 @@
             }
         };
     }
+
+    /**
+     * Holds information about a reparent/reorder operation in the hierarchy. This is separate from
+     * Changes because they must be executed in the same order that they are added.
+     */
+    public static class HierarchyOp implements Parcelable {
+        private final IBinder mContainer;
+
+        // If this is same as mContainer, then only change position, don't reparent.
+        private final IBinder mReparent;
+
+        // Moves/reparents to top of parent when {@code true}, otherwise moves/reparents to bottom.
+        private final boolean mToTop;
+
+        public HierarchyOp(@NonNull IBinder container, @Nullable IBinder reparent, boolean toTop) {
+            mContainer = container;
+            mReparent = reparent;
+            mToTop = toTop;
+        }
+
+        public HierarchyOp(@NonNull IBinder container, boolean toTop) {
+            mContainer = container;
+            mReparent = container;
+            mToTop = toTop;
+        }
+
+        protected HierarchyOp(Parcel in) {
+            mContainer = in.readStrongBinder();
+            mReparent = in.readStrongBinder();
+            mToTop = in.readBoolean();
+        }
+
+        public boolean isReparent() {
+            return mContainer != mReparent;
+        }
+
+        @Nullable
+        public IBinder getNewParent() {
+            return mReparent;
+        }
+
+        @NonNull
+        public IBinder getContainer() {
+            return mContainer;
+        }
+
+        public boolean getToTop() {
+            return mToTop;
+        }
+
+        @Override
+        public String toString() {
+            if (isReparent()) {
+                return "{reparent: " + mContainer + " to " + (mToTop ? "top of " : "bottom of ")
+                        + mReparent + "}";
+            } else {
+                return "{reorder: " + mContainer + " to " + (mToTop ? "top" : "bottom") + "}";
+            }
+        }
+
+        @Override
+        public void writeToParcel(Parcel dest, int flags) {
+            dest.writeStrongBinder(mContainer);
+            dest.writeStrongBinder(mReparent);
+            dest.writeBoolean(mToTop);
+        }
+
+        @Override
+        public int describeContents() {
+            return 0;
+        }
+
+        public static final Creator<HierarchyOp> CREATOR = new Creator<HierarchyOp>() {
+            @Override
+            public HierarchyOp createFromParcel(Parcel in) {
+                return new HierarchyOp(in);
+            }
+
+            @Override
+            public HierarchyOp[] newArray(int size) {
+                return new HierarchyOp[size];
+            }
+        };
+    }
 }