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This is the official Firebase Admin Java SDK. Build extraordinary native JVM apps in
minutes with Firebase. The Firebase platform can power your app’s backend, user
authentication, static hosting, and more.
/*
* Copyright 2017 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.firebase.database.core.view.filter;
import com.google.firebase.database.core.Path;
import com.google.firebase.database.core.view.Change;
import com.google.firebase.database.core.view.QueryParams;
import com.google.firebase.database.snapshot.ChildKey;
import com.google.firebase.database.snapshot.EmptyNode;
import com.google.firebase.database.snapshot.Index;
import com.google.firebase.database.snapshot.IndexedNode;
import com.google.firebase.database.snapshot.NamedNode;
import com.google.firebase.database.snapshot.Node;
import com.google.firebase.database.snapshot.PriorityUtilities;
import java.util.Iterator;
/**
* Applies a limit and a range to a node and uses RangedFilter to do the heavy lifting where
* possible
*/
public class LimitedFilter implements NodeFilter {
private final RangedFilter rangedFilter;
private final Index index;
private final int limit;
private final boolean reverse;
public LimitedFilter(QueryParams params) {
this.rangedFilter = new RangedFilter(params);
this.index = params.getIndex();
this.limit = params.getLimit();
this.reverse = !params.isViewFromLeft();
}
@Override
public IndexedNode updateChild(
IndexedNode snap,
ChildKey key,
Node newChild,
Path affectedPath,
CompleteChildSource source,
ChildChangeAccumulator optChangeAccumulator) {
if (!rangedFilter.matches(new NamedNode(key, newChild))) {
newChild = EmptyNode.Empty();
}
if (snap.getNode().getImmediateChild(key).equals(newChild)) {
// No change
return snap;
} else if (snap.getNode().getChildCount() < this.limit) {
return rangedFilter
.getIndexedFilter()
.updateChild(snap, key, newChild, affectedPath, source, optChangeAccumulator);
} else {
return fullLimitUpdateChild(snap, key, newChild, source, optChangeAccumulator);
}
}
private IndexedNode fullLimitUpdateChild(
IndexedNode oldIndexed,
ChildKey childKey,
Node childSnap,
CompleteChildSource source,
ChildChangeAccumulator optChangeAccumulator) {
// TODO: rename all cache stuff etc to general snap terminology
assert oldIndexed.getNode().getChildCount() == this.limit;
NamedNode newChildNamedNode = new NamedNode(childKey, childSnap);
NamedNode windowBoundary =
this.reverse ? oldIndexed.getFirstChild() : oldIndexed.getLastChild();
boolean inRange = rangedFilter.matches(newChildNamedNode);
if (oldIndexed.getNode().hasChild(childKey)) {
Node oldChildSnap = oldIndexed.getNode().getImmediateChild(childKey);
NamedNode nextChild = source.getChildAfterChild(this.index, windowBoundary, this.reverse);
while (nextChild != null
&& (nextChild.getName().equals(childKey)
|| oldIndexed.getNode().hasChild(nextChild.getName()))) {
// There is a weird edge case where a node is updated as part of a merge in the
// write tree,
// but hasn't been applied to the limited filter yet. Ignore this next child
// which will be
// updated later in the limited filter...
nextChild = source.getChildAfterChild(this.index, nextChild, this.reverse);
}
int compareNext =
nextChild == null ? 1 : index.compare(nextChild, newChildNamedNode, this.reverse);
boolean remainsInWindow = inRange && !childSnap.isEmpty() && compareNext >= 0;
if (remainsInWindow) {
if (optChangeAccumulator != null) {
optChangeAccumulator.trackChildChange(
Change.childChangedChange(childKey, childSnap, oldChildSnap));
}
return oldIndexed.updateChild(childKey, childSnap);
} else {
if (optChangeAccumulator != null) {
optChangeAccumulator.trackChildChange(Change.childRemovedChange(childKey, oldChildSnap));
}
IndexedNode newIndexed = oldIndexed.updateChild(childKey, EmptyNode.Empty());
boolean nextChildInRange = nextChild != null && rangedFilter.matches(nextChild);
if (nextChildInRange) {
if (optChangeAccumulator != null) {
optChangeAccumulator.trackChildChange(
Change.childAddedChange(nextChild.getName(), nextChild.getNode()));
}
return newIndexed.updateChild(nextChild.getName(), nextChild.getNode());
} else {
return newIndexed;
}
}
} else if (childSnap.isEmpty()) {
// we're deleting a node, but it was not in the window, so ignore it
return oldIndexed;
} else if (inRange) {
if (this.index.compare(windowBoundary, newChildNamedNode, this.reverse) >= 0) {
if (optChangeAccumulator != null) {
optChangeAccumulator.trackChildChange(
Change.childRemovedChange(windowBoundary.getName(), windowBoundary.getNode()));
optChangeAccumulator.trackChildChange(Change.childAddedChange(childKey, childSnap));
}
return oldIndexed
.updateChild(childKey, childSnap)
.updateChild(windowBoundary.getName(), EmptyNode.Empty());
} else {
return oldIndexed;
}
} else {
return oldIndexed;
}
}
@Override
public IndexedNode updateFullNode(
IndexedNode oldSnap, IndexedNode newSnap, ChildChangeAccumulator optChangeAccumulator) {
IndexedNode filtered;
if (newSnap.getNode().isLeafNode() || newSnap.getNode().isEmpty()) {
// Make sure we have a children node with the correct index, not an empty or leaf node;
filtered = IndexedNode.from(EmptyNode.Empty(), this.index);
} else {
filtered = newSnap;
// Don't support priorities on queries
filtered = filtered.updatePriority(PriorityUtilities.NullPriority());
NamedNode startPost;
NamedNode endPost;
Iterator iterator;
int sign;
if (this.reverse) {
iterator = newSnap.reverseIterator();
startPost = rangedFilter.getEndPost();
endPost = rangedFilter.getStartPost();
sign = -1;
} else {
iterator = newSnap.iterator();
startPost = rangedFilter.getStartPost();
endPost = rangedFilter.getEndPost();
sign = 1;
}
int count = 0;
boolean foundStartPost = false;
while (iterator.hasNext()) {
NamedNode next = iterator.next();
if (!foundStartPost && index.compare(startPost, next) * sign <= 0) {
// start adding
foundStartPost = true;
}
boolean inRange =
foundStartPost && count < this.limit && index.compare(next, endPost) * sign <= 0;
if (inRange) {
count++;
} else {
filtered = filtered.updateChild(next.getName(), EmptyNode.Empty());
}
}
}
return rangedFilter.getIndexedFilter().updateFullNode(oldSnap, filtered, optChangeAccumulator);
}
@Override
public IndexedNode updatePriority(IndexedNode oldSnap, Node newPriority) {
// Don't support priorities on queries
return oldSnap;
}
@Override
public NodeFilter getIndexedFilter() {
return rangedFilter.getIndexedFilter();
}
@Override
public Index getIndex() {
return this.index;
}
@Override
public boolean filtersNodes() {
return true;
}
}