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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 2020 Google LLC
*
* 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.remoteconfig;
import static com.google.common.base.Preconditions.checkNotNull;
import com.google.api.gax.paging.Page;
import com.google.common.collect.ImmutableList;
import com.google.firebase.internal.NonNull;
import com.google.firebase.remoteconfig.internal.TemplateResponse;
import java.util.Iterator;
import java.util.List;
import java.util.NoSuchElementException;
/**
* Represents a page of {@link Version} instances. Provides methods for iterating
* over the versions in the current page, and calling up subsequent pages of versions. Instances of
* this class are thread-safe and immutable.
*/
public final class ListVersionsPage implements Page {
static final String END_OF_LIST = "";
private final VersionsResultBatch currentBatch;
private final VersionSource source;
private final ListVersionsOptions listVersionsOptions;
private ListVersionsPage(
@NonNull VersionsResultBatch currentBatch, @NonNull VersionSource source,
@NonNull ListVersionsOptions listVersionsOptions) {
this.currentBatch = checkNotNull(currentBatch);
this.source = checkNotNull(source);
this.listVersionsOptions = listVersionsOptions;
}
/**
* Checks if there is another page of versions available to retrieve.
*
* @return true if another page is available, or false otherwise.
*/
@Override
public boolean hasNextPage() {
return !END_OF_LIST.equals(currentBatch.getNextPageToken());
}
/**
* Returns the next page of versions.
*
* @return A new {@link ListVersionsPage} instance, or null if there are no more pages.
*/
@NonNull
@Override
public ListVersionsPage getNextPage() {
if (hasNextPage()) {
ListVersionsOptions options;
if (listVersionsOptions != null) {
options = listVersionsOptions.toBuilder().setPageToken(currentBatch.getNextPageToken())
.build();
} else {
options = ListVersionsOptions.builder().setPageToken(currentBatch.getNextPageToken())
.build();
}
Factory factory = new Factory(source, options);
try {
return factory.create();
} catch (FirebaseRemoteConfigException e) {
throw new RuntimeException(e);
}
}
return null;
}
/**
* Returns the string token that identifies the next page. Never returns null. Returns an empty
* string if there are no more pages available to be retrieved.
*
* @return A non-null string token (possibly empty, representing no more pages)
*/
@NonNull
@Override
public String getNextPageToken() {
return currentBatch.getNextPageToken();
}
/**
* Returns an {@code Iterable} over the versions in this page.
*
* @return a {@code Iterable} instance.
*/
@NonNull
@Override
public Iterable getValues() {
return currentBatch.getVersions();
}
/**
* Returns an {@code Iterable} that facilitates transparently iterating over all the versions in
* the current Firebase project, starting from this page. The {@code Iterator} instances produced
* by the returned {@code Iterable} never buffers more than one page of versions at a time. It is
* safe to abandon the iterators (i.e. break the loops) at any time.
*
* @return a new {@code Iterable} instance.
*/
@NonNull
@Override
public Iterable iterateAll() {
return new VersionIterable(this);
}
private static class VersionIterable implements Iterable {
private final ListVersionsPage startingPage;
VersionIterable(@NonNull ListVersionsPage startingPage) {
this.startingPage = checkNotNull(startingPage, "starting page must not be null");
}
@Override
@NonNull
public Iterator iterator() {
return new VersionIterable.VersionIterator(startingPage);
}
/**
* An {@code Iterator} that cycles through versions, one at a time. It buffers the
* last retrieved batch of versions in memory.
*/
private static class VersionIterator implements Iterator {
private ListVersionsPage currentPage;
private List batch;
private int index = 0;
private VersionIterator(ListVersionsPage startingPage) {
setCurrentPage(startingPage);
}
@Override
public boolean hasNext() {
if (index == batch.size()) {
if (currentPage.hasNextPage()) {
setCurrentPage(currentPage.getNextPage());
} else {
return false;
}
}
return index < batch.size();
}
@Override
public Version next() {
if (!hasNext()) {
throw new NoSuchElementException();
}
return batch.get(index++);
}
@Override
public void remove() {
throw new UnsupportedOperationException("remove operation not supported");
}
private void setCurrentPage(ListVersionsPage page) {
this.currentPage = checkNotNull(page);
this.batch = ImmutableList.copyOf(page.getValues());
this.index = 0;
}
}
}
static final class VersionsResultBatch {
private final List versions;
private final String nextPageToken;
VersionsResultBatch(@NonNull List versions, @NonNull String nextPageToken) {
this.versions = checkNotNull(versions);
this.nextPageToken = checkNotNull(nextPageToken); // Can be empty
}
@NonNull
List getVersions() {
return versions;
}
@NonNull
String getNextPageToken() {
return nextPageToken;
}
}
/**
* Represents a source of Remote Config version data that can be queried to load a batch
* of versions.
*/
interface VersionSource {
@NonNull
VersionsResultBatch fetch(
ListVersionsOptions listVersionsOptions) throws FirebaseRemoteConfigException;
}
static class DefaultVersionSource implements VersionSource {
private final FirebaseRemoteConfigClient remoteConfigClient;
DefaultVersionSource(FirebaseRemoteConfigClient remoteConfigClient) {
this.remoteConfigClient = checkNotNull(remoteConfigClient,
"remote config client must not be null");
}
@Override
public VersionsResultBatch fetch(
ListVersionsOptions listVersionsOptions) throws FirebaseRemoteConfigException {
TemplateResponse.ListVersionsResponse response = remoteConfigClient
.listVersions(listVersionsOptions);
ImmutableList.Builder builder = ImmutableList.builder();
if (response.hasVersions()) {
for (TemplateResponse.VersionResponse versionResponse : response.getVersions()) {
builder.add(new Version(versionResponse));
}
}
String nextPageToken = response.getNextPageToken() != null
? response.getNextPageToken() : END_OF_LIST;
return new VersionsResultBatch(builder.build(), nextPageToken);
}
}
/**
* A simple factory class for {@link ListVersionsPage} instances. Performs argument validation
* before attempting to load any version data (which is expensive, and hence may be performed
* asynchronously on a separate thread).
*/
static class Factory {
private final VersionSource source;
private final ListVersionsOptions listVersionsOptions;
Factory(@NonNull VersionSource source) {
this(source, null);
}
Factory(@NonNull VersionSource source, @NonNull ListVersionsOptions listVersionsOptions) {
this.source = checkNotNull(source, "source must not be null");
this.listVersionsOptions = listVersionsOptions;
}
ListVersionsPage create() throws FirebaseRemoteConfigException {
VersionsResultBatch batch = source.fetch(listVersionsOptions);
return new ListVersionsPage(batch, source, listVersionsOptions);
}
}
}