/*
* Copyright (C) 2016 The Android Open Source Project
*
* 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.android.printservice.recommendation.util;
import android.content.Context;
import android.net.nsd.NsdManager;
import android.net.nsd.NsdServiceInfo;
import android.annotation.NonNull;
import android.annotation.Nullable;
import android.util.Log;
import com.android.internal.annotations.GuardedBy;
import com.android.internal.util.Preconditions;
import com.android.printservice.recommendation.PrintServicePlugin;
import java.util.HashSet;
import java.util.Set;
/**
* A discovery listening for mDNS results and only adding the ones that {@link
* PrinterFilter#matchesCriteria match} configured list
*/
public class MDNSFilteredDiscovery implements NsdManager.DiscoveryListener {
private static final String LOG_TAG = "MDNSFilteredDiscovery";
/**
* mDNS service filter interface.
* Implement {@link PrinterFilter#matchesCriteria} to filter out supported services
*/
public interface PrinterFilter {
/**
* Main filter method. Should return true if mDNS service is supported
* by the print service plugin
*
* @param nsdServiceInfo The service info to check
*
* @return True if service is supported by the print service plugin
*/
boolean matchesCriteria(NsdServiceInfo nsdServiceInfo);
}
/** Printer identifiers of the mPrinters found. */
@GuardedBy("mLock")
private final @NonNull HashSet<String> mPrinters;
/** Service types discovered by this plugin */
private final @NonNull HashSet<String> mServiceTypes;
/** Context of the user of this plugin */
private final @NonNull Context mContext;
/** mDNS services filter */
private final @NonNull PrinterFilter mPrinterFilter;
/**
* Call back to report the number of mPrinters found.
*
* We assume that {@link #start} and {@link #stop} are never called in parallel, hence it is
* safe to not synchronize access to this field.
*/
private @Nullable PrintServicePlugin.PrinterDiscoveryCallback mCallback;
/** Queue used to resolve nsd infos */
private final @NonNull NsdResolveQueue mResolveQueue;
/**
* Create new stub that assumes that a print service can be used to print on all mPrinters
* matching some mDNS names.
*
* @param context The context the plugin runs in
* @param serviceTypes The mDNS service types to listen to.
* @param printerFilter The filter for mDNS services
*/
public MDNSFilteredDiscovery(@NonNull Context context,
@NonNull Set<String> serviceTypes,
@NonNull PrinterFilter printerFilter) {
mContext = Preconditions.checkNotNull(context, "context");
mServiceTypes = new HashSet<>(Preconditions
.checkCollectionNotEmpty(Preconditions.checkCollectionElementsNotNull(serviceTypes,
"serviceTypes"), "serviceTypes"));
mPrinterFilter = Preconditions.checkNotNull(printerFilter, "printerFilter");
mResolveQueue = NsdResolveQueue.getInstance();
mPrinters = new HashSet<>();
}
/**
* @return The NDS manager
*/
private NsdManager getNDSManager() {
return (NsdManager) mContext.getSystemService(Context.NSD_SERVICE);
}
/**
* Start the discovery.
*
* @param callback Callbacks used by this plugin.
*/
public void start(@NonNull PrintServicePlugin.PrinterDiscoveryCallback callback) {
mCallback = callback;
mCallback.onChanged(mPrinters.size());
for (String serviceType : mServiceTypes) {
DiscoveryListenerMultiplexer.addListener(getNDSManager(), serviceType, this);
}
}
/**
* Stop the discovery. This can only return once the plugin is completely finished and cleaned up.
*/
public void stop() {
mCallback.onChanged(0);
mCallback = null;
for (int i = 0; i < mServiceTypes.size(); ++i) {
DiscoveryListenerMultiplexer.removeListener(getNDSManager(), this);
}
}
/**
*
* @return The number of discovered printers
*/
public int getCount() {
return mPrinters.size();
}
@Override
public void onStartDiscoveryFailed(String serviceType, int errorCode) {
Log.w(LOG_TAG, "Failed to start network discovery for type " + serviceType + ": "
+ errorCode);
}
@Override
public void onStopDiscoveryFailed(String serviceType, int errorCode) {
Log.w(LOG_TAG, "Failed to stop network discovery for type " + serviceType + ": "
+ errorCode);
}
@Override
public void onDiscoveryStarted(String serviceType) {
// empty
}
@Override
public void onDiscoveryStopped(String serviceType) {
mPrinters.clear();
}
@Override
public void onServiceFound(NsdServiceInfo serviceInfo) {
mResolveQueue.resolve(getNDSManager(), serviceInfo,
new NsdManager.ResolveListener() {
@Override
public void onResolveFailed(NsdServiceInfo serviceInfo, int errorCode) {
Log.w(LOG_TAG, "Service found: could not resolve " + serviceInfo + ": " +
errorCode);
}
@Override
public void onServiceResolved(NsdServiceInfo serviceInfo) {
if (mPrinterFilter.matchesCriteria(serviceInfo)) {
if (mCallback != null) {
boolean added = mPrinters.add(serviceInfo.getHost().getHostAddress());
if (added) {
mCallback.onChanged(mPrinters.size());
}
}
}
}
});
}
@Override
public void onServiceLost(NsdServiceInfo serviceInfo) {
mResolveQueue.resolve(getNDSManager(), serviceInfo,
new NsdManager.ResolveListener() {
@Override
public void onResolveFailed(NsdServiceInfo serviceInfo, int errorCode) {
Log.w(LOG_TAG, "Service lost: Could not resolve " + serviceInfo + ": "
+ errorCode);
}
@Override
public void onServiceResolved(NsdServiceInfo serviceInfo) {
if (mPrinterFilter.matchesCriteria(serviceInfo)) {
if (mCallback != null) {
boolean removed = mPrinters
.remove(serviceInfo.getHost().getHostAddress());
if (removed) {
mCallback.onChanged(mPrinters.size());
}
}
}
}
});
}
}