[webnfc] Implement push method for Android nfc mojo service.

device/nfc/android/java/src/org/chromium/device/nfc/NfcImpl.java

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.device.nfc;
+
+import android.Manifest;
+import android.annotation.TargetApi;
+import android.app.Activity;
+import android.content.Context;
+import android.content.pm.PackageManager;
+import android.nfc.FormatException;
+import android.nfc.NfcAdapter;
+import android.nfc.NfcAdapter.ReaderCallback;
+import android.nfc.NfcManager;
+import android.nfc.Tag;
+import android.nfc.TagLostException;
+import android.os.Build;
+import android.os.Process;
+import android.support.annotation.Nullable;
+
+import org.chromium.base.Log;
+import org.chromium.mojo.bindings.Callbacks;
+import org.chromium.mojo.system.MojoException;
+import org.chromium.mojom.device.nfc.Nfc;
+import org.chromium.mojom.device.nfc.NfcClient;
+import org.chromium.mojom.device.nfc.NfcError;
+import org.chromium.mojom.device.nfc.NfcErrorType;
+import org.chromium.mojom.device.nfc.NfcMessage;
+import org.chromium.mojom.device.nfc.NfcPushOptions;
+import org.chromium.mojom.device.nfc.NfcPushTarget;
+import org.chromium.mojom.device.nfc.NfcWatchOptions;
+
+import java.io.IOException;
+
+/**
+ * Android implementation of the NFC mojo service defined in
+ * device/nfc/nfc.mojom.
+ */
+public class NfcImpl implements Nfc {
+    private static final String TAG = "NfcImpl";
+
+    /**
+     * Used to get instance of NFC adapter, @see android.nfc.NfcManager
+     */
+    private final NfcManager mNfcManager;
+
+    /**
+     * NFC adapter. @see android.nfc.NfcAdapter
+     */
+    private final NfcAdapter mNfcAdapter;
+
+    /**
+     * Activity that is in foreground and is used to enable / disable NFC reader mode operations.
+     * Can be Updated when activity associated with web page is changed. @see #setActivity

[Reilly Grant (use Gerrit), 2016/07/01 20:51:44]

s/Updated/updated/

[shalamov, 2016/07/04 10:08:16]

Done.

+     */
+    private Activity mActivity;
+
+    /**
+     * Flag that indicates whether NFC permission is granted.
+     */
+    private final boolean mHasPermission;
+
+    /**
+     * Implementation of android.nfc.NfcAdapter.ReaderCallback. @see ReaderCallbackHandler
+     */
+    private ReaderCallbackHandler mReaderCallbackHandler;
+
+    /**
+     * Object that contains data that was passed to method
+     * #push(NfcMessage message, NfcPushOptions options, PushResponse callback)
+     * @see PendingPushOperation
+     */
+    private PendingPushOperation mPendingPushOperation;
+
+    /**
+     * Utility that provides I/O operations for a Tag. Created on demand when Tag is found.
+     * @see NfcTagHandler
+     */
+    private NfcTagHandler mTagHandler;
+
+    public NfcImpl(Context context) {
+        int permission =
+                context.checkPermission(Manifest.permission.NFC, Process.myPid(), Process.myUid());
+        mHasPermission = permission == PackageManager.PERMISSION_GRANTED;
+
+        if (mHasPermission && Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
+            mNfcManager = (NfcManager) context.getSystemService(Context.NFC_SERVICE);
+            if (mNfcManager != null) {

[Reilly Grant (use Gerrit), 2016/07/01 20:51:44]

nit: Inverting this conditional will make the code clearer:

if (mNfcManager == null) {
  Log.w(TAG, "NFC is not supported.");
} else {
  mNfcAdapter = mNfcManager.getDefaultAdapter();
}

There's no need to set mNfcAdapter to null because this is the constructor.

[shalamov, 2016/07/04 10:08:16]

I inverted conditional. Blank final class variables must be initialized,
otherwise, there would be a compile error.

[Reilly Grant (use Gerrit), 2016/07/06 20:01:02]

My apologies. I don't review very much Java code.

+                mNfcAdapter = mNfcManager.getDefaultAdapter();
+            } else {
+                Log.w(TAG, "NFC is not supported.");
+                mNfcAdapter = null;
+            }
+        } else {
+            Log.w(TAG, "NFC operations are not permitted.");
+            mNfcAdapter = null;
+            mNfcManager = null;

[Reilly Grant (use Gerrit), 2016/07/01 20:51:45]

Ditto here, these fields will already be null.

[shalamov, 2016/07/04 10:08:16]

same as above, blank final class members must be definitely assigned in the
constructor.

+        }
+    }
+
+    /**
+     * Sets Activity that is used to enable / disable NFC reader mode. When Activity is set,
+     * reader mode is disabled for old Activity and enabled for the new Activity.
+     */
+    protected void setActivity(Activity activity) {
+        disableReaderMode();
+        mActivity = activity;
+        enableReaderMode();
+    }
+
+    /**
+     * Sets NfcClient. NfcClient interface is used to notify mojo NFC service client when NFC
+     * device is in proximity and has NfcMessage that matches NfcWatchOptions criteria.
+     * @see Nfc#watch(NfcWatchOptions options, WatchResponse callback)
+     *
+     * @param client @see NfcClient
+     */
+    @Override
+    public void setClient(NfcClient client) {
+        // TODO(shalamov): Should be implemented when watch() is implemented.

[Reilly Grant (use Gerrit), 2016/07/01 20:51:44]

Please use TODO(crbug.com/XXXXXX) instead of a username so that it is easier to
track ownership and completion of this work.

[shalamov, 2016/07/04 10:08:16]

Done.

+    }
+
+    /**
+     * Pushes NfcMessage to Tag or Peer, whenever NFC device is in proximity. At the moment, only
+     * passive NFC devices are supported (NfcPushTarget.TAG).
+     *
+     * @param message that should be pushed to NFC device.
+     * @param options that contain information about timeout and target device type.
+     * @param callback that is used to notify when push operation is completed.
+     */
+    @Override
+    public void push(NfcMessage message, NfcPushOptions options, PushResponse callback) {
+        if (!checkIfReady(callback)) return;
+
+        if (options.target == NfcPushTarget.PEER) {
+            callback.call(createError(NfcErrorType.NOT_SUPPORTED));
+            return;
+        }
+
+        // If previous pending push operation is not completed, cancel it.
+        if (mPendingPushOperation != null) {
+            mPendingPushOperation.complete(createError(NfcErrorType.OPERATION_CANCELLED));
+        }
+
+        mPendingPushOperation = new PendingPushOperation(message, options, callback);
+        enableReaderMode();
+        processPendingPushOperation();
+    }
+
+    /**
+     * Cancels pending push operation.
+     * At the moment, only passive NFC devices are supported (NfcPushTarget.TAG).
+     *
+     * @param target @see NfcPushTarget
+     * @param callback that is used to notify caller when cancelPush() is completed.
+     */
+    @Override
+    public void cancelPush(int target, CancelPushResponse callback) {
+        if (!checkIfReady(callback)) return;
+
+        if (target == NfcPushTarget.PEER) {
+            callback.call(createError(NfcErrorType.NOT_SUPPORTED));
+            return;
+        }
+
+        if (mPendingPushOperation != null) {

[Reilly Grant (use Gerrit), 2016/07/01 20:51:44]

nit: Invert this condition for better readability.

[shalamov, 2016/07/04 10:08:16]

Done.

+            mPendingPushOperation.complete(createError(NfcErrorType.OPERATION_CANCELLED));
+            mPendingPushOperation = null;
+            callback.call(null);
+            disableReaderMode();
+        } else {
+            callback.call(createError(NfcErrorType.NOT_FOUND));
+        }
+    }
+
+    /**
+     * Watch method allows to set filtering criteria for NfcMessages that are found when NFC device
+     * is within proximity. On success, watch ID is returned to caller through WatchResponse
+     * callback. When NfcMessage that matches NfcWatchOptions is found, it is passed to NfcClient
+     * interface together with corresponding watch ID.
+     * @see NfcClient#onWatch(int[] id, NfcMessage message)
+     *
+     * @param options used to filter NfcMessages, @see NfcWatchOptions.
+     * @param callback that is used to notify caller when watch() is completed and return watch ID.
+     */
+    @Override
+    public void watch(NfcWatchOptions options, WatchResponse callback) {
+        if (!checkIfReady(callback)) return;
+        // TODO(shalamov): Not implemented.

[Reilly Grant (use Gerrit), 2016/07/01 20:51:44]

Same here, please file a bug.

[shalamov, 2016/07/04 10:08:16]

Done.

+        callback.call(0, createError(NfcErrorType.NOT_SUPPORTED));
+    }
+
+    /**
+     * Cancels NFC watch operation.
+     *
+     * @param id of watch operation.
+     * @param callback that is used to notify caller when cancelWatch() is completed.
+     */
+    @Override
+    public void cancelWatch(int id, CancelWatchResponse callback) {
+        if (!checkIfReady(callback)) return;

[Reilly Grant (use Gerrit), 2016/07/01 20:51:44]

Bug.

[shalamov, 2016/07/04 10:08:16]

Done.

+        // TODO(shalamov): Not implemented.
+        callback.call(createError(NfcErrorType.NOT_SUPPORTED));
+    }
+
+    /**
+     * Cancels all NFC watch operations.
+     *
+     * @param callback that is used to notify caller when cancelAllWatches() is completed.
+     */
+    @Override
+    public void cancelAllWatches(CancelAllWatchesResponse callback) {
+        if (!checkIfReady(callback)) return;
+        // TODO(shalamov): Not implemented.

[Reilly Grant (use Gerrit), 2016/07/01 20:51:44]

Bug (note, this can all be the same bug).

[shalamov, 2016/07/04 10:08:16]

Done.

+        callback.call(createError(NfcErrorType.NOT_SUPPORTED));
+    }
+
+    /**
+     * Suspends all pending operations. Should be called when web page visibility is lost.
+     */
+    @Override
+    public void suspendNfcOperations() {
+        disableReaderMode();
+    }
+
+    /**
+     * Resumes all pending watch / push operations. Should be called when web page becomes visible.
+     */
+    @Override
+    public void resumeNfcOperations() {
+        enableReaderMode();
+    }
+
+    @Override
+    public void close() {
+        disableReaderMode();
+    }
+
+    @Override
+    public void onConnectionError(MojoException e) {
+        close();
+    }
+
+    /**
+     * Holds information about pending push operation.
+     */
+    private static class PendingPushOperation {
+        public final NfcMessage nfcMessage;
+        public final NfcPushOptions nfcPushOptions;
+        private final PushResponse mPushResponseCallback;
+
+        public PendingPushOperation(
+                NfcMessage message, NfcPushOptions options, PushResponse callback) {
+            nfcMessage = message;
+            nfcPushOptions = options;
+            mPushResponseCallback = callback;
+        }
+
+        /**
+         * Completes pending push operation.
+         *
+         * @param error should be null when operation is completed successfully, otherwise,
+         * error object with corresponding NfcErrorType should be provided.
+         */
+        public void complete(NfcError error) {
+            if (mPushResponseCallback != null) mPushResponseCallback.call(error);

[Reilly Grant (use Gerrit), 2016/07/01 20:51:44]

Please break this into two lines here and elsewhere.

[shalamov, 2016/07/04 10:08:16]

I think it is default java style that is used in Chromium, if I do as you
mentioned and then, 'git cl format device/nfc', formatter reverts changes.

+        }
+    }
+
+    /**
+     * Helper method that creates NfcError object from NfcErrorType.
+     */
+    private NfcError createError(int errorType) {
+        NfcError error = new NfcError();
+        error.errorType = errorType;
+        return error;
+    }
+
+    /**
+     * Checks if NFC funcionality can be used by the mojo service. If permission to use NFC is
+     * granted and hardware is enabled, returns null.
+     */
+    @Nullable
+    private NfcError checkIfReady() {
+        if (!mHasPermission || mActivity == null) {
+            return createError(NfcErrorType.SECURITY);
+        } else if (mNfcManager == null || mNfcAdapter == null) {
+            return createError(NfcErrorType.NOT_SUPPORTED);
+        } else if (!mNfcAdapter.isEnabled()) {
+            return createError(NfcErrorType.DEVICE_DISABLED);
+        }
+        return null;
+    }
+
+    /**
+     * Uses checkIfReady() method and if NFC cannot be used, calls mojo callback with NfcError.
+     *
+     * @param WatchResponse Callback that is provided to watch() method.
+     * @return boolean true if NFC functionality can be used, false otherwise.
+     */
+    private boolean checkIfReady(WatchResponse callback) {
+        NfcError error = checkIfReady();
+        if (error == null) return true;
+        callback.call(0, error);
+        return false;
+    }
+
+    /**
+     * Uses checkIfReady() method and if NFC cannot be used, calls mojo callback with NfcError.
+     *
+     * @param callback Generic callback that is provided to push(), cancelPush(),
+     * cancelWatch() and cancelAllWatches() methods.
+     * @return boolean true if NFC functionality can be used, false otherwise.
+     */
+    private boolean checkIfReady(Callbacks.Callback1<NfcError> callback) {
+        NfcError error = checkIfReady();
+        if (error == null) return true;
+        callback.call(error);
+        return false;
+    }
+
+    /**
+     * Implementation of android.nfc.NfcAdapter.ReaderCallback. Callback is called when NFC tag is
+     * discovered, Tag object is delegated to mojo service implementation method
+     * NfcImpl.onTagDiscovered().
+     */
+    @TargetApi(Build.VERSION_CODES.KITKAT)
+    private static class ReaderCallbackHandler implements ReaderCallback {
+        private final NfcImpl mNfcImpl;
+
+        public ReaderCallbackHandler(NfcImpl impl) {
+            mNfcImpl = impl;
+        }
+
+        @Override
+        public void onTagDiscovered(Tag tag) {
+            mNfcImpl.onTagDiscovered(tag);
+        }
+    }
+
+    /**
+     * Enables reader mode, allowing NFC device to read / write NFC tags.
+     * @see android.nfc.NfcAdapter#enableReaderMode
+     */
+    private void enableReaderMode() {
+        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.KITKAT) return;
+        if (mReaderCallbackHandler != null || mActivity == null) return;
+
+        // TODO(shalamov): Check if there are active watch operations.
+        if (mPendingPushOperation == null) return;
+
+        mReaderCallbackHandler = new ReaderCallbackHandler(this);
+        mNfcAdapter.enableReaderMode(mActivity, mReaderCallbackHandler,
+                NfcAdapter.FLAG_READER_NFC_A | NfcAdapter.FLAG_READER_NFC_B
+                        | NfcAdapter.FLAG_READER_NFC_F | NfcAdapter.FLAG_READER_NFC_V,
+                null);
+    }
+
+    /**
+     * Disables reader mode.
+     * @see android.nfc.NfcAdapter#disableReaderMode
+     */
+    private void disableReaderMode() {
+        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.KITKAT) return;
+
+        mReaderCallbackHandler = null;
+        if (mActivity != null) {
+            mNfcAdapter.disableReaderMode(mActivity);
+        }
+    }
+
+    /**
+     * Completes pending push operation. On error, invalidates #mTagHandler.
+     */
+    private void pendingPushOperationCompleted(NfcError error) {
+        if (mPendingPushOperation != null) {
+            mPendingPushOperation.complete(error);
+            mPendingPushOperation = null;
+
+            // TODO(shalamov): When nfc.watch is implemented, disable reader mode
+            // only when there are no active watch operations.
+            disableReaderMode();
+        }
+
+        if (error != null) mTagHandler = null;
+    }
+
+    /**
+     * Checks whether there is a #mPendingPushOperation and writes data to NFC tag. In case of
+     * exception calls pendingPushOperationCompleted() with appropriate error object.
+     */
+    private void processPendingPushOperation() {
+        if (mTagHandler == null || mPendingPushOperation == null) return;
+
+        if (mTagHandler.isTagOutOfRange()) {
+            mTagHandler = null;
+            return;
+        }
+
+        try {
+            mTagHandler.connect();
+            mTagHandler.write(NfcTypeConverter.toNdefMessage(mPendingPushOperation.nfcMessage));
+            pendingPushOperationCompleted(null);
+            mTagHandler.close();
+        } catch (InvalidNfcMessageException e) {
+            Log.w(TAG, "Cannot write data to NFC tag. Invalid NfcMessage.");
+            pendingPushOperationCompleted(createError(NfcErrorType.INVALID_MESSAGE));
+        } catch (TagLostException e) {
+            Log.w(TAG, "Cannot write data to NFC tag. Tag is lost.");
+            pendingPushOperationCompleted(createError(NfcErrorType.IO_ERROR));
+        } catch (FormatException | IOException e) {
+            Log.w(TAG, "Cannot write data to NFC tag. IO_ERROR.");
+            pendingPushOperationCompleted(createError(NfcErrorType.IO_ERROR));
+        }
+    }
+
+    /**
+     * Called by ReaderCallbackHandler when NFC tag is in proximity.
+     */
+    public void onTagDiscovered(Tag tag) {
+        mTagHandler = NfcTagHandler.create(tag);
+        processPendingPushOperation();
+    }
+}