NativeAppCallContentProvider.java

/**
 * Copyright 2010-present Facebook.
 *
 * 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.facebook;

import android.content.ContentProvider;
import android.content.ContentValues;
import android.database.Cursor;
import android.net.Uri;
import android.os.ParcelFileDescriptor;
import android.util.Log;
import android.util.Pair;

import java.io.File;
import java.io.FileNotFoundException;
import java.util.UUID;

/**
 * <p>Implements a <a href="http://developer.android.com/reference/android/content/ContentProvider.html">
 * ContentProvider</a> that can be used to provide binary attachments (e.g., images) to calls made
 * via @link FacebookDialog}. The {@link NativeAppCallAttachmentStore} class provides methods to attach
 * and clean up the attachments.
 *
 * <p>Note that this ContentProvider is only necessary if an application wishes to attach images, etc., that are
 * stored in memory and do not have another way to be referenced by a content URI. For images obtained from,
 * e.g., the Camera or Gallery, that already have a content URI associated with them, use of this class is not
 * necessary.</p>
 *
 * <p>If an application wishes to attach images that are stored in-memory within the application, this content
 * provider must be listed in the application's AndroidManifest.xml, and it should be named according to the
 * pattern <code>"com.facebook.app.NativeAppCallContentProvider{FACEBOOK_APP_ID}"</code>. See the
 * {@link NativeAppCallContentProvider#getAttachmentUrl(String) getContentProviderName} method.</p>
 */
public class NativeAppCallContentProvider extends ContentProvider {
    private static final String TAG = NativeAppCallContentProvider.class.getName();
    private static final String ATTACHMENT_URL_BASE = "content://com.facebook.app.NativeAppCallContentProvider";

    private final AttachmentDataSource dataSource;

    public NativeAppCallContentProvider() {
        this(new NativeAppCallAttachmentStore());
    }

    NativeAppCallContentProvider(AttachmentDataSource dataSource) {
        this.dataSource = dataSource;
    }

    interface AttachmentDataSource {
        File openAttachment(UUID callId, String attachmentName) throws FileNotFoundException;
    }

    /**
     * Returns the name of the content provider formatted correctly for constructing URLs.
     * @param applicationId the Facebook application ID of the application
     * @return the String to use as the authority portion of a content URI.
     */
    public static String getAttachmentUrl(String applicationId, UUID callId, String attachmentName) {
        return String.format("%s%s/%s/%s", ATTACHMENT_URL_BASE, applicationId, callId.toString(), attachmentName);
    }

    @Override
    public boolean onCreate() {
        return true;
    }

    @Override
    public Cursor query(Uri uri, String[] strings, String s, String[] strings2, String s2) {
        return null;
    }

    @Override
    public String getType(Uri uri) {
        return null;
    }

    @Override
    public Uri insert(Uri uri, ContentValues contentValues) {
        return null;
    }

    @Override
    public int delete(Uri uri, String s, String[] strings) {
        return 0;
    }

    @Override
    public int update(Uri uri, ContentValues contentValues, String s, String[] strings) {
        return 0;
    }

    @Override
    public android.os.ParcelFileDescriptor openFile(android.net.Uri uri, java.lang.String mode)
            throws java.io.FileNotFoundException {

        Pair<UUID, String> callIdAndAttachmentName = parseCallIdAndAttachmentName(uri);
        if (callIdAndAttachmentName == null) {
            throw new FileNotFoundException();
        }

        try {
            File file = dataSource.openAttachment(callIdAndAttachmentName.first, callIdAndAttachmentName.second);

            return ParcelFileDescriptor.open(file, ParcelFileDescriptor.MODE_READ_ONLY);
        } catch (FileNotFoundException exception) {
            Log.e(TAG, "Got unexpected exception:" + exception);
            throw exception;
        }
    }

    Pair<UUID, String> parseCallIdAndAttachmentName(Uri uri) {
        try {
            // We don't do explicit format checking here. Malformed URIs may generate NullPointerExceptions or
            // array bounds exceptions, which we'll catch and return null. All of these will result in a
            // FileNotFoundException being thrown in openFile.
            String callIdAndAttachmentName = uri.getPath().substring(1);
            String [] parts = callIdAndAttachmentName.split("/");

            String callIdString = parts[0];
            String attachmentName = parts[1];
            UUID callId = UUID.fromString(callIdString);

            return new Pair<UUID, String>(callId, attachmentName);
        } catch (Exception exception) {
            return null;
        }
    }
}