UserInfoCache.java

/**
 * Copyright (c) 2014-present, Facebook, Inc. All rights reserved.
 *
 * You are hereby granted a non-exclusive, worldwide, royalty-free license to use,
 * copy, modify, and distribute this software in source code or binary form for use
 * in connection with the web services and APIs provided by Facebook.
 *
 * As with any software that integrates with the Facebook platform, your use of
 * this software is subject to the Facebook Developer Principles and Policies
 * [http://developers.facebook.com/policy/]. This copyright notice shall be
 * included in all copies or substantial portions of the software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
 * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
 * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
 * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

package com.example.switchuser;

import android.content.Context;
import android.content.SharedPreferences;
import android.os.Parcel;
import android.util.Base64;

import com.facebook.FacebookSdk;

class UserInfoCache {
    private static final String USER_INFO_CACHE_FORMAT = "userInfo%d";
    private final String userInfoCacheKey;
    private final int slot;

    public UserInfoCache(int slotNumber) {
        userInfoCacheKey = String.format(USER_INFO_CACHE_FORMAT, slotNumber);
        slot = slotNumber;
    }
    public UserInfo get() {
        SharedPreferences prefs = getSharedPrefs();
        String encodedToken = prefs.getString(userInfoCacheKey, null);
        if(encodedToken == null) {
            return null;
        }
        UserInfo info = decodeUserInfo(encodedToken);
        if (info.getAccessToken().isExpired()) {
            clear();
            return null;
        }
        return info;
    }

    public void put(UserInfo userInfo) {
        SharedPreferences.Editor editor = getSharedPrefs().edit();
        String encodedToken = encodeUserInfo(userInfo);
        editor.putString(userInfoCacheKey, encodedToken);
        editor.apply();
    }

    public void clear() {
        SharedPreferences.Editor editor = getSharedPrefs().edit();
        editor.remove(userInfoCacheKey);
        editor.apply();
    }

    private static SharedPreferences getSharedPrefs() {
        return FacebookSdk.getApplicationContext().getSharedPreferences(
                "accessTokens",
                Context.MODE_PRIVATE);
    }

    private static UserInfo decodeUserInfo(String base64EncodedToken) {
        byte[] data = Base64.decode(base64EncodedToken, Base64.DEFAULT);
        Parcel parcel = Parcel.obtain();
        parcel.unmarshall(data, 0, data.length);
        parcel.setDataPosition(0);
        UserInfo userInfo = (UserInfo) parcel.readValue(UserInfo.class.getClassLoader());
        parcel.recycle();
        return userInfo;
    }

    private static String encodeUserInfo(UserInfo userInfo) {
        Parcel parcel = Parcel.obtain();
        parcel.writeValue(userInfo);
        byte[] data = parcel.marshall();
        parcel.recycle();
        return Base64.encodeToString(data, Base64.DEFAULT);
    }
}