/*
 * Copyright (C) 2010 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.google.android.vending.licensing;

import android.content.SharedPreferences;
import android.util.Log;

/**
 * An wrapper for SharedPreferences that transparently performs data obfuscation.
 */
public class PreferenceObfuscator {

	private static final String TAG = "PreferenceObfuscator";

	private final SharedPreferences mPreferences;
	private final Obfuscator mObfuscator;
	private SharedPreferences.Editor mEditor;

	/**
     * Constructor.
     *
     * @param sp A SharedPreferences instance provided by the system.
     * @param o The Obfuscator to use when reading or writing data.
     */
	public PreferenceObfuscator(SharedPreferences sp, Obfuscator o) {
		mPreferences = sp;
		mObfuscator = o;
		mEditor = null;
	}

	public void putString(String key, String value) {
		if (mEditor == null) {
			mEditor = mPreferences.edit();
			mEditor.apply();
		}
		String obfuscatedValue = mObfuscator.obfuscate(value, key);
		mEditor.putString(key, obfuscatedValue);
	}

	public String getString(String key, String defValue) {
		String result;
		String value = mPreferences.getString(key, null);
		if (value != null) {
			try {
				result = mObfuscator.unobfuscate(value, key);
			} catch (ValidationException e) {
				// Unable to unobfuscate, data corrupt or tampered
				Log.w(TAG, "Validation error while reading preference: " + key);
				result = defValue;
			}
		} else {
			// Preference not found
			result = defValue;
		}
		return result;
	}

	public void commit() {
		if (mEditor != null) {
			mEditor.commit();
			mEditor = null;
		}
	}
}
