// Copyright 2018 Google LLC
//
// 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
//
//     https://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.

using System.Linq;
using Google.Play.Common;
using Google.Play.Common.Internal;
using UnityEngine;

namespace Google.Play.Instant
{
    /// <summary>
    /// Provides methods that verify whether a package's signature matches the expected value.
    /// </summary>
    public static class PlaySignatureVerifier
    {
        /// <summary>
        /// Scripting define symbol that causes <see cref="VerifyGooglePlayServices"/> to always return true.
        /// </summary>
        public const string SkipVerifyGooglePlayServicesScriptingDefineSymbol =
            "PLAY_INSTANT_SKIP_VERIFY_GOOGLE_PLAY_SERVICES";

        /// <summary>
        /// Returns true if Google Play Services is installed and its signature matches the expected value.
        /// </summary>
        public static bool VerifyGooglePlayServices(AndroidJavaObject packageManager)
        {
#if PLAY_INSTANT_SKIP_VERIFY_GOOGLE_PLAY_SERVICES
            // Some Google-internal builds of Google Play Services have a different signature.
            Debug.Log("Skipped Google Play Services signature verification.");
            return true;
#else
            return VerifyGooglePlayPackage(packageManager, AndroidConstants.GooglePlayServicesPackageName);
#endif
        }

        private static bool VerifyGooglePlayPackage(AndroidJavaObject packageManager, string packageName)
        {
            try
            {
                // Java: PackageInfo packageInfo =
                //           packageManager.getPackageInfo(packageName, PackageManager.GET_SIGNATURES)
                using (var packageInfo = packageManager.Call<AndroidJavaObject>(
                    AndroidConstants.PackageManagerMethodGetPackageInfo, packageName, AndroidConstants.PackageManagerFieldGetSignatures))
                {
                    // Java: Signature[] signatures = packageInfo.signatures
                    var signatures = packageInfo.Get<AndroidJavaObject[]>(AndroidConstants.PackageInfoFieldSignatures);
                    if (signatures.Length != 1)
                    {
                        Debug.LogErrorFormat(
                            "Unexpected signature count {0} for package {1}", signatures.Length, packageName);
                        return false;
                    }

                    // Java: byte[] bytes = signatures[0].toByteArray()
                    var signature = signatures[0];
                    var bytes = signature.Call<byte[]>(AndroidConstants.SignatureMethodToByteArray);
                    return Enumerable.SequenceEqual(bytes, GooglePlayPackageSignature);
                }
            }
            catch (AndroidJavaException ex)
            {
                // Most likely a NameNotFoundException indicating the package is not installed on this device.
                Debug.LogErrorFormat("Exception verifying package {0}: {1}", packageName, ex);
                return false;
            }
        }

        /// <summary>
        /// Bytes representing the signing certificate of certain Google Play apps.
        /// </summary>
        private static readonly byte[] GooglePlayPackageSignature =
        {
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    }
}