/* Copyright (c) Cloud Software Group, Inc. 
 * 
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 * with or without modification, are permitted provided 
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 *     following disclaimer. 
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 *     following disclaimer in the documentation and/or other 
 *     materials provided with the distribution. 
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 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF 
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using System;
using System.ComponentModel;
using System.IO;
using System.Linq;
using System.Net;
using System.Net.Cache;
using System.Net.NetworkInformation;
using System.Security.Cryptography.X509Certificates;
using System.Threading;
using XenAdmin.Core;
using XenCenterLib;

namespace XenAdmin.Actions.Updates
{
    public class DownloadAndUpdateClientAction : AsyncAction, IByteProgressAction
    {
        private static readonly log4net.ILog log = log4net.LogManager.GetLogger(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType);

        private const int SLEEP_TIME_TO_CHECK_DOWNLOAD_STATUS_MS = 900;
        private const int SLEEP_TIME_BEFORE_RETRY_MS = 5000;

        //If you consider increasing this for any reason (I think 5 is already more than enough), have a look at the usage of SLEEP_TIME_BEFORE_RETRY_MS in DownloadFile() as well.
        private const int MAX_NUMBER_OF_TRIES = 5;

        private readonly Uri _address;
        private readonly string _outputPathAndFileName;
        private readonly string _updateName;
        private readonly bool _downloadUpdate;
        private DownloadState _updateDownloadState;
        private Exception _updateDownloadError;
        private readonly string _checksum;
        private readonly string _authToken;
        private WebClient _client;
        private FileStream _msiStream;

        public string ByteProgressDescription { get; set; }

        public DownloadAndUpdateClientAction(string updateName, Uri uri, string outputFileName, string checksum)
            : base(null, string.Format(Messages.DOWNLOAD_CLIENT_INSTALLER_ACTION_TITLE, updateName),
                string.Empty, true)
        {
            _updateName = updateName;
            _address = uri;
            _downloadUpdate = _address != null;
            _outputPathAndFileName = outputFileName;
            _checksum = checksum;
            _authToken = XenAdminConfigManager.Provider.GetClientUpdatesQueryParam();
        }

        private void DownloadFile()
        {
            int errorCount = 0;
            bool needToRetry = false;

            _client = new WebClient();
            _client.DownloadProgressChanged += client_DownloadProgressChanged;
            _client.DownloadFileCompleted += client_DownloadFileCompleted;
            _client.CachePolicy = new RequestCachePolicy(RequestCacheLevel.NoCacheNoStore);

            // register event handler to detect changes in network connectivity
            NetworkChange.NetworkAvailabilityChanged += NetworkAvailabilityChanged;

            try
            {
                do
                {
                    if (Cancelling)
                        throw new CancelledException();

                    if (needToRetry)
                        Thread.Sleep(SLEEP_TIME_BEFORE_RETRY_MS);

                    needToRetry = false;

                    _client.Proxy = XenAdminConfigManager.Provider.GetProxyFromSettings(null, false);

                    //start the download
                    _updateDownloadState = DownloadState.InProgress;

                    var uriBuilder = new UriBuilder(_address);

                    if (!string.IsNullOrEmpty(_authToken))
                    {
                        var uri = uriBuilder.Uri;
                        if (!uri.IsFile)
                        {
                            uriBuilder.Query = Helpers.AddAuthTokenToQueryString(_authToken, uriBuilder.Query);
                        }
                    }
                    _client.DownloadFileAsync(uriBuilder.Uri, _outputPathAndFileName);

                    bool updateDownloadCancelling = false;

                    //wait for the file to be downloaded
                    while (_updateDownloadState == DownloadState.InProgress)
                    {
                        if (!updateDownloadCancelling && (Cancelling || Cancelled))
                        {
                            Description = Messages.DOWNLOAD_AND_EXTRACT_ACTION_DOWNLOAD_CANCELLED_DESC;
                            _client.CancelAsync();
                            updateDownloadCancelling = true;
                        }

                        Thread.Sleep(SLEEP_TIME_TO_CHECK_DOWNLOAD_STATUS_MS);
                    }

                    if (_updateDownloadState == DownloadState.Cancelled)
                        throw new CancelledException();

                    if (_updateDownloadState == DownloadState.Error)
                    {
                        needToRetry = true;

                        // this many errors so far - including this one
                        errorCount++;

                        // logging only, it will retry again.
                        log.ErrorFormat(
                            "Error while downloading from '{0}'. Number of errors so far (including this): {1}. Trying maximum {2} times.",
                            _address, errorCount, MAX_NUMBER_OF_TRIES);

                        if (_updateDownloadError == null)
                            log.Error("An unknown error occurred.");
                        else
                            log.Error(_updateDownloadError);
                    }
                } while (errorCount < MAX_NUMBER_OF_TRIES && needToRetry);
            }
            finally
            {
                _client.DownloadProgressChanged -= client_DownloadProgressChanged;
                _client.DownloadFileCompleted -= client_DownloadFileCompleted;

                NetworkChange.NetworkAvailabilityChanged -= NetworkAvailabilityChanged;

                _client.Dispose();
            }

            //if this is still the case after having retried MAX_NUMBER_OF_TRIES number of times.
            if (_updateDownloadState == DownloadState.Error)
            {
                log.ErrorFormat("Giving up - Maximum number of retries ({0}) has been reached.", MAX_NUMBER_OF_TRIES);
                throw _updateDownloadError ?? new Exception(Messages.ERROR_UNKNOWN);
            }
        }

        private void NetworkAvailabilityChanged(object sender, NetworkAvailabilityEventArgs e)
        {
            if (!e.IsAvailable && _client != null && _updateDownloadState == DownloadState.InProgress)
            {
                _updateDownloadError = new WebException(Messages.NETWORK_CONNECTIVITY_ERROR);
                _updateDownloadState = DownloadState.Error;
                _client.CancelAsync();
            }
        }

        protected override void Run()
        {
            if (!_downloadUpdate)
                return;

            log.InfoFormat("Downloading '{0}' installer (from '{1}') to '{2}'", _updateName, _address, _outputPathAndFileName);
            Description = string.Format(Messages.DOWNLOAD_CLIENT_INSTALLER_ACTION_DESCRIPTION, _updateName);
            LogDescriptionChanges = false;
            DownloadFile();
            LogDescriptionChanges = true;

            if (IsCompleted || Cancelled)
                return;

            if (Cancelling)
                throw new CancelledException();

            if (!File.Exists(_outputPathAndFileName))
                throw new Exception(Messages.DOWNLOAD_CLIENT_INSTALLER_MSI_NOT_FOUND);

            ValidateMsi();

            Description = Messages.COMPLETED;
        }

        protected override void CleanOnError()
        {
            ReleaseInstaller(true);
        }

        public void ReleaseInstaller(bool deleteMsi = false)
        {
            _msiStream?.Dispose();

            if (!deleteMsi)
                return;

            try
            {
                if (File.Exists(_outputPathAndFileName))
                    File.Delete(_outputPathAndFileName);
            }
            catch
            {
                //ignore
            }
        }

        private void ValidateMsi()
        {
            Description = Messages.UPDATE_CLIENT_VALIDATING_INSTALLER;

            _msiStream = new FileStream(_outputPathAndFileName, FileMode.Open, FileAccess.Read);

            var calculatedChecksum = string.Empty; 

            var hash = StreamUtilities.ComputeHash(_msiStream, out _);
            if (hash != null)
                calculatedChecksum = string.Join(string.Empty, hash.Select(b => $"{b:x2}"));

            // Check if calculatedChecksum matches what is in chcupdates.xml
            if (!_checksum.Equals(calculatedChecksum, StringComparison.InvariantCultureIgnoreCase))
                throw new Exception(Messages.UPDATE_CLIENT_INVALID_CHECKSUM );

            bool valid;
            try
            {
                // Check digital signature of .msi
                using (var basicSigner = X509Certificate.CreateFromSignedFile(_outputPathAndFileName))
                {
                    using (var cert = new X509Certificate2(basicSigner))
                        valid = cert.Verify();
                }
            }
            catch (Exception e)
            {
                throw new Exception(Messages.UPDATE_CLIENT_FAILED_CERTIFICATE_CHECK, e);
            }

            if (!valid)
                throw new Exception(Messages.UPDATE_CLIENT_INVALID_DIGITAL_CERTIFICATE);
        }

        private void client_DownloadProgressChanged(object sender, DownloadProgressChangedEventArgs e)
        {
            int pc = (int)(95.0 * e.BytesReceived / e.TotalBytesToReceive);
            var descr = string.Format(Messages.DOWNLOAD_CLIENT_INSTALLER_ACTION_PROGRESS_DESCRIPTION, _updateName,
                                            Util.DiskSizeString(e.BytesReceived, "F1"),
                                            Util.DiskSizeString(e.TotalBytesToReceive));
            ByteProgressDescription = descr;
            Tick(pc, descr);
        }

        private void client_DownloadFileCompleted(object sender, AsyncCompletedEventArgs e)
        {
            if (e.Cancelled && _updateDownloadState == DownloadState.Error) // cancelled due to network connectivity issue (see NetworkAvailabilityChanged)
                return;

            if (e.Cancelled)
            {
                _updateDownloadState = DownloadState.Cancelled;
                log.DebugFormat("Client update '{0}' download cancelled by the user", _updateName);
                return;
            }

            if (e.Error != null)
            {
                _updateDownloadError = e.Error;
                log.DebugFormat("Client update '{0}' download failed", _updateName);
                _updateDownloadState = DownloadState.Error;
                return;
            }

            _updateDownloadState = DownloadState.Completed;
            log.DebugFormat("Client update '{0}' download completed successfully", _updateName);
        }

        public override void RecomputeCanCancel()
        {
            CanCancel = !Cancelling && !IsCompleted && (_updateDownloadState == DownloadState.InProgress);
        }
    }
}