513 lines
16 KiB
C#
513 lines
16 KiB
C#
/*
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* Copyright (c) 2021 ETH Zürich, Educational Development and Technology (LET)
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*
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/.
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*/
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using System;
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using System.Collections.Concurrent;
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using System.Collections.Generic;
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using System.Linq;
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using System.Net.Http;
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using System.Net.Http.Headers;
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using System.Text;
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using System.Threading;
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using System.Threading.Tasks;
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using System.Timers;
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using Newtonsoft.Json;
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using Newtonsoft.Json.Linq;
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using SafeExamBrowser.Configuration.Contracts;
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using SafeExamBrowser.Logging.Contracts;
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using SafeExamBrowser.Server.Contracts;
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using SafeExamBrowser.Server.Contracts.Data;
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using SafeExamBrowser.Server.Contracts.Events;
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using SafeExamBrowser.Server.Data;
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using SafeExamBrowser.Settings.Logging;
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using SafeExamBrowser.Settings.Server;
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using SafeExamBrowser.SystemComponents.Contracts.PowerSupply;
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using SafeExamBrowser.SystemComponents.Contracts.WirelessNetwork;
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using Timer = System.Timers.Timer;
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namespace SafeExamBrowser.Server
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{
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public class ServerProxy : ILogObserver, IServerProxy
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{
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private ApiVersion1 api;
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private AppConfig appConfig;
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private CancellationTokenSource cancellationTokenSource;
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private FileSystem fileSystem;
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private string connectionToken;
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private int currentPowerSupplyValue;
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private int currentWlanValue;
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private string examId;
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private HttpClient httpClient;
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private ConcurrentQueue<string> instructionConfirmations;
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private ILogger logger;
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private ConcurrentQueue<ILogContent> logContent;
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private Parser parser;
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private string oauth2Token;
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private int pingNumber;
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private IPowerSupply powerSupply;
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private ServerSettings settings;
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private Task task;
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private Timer timer;
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private IWirelessAdapter wirelessAdapter;
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public event ProctoringConfigurationReceivedEventHandler ProctoringConfigurationReceived;
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public event ProctoringInstructionReceivedEventHandler ProctoringInstructionReceived;
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public event TerminationRequestedEventHandler TerminationRequested;
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public ServerProxy(
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AppConfig appConfig,
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ILogger logger,
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IPowerSupply powerSupply = default(IPowerSupply),
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IWirelessAdapter wirelessAdapter = default(IWirelessAdapter))
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{
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this.api = new ApiVersion1();
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this.appConfig = appConfig;
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this.cancellationTokenSource = new CancellationTokenSource();
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this.fileSystem = new FileSystem(appConfig, logger);
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this.httpClient = new HttpClient();
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this.instructionConfirmations = new ConcurrentQueue<string>();
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this.logger = logger;
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this.logContent = new ConcurrentQueue<ILogContent>();
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this.parser = new Parser(logger);
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this.powerSupply = powerSupply;
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this.timer = new Timer();
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this.wirelessAdapter = wirelessAdapter;
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}
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public ServerResponse Connect()
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{
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var success = TryExecute(HttpMethod.Get, settings.ApiUrl, out var response);
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var message = response.ToLogString();
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if (success && parser.TryParseApi(response.Content, out api))
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{
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logger.Info("Successfully loaded server API.");
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var secret = Convert.ToBase64String(Encoding.UTF8.GetBytes($"{settings.ClientName}:{settings.ClientSecret}"));
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var authorization = ("Authorization", $"Basic {secret}");
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var content = "grant_type=client_credentials&scope=read write";
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var contentType = "application/x-www-form-urlencoded";
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success = TryExecute(HttpMethod.Post, api.AccessTokenEndpoint, out response, content, contentType, authorization);
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message = response.ToLogString();
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if (success && parser.TryParseOauth2Token(response.Content, out oauth2Token))
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{
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logger.Info("Successfully retrieved OAuth2 token.");
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}
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else
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{
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logger.Error("Failed to retrieve OAuth2 token!");
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}
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}
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else
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{
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logger.Error("Failed to load server API!");
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}
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return new ServerResponse(success, message);
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}
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public ServerResponse Disconnect()
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{
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var authorization = ("Authorization", $"Bearer {oauth2Token}");
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var content = "delete=true";
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var contentType = "application/x-www-form-urlencoded";
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var token = ("SEBConnectionToken", connectionToken);
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var success = TryExecute(HttpMethod.Delete, api.HandshakeEndpoint, out var response, content, contentType, authorization, token);
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var message = response.ToLogString();
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if (success)
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{
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logger.Info("Successfully terminated connection.");
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}
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else
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{
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logger.Error("Failed to terminate connection!");
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}
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return new ServerResponse(success, message);
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}
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public ServerResponse<IEnumerable<Exam>> GetAvailableExams(string examId = default(string))
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{
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var authorization = ("Authorization", $"Bearer {oauth2Token}");
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var content = $"institutionId={settings.Institution}{(examId == default(string) ? "" : $"&examId={examId}")}";
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var contentType = "application/x-www-form-urlencoded";
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var exams = default(IList<Exam>);
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var success = TryExecute(HttpMethod.Post, api.HandshakeEndpoint, out var response, content, contentType, authorization);
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var message = response.ToLogString();
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if (success)
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{
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var hasExams = parser.TryParseExams(response.Content, out exams);
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var hasToken = parser.TryParseConnectionToken(response, out connectionToken);
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success = hasExams && hasToken;
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if (success)
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{
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logger.Info("Successfully retrieved connection token and available exams.");
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}
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else if (!hasExams)
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{
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logger.Error("Failed to retrieve available exams!");
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}
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else if (!hasToken)
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{
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logger.Error("Failed to retrieve connection token!");
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}
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}
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else
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{
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logger.Error("Failed to load connection token and available exams!");
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}
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return new ServerResponse<IEnumerable<Exam>>(success, exams, message);
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}
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public ServerResponse<Uri> GetConfigurationFor(Exam exam)
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{
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var authorization = ("Authorization", $"Bearer {oauth2Token}");
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var token = ("SEBConnectionToken", connectionToken);
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var uri = default(Uri);
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var success = TryExecute(HttpMethod.Get, $"{api.ConfigurationEndpoint}?examId={exam.Id}", out var response, default(string), default(string), authorization, token);
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var message = response.ToLogString();
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if (success)
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{
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logger.Info("Successfully retrieved exam configuration.");
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success = fileSystem.TrySaveFile(response.Content, out uri);
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if (success)
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{
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logger.Info($"Successfully saved exam configuration as '{uri}'.");
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}
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else
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{
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logger.Error("Failed to save exam configuration!");
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}
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}
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else
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{
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logger.Error("Failed to retrieve exam configuration!");
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}
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return new ServerResponse<Uri>(success, uri, message);
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}
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public ConnectionInfo GetConnectionInfo()
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{
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return new ConnectionInfo
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{
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Api = JsonConvert.SerializeObject(api),
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ConnectionToken = connectionToken,
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Oauth2Token = oauth2Token
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};
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}
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public void Initialize(ServerSettings settings)
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{
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this.settings = settings;
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httpClient.BaseAddress = new Uri(settings.ServerUrl);
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if (settings.RequestTimeout > 0)
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{
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httpClient.Timeout = TimeSpan.FromMilliseconds(settings.RequestTimeout);
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}
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}
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public void Initialize(string api, string connectionToken, string examId, string oauth2Token, ServerSettings settings)
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{
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this.api = JsonConvert.DeserializeObject<ApiVersion1>(api);
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this.connectionToken = connectionToken;
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this.examId = examId;
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this.oauth2Token = oauth2Token;
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Initialize(settings);
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}
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public void Notify(ILogContent content)
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{
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logContent.Enqueue(content);
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}
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public ServerResponse SendSessionIdentifier(string identifier)
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{
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var authorization = ("Authorization", $"Bearer {oauth2Token}");
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var content = $"examId={examId}&seb_user_session_id={identifier}";
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var contentType = "application/x-www-form-urlencoded";
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var token = ("SEBConnectionToken", connectionToken);
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var success = TryExecute(HttpMethod.Put, api.HandshakeEndpoint, out var response, content, contentType, authorization, token);
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var message = response.ToLogString();
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if (success)
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{
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logger.Info("Successfully sent session identifier.");
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}
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else
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{
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logger.Error("Failed to send session identifier!");
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}
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return new ServerResponse(success, message);
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}
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public void StartConnectivity()
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{
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foreach (var item in logger.GetLog())
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{
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logContent.Enqueue(item);
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}
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logger.Subscribe(this);
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task = new Task(SendLog, cancellationTokenSource.Token);
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task.Start();
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logger.Info("Started sending log items.");
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timer.AutoReset = false;
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timer.Elapsed += Timer_Elapsed;
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timer.Interval = 1000;
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timer.Start();
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logger.Info("Started sending pings.");
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if (powerSupply != default(IPowerSupply) && wirelessAdapter != default(IWirelessAdapter))
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{
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powerSupply.StatusChanged += PowerSupply_StatusChanged;
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wirelessAdapter.NetworksChanged += WirelessAdapter_NetworksChanged;
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logger.Info("Started monitoring system components.");
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}
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}
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public void StopConnectivity()
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{
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if (powerSupply != default(IPowerSupply) && wirelessAdapter != default(IWirelessAdapter))
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{
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powerSupply.StatusChanged -= PowerSupply_StatusChanged;
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wirelessAdapter.NetworksChanged -= WirelessAdapter_NetworksChanged;
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logger.Info("Stopped monitoring system components.");
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}
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logger.Unsubscribe(this);
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cancellationTokenSource.Cancel();
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task?.Wait();
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logger.Info("Stopped sending log items.");
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timer.Stop();
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timer.Elapsed -= Timer_Elapsed;
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logger.Info("Stopped sending pings.");
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}
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private void SendLog()
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{
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var authorization = ("Authorization", $"Bearer {oauth2Token}");
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var contentType = "application/json;charset=UTF-8";
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var token = ("SEBConnectionToken", connectionToken);
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while (!cancellationTokenSource.IsCancellationRequested)
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{
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try
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{
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if (logContent.TryDequeue(out var c) && c is ILogMessage message)
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{
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var json = new JObject
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{
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["type"] = message.Severity.ToLogType(),
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["timestamp"] = message.DateTime.ToUnixTimestamp(),
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["text"] = message.Message
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};
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var content = json.ToString();
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TryExecute(HttpMethod.Post, api.LogEndpoint, out var response, content, contentType, authorization, token);
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}
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}
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catch (Exception e)
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{
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logger.Error("Failed to send log!", e);
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}
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}
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}
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private void PowerSupply_StatusChanged(IPowerSupplyStatus status)
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{
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try
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{
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var value = Convert.ToInt32(status.BatteryCharge * 100);
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if (value != currentPowerSupplyValue)
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{
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var authorization = ("Authorization", $"Bearer {oauth2Token}");
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var chargeInfo = $"{status.BatteryChargeStatus} at {value}%";
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var contentType = "application/json;charset=UTF-8";
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var gridInfo = $"{(status.IsOnline ? "connected to" : "disconnected from")} the power grid";
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var token = ("SEBConnectionToken", connectionToken);
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var json = new JObject
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{
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["type"] = LogLevel.Info.ToLogType(),
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["timestamp"] = DateTime.Now.ToUnixTimestamp(),
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["text"] = $"<battery> {chargeInfo}, {status.BatteryTimeRemaining} remaining, {gridInfo}",
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["numericValue"] = value
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};
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var content = json.ToString();
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TryExecute(HttpMethod.Post, api.LogEndpoint, out var response, content, contentType, authorization, token);
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currentPowerSupplyValue = value;
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}
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}
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catch (Exception e)
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{
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logger.Error("Failed to send power supply status!", e);
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}
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}
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private void Timer_Elapsed(object sender, ElapsedEventArgs args)
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{
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try
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{
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var authorization = ("Authorization", $"Bearer {oauth2Token}");
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var content = $"timestamp={DateTime.Now.ToUnixTimestamp()}&ping-number={++pingNumber}";
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var contentType = "application/x-www-form-urlencoded";
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var token = ("SEBConnectionToken", connectionToken);
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if (instructionConfirmations.TryDequeue(out var confirmation))
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{
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content = $"{content}&instruction-confirm={confirmation}";
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}
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var success = TryExecute(HttpMethod.Post, api.PingEndpoint, out var response, content, contentType, authorization, token);
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if (success)
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{
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if (parser.TryParseInstruction(response.Content, out var attributes, out var instruction, out var instructionConfirmation))
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{
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switch (instruction)
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{
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case Instructions.PROCTORING:
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Task.Run(() => ProctoringInstructionReceived?.Invoke(attributes.Instruction));
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break;
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case Instructions.PROCTORING_RECONFIGURATION:
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Task.Run(() => ProctoringConfigurationReceived?.Invoke(attributes.AllowChat, attributes.ReceiveAudio, attributes.ReceiveVideo));
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break;
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case Instructions.QUIT:
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Task.Run(() => TerminationRequested?.Invoke());
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break;
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}
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if (instructionConfirmation != default(string))
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{
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instructionConfirmations.Enqueue(instructionConfirmation);
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}
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}
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}
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else
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{
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logger.Error($"Failed to send ping: {response.ToLogString()}");
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}
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}
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catch (Exception e)
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{
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logger.Error("Failed to send ping!", e);
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}
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timer.Start();
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}
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private void WirelessAdapter_NetworksChanged()
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{
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const int NOT_CONNECTED = -1;
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try
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{
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var network = wirelessAdapter.GetNetworks().FirstOrDefault(n => n.Status == WirelessNetworkStatus.Connected);
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if (network?.SignalStrength != currentWlanValue)
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{
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var authorization = ("Authorization", $"Bearer {oauth2Token}");
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var contentType = "application/json;charset=UTF-8";
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var token = ("SEBConnectionToken", connectionToken);
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var json = new JObject { ["type"] = LogLevel.Info.ToLogType(), ["timestamp"] = DateTime.Now.ToUnixTimestamp() };
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if (network != default(IWirelessNetwork))
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{
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json["text"] = $"<wlan> {network.Name}: {network.Status}, {network.SignalStrength}%";
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json["numericValue"] = network.SignalStrength;
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}
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else
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{
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json["text"] = "<wlan> not connected";
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}
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TryExecute(HttpMethod.Post, api.LogEndpoint, out var response, json.ToString(), contentType, authorization, token);
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currentWlanValue = network?.SignalStrength ?? NOT_CONNECTED;
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}
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}
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catch (Exception e)
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{
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logger.Error("Failed to send wireless status!", e);
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}
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}
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private bool TryExecute(
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HttpMethod method,
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string url,
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out HttpResponseMessage response,
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string content = default(string),
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string contentType = default(string),
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params (string name, string value)[] headers)
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{
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response = default(HttpResponseMessage);
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for (var attempt = 0; attempt < settings.RequestAttempts && (response == default(HttpResponseMessage) || !response.IsSuccessStatusCode); attempt++)
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{
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var request = new HttpRequestMessage(method, url);
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if (content != default(string))
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{
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request.Content = new StringContent(content, Encoding.UTF8);
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if (contentType != default(string))
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{
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request.Content.Headers.ContentType = MediaTypeHeaderValue.Parse(contentType);
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}
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}
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foreach (var (name, value) in headers)
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{
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request.Headers.Add(name, value);
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}
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try
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{
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response = httpClient.SendAsync(request).GetAwaiter().GetResult();
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if (request.RequestUri.AbsolutePath != api.LogEndpoint && request.RequestUri.AbsolutePath != api.PingEndpoint)
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{
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logger.Debug($"Completed request: {request.Method} '{request.RequestUri}' -> {response.ToLogString()}");
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}
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}
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catch (TaskCanceledException)
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{
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logger.Debug($"Request {request.Method} '{request.RequestUri}' did not complete within {settings.RequestTimeout}ms!");
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break;
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}
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catch (Exception e)
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{
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logger.Debug($"Request {request.Method} '{request.RequestUri}' failed due to {e}");
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}
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}
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return response != default(HttpResponseMessage) && response.IsSuccessStatusCode;
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}
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}
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}
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