/*
 * Copyright (c) 2020 ETH Zürich, Educational Development and Technology (LET)
 * 
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 */

using System;
using SafeExamBrowser.Logging.Contracts;
using SafeExamBrowser.WindowsApi.Contracts;
using SafeExamBrowser.WindowsApi.Contracts.Events;

namespace SafeExamBrowser.WindowsApi
{
	internal class Process : IProcess
	{
		private bool eventInitialized;
		private ILogger logger;
		private System.Diagnostics.Process process;

		public bool HasTerminated
		{
			get { return IsTerminated(); }
		}

		public int Id
		{
			get { return process.Id; }
		}

		public string Name { get; }
		public string OriginalName { get; }

		private event ProcessTerminatedEventHandler TerminatedEvent;

		public event ProcessTerminatedEventHandler Terminated
		{
			add { TerminatedEvent += value; InitializeEvent(); }
			remove { TerminatedEvent -= value; }
		}

		internal Process(System.Diagnostics.Process process, string name, string originalName, ILogger logger)
		{
			this.logger = logger;
			this.process = process;
			this.Name = name;
			this.OriginalName = originalName;
		}

		public bool TryClose(int timeout_ms = 0)
		{
			try
			{
				logger.Debug("Attempting to close process...");
				process.Refresh();

				var success = process.CloseMainWindow();

				if (success)
				{
					logger.Debug("Successfully sent close message to main window.");
				}
				else
				{
					logger.Warn("Failed to send close message to main window!");
				}

				return success && WaitForTermination(timeout_ms);
			}
			catch (Exception e)
			{
				logger.Error("Failed to close main window!", e);
			}

			return false;
		}

		public bool TryKill(int timeout_ms = 0)
		{
			try
			{
				logger.Debug("Attempting to kill process...");

				process.Refresh();
				process.Kill();

				return WaitForTermination(timeout_ms);
			}
			catch (Exception e)
			{
				logger.Error("Failed to kill process!", e);
			}

			return false;
		}

		public override string ToString()
		{
			return $"'{Name}' ({Id})";
		}

		private bool IsTerminated()
		{
			try
			{
				process.Refresh();

				return process.HasExited;
			}
			catch (Exception e)
			{
				logger.Error("Failed to check whether process is terminated!", e);
			}

			return false;
		}

		private void InitializeEvent()
		{
			if (!eventInitialized)
			{
				eventInitialized = true;
				process.Exited += Process_Exited;
				process.EnableRaisingEvents = true;
				logger.Debug("Initialized termination event.");
			}
		}

		private bool WaitForTermination(int timeout_ms)
		{
			var terminated = process.WaitForExit(timeout_ms);

			if (terminated)
			{
				logger.Debug($"Process has terminated within {timeout_ms}ms.");
			}
			else
			{
				logger.Warn($"Process failed to terminate within {timeout_ms}ms!");
			}

			return terminated;
		}

		private void Process_Exited(object sender, EventArgs e)
		{
			TerminatedEvent?.Invoke(process.ExitCode);
			logger.Debug("Process has terminated.");
		}
	}
}
