using System;
using System.Management;

namespace Endpoint
{
	/// <summary>
	/// Endpoint for Windows Management Instrumentation (WMI)
	/// </summary>
	public class WmiEndpoint : IEndpoint
	{
		/// <summary>
		/// Gets the service name
		/// </summary>
		public string Name { get; set; }

		/// <summary>
		/// Returns a string explaining details on the current status
		/// </summary>
		/// <returns>string with status message</returns>
		public string StatusDescription { get; protected set; }

		/// <summary>
		/// Gets or sets the name of the machine to query with WMI.
		/// </summary>
		/// <value>The name of the machine.</value>
		public string MachineName { get; set; }

		/// <summary>
		/// Gets or sets the object query string.
		/// </summary>
		/// <value>The object query string.</value>
		public string ObjectQueryString { get; set; }

		/// <summary>
		/// Gets or sets the connection username.
		/// </summary>
		/// <value>The connection username.</value>
		public string ConnectionUsername { get; set; }

		/// <summary>
		/// Gets or sets the connection password.
		/// </summary>
		/// <value>The connection password.</value>
		public string ConnectionPassword { get; set; }

		/// <summary>
		/// Gets or sets the name of the result property - this needs to be returned by the query.
		/// </summary>
		/// <value>The name of the result property.</value>
		public string ResultPropertyName { get; set; }

		/// <summary>
		/// Report error when result is this value.
		/// </summary>
		/// <value>A result indicating an error.</value>
		public string ErrorResult { get; set; }
	
		/// <summary>
		/// Report up when result is this value.
		/// </summary>
		/// <value>A result indicating everything is ok.</value>
		public string UpResult { get; set; }

		/// <summary>
		/// Report error when result is below this number
		/// </summary>
		/// <value></value>
		public double MinimumThreshold { get; set; }

		/// <summary>
		/// Report error when result is above this number
		/// </summary>
		/// <value></value>
		public double MaximumThreshold { get; set; }

		/// <summary>
		/// Initializes a new instance of the <see cref="WmiEndpoint"/> class.
		/// </summary>
		public WmiEndpoint()
		{
			MinimumThreshold = double.MinValue;
			MaximumThreshold = double.MaxValue;
		}

		/// <summary>
		/// Gets the current status result of the endpoint
		/// </summary>
		/// <returns>Status</returns>
		public Status GetStatus()
		{
			var connectionOptions = new ConnectionOptions();
			if (!string.IsNullOrEmpty(ConnectionUsername) && !string.IsNullOrEmpty(ConnectionPassword))
			{
				connectionOptions.Username = ConnectionUsername;
				connectionOptions.Password = ConnectionPassword;
			}

			ManagementScope managementScope;
			try
			{
				managementScope = new ManagementScope(MachineName, connectionOptions);
			}
			catch (Exception e)
			{
				StatusDescription = string.Format("Management Scope for MachineName \"{1}\" Failed : \"{0}\"", e.Message, MachineName);
				return Status.Error;
			}

			ObjectQuery objectQuery;
			try
			{
				objectQuery = new ObjectQuery(ObjectQueryString);
			}
			catch (Exception e)
			{
				StatusDescription = string.Format("ObjectQuery initialization \"{1}\" Failed : \"{0}\"", e.Message, ObjectQueryString);
				return Status.Error;
			}

			ManagementObjectSearcher results;
			try
			{
				//Execute the query 
				results = new ManagementObjectSearcher(managementScope, objectQuery);
			}
			catch (Exception e)
			{
				StatusDescription = string.Format("Building Query failed : \"{0}\"", e.Message);
				return Status.Error;
			}

			ManagementObjectCollection managementObjectCollection;
			try
			{
				//Get the results
				managementObjectCollection = results.Get();

				if (managementObjectCollection.Count == 0)
				{
					StatusDescription = string.Format("Query returned 0 results : \"{0}\"", ObjectQueryString);
					return Status.Error;
				}
			}
			catch (Exception ex)
			{
				StatusDescription = "Error retrieving results. Exception: " + ex.Message;
				return Status.Unreachable;
			}

			ManagementObject firstResult = null;

			//take only the first result if there are more than one
			foreach (ManagementObject result in managementObjectCollection)
			{
				firstResult = result;
				break;
			}

			if (firstResult == null)
			{
				StatusDescription = "Problem accessing first result object";
				return Status.Error;
			}

			object resultValue;
			try
			{
				resultValue = firstResult[ResultPropertyName];
			}
			catch (Exception ex)
			{
				StatusDescription = string.Format("Error retrieving result property \"{0}\".  Exception: {1}",
				                                  ResultPropertyName, ex.Message);
				return Status.Error;
			}

			if (resultValue == null)
			{
				StatusDescription = string.Format("Result value was null for property \"{0}\".", ResultPropertyName);
				return Status.Error;
			}

			return getStatus(resultValue.ToString());
		}

		/// <summary>
		/// Gets the status.
		/// </summary>
		/// <param name="resultValueString">The result value string.</param>
		/// <returns></returns>
		private Status getStatus(string resultValueString)
		{
			// Up Value
			if (!string.IsNullOrEmpty(UpResult) && UpResult != resultValueString)
			{
				StatusDescription =
					string.Format("Result for property \"{0}\" was not expected value. Expected \"{1}\" but was \"{2}\"",
					              ResultPropertyName, UpResult ?? "(NULL)", resultValueString);
				return Status.Error;
			}

			// Error Value
			if (!string.IsNullOrEmpty(ErrorResult) && ErrorResult == resultValueString)
			{
				StatusDescription =
					string.Format("Result for property \"{0}\" was error value - \"{1}\"",
					              ResultPropertyName, resultValueString);
				return Status.Error;
			}

			if (MinimumThreshold != double.MinValue || MaximumThreshold != double.MaxValue)
			{
				double resultValueDouble;
				if (Double.TryParse(resultValueString, out resultValueDouble))
				{
					if (resultValueDouble < MinimumThreshold)
					{
						StatusDescription =
							string.Format("Result for property \"{0}\" was less then threshold - {1} < {2}",
							              ResultPropertyName, resultValueDouble, MinimumThreshold);
						return Status.Error;
					}
					if (resultValueDouble > MaximumThreshold)
					{
						StatusDescription =
							string.Format("Result for property \"{0}\" was more then threshold - {1} > {2}",
							              ResultPropertyName, resultValueDouble, MaximumThreshold);
						return Status.Error;
					}
				}
				else
				{
					StatusDescription =
						string.Format("Result for property \"{0}\" was not a number - \"{1}\"",
						              ResultPropertyName, resultValueString);
					return Status.Error;
				}
			}

			StatusDescription = resultValueString;
			return Status.Up;
		}
	}
}