Imports System
Imports System.Configuration
Imports System.IO
Imports System.Net
Imports System.Text
Imports System.Web
Imports System.Web.UI
Imports System.Web.UI.WebControls

Namespace Validators

	Public Class ReCaptchaValidator
		Inherits BaseValidator

#Region "Fields"

		Protected dummy As New TextBox()

#End Region

#Region "Properties"

		''' <summary>
		''' Gets the Public Key generated by reCaptcha
		''' </summary>
		Private Shared ReadOnly Property PublicKey() As String
			Get
				Return ConfigurationManager.AppSettings("publicKey")
			End Get
		End Property

		''' <summary>
		''' Gets the Private Key generated by reCaptcha
		''' </summary>
		Private Shared ReadOnly Property PrivateKey() As String
			Get
				Return ConfigurationManager.AppSettings("privateKey")
			End Get
		End Property

#End Region

#Region "Private"

		''' <summary>
		''' Obtains the value of the passed key in the http form
		''' </summary>
		''' <param name="value"></param>
		''' <returns></returns>
		Private Shared Function GetFormValue(ByVal value As String) As String
			Return HttpContext.Current.Request.Form(value)
		End Function

		''' <summary>
		''' Gathers the parameters for reCaptchaValidator
		''' </summary>
		''' <returns></returns>
		Private Shared Function ReCaptchaParameters() As String
			Dim response As String = GetFormValue("recaptcha_response_field")
			Dim challenge As String = GetFormValue("recaptcha_challenge_field")
			Dim IP As String = HttpContext.Current.Request.UserHostName

			Dim builder As New StringBuilder()

			builder.AppendFormat("privatekey={0}&", PrivateKey)
			builder.AppendFormat("remoteip={0}&", IP)
			builder.AppendFormat("challenge={0}&", challenge)
			builder.AppendFormat("response={0}", response)

			Return builder.ToString()
		End Function

		''' <summary>
		''' Validates the capcha inserted by the user
		''' </summary>
		''' <param name="parameters">parameters to verify</param>
		''' <returns>response of the capcth</returns>
		Private Shared Function ValidateCaptcha(ByVal parameters As String) As String
			Try
				Dim request As WebRequest = WebRequest.Create("http://api-verify.recaptcha.net/verify")

				request.ContentType = "application/x-www-form-urlencoded"
				request.Method = "POST"

				Dim writer As New StreamWriter(request.GetRequestStream())
				writer.Write(parameters)
				writer.Close()

				'Response
				Dim webResponse As HttpWebResponse = DirectCast(request.GetResponse(), HttpWebResponse)
				Dim myReader As New StreamReader(webResponse.GetResponseStream())

				Dim response As String = myReader.ReadToEnd()

				myReader.Close()
				webResponse.Close()

				Return response
			Catch generatedExceptionName As WebException
				Return String.Empty
			End Try
		End Function

#End Region

#Region "Public"

		Protected Overloads Overrides Function EvaluateIsValid() As Boolean
			Dim parameters As String = ReCaptchaParameters()

			Dim result As String = ValidateCaptcha(parameters)
			Dim isValid As Boolean = result.Equals("true" & Chr(10) & "success")

			If Not isValid Then
				ErrorMessage = "Your are not a human!"
				Controls.Add(New LiteralControl(ErrorMessage))
			End If

			Return isValid
		End Function

#End Region

#Region "Control Events"

		Protected Overloads Overrides Sub OnInit(ByVal e As EventArgs)
			dummy.ID = "aaa"
			Controls.Add(dummy)
			ControlToValidate = "aaa"

			MyBase.OnInit(e)
		End Sub

		''' <summary>
		''' Writes the to show the validation Captcha
		''' </summary>
		''' <param name="writer"></param>
		Protected Overloads Overrides Sub Render(ByVal writer As HtmlTextWriter)
			writer.Write("" & Chr(13) & "" & Chr(10) & "<script>" & Chr(13) & "" & Chr(10) & "var RecaptchaOptions = {{theme : 'blackglass', tabindex : 2}};" & Chr(13) & "" & Chr(10) & "</script>" & Chr(13) & "" & Chr(10) & "<script type='text/javascript' src='http://api.recaptcha.net/challenge?k={0}'></script>" & Chr(13) & "" & Chr(10) & "<noscript>" & Chr(13) & "" & Chr(10) & " <iframe src='http://api.recaptcha.net/noscript?k={0}' height='300' width='500' frameborder='0'></iframe><br/>" & Chr(13) & "" & Chr(10) & " <textarea name='recaptcha_challenge_field' rows='3' cols='40'></textarea>" & Chr(13) & "" & Chr(10) & " <input type='hidden' name='recaptcha_response_field' value='manual_challenge'>" & Chr(13) & "" & Chr(10) & "</noscript>", PublicKey)

			dummy.Visible = False

			MyBase.Render(writer)
		End Sub

#End Region

	End Class
End Namespace