Imports System
Imports System.Security.Cryptography
Imports System.Collections.Generic
Imports System.Text
Imports System.Web

' This code is an translation of Eran Sandlers C# class OAuthBase in Visual Basic
' by Simon A. Frank (http://www.frank-it-beratung.com)

' Original Sourcecode in C#
' http://oauth.googlecode.com/svn/code/csharp/OAuthBase.cs

' Erans Homepage: http://eran.sandler.co.il/

' Details (in German language only) see:
' http://frank-it-beratung.com/2010/11/11/twitter-api-mit-oauth-und-visual-basic/

' Date: 2010-11-11


Public Class OAuthBase

    ''' <summary>
    ''' Provides a predefined set of algorithms that are supported officially by the protocol
    ''' </summary>
    Public Enum SignatureTypes
        HMACSHA1
        PLAINTEXT
        RSASHA1
    End Enum

    ''' <summary>
    ''' Provides an internal structure to sort the query parameter
    ''' </summary>
    Protected Class QueryParameter
        Private m_name As String = Nothing
        Private m_value As String = Nothing

        Public Sub New(ByVal name As String, ByVal value As String)
            Me.m_name = name
            Me.m_value = value
        End Sub

        Public ReadOnly Property Name() As String
            Get
                Return m_name
            End Get
        End Property

        Public ReadOnly Property Value() As String
            Get
                Return m_value
            End Get
        End Property
    End Class

    ''' <summary>
    ''' Comparer class used to perform the sorting of the query parameters
    ''' </summary>
    Protected Class QueryParameterComparer
        Implements IComparer(Of QueryParameter)
        Public Function Compare(ByVal x As QueryParameter, ByVal y As QueryParameter) As Integer Implements IComparer(Of QueryParameter).Compare
            If x.Name = y.Name Then
                Return String.Compare(x.Value, y.Value)
            Else
                Return String.Compare(x.Name, y.Name)
            End If
        End Function
    End Class

    Protected Const OAuthVersion As String = "1.0"
    Protected Const OAuthParameterPrefix As String = "oauth_"

    '
    ' List of know and used oauth parameters' names
    '        
    Protected Const OAuthConsumerKeyKey As String = "oauth_consumer_key"
    Protected Const OAuthCallbackKey As String = "oauth_callback"
    Protected Const OAuthVersionKey As String = "oauth_version"
    Protected Const OAuthSignatureMethodKey As String = "oauth_signature_method"
    Protected Const OAuthSignatureKey As String = "oauth_signature"
    Protected Const OAuthTimestampKey As String = "oauth_timestamp"
    Protected Const OAuthNonceKey As String = "oauth_nonce"
    Protected Const OAuthTokenKey As String = "oauth_token"
    Protected Const OAuthTokenSecretKey As String = "oauth_token_secret"

    Protected Const HMACSHA1SignatureType As String = "HMAC-SHA1"
    Protected Const PlainTextSignatureType As String = "PLAINTEXT"
    Protected Const RSASHA1SignatureType As String = "RSA-SHA1"

    Protected random As New Random()

    Protected unreservedChars As String = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789-_.~"

    ''' <summary>
    ''' Helper function to compute a hash value
    ''' </summary>
    ''' <param name="hashAlgorithm">The hashing algoirhtm used. If that algorithm needs some initialization, like HMAC and its derivatives, they should be initialized prior to passing it to this function</param>
    ''' <param name="data">The data to hash</param>
    ''' <returns>a Base64 string of the hash value</returns>
    Private Function ComputeHash(ByVal hashAlgorithm As HashAlgorithm, ByVal data As String) As String
        If hashAlgorithm Is Nothing Then
            Throw New ArgumentNullException("hashAlgorithm")
        End If

        If String.IsNullOrEmpty(data) Then
            Throw New ArgumentNullException("data")
        End If

        Dim dataBuffer As Byte() = System.Text.Encoding.ASCII.GetBytes(data)
        Dim hashBytes As Byte() = hashAlgorithm.ComputeHash(dataBuffer)

        Return Convert.ToBase64String(hashBytes)
    End Function

    ''' <summary>
    ''' Internal function to cut out all non oauth query string parameters (all parameters not begining with "oauth_")
    ''' </summary>
    ''' <param name="parameters">The query string part of the Url</param>
    ''' <returns>A list of QueryParameter each containing the parameter name and value</returns>
    Private Function GetQueryParameters(ByVal parameters As String) As List(Of QueryParameter)
        If parameters.StartsWith("?") Then
            parameters = parameters.Remove(0, 1)
        End If

        Dim result As New List(Of QueryParameter)()

        If Not String.IsNullOrEmpty(parameters) Then
            Dim p As String() = parameters.Split("&"c)
            For Each s As String In p
                If Not String.IsNullOrEmpty(s) AndAlso Not s.StartsWith(OAuthParameterPrefix) Then
                    If s.IndexOf("="c) > -1 Then
                        Dim temp As String() = s.Split("="c)
                        result.Add(New QueryParameter(temp(0), temp(1)))
                    Else
                        result.Add(New QueryParameter(s, String.Empty))
                    End If
                End If
            Next
        End If

        Return result
    End Function

    ''' <summary>
    ''' This is a different Url Encode implementation since the default .NET one outputs the percent encoding in lower case.
    ''' While this is not a problem with the percent encoding spec, it is used in upper case throughout OAuth
    ''' </summary>
    ''' <param name="value">The value to Url encode</param>
    ''' <returns>Returns a Url encoded string</returns>
    Public Function UrlEncode(ByVal value As String) As String
        Dim result As New StringBuilder()

        For Each symbol As Char In value
            If unreservedChars.IndexOf(symbol) <> -1 Then
                result.Append(symbol)
            Else
                result.Append("%"c & [String].Format("{0:X2}", AscW(symbol)))
            End If
        Next

        Return result.ToString()
    End Function

    ''' <summary>
    ''' Normalizes the request parameters according to the spec
    ''' </summary>
    ''' <param name="parameters">The list of parameters already sorted</param>
    ''' <returns>a string representing the normalized parameters</returns>
    Protected Function NormalizeRequestParameters(ByVal parameters As IList(Of QueryParameter)) As String
        Dim sb As New StringBuilder()
        Dim p As QueryParameter = Nothing
        For i As Integer = 0 To parameters.Count - 1
            p = parameters(i)
            sb.AppendFormat("{0}={1}", p.Name, p.Value)

            If i < parameters.Count - 1 Then
                sb.Append("&")
            End If
        Next

        Return sb.ToString()
    End Function

    ''' <summary>
    ''' Generate the signature base that is used to produce the signature
    ''' </summary>
    ''' <param name="url">The full url that needs to be signed including its non OAuth url parameters</param>
    ''' <param name="consumerKey">The consumer key</param>        
    ''' <param name="token">The token, if available. If not available pass null or an empty string</param>
    ''' <param name="tokenSecret">The token secret, if available. If not available pass null or an empty string</param>
    ''' <param name="httpMethod">The http method used. Must be a valid HTTP method verb (POST,GET,PUT, etc)</param>
    ''' <param name="signatureType">The signature type. To use the default values use <see cref="OAuthBase.SignatureTypes">OAuthBase.SignatureTypes</see>.</param>
    ''' <returns>The signature base</returns>
    Public Function GenerateSignatureBase(ByVal url As Uri, ByVal consumerKey As String, ByVal token As String, ByVal tokenSecret As String, ByVal httpMethod As String, ByVal timeStamp As String, _
     ByVal nonce As String, ByVal signatureType As String, ByRef normalizedUrl As String, ByRef normalizedRequestParameters As String) As String
        If token Is Nothing Then
            token = String.Empty
        End If

        If tokenSecret Is Nothing Then
            tokenSecret = String.Empty
        End If

        If String.IsNullOrEmpty(consumerKey) Then
            Throw New ArgumentNullException("consumerKey")
        End If

        If String.IsNullOrEmpty(httpMethod) Then
            Throw New ArgumentNullException("httpMethod")
        End If

        If String.IsNullOrEmpty(signatureType) Then
            Throw New ArgumentNullException("signatureType")
        End If

        normalizedUrl = Nothing
        normalizedRequestParameters = Nothing

        Dim parameters As List(Of QueryParameter) = GetQueryParameters(url.Query)
        parameters.Add(New QueryParameter(OAuthVersionKey, OAuthVersion))
        parameters.Add(New QueryParameter(OAuthNonceKey, nonce))
        parameters.Add(New QueryParameter(OAuthTimestampKey, timeStamp))
        parameters.Add(New QueryParameter(OAuthSignatureMethodKey, signatureType))
        parameters.Add(New QueryParameter(OAuthConsumerKeyKey, consumerKey))

        If Not String.IsNullOrEmpty(token) Then
            parameters.Add(New QueryParameter(OAuthTokenKey, token))
        End If

        parameters.Sort(New QueryParameterComparer())

        normalizedUrl = String.Format("{0}://{1}", url.Scheme, url.Host)
        If Not ((url.Scheme = "http" AndAlso url.Port = 80) OrElse (url.Scheme = "https" AndAlso url.Port = 443)) Then
            normalizedUrl += ":" & url.Port
        End If
        normalizedUrl += url.AbsolutePath
        normalizedRequestParameters = NormalizeRequestParameters(parameters)


        Dim signatureBase As New StringBuilder()
        signatureBase.AppendFormat("{0}&", httpMethod.ToUpper())
        signatureBase.AppendFormat("{0}&", UrlEncode(normalizedUrl))
        signatureBase.AppendFormat("{0}", UrlEncode(normalizedRequestParameters))

        Return signatureBase.ToString()
    End Function

    ''' <summary>
    ''' Generate the signature value based on the given signature base and hash algorithm
    ''' </summary>
    ''' <param name="signatureBase">The signature based as produced by the GenerateSignatureBase method or by any other means</param>
    ''' <param name="hash">The hash algorithm used to perform the hashing. If the hashing algorithm requires initialization or a key it should be set prior to calling this method</param>
    ''' <returns>A base64 string of the hash value</returns>
    Public Function GenerateSignatureUsingHash(ByVal signatureBase As String, ByVal hash As HashAlgorithm) As String
        Return ComputeHash(hash, signatureBase)
    End Function

    ''' <summary>
    ''' Generates a signature using the HMAC-SHA1 algorithm
    ''' </summary>		
    ''' <param name="url">The full url that needs to be signed including its non OAuth url parameters</param>
    ''' <param name="consumerKey">The consumer key</param>
    ''' <param name="consumerSecret">The consumer seceret</param>
    ''' <param name="token">The token, if available. If not available pass null or an empty string</param>
    ''' <param name="tokenSecret">The token secret, if available. If not available pass null or an empty string</param>
    ''' <param name="httpMethod">The http method used. Must be a valid HTTP method verb (POST,GET,PUT, etc)</param>
    ''' <returns>A base64 string of the hash value</returns>
    Public Function GenerateSignature(ByVal url As Uri, ByVal consumerKey As String, ByVal consumerSecret As String, ByVal token As String, ByVal tokenSecret As String, ByVal httpMethod As String, _
     ByVal timeStamp As String, ByVal nonce As String, ByRef normalizedUrl As String, ByRef normalizedRequestParameters As String) As String
        Return GenerateSignature(url, consumerKey, consumerSecret, token, tokenSecret, httpMethod, _
         timeStamp, nonce, SignatureTypes.HMACSHA1, normalizedUrl, normalizedRequestParameters)
    End Function

    ''' <summary>
    ''' Generates a signature using the specified signatureType 
    ''' </summary>		
    ''' <param name="url">The full url that needs to be signed including its non OAuth url parameters</param>
    ''' <param name="consumerKey">The consumer key</param>
    ''' <param name="consumerSecret">The consumer seceret</param>
    ''' <param name="token">The token, if available. If not available pass null or an empty string</param>
    ''' <param name="tokenSecret">The token secret, if available. If not available pass null or an empty string</param>
    ''' <param name="httpMethod">The http method used. Must be a valid HTTP method verb (POST,GET,PUT, etc)</param>
    ''' <param name="signatureType">The type of signature to use</param>
    ''' <returns>A base64 string of the hash value</returns>
    Public Function GenerateSignature(ByVal url As Uri, ByVal consumerKey As String, ByVal consumerSecret As String, ByVal token As String, ByVal tokenSecret As String, ByVal httpMethod As String, _
     ByVal timeStamp As String, ByVal nonce As String, ByVal signatureType As SignatureTypes, ByRef normalizedUrl As String, ByRef normalizedRequestParameters As String) As String
        normalizedUrl = Nothing
        normalizedRequestParameters = Nothing

        Select Case signatureType
		    ' Sowieso nicht notwendig - spart das etwas aufwendige Einbinden von HttpUtility 
            'Case SignatureTypes.PLAINTEXT
            '    Return HttpUtility.UrlEncode(String.Format("{0}&{1}", consumerSecret, tokenSecret))
            Case SignatureTypes.HMACSHA1
                Dim signatureBase As String = GenerateSignatureBase(url, consumerKey, token, tokenSecret, httpMethod, timeStamp, _
                 nonce, HMACSHA1SignatureType, normalizedUrl, normalizedRequestParameters)

                Dim hmacsha1 As New HMACSHA1()
                hmacsha1.Key = Encoding.ASCII.GetBytes(String.Format("{0}&{1}", UrlEncode(consumerSecret), If(String.IsNullOrEmpty(tokenSecret), "", UrlEncode(tokenSecret))))

                Return GenerateSignatureUsingHash(signatureBase, hmacsha1)
            Case SignatureTypes.RSASHA1
                Throw New NotImplementedException()
            Case Else
                Throw New ArgumentException("Unknown signature type", "signatureType")
        End Select
    End Function

    ''' <summary>
    ''' Generate the timestamp for the signature        
    ''' </summary>
    ''' <returns></returns>
    Public Overridable Function GenerateTimeStamp() As String
        ' Default implementation of UNIX time of the current UTC time
        Dim ts As TimeSpan = DateTime.UtcNow - New DateTime(1970, 1, 1, 0, 0, 0, _
         0)
        Return Convert.ToInt64(ts.TotalSeconds).ToString()
    End Function

    ''' <summary>
    ''' Generate a nonce
    ''' </summary>
    ''' <returns></returns>
    Public Overridable Function GenerateNonce() As String
        ' Just a simple implementation of a random number between 123400 and 9999999
        Return random.[Next](123400, 9999999).ToString()
    End Function

End Class