Messaging: WIP MailFetcher, MailSession

Messaging/Mail/OAuth2.vb

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+Imports DigitalData.Modules.Base
+Imports DigitalData.Modules.Logging
+Imports DigitalData.Modules.Messaging.Mail.MailSession
+Imports Microsoft.Identity.Client
+
+Public Class OAuth2
+    Inherits BaseClass
+
+    Private ReadOnly TenantId As String
+    Private ReadOnly ClientId As String
+    Private ReadOnly ClientSecret As String
+
+    Public Const O365_SCOPE = "https://outlook.office365.com/.default"
+    Public Const O365_SERVER = "outlook.office365.com"
+
+    Private _AccessToken As String
+    Public ReadOnly Property AccessToken
+        Get
+            Return _AccessToken
+        End Get
+    End Property
+
+    Public Sub New(pLogConfig As LogConfig, pTenantId As String, pClientId As String, pClientSecret As String)
+        MyBase.New(pLogConfig)
+        TenantId = pTenantId
+        ClientId = pClientId
+        ClientSecret = pClientSecret
+    End Sub
+
+    Private Async Function GetAccessToken(pSession As SessionInfo) As Task(Of String)
+        Try
+            ' Create the application, which is defined in
+            ' Microsoft.Identity.Client
+            Dim oApp = ConfidentialClientApplicationBuilder.
+            Create(pSession.ClientId).
+            WithTenantId(pSession.TenantId).
+            WithClientSecret(pSession.ClientSecret).
+            Build()
+
+            ' Request an access token
+            Dim oScopes = New List(Of String) From {O365_SCOPE}
+            Dim oResult = Await oApp.
+                    AcquireTokenForClient(oScopes).
+                    ExecuteAsync()
+
+            Return oResult.AccessToken
+        Catch ex As Exception
+            Logger.Warn("Could not request access token!")
+            Logger.Error(ex)
+            Return Nothing
+        End Try
+    End Function
+End Class