Imports System
Imports System.IO
Imports System.Net.Http
Imports System.Text
Imports System.Web
Imports Newtonsoft.Json

' NuGet: Newtonsoft.Json (>= 13.x)

Public Class cRelayHubToken

    ' ======= KONFIG =======
    Private Shared ReadOnly TOKEN_ENDPOINT As String =
        "https://dev-kc.singlewindow.io/auth/realms/agsw/protocol/openid-connect/token"

    Private Shared ReadOnly CLIENT_ID As String = "agsw-admin"

    ' Gewünscht: Zugangsdaten in der Klasse definieren
    Private Shared ReadOnly USERNAME As String = "andreas.test@test.com"
    Private Shared ReadOnly PASSWORD As String = "Password.123"

    ' Token-File pro Benutzer unter %AppData%
    Private Shared ReadOnly StorePath As String =
        Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData),
                     "RelayHub", "token.json")

    ' Sicherheitspuffer, bevor wir erneuern (Sekunden)
    Private Const ExpirySkewSeconds As Integer = 60

    ' ======= ÖFFENTLICHE API =======
    ''' <summary>
    ''' Liefert einen gültigen Access Token (nie Leerstring).
    ''' </summary>
    Public Shared Function GetAccessToken() As String
        Dim store = LoadStore()

        ' 1) Wenn wir einen (noch) gültigen Token haben
        If store IsNot Nothing AndAlso Not String.IsNullOrWhiteSpace(store.AccessToken) Then
            If store.ExpiresAtUtc > DateTimeOffset.UtcNow.AddSeconds(ExpirySkewSeconds) Then
                Return store.AccessToken
            End If
        End If

        ' 2) Versuche Refresh, falls vorhanden
        If store IsNot Nothing AndAlso Not String.IsNullOrWhiteSpace(store.RefreshToken) Then
            store = TryRefresh(store.RefreshToken)
        End If

        ' 3) Fallback: Password-Grant Login
        If store Is Nothing OrElse String.IsNullOrWhiteSpace(store.AccessToken) Then
            store = PasswordLogin()
        End If

        ' Validierung
        If store Is Nothing OrElse String.IsNullOrWhiteSpace(store.AccessToken) Then
            Throw New ApplicationException("Konnte keinen gültigen Access Token erhalten (leer).")
        End If

        ' Persistieren & zurück
        SaveStore(store)
        Return store.AccessToken
    End Function

    ' ======= INTERNES =======
    Private Shared Function PasswordLogin() As TokenStore
        Dim form = New Dictionary(Of String, String) From {
            {"grant_type", "password"},
            {"username", USERNAME},
            {"password", PASSWORD},
            {"client_id", CLIENT_ID}
        }

        Dim resp = PostForm(form)
        Dim token = ParseTokenResponse(resp)

        Return token
    End Function

    Private Shared Function TryRefresh(refreshToken As String) As TokenStore
        Try
            Dim form = New Dictionary(Of String, String) From {
                {"grant_type", "refresh_token"},
                {"refresh_token", refreshToken},
                {"client_id", CLIENT_ID}
            }
            Dim resp = PostForm(form)
            Dim token = ParseTokenResponse(resp)

            ' Nur speichern, wenn ein Access Token vorhanden ist
            If Not String.IsNullOrWhiteSpace(token.AccessToken) Then
                SaveStore(token)
                Return token
            End If
        Catch ex As Exception
            ' Ignorieren -> fällt auf PasswordLogin zurück
        End Try

        Return Nothing
    End Function

    Private Shared Function PostForm(formFields As Dictionary(Of String, String)) As String
        Using client As New HttpClient()
            Using content As New FormUrlEncodedContent(formFields)
                Dim response = client.PostAsync(TOKEN_ENDPOINT, content).Result
                Dim body = response.Content.ReadAsStringAsync().Result

                If Not response.IsSuccessStatusCode Then
                    Throw New ApplicationException(
                        $"Token-Endpoint Fehler ({CInt(response.StatusCode)}): {body}")
                End If

                Return body
            End Using
        End Using
    End Function

    Private Shared Function ParseTokenResponse(json As String) As TokenStore
        Dim r = JsonConvert.DeserializeObject(Of TokenResponse)(json)

        If r Is Nothing OrElse String.IsNullOrWhiteSpace(r.access_token) Then
            Throw New ApplicationException("Token-Antwort ungültig oder ohne access_token.")
        End If

        Dim now = DateTimeOffset.UtcNow
        Dim expiresIn = If(r.expires_in <= 0, 3600, r.expires_in) ' Fallback 1h

        Dim store = New TokenStore With {
        .AccessToken = r.access_token.Trim(),
        .RefreshToken = If(r.refresh_token, String.Empty),
        .ExpiresAtUtc = now.AddSeconds(expiresIn)
    }

        ' === Konsolen-Ausgabe ===
        Console.WriteLine("== Neuer Token erhalten ==")
        Console.WriteLine("Access Token: " & store.AccessToken)
        Console.WriteLine("Refresh Token: " & store.RefreshToken)
        Console.WriteLine("Gültig bis UTC: " & store.ExpiresAtUtc.ToString("yyyy-MM-dd HH:mm:ss"))

        Return store
    End Function

    ' ======= PERSISTENZ =======
    Private Shared Function LoadStore() As TokenStore
        Try
            If File.Exists(StorePath) Then
                Dim json = File.ReadAllText(StorePath, Encoding.UTF8)
                Dim s = JsonConvert.DeserializeObject(Of TokenStore)(json)
                ' Ausgabe in Konsole
                If s IsNot Nothing Then
                    Console.WriteLine("== Token aus Datei geladen ==")
                    Console.WriteLine("Access Token: " & (If(String.IsNullOrWhiteSpace(s.AccessToken), "<leer>", s.AccessToken)))
                    Console.WriteLine("Refresh Token: " & (If(String.IsNullOrWhiteSpace(s.RefreshToken), "<leer>", s.RefreshToken)))
                    Console.WriteLine("Gültig bis UTC: " & s.ExpiresAtUtc.ToString("yyyy-MM-dd HH:mm:ss"))
                End If
                Return s
            Else
                ' Datei existiert nicht -> Info ausgeben
                Console.WriteLine("Keine Token-Datei vorhanden, neuer Login erforderlich.")
            End If
        Catch ex As Exception
            Console.WriteLine("Fehler beim Laden der Token-Datei: " & ex.Message)
            ' Datei defekt? -> Ignorieren, neu holen
        End Try
        Return Nothing
    End Function

    Private Shared Sub SaveStore(store As TokenStore)
        Try
            Dim dir = Path.GetDirectoryName(StorePath)
            If Not Directory.Exists(dir) Then Directory.CreateDirectory(dir)

            ' Datei immer neu schreiben/überschreiben
            Dim json = JsonConvert.SerializeObject(store, Formatting.Indented)
            File.WriteAllText(StorePath, json, Encoding.UTF8)

            Console.WriteLine("Token-Datei gespeichert: " & StorePath)
        Catch ex As Exception
            Console.WriteLine("Fehler beim Speichern der Token-Datei: " & ex.Message)
        End Try
    End Sub

    ' ======= DTOs =======
    Private Class TokenResponse
        Public Property access_token As String
        Public Property expires_in As Integer
        Public Property refresh_expires_in As Integer
        Public Property refresh_token As String
        Public Property token_type As String
        Public Property scope As String
        ' … weitere Felder bei Bedarf
    End Class

    Private Class TokenStore
        Public Property AccessToken As String
        Public Property RefreshToken As String
        Public Property ExpiresAtUtc As DateTimeOffset
    End Class

End Class