Imports System.DirectoryServices
Imports System.DirectoryServices.AccountManagement
Imports DigitalData.Modules.Database
Imports DigitalData.Modules.Logging

Public Class ActiveDirectoryInterface
    Private _logConfig As LogConfig
    Private _logger As Logger
    Private _firebird As Firebird

    Private _rootPath As String
    Private _rootNode As DirectoryEntry

    Private Const SEARCH_LIMIT = 50000

    Private Const SAMACCOUNTNAME = "samaccountname"
    Private Const OBJECTCLASS = "objectClass"
    Private Const CN = "cn"
    Private Const DESCRIPTION = "description"
    Private Const DISINGUISHEDNAME = "distinguishedName"
    Private Const NAME = "name"
    Private Const OBJECTCATEGORY = "objectCategory"

    Public Sub New(LogConfig As LogConfig, Firebird As Firebird, Optional RootPath As String = Nothing)
        _logConfig = LogConfig
        _logger = _logConfig.GetLogger()
        _firebird = Firebird

        If RootPath Is Nothing Then
            _rootPath = $"LDAP://{Environment.UserDomainName}"
        Else
            _rootPath = RootPath
        End If
    End Sub

    Public Function SyncUsersForGroup(GroupName As String) As List(Of ADUser)
        Dim oUsers As New List(Of ADUser)
        Dim oSyncedUsers As New List(Of ADUser)
        Dim oGroupId As Int64 = Nothing

        Try
            _logger.Debug("Fetching users from ActiveDirectory")
            oUsers = ListUsers(GroupName)
            _logger.Debug("Found {0} users", oUsers.Count)
        Catch ex As Exception
            _logger.Error(ex)
            Return Nothing
        End Try

        If oUsers.Count = 0 Then
            _logger.Debug("Group {0} does not contain any users.", GroupName)
            Return oSyncedUsers
        End If

        Try
            _logger.Debug("Getting group Id for group {0}", GroupName)
            oGroupId = GetGroupId(GroupName)


            If oGroupId = 0 Then
                _logger.Warn("Group {0} does not exist in database. Exiting", GroupName)
                Return Nothing
            End If

            _logger.Debug("Using group Id {0}", oGroupId)
        Catch ex As Exception
            _logger.Error(ex)
            Return Nothing
        End Try

        For Each oUser In oUsers
            Dim oUserId As Int64
            Dim oUserExists As Boolean = False

            ' Check if user already exists
            Try
                _logger.Debug("Checking if user {0} exists", oUser)
                oUserId = GetUserId(oUser.samAccountName)
                oUserExists = Not IsNothing(oUserId)
                _logger.Debug("User {0} exists in database: ", oUser, oUserExists)
            Catch ex As Exception
                _logger.Error(ex)
                _logger.Warn("Could not get UserId for user. Skipping")
                Continue For
            End Try

            ' I user does not exist, create a new user
            Try
                If Not oUserExists Then
                    _logger.Debug("Creating new user for {0}", oUser)
                    oUserId = CreateUser(oUser)
                    _logger.Debug("User created with Id {0}", oUserId)
                End If
            Catch ex As Exception
                _logger.Error(ex)
                _logger.Warn("Could not create user. Skipping")
                Continue For
            End Try

            ' Add the user to group
            Try
                AddUserToGroup(oUserId, oGroupId)
            Catch ex As Exception
                _logger.Error(ex)
                _logger.Warn("Could not add user to group. Skipping")
                Continue For
            End Try

            oSyncedUsers.Add(oUser)
        Next

        Return oSyncedUsers
    End Function

    Public Function Authenticate() As Boolean
        Try
            Dim oEntry = GetRootNode()
            oEntry.RefreshCache()

            _rootNode = oEntry
            Return True
        Catch ex As Exception
            _logger.Error(ex)
            _logger.Warn("Could not authenticate with Active Directory.")
            Return False
        End Try
    End Function
    Public Function Authenticate(Username As String, Password As String) As Boolean
        Try
            Dim oEntry = GetRootNode(Username, Password)
            oEntry.RefreshCache()

            _rootNode = oEntry
            Return True
        Catch ex As Exception
            _logger.Error(ex)
            _logger.Warn("Could not authenticate with Active Directory.")
            Return False
        End Try
    End Function

    Public Function ListGroups(Optional Query As String = "(&(objectClass=group) (samAccountName=*))") As List(Of ADGroup)
        Return ListGroups(_rootNode, Query)
    End Function
    Public Function ListGroups(RootNode As DirectoryEntry, Optional Query As String = "(&(objectClass=group) (samAccountName=*))") As List(Of ADGroup)
        Dim oGroups As New List(Of ADGroup)

        Try
            Dim oDirectorySearcher As New DirectorySearcher(RootNode) With {
                .SearchScope = SearchScope.Subtree,
                .SizeLimit = SEARCH_LIMIT,
                .Filter = Query
            }
            Dim oResults As SearchResultCollection = oDirectorySearcher.FindAll()

            _logger.Info("Found {0} Groups.", oResults.Count)

            Return GroupResultsToList(oResults)
        Catch ex As Exception
            _logger.Error(ex)
            Return oGroups
        End Try
    End Function

    Public Function ListUsers(GroupName As String) As List(Of ADUser)
        Dim oUsers As New List(Of ADUser)

        Try
            Using oContext As New PrincipalContext(ContextType.Domain)
                Using oGroupPrincipal As GroupPrincipal = GroupPrincipal.FindByIdentity(oContext, IdentityType.Name, GroupName)
                    If oGroupPrincipal Is Nothing Then
                        _logger.Warn("Group {0} does not exist.", GroupName)
                        Return oUsers
                    End If

                    Using oMembers = oGroupPrincipal.GetMembers(True)
                        For Each oMember As Principal In oMembers
                            If TypeOf oMember Is UserPrincipal Then
                                Dim oUser As UserPrincipal = DirectCast(oMember, UserPrincipal)

                                oUsers.Add(New ADUser() With {
                                    .GUID = oUser.Guid,
                                    .SId = oUser.Sid,
                                    .samAccountName = oUser.SamAccountName,
                                    .Surname = oUser.Surname,
                                    .Middlename = oUser.MiddleName,
                                    .GivenName = oUser.GivenName,
                                    .Email = oUser.EmailAddress
                                })
                            End If
                        Next
                    End Using
                End Using
            End Using

            Return oUsers
        Catch ex As Exception
            _logger.Error(ex)
            Throw ex
        End Try
    End Function

    Private Function GetGroupId(GroupName As String) As Integer
        Try
            Dim oSQL As String = $"SELECT FNICM_GET_RECORD4SYSKEY('{GroupName}','002-NAME') from RDB$DATABASE"
            Dim oGroupId = _firebird.GetScalarValue(oSQL)

            If IsDBNull(oGroupId) OrElse oGroupId = 0 Then
                _logger.Debug("Group {0} not found in database", GroupName)
                Return Nothing
            End If

            Return oGroupId
        Catch ex As Exception
            _logger.Error(ex)
            Throw ex
        End Try
    End Function

    Private Function GetUserId(UserName As String) As Integer
        Try
            Dim oSQL As String = $"SELECT FNICM_GET_RECORD4SYSKEY('{UserName}','001-USRNAME') from RDB$DATABASE"
            Dim oResult = _firebird.GetScalarValue(oSQL)

            If IsDBNull(oResult) Then
                Return Nothing
            End If

            Return oResult
        Catch ex As Exception
            _logger.Error(ex)
            Throw ex
        End Try
    End Function

    Private Function CreateUser(User As ADUser) As Int64
        Try
            Dim oSQL = $"SELECT FNICM_RADM_NEW_USER('{User.GivenName}', '{User.Surname}', '{User.samAccountName}', 'AD-Sync') from RDB$DATABASE"
            Dim oUserId As Integer = _firebird.GetScalarValue(oSQL)

            Return oUserId
        Catch ex As Exception
            _logger.Error(ex)
            Throw ex
        End Try
    End Function

    Private Function AddUserToGroup(UserId As Integer, GroupId As Integer) As Int64
        Try
            Dim oSQL = $"SELECT FNICM_RADM_NEW_USER2GROUP({UserId}, {GroupId}, 'AD-Sync') from RDB$DATABASE"
            Dim oRecordId = _firebird.GetScalarValue(oSQL)

            If IsDBNull(oRecordId) Then
                _logger.Warn("UserId {0} - GroupId {1} relation already exists.", UserId, GroupId)
                Return Nothing
            End If

            Return oRecordId
        Catch ex As Exception
            _logger.Error(ex)
            Throw ex
        End Try
    End Function

    Private Function GetRootNode() As DirectoryEntry
        Dim oEntry As New DirectoryEntry(_rootPath) With {
            .AuthenticationType = AuthenticationTypes.Secure,
            .Password = Nothing,
            .Username = Nothing
        }

        Return oEntry
    End Function
    Private Function GetRootNode(Username As String, Password As String) As DirectoryEntry
        Dim oEntry As New DirectoryEntry(_rootPath) With {
            .AuthenticationType = AuthenticationTypes.Secure,
            .Password = Username,
            .Username = Password
        }

        Return oEntry
    End Function

    Private Function GroupResultsToList(Results As SearchResultCollection) As List(Of ADGroup)
        Dim oGroups As New List(Of ADGroup)

        For Each oResult As SearchResult In Results
            oGroups.Add(New ADGroup() With {
                .Name = TryGetProperty(oResult, NAME),
                .SAMAccountName = TryGetProperty(oResult, SAMACCOUNTNAME),
                .CN = TryGetProperty(oResult, CN),
                .Description = TryGetProperty(oResult, DESCRIPTION),
                .DistinguishedName = TryGetProperty(oResult, DISINGUISHEDNAME),
                .ObjectCategory = TryGetProperty(oResult, OBJECTCATEGORY),
                .ObjectClass = TryGetProperty(oResult, OBJECTCLASS)
            })
        Next

        Return oGroups
    End Function

    Private Function TryGetProperty(Result As SearchResult, PropertyName As String) As String
        Try
            Return Result.Properties.Item(PropertyName).Item(0)
        Catch ex As Exception
            _logger.Warn("Property {0} not found")
            Return String.Empty
        End Try
    End Function
End Class