Imports FirebirdSql.Data.FirebirdClient
Public Class Firebird
    Private Shared Logger As NLog.Logger = NLog.LogManager.GetCurrentClassLogger
    Public DBInitialized As Boolean = False
    Private _connectionEstablished As Boolean = False
    Private _connectionFailed As Boolean = False
    Private ReadOnly dataSource As String
    Private ReadOnly database As String
    Private ReadOnly user As String
    Private ReadOnly password As String
    Public CurrentFBDConnectionString As String = ""
    Public ReadOnly Property ConnectionString As String
    Public ReadOnly Property ConnectionEstablished As Boolean
        Get
            Return _connectionEstablished
        End Get
    End Property

    Public ReadOnly Property ConnectionFailed As Boolean
        Get
            Return _connectionFailed
        End Get
    End Property
    Public Sub New(dataSource As String, database As String, user As String, password As String)
        ConnectionString = BuildConnectionString(dataSource, database, user, password)
        ' Save connection credentials
        dataSource = dataSource
        database = database
        user = user
        password = password
        ' Test the connection first
        Dim conn = Connect(ConnectionString)
        ' If initial connection was successfully, close it
        conn?.Close()
    End Sub

    Private Function Connect(ConnectionString As String) As FbConnection
        Try
            Dim conn = New FbConnection(ConnectionString)
            conn.Open()
            _connectionEstablished = True
            _connectionFailed = False
            Logger.Debug("Connection established!")
            Logger.Debug($"User: {user}")
            Logger.Debug($"DatabaseLocation: {database}")
            Logger.Debug($"DatabaseServer: {dataSource}")

            Return conn
        Catch ex As Exception
            _connectionFailed = True
            _connectionEstablished = False
            Logger.Error(ex)

            Return Nothing
        End Try
    End Function

    ''' <summary>
    ''' Builds a connectionstring from the provided arguments.
    ''' </summary>
    ''' <param name="dataSource">The database server where to connect to</param>
    ''' <param name="database">The datasource, eg. the path of the FDB-file</param>
    ''' <param name="user">The user used to connect to the database</param>
    ''' <param name="password">The password of the connecting user</param>
    ''' <returns>A connectionstring</returns>
    Private Function BuildConnectionString(dataSource As String, database As String, user As String, password As String) As String
        Dim connectionStringBuilder = New FbConnectionStringBuilder With {
            .DataSource = dataSource,
            .Database = database,
            .UserID = user,
            .Password = password
        }
        Return connectionStringBuilder.ConnectionString
    End Function

    ''' <summary>
    ''' Executes a non-query command.
    ''' </summary>
    ''' <param name="sqlCommand">The command to execute</param>
    ''' <returns>True, if command was executed sucessfully. Otherwise false.</returns>
    Public Function NewExecuteNonQuery(sqlCommand As String) As Boolean
        Try
            Dim conn As FbConnection = Connect(ConnectionString)

            If conn Is Nothing Then
                Return False
            End If

            Dim transaction As FbTransaction = conn.BeginTransaction()
            Dim command As New FbCommand With {
                .CommandText = sqlCommand,
                .Connection = conn,
                .Transaction = transaction
            }
            command.ExecuteNonQuery()

            transaction.Commit()
            conn.Close()

            Return True
        Catch ex As Exception
            Logger.Error(ex, $"Error in ExecuteNonQuery while executing command: '{sqlCommand}'")
            Return False
        End Try
    End Function

    ''' <summary>
    ''' Executes a sql query resulting in a scalar value.
    ''' </summary>
    ''' <param name="sqlQuery">The query to execute</param>
    ''' <returns>The scalar value if the command was executed successfully. Nothing otherwise.</returns>
    Public Function GetExecuteScalar(sqlQuery As String) As Object
        Try
            Dim conn As FbConnection = Connect(ConnectionString)

            If conn Is Nothing Then
                Return Nothing
            End If

            Dim transaction As FbTransaction = conn.BeginTransaction()
            Dim command As New FbCommand With {
                .CommandText = sqlQuery,
                .Connection = conn,
                .Transaction = transaction
            }
            Dim result As Object = command.ExecuteScalar()

            transaction.Commit()
            conn.Close()

            Return result
        Catch ex As Exception
            Logger.Error(ex, $"Error in ReturnScalar while executing command: '{sqlQuery}'")
            Return Nothing
        End Try
    End Function

    ''' <summary>
    ''' Executes a sql query resulting in a table of values.
    ''' </summary>
    ''' <param name="sqlQuery">The query to execute</param>
    ''' <returns>A datatable containing the results if the command was executed successfully. Nothing otherwise.</returns>
    Public Function GetDatatable(sqlQuery As String) As DataTable
        Try
            Dim conn As FbConnection = Connect(ConnectionString)

            If conn Is Nothing Then
                Return Nothing
            End If

            Dim command As New FbCommand With {
                .CommandText = sqlQuery,
                .Connection = conn
            }
            Dim adapter As New FbDataAdapter(command)
            Dim dt As New DataTable()

            adapter.Fill(dt)
            conn.Close()

            Return dt
        Catch ex As Exception
            Logger.Error(ex, $"Error in ReturnDatatable while executing command: '{sqlQuery}'")
            Return Nothing
        End Try
    End Function
End Class