Imports System.IO
Imports System.Xml
Imports System.Xml.XPath
Imports DigitalData.Modules.Logging

Namespace Schemas
    Public Class SchemaLoader
        Inherits BaseClass

        Private ReadOnly ns As XNamespace = "http://www.w3.org/2001/XMLSchema"

        Public SchemaList As List(Of FileInfo)

        Public Sub New(pLogConfig As LogConfig)
            MyBase.New(pLogConfig, pLogConfig.GetLogger)
        End Sub

        Public Function LoadFiles(pSchemaDirectory) As Boolean
            If pSchemaDirectory = String.Empty Then
                Throw New ArgumentNullException("SchemaDirectory")
            End If

            Logger.Info("Loading files from directory [{0}]", pSchemaDirectory)

            Try
                Dim oDirectory As New DirectoryInfo(pSchemaDirectory)
                Dim oFiles = oDirectory.GetFiles()

                Logger.Debug("Found [{0}] files in directory [{1}]", oFiles.Count, oDirectory)

                SchemaList = oFiles.ToList()

                Return True

            Catch ex As Exception
                Logger.Error(ex)
                Throw New IO.IOException($"Could not load files from directory {pSchemaDirectory}", ex)

            End Try
        End Function

        Public Function GetSchemaFromFile(pSchemaFilePath As String) As Schema
            Dim oSchema As New Schema
            Dim oFileInfo As New FileInfo(pSchemaFilePath)
            Dim oElements = GetSchemaElements(pSchemaFilePath)

            oSchema.Name = oFileInfo.Name

            For Each oElement In oElements
                Dim oColumns = GetElementColumns(oElement)
                Dim oSchemaColumns As New List(Of Schema.Column)

                For Each oColumn As XElement In oColumns
                    Dim oName = XmlData.GetElementAttribute(oColumn, "name")
                    Dim oMinOccurs = XmlData.GetElementAttribute(oColumn, "minOccurs")
                    Dim oMaxOccurs = XmlData.GetElementAttribute(oColumn, "maxOccurs")
                    Dim oType = GetElementType(oColumn)
                    Dim oRequired = False

                    If oMinOccurs = 1 And oMaxOccurs = 1 Then
                        oRequired = True
                    End If

                    Dim oSchemaColumn As New Schema.Column With {
                        .Name = oName,
                        .Required = oRequired,
                        .DataType = oType
                    }
                    oSchemaColumns.Add(oSchemaColumn)
                Next

                oSchema.Tables.Add(New Schema.Table With {
                    .Name = XmlData.GetElementAttribute(oElement, "name"),
                    .Columns = oSchemaColumns
                })

            Next

            Return oSchema
        End Function

        Public Function GetElementType(pElement As XElement) As Constants.ColumnType
            Dim oTypeString = XmlData.GetElementAttribute(pElement, "type")

            If oTypeString Is Nothing Then
                Dim oRestrictionElement As XElement = pElement.
                    Descendants(ns + "restriction").
                    FirstOrDefault()

                oTypeString = XmlData.GetElementAttribute(oRestrictionElement, "base")
            End If

            Select Case oTypeString
                Case "xs:date"
                    Return Constants.ColumnType.Date
                Case "xs:integer"
                    Return Constants.ColumnType.Integer
                Case "xs:decimal"
                    Return Constants.ColumnType.Decimal
                Case "xs:boolean"
                    Return Constants.ColumnType.Boolean
                Case Else
                    Return Constants.ColumnType.String
            End Select
        End Function

        Public Function GetSchemaElements(pSchemaFilePath As String) As List(Of XElement)
            Dim oText As String = IO.File.ReadAllText(pSchemaFilePath)
            Dim oDoc = XDocument.Parse(oText)

            Return XmlData.GetElementsFromElement(oDoc, "choice", ns)
        End Function

        Public Function GetElementColumns(pElement As XElement) As List(Of XElement)
            Return XmlData.GetElementsFromElement(pElement, "sequence", ns)
        End Function
    End Class

End Namespace