Sql

0.6.0

src/Mapping/DataMapper.psm1

using namespace System.Collections
using namespace System.ComponentModel.DataAnnotations.Schema
using namespace System.Diagnostics.CodeAnalysis
using namespace System.Reflection

<#
.SYNOPSIS
    Maps data records to entity objects.
#>
class DataMapper {

    <#
    .SYNOPSIS
        The property maps, keyed by type.
    #>
    hidden static [hashtable] $PropertyMaps = @{}

    <#
    .SYNOPSIS
        Creates a new object of a given type from the specified data record.
    .PARAMETER Type
        The object type.
    .PARAMETER Record
        A data record providing the properties to be set on the created object.
    .OUTPUTS
        The newly created object.
    #>
    [SuppressMessage("PSUseDeclaredVarsMoreThanAssignments", "")]
    [object] CreateInstance([type] $Type, [System.Data.IDataRecord] $Record) {
        $properties = @{}
        for ($index = 0; $index -lt $Record.FieldCount; $index++) {
            $key = $Record.GetName($index)
            $properties.$key = $Record.IsDBNull($index) ? $null : $Record.GetValue($index)
        }

        return $discard = switch ($Type) {
            ([hashtable]) { $properties; break }
            ([psobject]) { [pscustomobject] $properties; break }
            default { $this.CreateInstance($Type, $properties) }
        }
    }

    <#
    .SYNOPSIS
        Creates a new object of a given type from the specified hash table.
    .PARAMETER Type
        The object type.
    .PARAMETER Properties
        A hash table providing the properties to be set on the created object.
    .OUTPUTS
        The newly created object.
    #>
    [object] CreateInstance([type] $Type, [hashtable] $Properties) {
        $culture = [cultureinfo]::InvariantCulture
        $object = $Type::new()
        $propertyMap = $this.GetPropertyMap($Type)

        foreach ($key in $Properties.Keys.Where{ $_ -in $propertyMap.Keys }) {
            $propertyInfo = $propertyMap.$key
            $propertyType = [Nullable]::GetUnderlyingType($propertyInfo.PropertyType) ?? $propertyInfo.PropertyType
            $value = $Properties.$key

            $object.$($propertyInfo.Name) = switch ($true) {
                ($null -eq $value) { $null; break }
                ($propertyType.IsEnum) { [Enum]::ToObject($propertyType, $value); break }
                default { [Convert]::ChangeType($value, $propertyType, $culture) }
            }
        }

        return $object
    }

    <#
    .SYNOPSIS
        Creates new objects of a given type from the specified data reader.
    .PARAMETER Type
        The object type.
    .PARAMETER Reader
        A data reader providing the properties to be set on the created objects.
    .OUTPUTS
        An array of newly created objects.
    #>
    [object[]] CreateInstances([type] $Type, [System.Data.IDataReader] $Reader) {
        $list = [ArrayList]::new()
        while ($Reader.Read()) { $list.Add($this.CreateInstance($Type, $Reader)) }
        $Reader.Close()
        return $list.ToArray()
    }

    <#
    .SYNOPSIS
        Retrives a hash table of mapped properties of the specified type.
    .PARAMETER Type
        The type to inspect.
    .OUTPUTS
        The hash table of mapped properties of the specified type.
    #>
    [hashtable] GetPropertyMap([type] $Type) {
        if ($Type -in [DataMapper]::PropertyMaps.Keys) { return [DataMapper]::PropertyMaps.$Type }

        $propertyMap = @{}
        $propertyInfos = $Type.GetProperties([BindingFlags]::Instance -bor [BindingFlags]::Public)
        foreach ($propertyInfo in $propertyInfos.Where{ $_.CanWrite -and (-not [Attribute]::IsDefined($_, ([NotMappedAttribute])))}) {
            $column = [Attribute]::GetCustomAttribute($propertyInfo, ([ColumnAttribute]))
            $propertyMap.$($column ? $column.Name : $propertyInfo.Name) = $propertyInfo
        }

        return [DataMapper]::PropertyMaps.$Type = $propertyMap
    }
}