gistfile1.txt

Function New-DynamicParameter {
    [CmdletBinding(PositionalBinding = $false, DefaultParameterSetName = 'DynamicParameter')]
    Param
    (
        [Parameter(Mandatory = $true, ValueFromPipeline = $true, ValueFromPipelineByPropertyName = $true, ParameterSetName = 'DynamicParameter')]
        [ValidateNotNullOrEmpty()]
        [string]$Name,

        [Parameter(ValueFromPipelineByPropertyName = $true, 
            ParameterSetName = 'DynamicParameter')]
        [System.Type]$Type = [int],

        [Parameter(ValueFromPipelineByPropertyName = $true, 
            ParameterSetName = 'DynamicParameter')]
        [string[]]$Alias,

        [Parameter(ValueFromPipelineByPropertyName = $true, 
            ParameterSetName = 'DynamicParameter')]
        [switch]$Mandatory,

        [Parameter(ValueFromPipelineByPropertyName = $true, 
            ParameterSetName = 'DynamicParameter')]
        [int]$Position,

        [Parameter(ValueFromPipelineByPropertyName = $true, 
            ParameterSetName = 'DynamicParameter')]
        [string]$HelpMessage,

        [Parameter(ValueFromPipelineByPropertyName = $true, 
            ParameterSetName = 'DynamicParameter')]
        [switch]$DontShow,

        [Parameter(ValueFromPipelineByPropertyName = $true, 
            ParameterSetName = 'DynamicParameter')]
        [switch]$ValueFromPipeline,

        [Parameter(ValueFromPipelineByPropertyName = $true, 
            ParameterSetName = 'DynamicParameter')]
        [switch]$ValueFromPipelineByPropertyName,

        [Parameter(ValueFromPipelineByPropertyName = $true, 
            ParameterSetName = 'DynamicParameter')]
        [switch]$ValueFromRemainingArguments,

        [Parameter(ValueFromPipelineByPropertyName = $true, 
            ParameterSetName = 'DynamicParameter')]
        [string]$ParameterSetName = '__AllParameterSets',

        [Parameter(ValueFromPipelineByPropertyName = $true, 
            ParameterSetName = 'DynamicParameter')]
        [switch]$AllowNull,

        [Parameter(ValueFromPipelineByPropertyName = $true, 
            ParameterSetName = 'DynamicParameter')]
        [switch]$AllowEmptyString,

        [Parameter(ValueFromPipelineByPropertyName = $true, 
            ParameterSetName = 'DynamicParameter')]
        [switch]$AllowEmptyCollection,

        [Parameter(ValueFromPipelineByPropertyName = $true, 
            ParameterSetName = 'DynamicParameter')]
        [switch]$ValidateNotNull,

        [Parameter(ValueFromPipelineByPropertyName = $true, 
            ParameterSetName = 'DynamicParameter')]
        [switch]$ValidateNotNullOrEmpty,

        [Parameter(ValueFromPipelineByPropertyName = $true, 
            ParameterSetName = 'DynamicParameter')]
        [ValidateCount(2, 2)]
        [int[]]$ValidateCount,

        [Parameter(ValueFromPipelineByPropertyName = $true, 
            ParameterSetName = 'DynamicParameter')]
        [ValidateCount(2, 2)]
        [int[]]$ValidateRange,

        [Parameter(ValueFromPipelineByPropertyName = $true, 
            ParameterSetName = 'DynamicParameter')]
        [ValidateCount(2, 2)]
        [int[]]$ValidateLength,

        [Parameter(ValueFromPipelineByPropertyName = $true, 
            ParameterSetName = 'DynamicParameter')]
        [ValidateNotNullOrEmpty()]
        [string]$ValidatePattern,

        [Parameter(ValueFromPipelineByPropertyName = $true, 
            ParameterSetName = 'DynamicParameter')]
        [ValidateNotNullOrEmpty()]
        [scriptblock]$ValidateScript,

        [Parameter(ValueFromPipelineByPropertyName = $true, 
            ParameterSetName = 'DynamicParameter')]
        [ValidateNotNullOrEmpty()]
        [string[]]$ValidateSet,

        [Parameter(ValueFromPipelineByPropertyName = $true, 
            ParameterSetName = 'DynamicParameter')]
        [ValidateNotNullOrEmpty()]
        [ValidateScript( {
                if (!($_ -is [System.Management.Automation.RuntimeDefinedParameterDictionary])) {
                    Throw 'Dictionary must be a System.Management.Automation.RuntimeDefinedParameterDictionary object'
                }
                $true
            })]
        $Dictionary = $false,

        [Parameter(Mandatory = $true, 
            ValueFromPipelineByPropertyName = $true, 
            ParameterSetName = 'CreateVariables')]
        [switch]$CreateVariables,

        [Parameter(Mandatory = $true, 
            ValueFromPipelineByPropertyName = $true, 
            ParameterSetName = 'CreateVariables')]
        [ValidateNotNullOrEmpty()]
        [ValidateScript( {
                # System.Management.Automation.PSBoundParametersDictionary is an internal sealed class,
                # so one can't use PowerShell's '-is' operator to validate type.
                if ($_.GetType().Name -ne 'PSBoundParametersDictionary') {
                    Throw 'BoundParameters must be a System.Management.Automation.PSBoundParametersDictionary object'
                }
                $true
            })]
        $BoundParameters
    )

    Begin {
        Write-Verbose 'Creating new dynamic parameters dictionary'
        $InternalDictionary = New-Object -TypeName System.Management.Automation.RuntimeDefinedParameterDictionary

        Write-Verbose 'Getting common parameters'
        function _temp { [CmdletBinding()] Param() }
        $CommonParameters = (Get-Command _temp).Parameters.Keys
    }

    Process {
        if ($CreateVariables) {
            Write-Verbose 'Creating variables from bound parameters'
            Write-Debug 'Picking out bound parameters that are not in common parameters set'
            $BoundKeys = $BoundParameters.Keys | Where-Object { $CommonParameters -notcontains $_ }

            foreach ($Parameter in $BoundKeys) {
                Write-Debug "Setting existing variable for dynamic parameter '$Parameter' with value '$($BoundParameters.$Parameter)'"
                Set-Variable -Name $Parameter -Value $BoundParameters.$Parameter -Scope 1 -Force
            }
        }
        else {
            Write-Verbose 'Looking for cached bound parameters'
            Write-Debug 'More info: https://beatcracker.wordpress.com/2014/12/18/psboundparameters-pipeline-and-the-valuefrompipelinebypropertyname-parameter-attribute'
            $StaleKeys = @()
            $StaleKeys = $PSBoundParameters.GetEnumerator() |
                ForEach-Object {
                if ($_.Value.PSobject.Methods.Name -match '^Equals$') {
                    # If object has Equals, compare bound key and variable using it
                    if (!$_.Value.Equals((Get-Variable -Name $_.Key -ValueOnly -Scope 0))) {
                        $_.Key
                    }
                }
                else {
                    # If object doesn't has Equals (e.g. $null), fallback to the PowerShell's -ne operator
                    if ($_.Value -ne (Get-Variable -Name $_.Key -ValueOnly -Scope 0)) {
                        $_.Key
                    }
                }
            }
            if ($StaleKeys) {
                "Found $($StaleKeys.Count) cached bound parameters:", $StaleKeys | Write-Debug
                Write-Verbose 'Removing cached bound parameters'
                $StaleKeys | ForEach-Object {[void]$PSBoundParameters.Remove($_)}
            }

            # Since we rely solely on $PSBoundParameters, we don't have access to default values for unbound parameters
            Write-Verbose 'Looking for unbound parameters with default values'

            Write-Debug 'Getting unbound parameters list'
            $UnboundParameters = (Get-Command -Name ($PSCmdlet.MyInvocation.InvocationName)).Parameters.GetEnumerator()  |
                # Find parameters that are belong to the current parameter set
            Where-Object { $_.Value.ParameterSets.Keys -contains $PsCmdlet.ParameterSetName } |
                Select-Object -ExpandProperty Key |
                # Find unbound parameters in the current parameter set
            Where-Object { $PSBoundParameters.Keys -notcontains $_ }

            # Even if parameter is not bound, corresponding variable is created with parameter's default value (if specified)
            Write-Debug 'Trying to get variables with default parameter value and create a new bound parameter''s'
            $tmp = $null
            foreach ($Parameter in $UnboundParameters) {
                $DefaultValue = Get-Variable -Name $Parameter -ValueOnly -Scope 0
                if (!$PSBoundParameters.TryGetValue($Parameter, [ref]$tmp) -and $DefaultValue) {
                    $PSBoundParameters.$Parameter = $DefaultValue
                    Write-Debug "Added new parameter '$Parameter' with value '$DefaultValue'"
                }
            }

            if ($Dictionary) {
                Write-Verbose 'Using external dynamic parameter dictionary'
                $DPDictionary = $Dictionary
            }
            else {
                Write-Verbose 'Using internal dynamic parameter dictionary'
                $DPDictionary = $InternalDictionary
            }

            Write-Verbose "Creating new dynamic parameter: $Name"

            # Shortcut for getting local variables
            $GetVar = {Get-Variable -Name $_ -ValueOnly -Scope 0}

            # Strings to match attributes and validation arguments
            $AttributeRegex = '^(Mandatory|Position|ParameterSetName|DontShow|ValueFromPipeline|ValueFromPipelineByPropertyName|ValueFromRemainingArguments)$'
            $ValidationRegex = '^(AllowNull|AllowEmptyString|AllowEmptyCollection|ValidateCount|ValidateLength|ValidatePattern|ValidateRange|ValidateScript|ValidateSet|ValidateNotNull|ValidateNotNullOrEmpty)$'
            $AliasRegex = '^Alias$'

            Write-Debug 'Creating new parameter''s attirubutes object'
            $ParameterAttribute = New-Object -TypeName System.Management.Automation.ParameterAttribute

            Write-Debug 'Looping through the bound parameters, setting attirubutes...'
            switch -regex ($PSBoundParameters.Keys) {
                $AttributeRegex {
                    Try {
                        $ParameterAttribute.$_ = . $GetVar
                        Write-Debug "Added new parameter attribute: $_"
                    }
                    Catch {
                        $_
                    }
                    continue
                }
            }

            if ($DPDictionary.Keys -contains $Name) {
                Write-Verbose "Dynamic parameter '$Name' already exist, adding another parameter set to it"
                $DPDictionary.$Name.Attributes.Add($ParameterAttribute)
            }
            else {
                Write-Verbose "Dynamic parameter '$Name' doesn't exist, creating"

                Write-Debug 'Creating new attribute collection object'
                $AttributeCollection = New-Object -TypeName Collections.ObjectModel.Collection[System.Attribute]

                Write-Debug 'Looping through bound parameters, adding attributes'
                switch -regex ($PSBoundParameters.Keys) {
                    $ValidationRegex {
                        Try {
                            $ParameterOptions = New-Object -TypeName "System.Management.Automation.$_`Attribute" -ArgumentList (. $GetVar) -ErrorAction SilentlyContinue
                            $AttributeCollection.Add($ParameterOptions)
                            Write-Debug "Added attribute: $_"
                        }
                        Catch {
                            $_
                        }
                        continue
                    }

                    $AliasRegex {
                        Try {
                            $ParameterAlias = New-Object -TypeName System.Management.Automation.AliasAttribute -ArgumentList (. $GetVar) -ErrorAction SilentlyContinue
                            $AttributeCollection.Add((. $GetVar))
                            Write-Debug "Added alias: $_"
                            continue
                        }
                        Catch {
                            $_
                        }
                    }
                }

                Write-Debug 'Adding attributes to the attribute collection'
                $AttributeCollection.Add($ParameterAttribute)

                Write-Debug 'Finishing creation of the new dynamic parameter'
                $Parameter = New-Object -TypeName System.Management.Automation.RuntimeDefinedParameter -ArgumentList @($Name, $Type, $AttributeCollection)

                Write-Debug 'Adding dynamic parameter to the dynamic parameter dictionary'
                $DPDictionary.Add($Name, $Parameter)
            }
        }
    }

    End {
        if (!$CreateVariables -and !$Dictionary) {
            Write-Verbose 'Writing dynamic parameter dictionary to the pipeline'
            $DPDictionary
        }
    }
}