#requires -version 2.0

# -----------------------------------------------------------------------------
# Script: Get-VariableDefinition.ps1
# Author: Jeffery Hicks 
#    http://jdhitsolutions.com/blog
# Date: 3/3/2011
# Keywords:
# Comments:
#
# -----------------------------------------------------------------------------

Function Get-VariableDefinition {

<#
   .Synopsis
    Get a variable definition.
    .Description
    Search PowerShell's history buffer for a variable and return the command that was used
    to define it. To get the most value from this, make sure your $MaximumHistoryCount is
    set to a high value.
    
    This function cannot get definitions for variables defined in profile scripts.
    .Parameter Name
    The name of the variable you want to find without the $.
   .Example
    PS C:\> Get-VariableDefinition j
    $j=(Get-Wmiobject win32_volume -filter "name='J:\\'")
      
   .Notes
    NAME: Get-VariableDefinition
    VERSION: 1.0
    AUTHOR: Jeffery Hicks
    LASTEDIT: 03/03/2011
    
    Learn more with a copy of Windows PowerShell 2.0: TFM (SAPIEN Press 2010)
    
   .Link
    http://jdhitsolutions.com/blog/2011/03/get-variable-definition/
    
    .Link
    Get-Variable
    Get-History
    
   .Inputs
    None
   .Outputs
   String

#>

[cmdletBinding()]

Param(
    [Parameter(Position=0,Mandatory=$True,HelpMessage="Enter a variable name, without the `$")]
    [ValidateNotNullOrEmpty()]
    [string]$Name
)

Try 
{
    #make sure a valid variable name was passed
    $verify=Get-Variable $name -ErrorAction Stop
}

Catch
{
    Write-Warning "The variable $Name was not found."
}

if ($verify) 
{
    #search history and get the last assignment
    $item=Get-History -Count $MaximumHistoryCount | where {$_.commandline -match "^\`$$Name="} | Select -Last 1

    if ($item) 
    {
        #write the Commandline property to the pipeline if something was found
        $item.CommandLine
    }
    else
    {
        #the variable definition has expired
        Write-Host "Failed to find a definition for `$$Name in your existing history." -ForegroundColor Yellow
    } 
 } #close if $verify
} #end Function

#define an optional alias 
Set-Alias -name gvd -Value Get-VariableDefinition