## Specify output file to write data to
$CurrentDateTime = Get-Date -Format "yyyyMMddHHmmssffff"
$FILE = "${OutputDirectory}\${CurrentDateTime}_InstalledSoftware.csv"

## Clear content of output file
If ( Test-Path $FILE ) { Clear-Content -Path $FILE -Force }

## Function to append a line to a file
Function Write-LineToFile {
    param([Parameter(Mandatory=$true)][string]$Path,[Parameter(Mandatory=$true)][string]$Line)
    If ( -not (Test-Path $Path) ) {
        LogMsg "Creating file ""${Path}"""
        Try { New-Item -Path $Path -ItemType File -Force | Out-Null }
        Catch { LogErr $_.Exception.Message }
    }
    Try { Add-Content -Path $Path -Value $Line }
    Catch { LogErr $_.Exception.Message }
}

## Function to test whether or not an item has a specified property
Function Test-ItemProperty {
    param([Parameter(Mandatory=$true)][string]$Path,[Parameter(Mandatory=$true)][string]$Name)
    Try {
        $test = Get-ItemProperty -Path $Path -Name $Name -ErrorAction SilentlyContinue 
        If (($test -eq $null) -or ($test.Length -eq 0)) { Return $false } Else { Return $true }
    }
    Catch { Return $false }
}

## Function to retrieve an item property
Function Get-ItemPropertyInfo {
    param([Parameter(Mandatory=$true)][string]$Path,[Parameter(Mandatory=$true)][string]$Name)
    If ( Test-ItemProperty -Path $Path -Name $Name ) {
        $retval = $(Get-ItemProperty -Path $Path).$Name
        $retval = $retval -replace ",", " "

        ## Additional processing for specific properties
        Switch ( $Name ) {

            ## Convert the estimated size into MB
            "EstimatedSize" {
                $size = [int]$retval
                $size = [Math]::Ceiling($size / 1024)
                $retval = [string]$size
            }

            ## Convert the date format into YYYY-MM-DD
            "InstallDate" {

                $origRetval = $retval
                
                ## Try to find each type of date string so we can convert it
                Switch -Regex ( $retval ) {
                    '^\d{8}$'                   { $formatstring = 'yyyyMMdd' }
                    '^\d{1,2}\\\d{1,2}\\\d{4}$' { $formatstring = 'MM\dd\yyyy' }
                    '^\d{4}\\\d{1,2}\\\d{1,2}$' { $formatstring = 'yyyy\MM\dd' }
                    Default                     { $formatstring = $null }
                }

                ## Make sure $formatstring has a value, if not just try to cast directly to a datetime
                Try {
                If ( $formatstring -eq $null ) {
                    $date = [datetime]$retval
                } Else {
                    $date = [datetime]::ParseExact($retval,$formatstring,$null)
                }

                ## Set $retval to a standard datetime format
                $retval = $date.ToString('yyyy-MM-dd')
                }
                Catch { LogErr $_.Exception.Message; $retval = $origRetval }
            }
            Default {}
        }
    }
    Else { $retval = "" }

    Return $retval
}

## Write the headers to the output file
Write-LineToFile -Path $FILE -Line "Name,Publisher,Version,InstallDate,EstimatedSize(MB),UninstallString,ModifyPath"

## Iterate through all Registry Uninstall keys and build the CSV file of all installed software
ForEach ( $item in $(Get-ChildItem -Path 'HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall','HKLM:\SOFTWARE\Wow6432Node\Microsoft\Windows\CurrentVersion\Uninstall') ) {
    $DisplayName     = Get-ItemPropertyInfo -Path $item.PSPath -Name DisplayName
    $DisplayVersion  = Get-ItemPropertyInfo -Path $item.PSPath -Name DisplayVersion
    $EstimatedSize   = Get-ItemPropertyInfo -Path $item.PSPath -Name EstimatedSize
    $InstallDate     = Get-ItemPropertyInfo -Path $item.PSPath -Name InstallDate
    $Publisher       = Get-ItemPropertyInfo -Path $item.PSPath -Name Publisher
    $UninstallString = Get-ItemPropertyInfo -Path $item.PSPath -Name UninstallString
    $ModifyPath      = Get-ItemPropertyInfo -Path $item.PSPath -Name ModifyPath

    ## Write installed software to output file only if it has a name and uninstall/modify path, otherwise discard
    If ( -not (($DisplayName -eq "") -and ($UninstallString -eq "") -and ($ModifyPath -eq "")) ) {
        $content = "${DisplayName},${Publisher},${DisplayVersion},${InstallDate},${EstimatedSize},${UninstallString},${ModifyPath}"
        Write-LineToFile -Path $FILE -Line $content
    }
}