<#
.SYNOPSIS
    Lists installed software on one or more Windows computers, straight from the registry.
.DESCRIPTION
    Reads the Uninstall keys (64-bit, 32-bit, and optionally the current user's) and returns one
    object per application with name, version, publisher, install date and architecture. Works
    locally, or remotely over PowerShell remoting. Doesn't touch Win32_Product.
.PARAMETER ComputerName
    One or more computers. Defaults to this one. Remote computers need PowerShell remoting enabled.
.PARAMETER Name
    Wildcard filter on the application name, for example '*Chrome*'. Default: everything.
.PARAMETER IncludeUser
    Also read HKEY_CURRENT_USER, for per-user installs. Only covers the account running the query.
.PARAMETER IncludeSystemComponents
    Include entries flagged as system components or updates, which Programs and Features hides.
.PARAMETER Credential
    Credentials for the remote connection.
.EXAMPLE
    .\Get-InstalledSoftware.ps1 -Name '*Java*'
.EXAMPLE
    .\Get-InstalledSoftware.ps1 -ComputerName PC-0142, PC-0187 | Export-Csv .\software.csv -NoTypeInformation
#>
[CmdletBinding()]
param(
    [Parameter(ValueFromPipeline, ValueFromPipelineByPropertyName)]
    [Alias('CN', 'DNSHostName')]
    [string[]]$ComputerName = $env:COMPUTERNAME,
    [string]$Name = '*',
    [switch]$IncludeUser,
    [switch]$IncludeSystemComponents,
    [pscredential]$Credential
)

begin {
    # This block runs on the target machine, so it can't use anything from outside it except its arguments.
    $collector = {
        param([string]$NameFilter, [bool]$User, [bool]$System)

        $keys = @(
            @{ Path = 'HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\*'; Arch = '64-bit' }
            @{ Path = 'HKLM:\SOFTWARE\WOW6432Node\Microsoft\Windows\CurrentVersion\Uninstall\*'; Arch = '32-bit' }
        )
        if (-not [Environment]::Is64BitOperatingSystem) { $keys[0].Arch = '32-bit'; $keys = @($keys[0]) }
        if ($User) { $keys += @{ Path = 'HKCU:\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\*'; Arch = 'User' } }

        foreach ($key in $keys) {
            Get-ItemProperty -Path $key.Path -ErrorAction SilentlyContinue |
                Where-Object { $_.DisplayName -and $_.DisplayName -like $NameFilter } |
                Where-Object { $System -or (-not $_.SystemComponent -and -not $_.ParentKeyName) } |
                ForEach-Object {
                    $installed = $null
                    if ($_.InstallDate -match '^\d{8}$') {
                        $installed = [datetime]::ParseExact($_.InstallDate, 'yyyyMMdd', $null)
                    }
                    [pscustomobject]@{
                        ComputerName    = $env:COMPUTERNAME
                        Name            = $_.DisplayName.Trim()
                        Version         = $_.DisplayVersion
                        Publisher       = $_.Publisher
                        InstallDate     = $installed
                        Architecture    = $key.Arch
                        UninstallString = $_.UninstallString
                    }
                }
        }
    }
}

process {
    foreach ($computer in $ComputerName) {
        $isLocal = $computer -in @('.', 'localhost', $env:COMPUTERNAME)
        try {
            $argsList = @($Name, $IncludeUser.IsPresent, $IncludeSystemComponents.IsPresent)
            $apps = if ($isLocal) {
                & $collector @argsList
            }
            else {
                $remote = @{ ComputerName = $computer; ScriptBlock = $collector; ArgumentList = $argsList; ErrorAction = 'Stop' }
                if ($Credential) { $remote.Credential = $Credential }
                Invoke-Command @remote | Select-Object * -ExcludeProperty PSComputerName, RunspaceId, PSShowComputerName
            }
            Write-Verbose "$computer : $(@($apps).Count) application(s)"
            $apps | Sort-Object Name, Architecture
        }
        catch {
            Write-Warning "$computer : $($_.Exception.Message)"
        }
    }
}