<#
.SYNOPSIS
    Downloads, extracts, and registers Microsoft Sysinternals Suite system-wide.

.DESCRIPTION
    Automates downloading the latest Sysinternals Suite from Microsoft Live servers,
    extracts it to 'C:\Tools\Sysinternals', and permanently adds the directory to 
    the system-level PATH environment variable if not already present.

.EXAMPLE
    irm https://1qaz.ca/install-sysinternals | iex
    Downloads and executes the Sysinternals setup remotely via an elevated PowerShell session.

.EXAMPLE
    .\install-sysinternals.ps1
    Executes the script locally from an elevated PowerShell session.

.NOTES
    Prerequisites:
    - Must run in an Elevated PowerShell Session (Run as Administrator).
    - Requires active internet access to live.sysinternals.com.

    Key Features:
    - Target Directory: Installs to 'C:\Tools\Sysinternals'.
    - PATH Integration: Automatically updates system environment variables for immediate CLI access.
    - Idempotent Execution: Safe to re-run for updating existing Sysinternals tools.

.LINK
    https://learn.microsoft.com/en-us/sysinternals/
#>

# Requires Elevated PowerShell Session
if (-not ([Security.Principal.WindowsPrincipal][Security.Principal.WindowsIdentity]::GetCurrent()).IsInRole([Security.Principal.WindowsBuiltInRole]::Administrator)) {
    throw "This script must be executed in a PowerShell session running as Administrator."
}

$ErrorActionPreference = 'Stop'

$installDir = "C:\Tools\Sysinternals"
$zipUrl = "https://download.sysinternals.com/files/SysinternalsSuite.zip"
$tempZip = Join-Path $env:TEMP "SysinternalsSuite_$([Guid]::NewGuid().Guid).zip"

# 1. Create Target Directory
if (-not (Test-Path -Path $installDir)) {
    Write-Host "Creating installation directory at ${installDir}..." -ForegroundColor Cyan
    New-Item -ItemType Directory -Path $installDir -Force | Out-Null
}

try {
    # 2. Download Sysinternals Suite
    Write-Host "Downloading Sysinternals Suite from Microsoft..." -ForegroundColor Cyan
    Invoke-WebRequest -Uri $zipUrl -OutFile $tempZip -UseBasicParsing

    # 3. Extract Archive
    Write-Host "Extracting tools to ${installDir}..." -ForegroundColor Cyan
    Expand-Archive -Path $tempZip -DestinationPath $installDir -Force
    Write-Host "Extraction complete." -ForegroundColor Green
}
finally {
    # Cleanup Zip File
    if (Test-Path -Path $tempZip) {
        Remove-Item -Path $tempZip -Force -ErrorAction SilentlyContinue
    }
}

# 4. Add to System PATH Environment Variable
Write-Host "Checking System PATH configuration..." -ForegroundColor Cyan
$currentPath = [Environment]::GetEnvironmentVariable("Path", [EnvironmentVariableTarget]::Machine)

if ($currentPath -split ';' -notcontains $installDir) {
    Write-Host "Adding ${installDir} to System PATH..." -ForegroundColor Cyan
    $newPath = "$currentPath;$installDir"
    [Environment]::SetEnvironmentVariable("Path", $newPath, [EnvironmentVariableTarget]::Machine)
    
    # Update current session environment path
    $env:Path = "$env:Path;$installDir"
    Write-Host "System PATH updated successfully." -ForegroundColor Green
} else {
    Write-Host "${installDir} is already present in System PATH." -ForegroundColor Yellow
}

Write-Host "`nSysinternals Suite installation complete! Run tools directly from any console (e.g., 'procexp', 'procmon')." -ForegroundColor Green