param(
    [string]$TargetUser = 'user'
)

[Console]::OutputEncoding = [Text.Encoding]::UTF8
$ErrorActionPreference = 'Stop'

$targetProfile = "C:\Users\$TargetUser"
if (-not (Test-Path $targetProfile)) { throw "Windows user '$TargetUser' not found ($targetProfile missing)" }

$installDir   = Join-Path $targetProfile 'AppData\Roaming\Telegram Desktop'
$startMenuDir = Join-Path $targetProfile 'AppData\Roaming\Microsoft\Windows\Start Menu\Programs'
$desktopDir   = Join-Path $targetProfile 'Desktop'

function Get-TelegramVersion($dir) {
    $exe = Join-Path $dir 'Telegram.exe'
    if (Test-Path $exe) { return (Get-Item $exe).VersionInfo.ProductVersion }
    return $null
}

# Already installed at target?
$existingVer = Get-TelegramVersion $installDir
if ($existingVer) {
    Write-Host "[=] Already installed for '$TargetUser': Telegram $existingVer at $installDir"
    exit 0
}

# Clean up any stray Admin-scoped install that we may have created earlier
$adminDir = 'C:\Users\Admin\AppData\Roaming\Telegram Desktop'
$adminUninst = Join-Path $adminDir 'unins000.exe'
if ((Test-Path $adminUninst) -and ($TargetUser -ne 'Admin')) {
    Write-Host "[*] Removing stray Admin-scoped install at $adminDir"
    Get-Process Telegram,Updater -ErrorAction SilentlyContinue | Stop-Process -Force
    $p = Start-Process -FilePath $adminUninst -ArgumentList '/VERYSILENT','/SUPPRESSMSGBOXES','/NORESTART' -Wait -PassThru
    if ($p.ExitCode -ne 0) { Write-Host "[!] Uninstall exited $($p.ExitCode), continuing anyway" }

    # Remove Admin's HKCU uninstall key (best-effort)
    Get-Item 'HKCU:\Software\Microsoft\Windows\CurrentVersion\Uninstall\*' -ErrorAction SilentlyContinue |
        Where-Object { (Get-ItemProperty $_.PSPath).DisplayName -match 'Telegram' } |
        ForEach-Object { Remove-Item $_.PSPath -Force -Recurse -ErrorAction SilentlyContinue }
    # Remove Admin's start menu shortcut
    $adminLnk = 'C:\Users\Admin\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Telegram.lnk'
    Remove-Item $adminLnk -ErrorAction SilentlyContinue
    Start-Sleep -Seconds 2
}

# Download installer
$url = 'https://telegram.org/dl/desktop/win64'
$dst = Join-Path $env:TEMP 'telegram-setup.exe'
Write-Host "[*] Downloading installer -> $dst"
[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12
Invoke-WebRequest -Uri $url -OutFile $dst -UseBasicParsing
if (-not (Test-Path $dst) -or (Get-Item $dst).Length -lt 10MB) {
    throw "Downloaded file looks wrong (< 10 MB)"
}

# Install into target user's AppData. /NOICONS = no shortcuts (we'll create them in target's profile).
New-Item -ItemType Directory -Force -Path $installDir | Out-Null
$argStr = '/VERYSILENT /SUPPRESSMSGBOXES /NORESTART /SP- /NOICONS /NOLAUNCH /DIR="' + $installDir + '"'
Write-Host "[*] Installing to $installDir"
$p = Start-Process -FilePath $dst -ArgumentList $argStr -Wait -PassThru
Remove-Item $dst -ErrorAction SilentlyContinue
if ($p.ExitCode -ne 0) { throw "Installer exited $($p.ExitCode)" }

# Verify binary appeared
$finalVer = Get-TelegramVersion $installDir
if (-not $finalVer) { throw "Telegram.exe not found at $installDir after install" }

# Give target user full control over the install tree
Write-Host "[*] Adjusting ACL on $installDir for '$TargetUser'"
& icacls $installDir /grant "${TargetUser}:(OI)(CI)F" /T /Q | Out-Null

# Create Start Menu shortcut in target user's profile
New-Item -ItemType Directory -Force -Path $startMenuDir | Out-Null
$wsh = New-Object -ComObject WScript.Shell
$lnk = $wsh.CreateShortcut((Join-Path $startMenuDir 'Telegram.lnk'))
$lnk.TargetPath       = Join-Path $installDir 'Telegram.exe'
$lnk.WorkingDirectory = $installDir
$lnk.IconLocation     = (Join-Path $installDir 'Telegram.exe') + ',0'
$lnk.Save()
Write-Host "[*] Start menu shortcut: $(Join-Path $startMenuDir 'Telegram.lnk')"

# Desktop shortcut
if (Test-Path $desktopDir) {
    $dlnk = $wsh.CreateShortcut((Join-Path $desktopDir 'Telegram.lnk'))
    $dlnk.TargetPath       = Join-Path $installDir 'Telegram.exe'
    $dlnk.WorkingDirectory = $installDir
    $dlnk.IconLocation     = (Join-Path $installDir 'Telegram.exe') + ',0'
    $dlnk.Save()
    Write-Host "[*] Desktop shortcut:    $(Join-Path $desktopDir 'Telegram.lnk')"
}

# Fix ACL on the shortcuts too
& icacls (Join-Path $startMenuDir 'Telegram.lnk') /grant "${TargetUser}:F" /Q | Out-Null
if (Test-Path (Join-Path $desktopDir 'Telegram.lnk')) {
    & icacls (Join-Path $desktopDir 'Telegram.lnk') /grant "${TargetUser}:F" /Q | Out-Null
}

Write-Host ""
Write-Host "[OK] Telegram $finalVer installed for '$TargetUser'"
Write-Host "     Location: $installDir"
Write-Host "     Data (tdata) will be created beside the exe on first launch."