<#
.SYNOPSIS
    Install wslx -- the Ubuntu WSL machine manager -- and uv, if it is missing.

.DESCRIPTION
    One typeable line that takes a bare Windows machine to a working `wslx`:

        iex (irm https://get.optersoft.com/wsl.ps1)

    The paren form rather than `irm ... | iex` because `|` is unmapped on a
    SPICE console and on several non-US keyboard layouts, and this script is
    often the first thing typed into a fresh VM by hand.

    It installs uv (Astral's Python installer) only if uv is not already
    there, then installs wslx as a uv tool. Both land in
    %USERPROFILE%\.local\bin, which is added to PATH for the current session
    immediately and to future shells via `uv tool update-shell` -- so `wslx`
    works in this window without reopening it.

    Idempotent: run it again to upgrade wslx to the latest release.

.NOTES
    wslx itself needs a WSL that supports systemd, because it seeds every
    distribution with cloud-init and cloud-init runs under systemd. The
    version of wsl.exe shipped in the Windows image predates that, so this
    script checks and says so rather than letting the failure surface later
    as a distribution with no `box` user. See the WSL check at the end.
#>

[CmdletBinding()]
param(
    # Skip the WSL health check (the install itself does not need WSL).
    [switch] $NoWslCheck
)

$ErrorActionPreference = 'Stop'
# PowerShell 5.1 defaults to TLS 1.0, which astral.sh and GitHub refuse.
[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12
# The uv installer draws a progress bar that is very slow over a remote shell.
$ProgressPreference = 'SilentlyContinue'

function Write-Step($msg) { Write-Host "==> $msg" -ForegroundColor Cyan }
function Write-Ok($msg)   { Write-Host "  ok  $msg" -ForegroundColor Green }
function Write-Skip($msg) { Write-Host "  --  $msg" -ForegroundColor DarkGray }
function Write-Warn($msg) { Write-Host "  !!  $msg" -ForegroundColor Yellow }

function Invoke-Native {
    <# Run a native executable and return its exit code.

    PowerShell 5.1 with $ErrorActionPreference='Stop' turns a single byte on a
    native command's stderr into a terminating NativeCommandError. uv writes
    ordinary progress there ("Executable directory ... is already in PATH"),
    and the in-box wsl.exe answers `--version` with its help text there, so
    both would abort this script despite succeeding. The exit code is the only
    reliable signal. #>
    param(
        [Parameter(Mandatory)][string] $Exe,
        [string[]] $Arguments = @(),
        [switch] $Quiet
    )
    $previous = $ErrorActionPreference
    $ErrorActionPreference = 'Continue'
    try {
        if ($Quiet) { & $Exe @Arguments 2>&1 | Out-Null }
        else { & $Exe @Arguments 2>&1 | ForEach-Object { Write-Host "      $_" } }
        return $LASTEXITCODE
    } finally { $ErrorActionPreference = $previous }
}

$binDir = Join-Path $env:USERPROFILE '.local\bin'

function Use-LocalBin {
    <# Put %USERPROFILE%\.local\bin first for this session.

    The uv installer tells you to restart your shell; we cannot, because the
    next thing this script does is call uv. #>
    if ($env:PATH -notlike "*$binDir*") { $env:PATH = "$binDir;$env:PATH" }
}

# ---------------------------------------------------------------- uv --------

Write-Step 'uv'
Use-LocalBin
if (Get-Command uv -ErrorAction SilentlyContinue) {
    Write-Skip "already installed -- $(uv --version)"
} else {
    iex (irm https://astral.sh/uv/install.ps1)
    Use-LocalBin
    if (-not (Get-Command uv -ErrorAction SilentlyContinue)) {
        throw "uv installed but is not on PATH -- expected it in $binDir"
    }
    Write-Ok (uv --version)
}

# -------------------------------------------------------------- wslx --------

Write-Step 'wslx'
if (Get-Command wslx -ErrorAction SilentlyContinue) {
    $code = Invoke-Native uv @('tool', 'upgrade', 'wslx')
} else {
    $code = Invoke-Native uv @('tool', 'install', 'wslx')
}
if ($code -ne 0) { throw "uv could not install wslx (exit $code)" }

# Persist the PATH entry so new shells find wslx too. Harmless if already done.
Invoke-Native uv @('tool', 'update-shell') -Quiet | Out-Null

Use-LocalBin
if (-not (Get-Command wslx -ErrorAction SilentlyContinue)) {
    throw "wslx installed but is not on PATH -- expected it in $binDir"
}
Write-Ok (wslx --version)

# --------------------------------------------------------------- WSL --------

if (-not $NoWslCheck) {
    Write-Step 'WSL'
    if (-not (Get-Command wsl.exe -ErrorAction SilentlyContinue)) {
        Write-Warn 'wsl.exe not found. Enable WSL before using wslx:'
        Write-Host '        wsl --install' -ForegroundColor DarkGray
    } else {
        # `wsl --version` exists only in the modern (MSI/Store) build. The
        # in-box wsl.exe answers it with its help text and a non-zero exit,
        # and that build has no systemd -- so cloud-init never runs and every
        # distribution wslx creates comes out with no box user, the wrong
        # hostname and no sudo rule.
        $env:WSL_UTF8 = '1'
        if ((Invoke-Native wsl.exe @('--version') -Quiet) -ne 0) {
            Write-Warn 'This is the in-box WSL, which has no systemd support.'
            Write-Warn 'wslx needs systemd for cloud-init, so seeding will not work.'
            Write-Host '        wsl --update' -ForegroundColor DarkGray
            Write-Host '        # if that fails, install the MSI:' -ForegroundColor DarkGray
            Write-Host '        # https://github.com/microsoft/WSL/releases/latest' -ForegroundColor DarkGray
        } else {
            Write-Ok ((wsl.exe --version) -split "`n" | Select-Object -First 1).Trim()
        }
    }
}

Write-Host ''
Write-Host 'Done. Try:' -ForegroundColor Cyan
Write-Host '    wslx connect alfa --new' -ForegroundColor DarkGray