penv.ps1

param (
    [Parameter(Mandatory=$true)]
    [ValidateSet('activate', 'init')]
    [string]$Command,
    [string]$VersionString
)

function Get-ExistingVirtualEnvironment {
    $directoryNames = '.venv', 'venv', '.env', 'env', '.penv', 'penv'
    foreach ($name in $directoryNames) {
        $activateScript = [IO.Path]::Combine($(Get-Location), $name, 'Scripts', 'Activate.ps1')
        if (Test-Path -LiteralPath $activateScript) {
            return $name
        }
    }
    return $null
}

function Initialize-VirtualEnvironment($folderpath) {
    $activateScript = [IO.Path]::Combine($folderpath, 'Scripts', 'Activate.ps1')

    # Create virtual environment if it doesn't already exist
    if (Test-Path $activateScript) {
        throw "Environment already exists: $($folderpath)"
    }

    python -m venv $folderpath
    if ($LastExitCode -ne 0) {
        throw "Failed to create virtual environment with: 'python -m venv $($folderpath)'"
    }

    # Ensure virtual environment's activate script exist
    if (-not (Test-Path $activateScript)) {
        throw 'Virtual environment or activate script not found'
    }

    & $activateScript
}

# Ensure we have python
if ((Get-Command 'python' -ErrorAction SilentlyContinue) -eq $null) {
    throw 'Python was not found'
}

switch ($Command) {
    'activate' {
        $virtualEnvName = Get-ExistingVirtualEnvironment
        if ($virtualEnvName) {
            & $([IO.Path]::Combine($(Get-Location), $virtualEnvName, 'Scripts', 'Activate.ps1'))
        } else {
            throw 'No virtual environment directory found in the current directory.'
        }
    }
    'init' {
        if ($VersionString) {
            pyenv local $version
        } else {
            pyenv local 3.12.2
        }
        $existing = Get-ExistingVirtualEnvironment
        if ($existing) {
            # $confirmation = Read-Host "An existing virtual environment was found. Overwrite? (Y/n)"
            $choice = $Host.UI.PromptForChoice(
                "An existing virtual environment was found: '$($existing)/'",
                "Overwrite?",
                @('&Yes'; '&No'),
                0
            )
            if ($choice -eq 0) {
                Remove-Item -LiteralPath $existing -Recurse
            }
            else { exit }
        }
        Initialize-VirtualEnvironment('.venv')
    }
}

# Ensure Python is running in a virtual environment
python -c 'import sys;sys.exit(0 if sys.prefix != sys.base_prefix else -1)'
if ($LastExitCode -ne 0) {
    throw 'Python was not virtualized'
}

echo ---
echo 'Python Virtual Environment Started'
echo "Running $(python --version)"
echo "Located from $(Get-Command python | Select Source -ExpandProperty Source)"
echo ---