# Keep arguments as data: never build a PowerShell -Command expression from them.
$cliTokens = @($args | ForEach-Object { [string]$_ })
Set-StrictMode -Version Latest
$ErrorActionPreference = 'Stop'
$repositoryRoot = Split-Path -Parent $PSScriptRoot

function Show-XasUsage {
    Write-Host @'
Usage:
  .\skills list
  .\skills install <name> [more-names...]
  .\skills install --all
  .\skills update
  .\skills help

Add --preview to install or update to inspect the operation without writing.
Example: .\skills install xas-skill-review --preview
'@
}

try {
    if ($cliTokens.Count -eq 0) { Show-XasUsage; exit 0 }
    $command = $cliTokens[0].ToLowerInvariant()
    $remaining = @($cliTokens | Select-Object -Skip 1)
    if ($command -in @('help', '--help', '-h', '/?')) {
        if ($remaining.Count -gt 0) { throw 'The help command does not accept additional arguments.' }
        Show-XasUsage
        exit 0
    }
    switch ($command) {
        'list' {
            if ($remaining.Count -gt 0) { throw 'Usage: .\skills list' }
            & (Join-Path $repositoryRoot 'install.ps1') -List
            exit $LASTEXITCODE
        }
        'install' {
            $selected = New-Object 'System.Collections.Generic.List[string]'
            $preview = $false
            $all = $false
            foreach ($token in $remaining) {
                switch ($token.ToLowerInvariant()) {
                    '--preview' {
                        if ($preview) { throw 'Specify --preview only once.' }
                        $preview = $true
                    }
                    '--all' {
                        if ($all) { throw 'Specify --all only once.' }
                        $all = $true
                    }
                    default {
                        if ($token -cnotmatch '^[a-z0-9]+(-[a-z0-9]+)*$') {
                            throw "Invalid skill name or option: $token. Use .\skills list to view available names."
                        }
                        $selected.Add($token)
                    }
                }
            }
            if ($all -and $selected.Count -gt 0) { throw 'Choose either skill names or --all, not both.' }
            if (-not $all -and $selected.Count -eq 0) { throw 'Specify at least one skill name or --all. Use .\skills list to view available names.' }
            $parameters = @{ WhatIf = $preview }
            if ($all) { $parameters['All'] = $true } else { $parameters['Skill'] = $selected.ToArray() }
            & (Join-Path $repositoryRoot 'install.ps1') @parameters
            exit $LASTEXITCODE
        }
        'update' {
            if ($remaining.Count -gt 1 -or ($remaining.Count -eq 1 -and $remaining[0] -ine '--preview')) {
                throw 'Usage: .\skills update [--preview]'
            }
            & (Join-Path $repositoryRoot 'update.ps1') -WhatIf:($remaining.Count -eq 1)
            exit $LASTEXITCODE
        }
        default { throw "Unknown command: $command" }
    }
} catch {
    Write-Error -Message $_.Exception.Message -ErrorAction Continue
    Show-XasUsage
    exit 2
}