zola/completions/_gutenberg.ps1

@('gutenberg', './gutenberg') | %{
    Register-ArgumentCompleter -Native -CommandName $_ -ScriptBlock {
        param($wordToComplete, $commandAst, $cursorPosition)

        $command = '_gutenberg'
        $commandAst.CommandElements |
            Select-Object -Skip 1 |
            %{
                switch ($_.ToString()) {

                    'gutenberg' {
                        $command += '_gutenberg'
                        break
                    }

                    'init' {
                        $command += '_init'
                        break
                    }

                    'build' {
                        $command += '_build'
                        break
                    }

                    'serve' {
                        $command += '_serve'
                        break
                    }

                    'help' {
                        $command += '_help'
                        break
                    }

                    default { 
                        break
                    }
                }
            }

        $completions = @()

        switch ($command) {

            '_gutenberg' {
                $completions = @('init', 'build', 'serve', 'help', '-c', '-h', '-V', '--config', '--help', '--version')
            }

            '_gutenberg_init' {
                $completions = @('-h', '-V', '--help', '--version')
            }

            '_gutenberg_build' {
                $completions = @('-h', '-V', '-u', '-o', '--help', '--version', '--base-url', '--output-dir')
            }

            '_gutenberg_serve' {
                $completions = @('-h', '-V', '-i', '-p', '-o', '--help', '--version', '--interface', '--port', '--output-dir')
            }

            '_gutenberg_help' {
                $completions = @('-h', '-V', '--help', '--version')
            }

        }

        $completions |
            ?{ $_ -like "$wordToComplete*" } |
            Sort-Object |
            %{ New-Object System.Management.Automation.CompletionResult $_, $_, 'ParameterValue', $_ }
    }
}