using namespace System.Management.Automation
using namespace System.Management.Automation.Language

Register-ArgumentCompleter -Native -CommandName 'complate' -ScriptBlock {
    param($wordToComplete, $commandAst, $cursorPosition)

    $commandElements = $commandAst.CommandElements
    $command = @(
        'complate'
        for ($i = 1; $i -lt $commandElements.Count; $i++) {
            $element = $commandElements[$i]
            if ($element -isnot [StringConstantExpressionAst] -or
                $element.StringConstantType -ne [StringConstantType]::BareWord -or
                $element.Value.StartsWith('-') -or
                $element.Value -eq $wordToComplete) {
                break
        }
        $element.Value
    }) -join ';'

    $completions = @(switch ($command) {
        'complate' {
            [CompletionResult]::new('-e', 'e', [CompletionResultType]::ParameterName, 'enables experimental features')
            [CompletionResult]::new('--experimental', 'experimental', [CompletionResultType]::ParameterName, 'enables experimental features')
            [CompletionResult]::new('-h', 'h', [CompletionResultType]::ParameterName, 'Print help')
            [CompletionResult]::new('--help', 'help', [CompletionResultType]::ParameterName, 'Print help')
            [CompletionResult]::new('-V', 'V ', [CompletionResultType]::ParameterName, 'Print version')
            [CompletionResult]::new('--version', 'version', [CompletionResultType]::ParameterName, 'Print version')
            [CompletionResult]::new('man', 'man', [CompletionResultType]::ParameterValue, 'Renders the manual.')
            [CompletionResult]::new('autocomplete', 'autocomplete', [CompletionResultType]::ParameterValue, 'Renders shell completion scripts.')
            [CompletionResult]::new('init', 'init', [CompletionResultType]::ParameterValue, 'Initializes a dummy default configuration in "./.complate/config.yaml".')
            [CompletionResult]::new('schema', 'schema', [CompletionResultType]::ParameterValue, 'Renders the configuration schema.')
            [CompletionResult]::new('render', 'render', [CompletionResultType]::ParameterValue, 'Renders a template by replacing values as specified by the configuration.')
            [CompletionResult]::new('help', 'help', [CompletionResultType]::ParameterValue, 'Print this message or the help of the given subcommand(s)')
            break
        }
        'complate;man' {
            [CompletionResult]::new('-o', 'o', [CompletionResultType]::ParameterName, 'o')
            [CompletionResult]::new('--out', 'out', [CompletionResultType]::ParameterName, 'out')
            [CompletionResult]::new('-f', 'f', [CompletionResultType]::ParameterName, 'f')
            [CompletionResult]::new('--format', 'format', [CompletionResultType]::ParameterName, 'format')
            [CompletionResult]::new('-h', 'h', [CompletionResultType]::ParameterName, 'Print help')
            [CompletionResult]::new('--help', 'help', [CompletionResultType]::ParameterName, 'Print help')
            [CompletionResult]::new('-V', 'V ', [CompletionResultType]::ParameterName, 'Print version')
            [CompletionResult]::new('--version', 'version', [CompletionResultType]::ParameterName, 'Print version')
            break
        }
        'complate;autocomplete' {
            [CompletionResult]::new('-o', 'o', [CompletionResultType]::ParameterName, 'o')
            [CompletionResult]::new('--out', 'out', [CompletionResultType]::ParameterName, 'out')
            [CompletionResult]::new('-s', 's', [CompletionResultType]::ParameterName, 's')
            [CompletionResult]::new('--shell', 'shell', [CompletionResultType]::ParameterName, 'shell')
            [CompletionResult]::new('-h', 'h', [CompletionResultType]::ParameterName, 'Print help')
            [CompletionResult]::new('--help', 'help', [CompletionResultType]::ParameterName, 'Print help')
            [CompletionResult]::new('-V', 'V ', [CompletionResultType]::ParameterName, 'Print version')
            [CompletionResult]::new('--version', 'version', [CompletionResultType]::ParameterName, 'Print version')
            break
        }
        'complate;init' {
            [CompletionResult]::new('-h', 'h', [CompletionResultType]::ParameterName, 'Print help')
            [CompletionResult]::new('--help', 'help', [CompletionResultType]::ParameterName, 'Print help')
            [CompletionResult]::new('-V', 'V ', [CompletionResultType]::ParameterName, 'Print version')
            [CompletionResult]::new('--version', 'version', [CompletionResultType]::ParameterName, 'Print version')
            break
        }
        'complate;schema' {
            [CompletionResult]::new('-h', 'h', [CompletionResultType]::ParameterName, 'Print help')
            [CompletionResult]::new('--help', 'help', [CompletionResultType]::ParameterName, 'Print help')
            [CompletionResult]::new('-V', 'V ', [CompletionResultType]::ParameterName, 'Print version')
            [CompletionResult]::new('--version', 'version', [CompletionResultType]::ParameterName, 'Print version')
            break
        }
        'complate;render' {
            [CompletionResult]::new('-c', 'c', [CompletionResultType]::ParameterName, 'The configuration file to use.')
            [CompletionResult]::new('--config', 'config', [CompletionResultType]::ParameterName, 'The configuration file to use.')
            [CompletionResult]::new('-t', 't', [CompletionResultType]::ParameterName, 'Specify the template to use from the config and skip it''s selection.')
            [CompletionResult]::new('--template', 'template', [CompletionResultType]::ParameterName, 'Specify the template to use from the config and skip it''s selection.')
            [CompletionResult]::new('-b', 'b', [CompletionResultType]::ParameterName, 'The execution backend (cli=native-terminal, ui=ui emulator in terminal).')
            [CompletionResult]::new('--backend', 'backend', [CompletionResultType]::ParameterName, 'The execution backend (cli=native-terminal, ui=ui emulator in terminal).')
            [CompletionResult]::new('-v', 'v', [CompletionResultType]::ParameterName, 'Overrides a certain value definition with a string.')
            [CompletionResult]::new('--value', 'value', [CompletionResultType]::ParameterName, 'Overrides a certain value definition with a string.')
            [CompletionResult]::new('--trust', 'trust', [CompletionResultType]::ParameterName, 'Enables the shell command execution. This is potentially insecure and should only be done for trustworthy sources.')
            [CompletionResult]::new('-l', 'l', [CompletionResultType]::ParameterName, 'Defines that the templating is done in non-strict mode (allow missing value for variable).')
            [CompletionResult]::new('--loose', 'loose', [CompletionResultType]::ParameterName, 'Defines that the templating is done in non-strict mode (allow missing value for variable).')
            [CompletionResult]::new('-h', 'h', [CompletionResultType]::ParameterName, 'Print help')
            [CompletionResult]::new('--help', 'help', [CompletionResultType]::ParameterName, 'Print help')
            [CompletionResult]::new('-V', 'V ', [CompletionResultType]::ParameterName, 'Print version')
            [CompletionResult]::new('--version', 'version', [CompletionResultType]::ParameterName, 'Print version')
            break
        }
        'complate;help' {
            [CompletionResult]::new('man', 'man', [CompletionResultType]::ParameterValue, 'Renders the manual.')
            [CompletionResult]::new('autocomplete', 'autocomplete', [CompletionResultType]::ParameterValue, 'Renders shell completion scripts.')
            [CompletionResult]::new('init', 'init', [CompletionResultType]::ParameterValue, 'Initializes a dummy default configuration in "./.complate/config.yaml".')
            [CompletionResult]::new('schema', 'schema', [CompletionResultType]::ParameterValue, 'Renders the configuration schema.')
            [CompletionResult]::new('render', 'render', [CompletionResultType]::ParameterValue, 'Renders a template by replacing values as specified by the configuration.')
            [CompletionResult]::new('help', 'help', [CompletionResultType]::ParameterValue, 'Print this message or the help of the given subcommand(s)')
            break
        }
        'complate;help;man' {
            break
        }
        'complate;help;autocomplete' {
            break
        }
        'complate;help;init' {
            break
        }
        'complate;help;schema' {
            break
        }
        'complate;help;render' {
            break
        }
        'complate;help;help' {
            break
        }
    })

    $completions.Where{ $_.CompletionText -like "$wordToComplete*" } |
        Sort-Object -Property ListItemText
}