begin

Code Explanation:

There are 3 types of things to auto-complete:

1. command: the command itself
2. parameters: command parameters.
3. options: command options

Here's an example:

mycli hello name --from me

* command: hello
* parameters: name
* option: --from

When command parameters are done processing, the remaining completion words will be options. We can tell that the command params are completed based on the method arity.

## Arity

For example, say you had a method for a CLI command with the following form:

ufo scale service count --cluster development

It's equivalent ruby method:

scale(service, count) = has an arity of 2

So typing:

ufo scale service count [TAB] # there are 3 parameters including the "scale" command according to Thor's CLI processing.

So the completion should only show options, something like this:

--noop --verbose --cluster

## Splat Arguments

When the ruby method has a splat argument, it's arity is negative. Here are some example methods and their arities.

ship(service) = 1
scale(service, count) = 2
ships(*services) = -1
foo(example, *rest) = -2

Fortunately, negative and positive arity values are processed the same way. So we take simply take the absolute value of the arity and process it the same.

Here are some test cases, hit TAB after typing the command:

<%= project_name %> completion
<%= project_name %> completion hello
<%= project_name %> completion hello name
<%= project_name %> completion hello name --
<%= project_name %> completion hello name --noop

<%= project_name %> completion
<%= project_name %> completion sub:goodbye
<%= project_name %> completion sub:goodbye name

## Subcommands and Thor::Group Registered Commands

Sometimes the commands are not simple thor commands but are subcommands or Thor::Group commands. A good specific example is the ufo tool.

* regular command: ufo ship
* subcommand: ufo docker
* Thor::Group command: ufo init

Auto-completion accounts for each of these type of commands.

end

module <%= project_class_name %>

class Completer
  def initialize(command_class, *params)
    @params = params
    @current_command = @params[0]
    @command_class = command_class # CLI initiall
  end

  def run
    if subcommand?(@current_command)
      subcommand_class = @command_class.subcommand_classes[@current_command]
      @params.shift # destructive
      Completer.new(subcommand_class, *@params).run # recursively use subcommand
      return
    end

    # full command has been found!
    unless found?(@current_command)
      puts all_commands
      return
    end

    # will only get to here if command aws found (above)
    arity = @command_class.instance_method(@current_command).arity.abs
    if @params.size > arity or thor_group_command?
      puts options_completion
    else
      puts params_completion
    end
  end

  def subcommand?(command)
    @command_class.subcommands.include?(command)
  end

  # hacky way to detect that command is a registered Thor::Group command
  def thor_group_command?
    command_params(raw=true) == [[:rest, :args]]
  end

  def found?(command)
    public_methods = @command_class.public_instance_methods(false)
    command && public_methods.include?(command.to_sym)
  end

  # all top-level commands
  def all_commands
    commands = @command_class.all_commands.reject do |k,v|
      v.is_a?(Thor::HiddenCommand)
    end
    commands.keys
  end

  def command_params(raw=false)
    params = @command_class.instance_method(@current_command).parameters
    # Example:
    # >> Sub.instance_method(:goodbye).parameters
    # => [[:req, :name]]
    # >>
    raw ? params : params.map!(&:last)
  end

  def params_completion
    offset = @params.size - 1
    offset_params = command_params[offset..-1]
    command_params[offset..-1].first
  end

  def options_completion
    used = ARGV.select { |a| a.include?('--') } # so we can remove used options

    method_options = @command_class.all_commands[@current_command].options.keys
    class_options = @command_class.class_options.keys

    all_options = method_options + class_options + ['help']

    all_options.map! { |o| "--#{o.to_s.gsub('_','-')}" }
    filtered_options = all_options - used
    filtered_options.uniq
  end

  # Useful for debugging. Using puts messes up completion.
  def log(msg)
    File.open("/tmp/complete.log", "a") do |file|
      file.puts(msg)
    end
  end
end

end