class Samovar::Nested

def initialize(key, commands, default: nil, required: false)
	@key = key
	@commands = commands
	
	# This is the default name [of a command], not the default command:
	@default = default
	
	@required = required
end

def parse(input, parent = nil, default = nil)
	if command = @commands[input.first]
		name = input.shift
		
		# puts "Instantiating #{command} with #{input}"
		command.new(input, name: name, parent: parent)
	elsif default
		return default
	elsif @default
		@commands[@default].new(input, name: @default, parent: parent)
	elsif @required
		raise MissingValueError.new(parent, self)
	end
end

def to_a
	usage = [self.to_s]
	
	if @commands.size == 0
		usage << "No commands available."
	elsif @commands.size == 1
		usage << "Only #{@commands.first}."
	else
		usage << "One of: #{@commands.keys.join(', ')}."
	end
	
	if @default
		usage << "(default: #{@default})"
	elsif @required
		usage << "(required)"
	end
	
	return usage
end

def to_s
	"<#{@key}>"
end

def usage(rows)
	rows << self
	
	@commands.each do |key, klass|
		klass.usage(rows, key)
	end
end