# Super class of all option's class
abstract class Option
	# Names for the option (including long and short ones)
	var names: Array[String]

	# Type of the value of the option
	type VALUE: nullable Object

	# Human readable description of the option
	var helptext: String

	# Gathering errors during parsing
	var errors: Array[String] = new Array[String]

	# Is this option mandatory?
	var mandatory: Bool = false is writable

	# Is this option hidden from `usage`?
	var hidden: Bool = false is writable

	# Has this option been read?
	var read: Bool = false is writable

	# Current value of this option
	var value: VALUE is writable

	# Default value of this option
	var default_value: VALUE is writable

	# Create a new option
	init(help: String, default: VALUE, names: nullable Array[String]) is old_style_init do
		init_opt(help, default, names)
	end

	# Init option `helptext`, `default_value` and `names`.
	#
	# Also set current `value` to `default`.
	fun init_opt(help: String, default: VALUE, names: nullable Array[String])
	do
		if names == null then
			self.names = new Array[String]
		else
			self.names = names.to_a
		end
		helptext = help
		default_value = default
		value = default
	end

	# Add new aliases for this option
	fun add_aliases(names: String...) do names.add_all(names)

	# An help text for this option with default settings
	redef fun to_s do return pretty(2)

	# A pretty print for this help
	fun pretty(off: Int): String
	do
		var text = new FlatBuffer.from("  ")
		text.append(names.join(", "))
		text.append("  ")
		var rest = off - text.length
		if rest > 0 then text.append(" " * rest)
		text.append(helptext)
		#text.append(pretty_default)
		return text.to_s
	end

	# Pretty print the default value.
	fun pretty_default: String
	do
		var dv = default_value
		if dv != null then return " ({dv.to_s})"
		return ""
	end

	# Consume parameters for this option
	protected fun read_param(opts: OptionContext, it: Iterator[String])
	do
		read = true
	end
end