class DenCli
	class UsageError < ::RuntimeError
	end
	class UnknownCommand < UsageError
	end

	class <<self
		# Helper Function for generate Regular Expressions of string,
		# which matches all strings which has parts fron beginning of the given string.
		# `n("abc")` would produce: `/(?:a|ab|abc)/`
		# You can define a minimum length to match:
		# `n("abcdef",4)` => `/abcd(?:|e|ef)/`
		def n s, min = nil
			min ||= 1
			/#{s.length <= min ?
				Regexp.quote(s) :
				"#{Regexp.quote s[0...min]}#{
					s[min...-1].
						reverse.
						each_char.
						reduce( "#{Regexp.quote s[-1]}?") {|f,n|
							"(?:#{Regexp.quote n}#{f})?"
					}
				}"
			}/
		end

		# Wraps `n(s,min=)` in a full matching RegExp with ending `\0`:
		# `r("abc")` would produce: `/\A(?:a|ab|abc)\0\z/`
		# You can define a minimum length to match:
		# `r("abcdef",4)` => `/\aabcd(?:|e|ef)\0\z/`
		def r s, min = nil
			/\A#{n s, min}\0\z/
		end

		# Generates a list of aliases for given `cmd`:
		# `g(:abc)` => `["a", "ab", "abc"]`
		# `g(:abcdef, 4)` => `["abcd", "abcde", "abcdef"]`
		def gen_aliases cmd, min = nil
			r = ((min||1)-1).upto cmd.length-1
			if block_given?
				r.each {|i| yield cmd[0..i] }
			else
				r.map  {|i| cmd[0..i] }
			end
		end
		alias g gen_aliases
	end

	class CMD
		attr_reader :parent, :name, :desc, :exe
		def initialize parent, name, desc, exe
			raise "Proc expected, instead of: #{exe.inspect}"  unless Proc === exe
			@parent, @name, @desc, @exe = parent, name, desc, exe
		end

		def _full_cmd post
			parent._full_cmd [@name]+post
		end

		def full_cmd
			_full_cmd []
		end

		def call *a
			@exe.call *a
		end

		def help
			"#{parent.full_cmd.join ' '} #{name}\n#{    desc}"
		end

		def inspect
			"#<%s:0x%x %s @name=%p @desc=%p @parent=<%s:0x%x %s> @exe=<arity=%d>>" % [
				self.class.name, self.object_id, self.full_cmd,
				@name, @desc, @parent.class.name, @parent.class.object_id, @parent.full_cmd,
				@exe.arity
			]
		end
	end

	class Sub
		attr_reader :parent, :name, :desc, :subs
		def initialize parent, name, desc
			@parent, @name, @desc, @subs, @aliases = parent, name, desc, {}, {}
		end

		def _full_cmd post
			parent._full_cmd [@name]+post
		end

		def full_cmd
			_full_cmd []
		end

		def [] k
			@aliases[k]
		end

		def help n = nil, *a
			if n.nil?
				r = "#{full_cmd.join ' '}: #{desc}\n\n"
				m = @subs.map {|k,_| k.length }.max
				@subs.each do |k, c|
					r += "  % -#{m}s  %s\n" % [k, c.desc]  unless k.nil?
				end
				r
			elsif @aliases.has_key? n
				@aliases[n].help *a
			else
				raise UnknownCommand, "unknown command: #{_full_cmd( [n])[1..-1].join ' '}, available for #{full_cmd[1..-1].join' '}: #{@subs.keys.inspect}"
			end
		end

		def call *a
			n, *a = *a
			if @aliases.has_key? n
				@aliases[n].call *a
			else
				raise UnknownCommand, "unknown command: #{_full_cmd( [n])[1..-1].join ' '}, available for #{full_cmd[1..-1].join' '}: #{@subs.keys.inspect}"
			end
		end

		def _add name, min, obj, aliases
			name = name.to_s  unless name.nil?
			@subs[name] = obj
			CL.gen_aliases( name, min) {|a| @aliases[a] = obj }
			if aliases
				[*aliases].each {|a| @aliases[a] = obj }
			end
			obj
		end
		private :_add

		def sub name, desc, min: nil, aliases: nil, &exe
			r = _add name, min, Sub.new( self, name, desc), aliases
			block_given? ? yield( r) : r
		end

		def cmd name, desc, min: nil, aliases: nil, &exe
			_add name, min, CMD.new( self, name, desc, exe), aliases
		end

		def inspect
			"#<%s:0x%x %s @name=%p @desc=%p @subs={%s} @aliases={%s} @parent=<%s:0x%x %s>>" % [
				self.class.name, self.object_id, self.full_cmd,
				@name, @desc, @subs.keys.join(', '), @aliases.keys.join(', '), @parent.class.name, @parent.class.object_id, @parent.full_cmd
			]
		end
	end

	def initialize progname, desc
		@subs = Sub.new self, progname, desc
	end

	def full_cmd
		[]
	end

	def _full_cmd post
		post
	end

	def sub *a, &exe
		@subs.sub *a, &exe
	end

	def cmd *a, &exe
		@subs.cmd *a, &exe
	end

	def call *a
		@subs.call *a
	end

	def help *args
		@subs.help *args
	end

	def [] k
		@subs[k]
	end
end