require 'RMagick'

module Krunimir

	# Prostredi pro zkompilovaneho Krunimira
	class Environment

		WIDTH = 701
		HEIGHT = 701

		# Inicializuje hlavnim telem zelvy.
		def initialize(turtle_body)
			@turtle_body = turtle_body

			@pos_x = WIDTH / 2
			@pos_y = HEIGHT / 2
			@angle_deg = 0
			@pen_size = 0
			color(0, 0, 0)

			@image = Magick::ImageList.new
			@image.new_image(WIDTH, HEIGHT)
			@context = Magick::Draw.new
		end

		# Zapocne kresleni (cely beh zelvy).
		def draw(draws)
			if draws > 0
				@draws = draws
			else
				@draws = nil
			end

			instance_eval &@turtle_body
		end

		# Ulozi vysledny PNG obrazek do souboru.
		def save_to(filename)
			@context.draw @image
			@image.write filename
		end

		private

		# Zelviny prikazy.

		def left(angle)
			@angle_deg -= angle
		end

		def right(angle)
			@angle_deg += angle
		end

		def pen(size)
			@pen_size = size
		end

		def forward(length)
			angle_rad = @angle_deg * Math::PI / 180.0

			x1 = @pos_x
			y1 = @pos_y
			x2 = x1 + length * Math.sin(angle_rad)
			y2 = y1 - length * Math.cos(angle_rad)

			if @pen_size > 0
				if @draws
					@draws -= 1
					return unless @draws >= 0
				end

				@context.stroke(@color)
				@context.stroke_width(@pen_size)
				@context.line(x1, y1, x2, y2)
			end

			@pos_x = x2
			@pos_y = y2
		end

		def color(r, g, b)
			# jednotlive slozky se nejdrive "orezou" do rozsahu 0..255 a pak se spoji
			# pomoci carek
			@color = "rgb(#{[r, g, b].map do |c|
				if c < 0
					0
				elsif c > 255
					255
				else
					c
				end
			end.join ","})"
		end

		def _define(name, &block)
			# TODO: definuje se metoda cele tridy Environment misto singletonu!
			self.class.send(:define_method, name, &block)
		end

		def _if(expr)
			yield if expr > 0
		end

		def _repeat(num)
			num.times { yield }
		end

		# vyhodnoti jakoby dalsiho zelvaka ale ne soucasne s ostatnima nybrz
		# samostatne, protoze vysledek je stejny (pokud nejde krokovat, coz nejde)
		def _split(&block)
			# ulozeni promennych aby se pote mohly obnovit
			to_restore = %w[pos_x pos_y angle_deg pen_size draws].map { |s| :"@#{s}" }

			values = {}
			to_restore.each do |ivar|
				values[ivar] = instance_variable_get ivar
			end

			instance_eval &block

			to_restore.each do |ivar|
				instance_variable_set ivar, values[ivar]
			end
		end
	end
end