module AGL
	# This class provides methods for easily drawing one or multiple lines of
	# text, with control over the text alignment and coloring.
	class TextHelper
		# Creates a TextHelper.
		# 
		# Parameters:
		# [font] A <code>Gosu::Font</code> that will be used to draw the text.
		# [line_spacing] When drawing multiple lines, the distance, in pixels,
		#                between each line.
		def initialize font, line_spacing = 0
			@font = font
			@line_spacing = line_spacing
		end
		
		# Draws a single line of text.
		# 
		# Parameters:
		# [text] The text to be drawn. No line breaks are allowed.
		# [x] The horizontal reference for drawing the text. If +mode+ is +:left+,
		#     all text will be drawn from this point to the right; if +mode+ is
		#     +:right+, all text will be drawn from this point to the left; and if
		#     +mode+ is +:center+, the text will be equally distributed to the
		#     left and to the right of this point.
		# [y] The vertical reference for drawing the text. All text will be drawn
		#     from this point down.
		# [mode] The alignment of the text. Valid values are +:left+, +:right+ and
		#        +:center+.
		# [color] The color of the text, in hexadecimal RRGGBB format.
		# [alpha] The opacity of the text. Valid values vary from 0 (fully
		#         transparent) to 255 (fully opaque).
		def write_line text, x, y, mode = :left, color = 0, alpha = 0xff
			color = (alpha << 24) | color
			rel =
				case mode
				when :left then 0
				when :center then 0.5
				when :right then 1
				else 0
				end
			@font.draw_rel text, x, y, 0, rel, 0, 1, 1, color
		end
		
		# Draws text, breaking lines when needed and when explicitly caused by the
		# "\n" character.
		# 
		# Parameters:
		# [text] The text to be drawn. Line breaks are allowed.
		# [x] The horizontal reference for drawing the text. Works like in
		#     +write_line+ for the +:left+, +:right+ and +:center+ modes. For the
		#     +:justified+ mode, works the same as for +:left+.
		# [y] The vertical reference for drawing the text. All text will be drawn
		#     from this point down.
		# [width] The maximum width for the lines of text. Line is broken when
		#         this width is exceeded.
		# [mode] The alignment of the text. Valid values are +:left+, +:right+,
		#        +:center+ and +:justified+.
		# [color] The color of the text, in hexadecimal RRGGBB format.
		# [alpha] The opacity of the text. Valid values vary from 0 (fully
		#         transparent) to 255 (fully opaque).
		def write_breaking text, x, y, width, mode = :left, color = 0, alpha = 0xff
			color = (alpha << 24) | color
			text.split("\n").each do |p|
				if mode == :justified
					y = write_paragraph_justified p, x, y, width, color
				else
					rel =
						case mode
						when :left then 0
						when :center then 0.5
						when :right then 1
						else 0
						end
					y = write_paragraph p, x, y, width, rel, color
				end
			end
		end
	
	private
		
		def write_paragraph text, x, y, width, rel, color
			line = ""
			line_width = 0
			text.split(' ').each do |word|
				w = @font.text_width word
				if line_width + w > width
					@font.draw_rel line.chop, x, y, 0, rel, 0, 1, 1, color
					line = ""
					line_width = 0
					y += @font.height + @line_spacing
				end
				line += "#{word} "
				line_width += @font.text_width "#{word} "
			end
			@font.draw_rel line.chop, x, y, 0, rel, 0, 1, 1, color if not line.empty?
			y + @font.height + @line_spacing
		end
	
		def write_paragraph_justified text, x, y, width, color
			space_width = @font.text_width " "
			spaces = [[]]
			line_index = 0
			new_x = x
			words = text.split(' ')
			words.each do |word|
				w = @font.text_width word
				if new_x + w > x + width
					space = x + width - new_x + space_width
					index = 0
					while space > 0
						spaces[line_index][index] += 1
						space -= 1
						index += 1
						index = 0 if index == spaces[line_index].size - 1
					end
				
					spaces << []
					line_index += 1
				
					new_x = x
				end
				new_x += @font.text_width(word) + space_width
				spaces[line_index] << space_width
			end
		
			index = 0
			spaces.each do |line|
				new_x = x
				line.each do |s|
					@font.draw words[index], new_x, y, 0, 1, 1, color
					new_x += @font.text_width(words[index]) + s
					index += 1
				end
				y += @font.height + @line_spacing
			end
			y
		end
	end
end