require "liquid"
require "jekyll"

module Jekyll
	module FractionaliseFilter
		def fractionalise(input, limit = 0)
			input  = input.to_s

			if not input.include? "."
				# if input is a whole number, just return it
				return input
			end

			if input.split(".").length != 2
				# generally when liquid filters fail they just print nothing, so we'll do that too
				return ""
			end

			leading_integer, decimal = input.split(".")
			decimal = "0.#{decimal}"

			rational = case decimal
			# handle common weird cases so that e.g. 0.3 returns "1/3" and not "3/10" or "5404319552844595/18014398509481984"
			when "0.3", "0.33", "0.333"
				Rational(1, 3)
			when "0.6", "0.67", "0.666"
				Rational(2, 3)
			else
				decimal.to_r
			end

			if limit != 0 and rational.denominator > limit
				# apply a maximum size for the denominator to avoid the (imo) much more readable "0.41" becoming "41/100" unless wanted
				return input
			end

			"<span title='#{input}'>#{leading_integer != "0" ? "#{leading_integer} " : ""}<span class='fraction'><span class='numerator'>#{rational.numerator}</span><span class='denominator'>#{rational.denominator}</span></span></span>"

		end
	end
end

Liquid::Template.register_filter(Jekyll::FractionaliseFilter)