Turns templated input into repeating blocks based on start and end numbers

template_increment.rb

#!/usr/bin/ruby
# Turns templated input into repeating blocks based on start and end numbers
# Basic syntax: `##0,5##` where 0 is start and 5 is end
# Modifiers may be included: `##+4##` will be replaced by the current counter plus four
# One start,end placeholder allowed, any number of modifers
# By Brett Terpstra, 2012 <http://brettterpstra.com>
# WTFPL License <http://en.wikipedia.org/wiki/WTFPL>

input = STDIN.read

template = input.match(/(\?\:)?##(\d+),(\d+)##/)
if template.nil?
	puts input
	exit
end

display = template[1].nil? ? true : false

modifier = input.scan(/(##([+\-])?(\d+)##)/)
modified = []

unless modifier.empty?
	modifier.each {|x|
		inc = 0
		if x[1] =~ /\+/
			inc = x[2].to_i
		else
			inc = x[2].to_i * -1
		end
		modified.push([Regexp.escape(x[0]),inc])
	}
end

count_start = template[2].to_i
count_end = template[3].to_i
duration = (count_end - count_start) + 1

duration.times do
	sub = display ? count_start.to_s : ''
	out = input.sub(/#{Regexp.escape(template[0])}/,sub)
	modified.each {|mod|
		out.sub!(/#{mod[0]}/,(count_start + mod[1]).to_s)
	}
	puts out
	count_start += 1
end