#!/usr/bin/env ruby

class Ctags
	attr_reader :tags_file, :target_dir

	def initialize(target_dir, tags_file=nil)
		@target_dir = target_dir + '/'
		tags_file ||= File.join(target_dir, '.autotags')
		@tags_file = tags_file
		refresh_tags
	end

	def refresh_tags
		cmd "rm '#{tags_file}'" if File.exists? tags_file
		cmd "ctags -f '#{tags_file}' -R #{target_dir}"
	end

	def append_tags_for(f)
		return if file_excluded? f
		cmd "ctags -f '#{tags_file}' -a '#{f}'"
	end

	def clear_tags_for(f)
		return if file_excluded? f
		cmd "sed -i -e '/#{sed_escape(f)}/d' '#{tags_file}'"
	end

	private

	def file_excluded?(f)
		return f == tags_file || f =~ /#{File.join(target_dir, 'sed')}.*/
	end

	def sed_escape(f)
		f.gsub(/\//, '\/')
	end

	def cmd(cmd)
		#puts cmd
		`#{cmd}`
	end
end

['sed', 'ctags', 'rm', 'inotifywait'].each do |c|
	if `which #{c}` == ""
		puts "'#{c}' is required on the path for autotags to work!"
		exit
	end
end

if ARGV.empty?
	puts "Usage: autotags <directory>"
	exit
end

ctf = Ctags.new ARGV[0]

procs = {
	/(.*) CREATE (.*)/ => Proc.new do |f|
		ctf.append_tags_for(f)
	end,
	/(.*) DELETE (.*)/ => Proc.new do |f|
		ctf.clear_tags_for(f)
	end,
	/(.*) MOVED_FROM (.*)/ => Proc.new do |f|
		ctf.clear_tags_for(f)
	end,
	/(.*) MOVED_TO (.*)/ => Proc.new do |f|
		ctf.append_tags_for(f)
	end,
	/(.*) MODIFY (.*)/ => Proc.new do |f|
		ctf.clear_tags_for(f)
		ctf.append_tags_for(f)
	end
}

pipe = IO.popen("inotifywait -r -m -e modify -e create -e move -e delete #{ARGV[0]}")
puts "Watching #{ARGV[0]}"

while(line = pipe.gets) do
	procs.each do |k,v|
		v.call("#{$1}#{$2}") if line =~ k
	end
end