require 'tempfile'

module Byteback
	module Util
		@@lockfile = "/var/lock/byteback/byteback.lock"

		def remove_lockfile!
		  begin
		    File.unlink(@@lockfile)
		  rescue Errno::ENOENT
		  end
		end

		def claim_lockfile!
			# Check the lockfile first
			if File.directory?(File.dirname(@@lockfile))
			  if File.exists? @@lockfile
			    # check the lockfile is sane
			    exist_pid = File.read(@@lockfile).to_i
			    if exist_pid > 1 and exist_pid < (File.read("/proc/sys/kernel/pid_max").to_i)
			      begin
			        Process.getpgid(exist_pid)
			        # if no exception, process is running, abort
			        fatal("Process is running (#{exist_pid} from #{@@lockfile})")
			      rescue Errno::ESRCH
			        # no process running with that pid, pidfile is stale
			        remove_lockfile!
			      end
			    else
			      # lockfile isn't sane, remove it and continue
			      remove_lockfile!
			    end
			  end
			else
			  Dir.mkdir(File.dirname(@@lockfile))
			  # lockfile didn't exist so just carry on
			end

			# Own the pidfile ourselves
			File.open(@@lockfile, "w") do |lockfile|
			  lockfile.puts Process::pid
			end
		end

		def lock_out_other_processes(name)
			@@lockfile = "/var/lock/byteback/#{name}.lock"
			claim_lockfile!
			at_exit { remove_lockfile! }
		end

		def log_system(*args)
			debug("system: " + args.map { |a| / /.match(a) ? "\"#{a}\"" : a }.join(" "))
			rd, wr = IO.pipe
			pid = fork
			if pid.nil? # child
				rd.close
				STDOUT.reopen(wr)
				STDERR.reopen(wr)
				# any cleanup actually necessary here?
				exec(*args)
			end
			wr.close
			rd.each_line { |line| debug(line.chomp) }
			pid2, status = Process.waitpid2(pid, 0)
			status.exitstatus
		end
	end
end