#!/usr/bin/env ruby
# vim:ft=ruby
#
# forks and executes the requested program with the temporary file given,
# allowing mutt to return to its message view while you view the attachment in
# the program
#
# usage in ~/.mailcap:
# application/pdf; ~/bin/mutt_bgrun xpdf %s
#

require "fileutils"
require "open3"

viewer = ARGV[0]
orig_file = ARGV[1]

if !orig_file
  STDERR.puts "usage: #{$0} <viewing application> <filename>"
  exit 1
end

tmp_dir = `mktemp -d -t`.chomp
tmp_file = tmp_dir + "/" + File.basename(orig_file).gsub(/[^A-Za-z_\.-]/, "")

system("cp", orig_file, tmp_file)

Kernel.fork do
  launch_file = tmp_file.dup
  if viewer == "firefox"
    launch_file = "file:///#{launch_file}"
  end

  i, _, _, w = Open3.popen3(viewer, launch_file)
  i.close

  begin
    Process.waitpid(w[:pid])
  rescue Errno::ECHILD
    # process ended really quickly, most likely just handed it off to another
    # process, so wait a bit for it to process the tmp file before removing it
    sleep 3
  end

  File.unlink tmp_file
  Dir.unlink tmp_dir
end