#!/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/*; ~/bin/mutt_bgrun %t %s
#

require "fileutils"
require "open3"

mime = ARGV[0]
orig_file = ARGV[1]

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

if mime == "application/octet-stream"
  if orig_file.to_s.match(/\.pdf$/i)
    mime = "application/pdf"
  end
end

viewer = nil
if `uname`.strip == "Darwin"
  viewer = "open"
else
  case mime.to_s.downcase
  when
  "application/pdf",
  /^image\//
    viewer = "firefox"
  end
end

if !viewer
  STDERR.puts "no viewer for type #{mime.inspect}"
  exit 1
end

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

if viewer == "firefox"
  launch_file = "file:///#{launch_file}"
end

system("cp", orig_file, tmp_file)

Kernel.fork do
  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 5
  end

  sleep 5

  File.unlink tmp_file
  Dir.unlink tmp_dir
end