#! /usr/bin/env ruby
require "fileutils"
require "getopts"
ENV['LANG']="C"

USAGE = <<USAGE
usage: #$0 [options] dir1 dir2\n
  options:
       -f     Force diffing. If not given, try to use cache under ~/.diffrb.
       -b     Ignore changes in amount of white space.
       -B     Ignore changes that just insert or delete blank lines.
       -N     treat only file as present but empty in the other directory.
       -p     Print diff(1) and exit.
       --change | --add |  --delete
              Reports only change/add/delete. No two of these can't be given.
       --diff
              Reports as diff command to leads "| sh". Implies --change.
       --noprefix
              Do not print one-letter prefix A, C, nor D.
USAGE

opterr = getopts("fpbNB0", "change", "add", "delete", "help", "noprefix", "diff")

if $OPT_diff
  $OPT_change = true
  $OPT_add, $OPT_delete = nil
end

if $OPT_change && $OPT_add or
    $OPT_change && $OPT_delete or
    $OPT_delete && $OPT_add
  abort USAGE
end

if ARGV.size != 2 or $OPT_help or !opterr
  abort USAGE
end

non_directory = ARGV.find_all{|d| !File.directory?(d)}
if !non_directory.empty?
  non_directory.each{|d|
    STDERR.puts "#$0: #{d}: not a directory"
  }
  abort USAGE
end

$OPT_all = !$OPT_add && !$OPT_change && !$OPT_delete

dir1, dir2 = ARGV.map{|i| i.dup}
dir1.sub!(%r#/+$#, '')
dir2.sub!(%r#/+$#, '')
opts = "-q"
opts << "b" if $OPT_b
opts << "B" if $OPT_B
opts << "N" if $OPT_N
uopts = "-u"
uopts << "b" if $OPT_b
uopts << "B" if $OPT_B
uopts << "N" if $OPT_N
uopts << "0" if $OPT_0

rcdir = ENV["HOME"]+"/.diffrb"
fn = ARGV.map{|d| File.expand_path(d).gsub("/", "___")}.join("---")
difffile = File.join(rcdir, fn+".txt")

if !File.exist?(difffile) or $OPT_f
  FileUtils.mkdir_p(rcdir)
  STDERR.puts("# #$0: executing diff -qr #{dir1} #{dir2}")
  system("diff -qr #{dir1} #{dir2} > #{difffile}")
end

diff = File.read(difffile)

if $OPT_p
  print diff
  exit
end

change = diff.scan(/Files #{Regexp::quote(dir1)}\/(.*?) and #{Regexp.quote(dir2)}\/\1 differ/u).flatten.sort
deleted = diff.scan(/Only in #{Regexp.quote(dir1)}\/(\S+): (.+)$/u).map{|i| i.join("/")}.sort
added = diff.scan(/Only in #{Regexp.quote(dir2)}\/(\S+): (.+)$/u).map{|i| i.join("/")}.sort

if !$OPT_add and !$OPT_delete
  if $OPT_diff
    change.each{|i| puts %<diff #{uopts} "#{dir1}/#{i}" "#{dir2}/#{i}">}
  else
    change.each{|i| puts $OPT_noprefix ? i : "C #{i}"}
  end
end
if !$OPT_change and !$OPT_delete
  added.each{|i| puts $OPT_noprefix ? i : "A #{i}"}
end
if !$OPT_add and !$OPT_change
  deleted.each{|i| puts $OPT_noprefix ? i : "D #{i}"}
end