#!/usr/bin/env ruby

# Script to concat files to a config file.

#

# Given a directory like this:

# /path/to/conf.d

# |-- fragments

# |   |-- 00_named.conf

# |   |-- 10_domain.net

# |   `-- zz_footer

#

# The script supports a test option that will build the concat file to a temp location and

# use /usr/bin/cmp to verify if it should be run or not.  This would result in the concat happening

# twice on each run but gives you the option to have an unless option in your execs to inhibit rebuilds.

#

# Without the test option and the unless combo your services that depend on the final file would end up

# restarting on each run, or in other manifest models some changes might get missed.

#

# OPTIONS:

#  -o	The file to create from the sources

#  -d	The directory where the fragments are kept

#  -t	Test to find out if a build is needed, basically concats the files to a temp

#       location and compare with what's in the final location, return codes are designed

#       for use with unless on an exec resource

#  -w   Add a shell style comment at the top of the created file to warn users that it

#       is generated by puppet

#  -f   Enables the creation of empty output files when no fragments are found

#  -n	Sort the output numerically rather than the default alpha sort

#

# the command:

#

#   concatfragments.rb -o /path/to/conffile.cfg -d /path/to/conf.d

#

# creates /path/to/conf.d/fragments.concat and copies the resulting

# file to /path/to/conffile.cfg.  The files will be sorted alphabetically

# pass the -n switch to sort numerically.

#

# The script does error checking on the various dirs and files to make

# sure things don't fail.

require 'optparse'

require 'fileutils'

settings = {

    :outfile => "",

    :workdir => "",

    :test => false,

    :force => false,

    :warn => "",

    :sortarg => "",

    :newline => false

}

OptionParser.new do |opts|

  opts.banner = "Usage: #{$0} [options]"

  opts.separator "Specific options:"

  opts.on("-o", "--outfile OUTFILE", String, "The file to create from the sources") do |o|

    settings[:outfile] = o

  end

  opts.on("-d", "--workdir WORKDIR", String, "The directory where the fragments are kept") do |d|

    settings[:workdir] = d

  end

  opts.on("-t", "--test", "Test to find out if a build is needed") do

    settings[:test] = true

  end

  opts.separator "Other options:"

  opts.on("-w", "--warn WARNMSG", String,

          "Add a shell style comment at the top of the created file to warn users that it is generated by puppet") do |w|

    settings[:warn] = w

  end

  opts.on("-f", "--force", "Enables the creation of empty output files when no fragments are found") do

    settings[:force] = true

  end

  opts.on("-n", "--sort", "Sort the output numerically rather than the default alpha sort") do

    settings[:sortarg] = "-n"

  end

  opts.on("-l", "--line", "Append a newline") do

    settings[:newline] = true

  end

end.parse!

# do we have -o?

raise 'Please specify an output file with -o' unless !settings[:outfile].empty?

# do we have -d?

raise 'Please specify fragments directory with -d' unless !settings[:workdir].empty?

# can we write to -o?

if File.file?(settings[:outfile])

  if !File.writable?(settings[:outfile])

    raise "Cannot write to #{settings[:outfile]}"

  end

else

  if !File.writable?(File.dirname(settings[:outfile]))

    raise "Cannot write to dirname #{File.dirname(settings[:outfile])} to create #{settings[:outfile]}"

  end

end

# do we have a fragments subdir inside the work dir?

if !File.directory?(File.join(settings[:workdir], "fragments")) && !File.executable?(File.join(settings[:workdir], "fragments"))

  raise "Cannot access the fragments directory"

end

# are there actually any fragments?

if (Dir.entries(File.join(settings[:workdir], "fragments")) - %w{ . .. }).empty?

  if !settings[:force]

    raise "The fragments directory is empty, cowardly refusing to make empty config files"

  end

end

Dir.chdir(settings[:workdir])

if settings[:warn].empty?

  File.open("fragments.concat", 'w') { |f| f.write("") }

else

  File.open("fragments.concat", 'w') { |f| f.write("#{settings[:warn]}\n") }

end

# find all the files in the fragments directory, sort them numerically and concat to fragments.concat in the working dir

open('fragments.concat', 'a') do |f|

  fragments = Dir.entries("fragments").sort

  if settings[:sortarg] == '-n'

    fragments = fragments.sort_by { |v| v.split('_').map(&:to_i) }

  end

  fragments.each { |entry|

    if File.file?(File.join("fragments", entry))

      f << File.read(File.join("fragments", entry))

      # append a newline if we were asked to (invoked with -l)

      if settings[:newline]

        f << "\n"

      end

    end

  }

end

if !settings[:test]

  # This is a real run, copy the file to outfile

  FileUtils.cp 'fragments.concat', settings[:outfile]

else

  # Just compare the result to outfile to help the exec decide

  if FileUtils.cmp 'fragments.concat', settings[:outfile]

    exit 0

  else

    exit 1

  end

end