#!/usr/bin/env ruby

ENV['TMPDIR']='/tmp/backup/'
require 'optparse'
require 'ostruct'
require 'fileutils'
require 'rdiff_simple'

options = OpenStruct.new
@verbose = false

usage = "Usage: understudy [options] job-name"

OptionParser.new do |opts|
  opts.banner = usage
  opts.on '-v', '--verbose', 'Output extra information' do |v|
    @verbose = v
  end
  opts.on '-f', '--first-time', 'Force first-time run' do |f|
    options.first = f
  end
end.parse!

def error msg
  STDERR.puts "ERROR: #{msg}"
  exit 255
end

error usage if ARGV.length != 1

job_name = ARGV.shift

config_file = "/etc/understudy/#{job_name}.conf"

error "Cannot find '#{config_file}'" unless File.exist? config_file

DATA_DIR = "/var/lib/understudy/#{job_name}"

FileUtils.mkdir_p DATA_DIR

lockfile = File.open( "#{DATA_DIR}/LOCK", File::RDWR|File::CREAT, 0644 )
unless lockfile.flock File::LOCK_EX|File::LOCK_NB
  error "Job #{job_name} is already running"
end
lockfile.puts $$
lockfile.flush

config = OpenStruct.new

# Any options that aren't our options go to rdiff-backup
OUR_OPTIONS = %w{source dest command}

rdiff_args = []

File.read( config_file ).split( /\n/ ).each do |line|
  line.sub! /#.*$/, ''
  line.sub! /^\s+/, ''
  line.sub! /\s+$/, ''
  next if line.empty?

  line =~ /^([-\w]+)(\s+=\s+(.*))?$/ or raise "Strange line in config: #{line}"
  key = $1
  val = $3
  if OUR_OPTIONS.member? key
    config.send "#{key}=".to_sym, val
  else
    rdiff_args.push "--#{key}" + ( val ? "=#{val}" : "" )
  end
end

error "Missing 'dest' config option" unless config.dest
error "Missing 'source' config option" unless config.source

rdiff_data = "#{config.dest}/rdiff-backup-data"
exists = File.directory? rdiff_data
if exists && options.first
  error "Cannot force first time, destination '#{config.dest}' already exists"
elsif !exists && !options.first
  error "Destination '#{config.dest}' does not appear to exist, try again with --first-time"
end

def info message
  return unless @verbose
end

def run command
  friendly = nil
  if command.is_a? Array
    friendly = command.map { |i| i =~ /[^-=\/\.\w]/ ? "#{i}" : i }.join ' '
    info "Running: #{friendly}"
    RdiffSimple.execute( friendly ) or error "Could not run #{friendly}"
  else
    friendly = command
    info "Running: #{friendly}"
    RdiffSimple.execute( friendly ) or error "Could not run #{friendly}"
  end
  if $? != 0
    error "Could not run #{friendly}"
  end
end

ENV['PATH'] += ":/etc/understudy"
run config.command if config.command

command = []

command << "--terminal-verbosity=5" if @verbose
command << "--print-statistics"

command += rdiff_args

command << config.source
command << config.dest

run command

info "Backup successful"

exit 0