#!/usr/bin/env ruby

require 'rubygems'
require 'aws/s3'

class SVNS3Backup
  def initialize
    AWS::S3::Base.establish_connection!(
      :access_key_id     => '00000000000000000000',
      :secret_access_key => '0000000000000000000000000000000000000000' )
    @backup_key = 'fcit_svn'
    @repository = '/srv/svn/repository'
    @youngest_revision = `svnlook youngest #{@repository}`.chomp.to_i
    @bucket = AWS::S3::Bucket.find '00000000000000000000.komodo_backups'
    @backups = @bucket.objects :prefix => @backup_key
  end

  def process!
    unless @backups.empty?
      revisions = @backups.collect { |obj| obj.key.split('.').last.to_i }.sort
      last_backup = revisions.last
      revised = revisions.all? { |r| r < @youngest_revision }
      revised ? svn_dump(last_backup+1) : log("No changes to repository since last backup (r#{last_backup}).")      
    else
      # No backups in the bucket so store the first one.
      log "No backups on file, sending entire repository."
      svn_dump
    end
  end

  private

    def svn_dump(from_revision = 0)
      base_name = [@backup_key, @youngest_revision].join('.')
      dump_path = "/tmp/#{base_name}"
      file_path = "#{dump_path}.tar.bz2"
      system "svnadmin dump #{@repository} -r #{from_revision}:#{@youngest_revision} --incremental > #{dump_path}"
      system "tar -cjf #{file_path} #{dump_path}"
      AWS::S3::S3Object.store base_name, open(file_path), @bucket.name
      system "rm #{dump_path} #{file_path}"
      log "Successfully backed up revisions #{from_revision} through #{@youngest_revision}."
    end
    
    def log(message)
      puts "[#{Time.now.strftime('%Y-%m-%d %H:%M:%S')}] #{message}"
    end
    
end

SVNS3Backup.new.process!