require 'mysql2'
require 'fulmar/infrastructure/service/tunnel_service'

module Fulmar
  module Infrastructure
    module Service
      module Database
        # Provides basic methods common to all database services
        class DatabaseService
          attr_accessor :client
          attr_reader :shell

          DEFAULT_CONFIG = {
            maria: {
              hostname: '127.0.0.1',
              port: 3306,
              user: 'root',
              password: '',
              encoding: 'utf8',
              backup_path: '/tmp'
            }
          }

          def initialize(config)
            @config = config
            @config.merge DEFAULT_CONFIG
            @shell = Fulmar::Infrastructure::Service::ShellService.new(config[:local_path], config[:hostname])
            @tunnel = nil
            @client = nil
            config_test
          end

          def connect
            options = compile_options

            if @config[:maria][:hostname] != 'localhost' && @config[:maria][:hostname] != '127.0.0.1'
              tunnel.open
              options[:port] = tunnel.local_port
            end

            # Wait max 3 seconds for the tunnel to establish
            4.times do |i|
              begin
                @client = Mysql2::Client.new options
                break
              rescue Mysql2::Error => e
                sleep 1 if i < 3
                fail e.message if i == 3
              end
            end

            @connected = true
          end

          def disconnect
            @connected = false
            @client.close
            @tunnel.close if @tunnel # using the variable directly avoids creating a tunnel instance when closing the database connection
          end

          def connected?
            @connected
          end

          def tunnel
            @tunnel ||= Fulmar::Infrastructure::Service::TunnelService.new(@config[:maria][:hostname], @config[:maria][:port])
          end

          # shortcut for DatabaseService.client.query
          def query(*arguments)
            @client.query(arguments)
          end

          def create(name)
            state_before = connected?
            connect unless connected?
            @client.query "CREATE DATABASE IF NOT EXISTS `#{name}`"
            disconnect unless state_before
          end

          def dump(filename = nil)

            if filename
              # Ensure path is absolute
              path = filename[0, 1] == '/' ? filename : @config[:maria][:backup_path] + '/' + filename
            else
              path = @config[:maria][:backup_path] + '/' + backup_filename
            end

            diffable = @config[:maria][:diffable_dump] ? '--skip-comments --skip-extended-insert ' : ''

            @shell.run "mysqldump -u #{@config[:maria][:user]} --password='#{@config[:maria][:password]}' " \
                       "#{@config[:maria][:database]} --single-transaction #{diffable}-r \"#{path}\""

            path
          end

          def load_dump(dump_file, database = @config[:maria][:database])
            @shell.run "mysql -u #{@config[:maria][:user]} --password='#{@config[:maria][:password]}' " \
                       "-D #{database} < #{dump_file}"
          end

          def download_dump(filename = backup_filename)
            local_path = filename[0, 1] == '/' ? filename : @config[:local_path] + '/' + filename
            remote_path = dump
            copy = system("scp -q #{@config[:maria][:hostname]}:#{remote_path} #{local_path}")
            system("ssh #{@config[:maria][:hostname]} 'rm -f #{remote_path}'") # delete temporary file
            if copy
              local_path
            else
              ''
            end
          end

          protected

          # Test configuration
          def config_test
            fail 'Configuration option "database" missing.' unless @config[:maria][:database]
            @shell.run "test -d '#{@config[:maria][:backup_path]}'"
          end

          # Builds the filename for a new database backup file
          # NOTE: The file might already exist, for example if this is run at the same
          # time from to different clients. I won't handle this as it is unlikely and
          # would result in more I/O
          def backup_filename
            "#{@config[:maria][:database]}_#{Time.now.strftime('%Y-%m-%dT%H%M%S')}.sql"
          end

          # Compiles a mysql config hash from valid options of the fulmar config
          def compile_options
            possible_options = [:host, :username, :password, :port, :encoding, :socket, :read_timeout, :write_timeout,
                             :connect_timeout, :reconnect, :local_infile, :secure_auth, :default_file, :default_group,
                             :init_command
                            ]
            options = {}
            options[:host] = '127.0.0.1'
            options[:username] = @config[:maria][:user]
            possible_options.each do |option|
              options[option] = @config[:maria][option] unless @config[:maria][option].nil?
            end

            options
          end

        end
      end
    end
  end
end