require 'flydata/mysql/binlog_position'
require 'flydata-core/mysql/command_generator'

module Flydata
module Mysql

class TableDdl
  VERSION0 = 0 # the version where no .generated_ddl file was generated.
               # Therefore, this version never shows up in anywhere.
  VERSION1 = 1 # the version which doesn't handle server side encoding support.
  VERSION2 = 2 # the version with server side encoding support, migrated from
               # the previous versions.  Format/functionality-wise, it's the
               # same as Version 3.
  VERSION3 = 3 # the version with server side encoding support, generated by
               # sync:generated_table_ddl command.
  VERSION4 = 4 # the version with server side encoding support, generated by
               # the auto-generated CREATE TABLE event.
  VERSION = VERSION3

  def self.migrate_tables(tables, mysql_opts, sync_fm, position_file, context,
                          &block)
    migrate_to_v2(tables, mysql_opts, sync_fm, position_file, context, &block)
  end

  private

  V2_TARGET_VERSION = VERSION2
  EVENT_TYPE = 'Query'
  ALTER_TABLE_CHARSET_SQL = <<EOS.strip
ALTER TABLE `%s`.`%s` CHARACTER SET = %s;
EOS
  CHANGE_COLUMN_SQL = <<EOS.strip
CHANGE COLUMN `%s` %s
EOS
  ALTER_TABLE_SQL = <<EOS.strip
ALTER TABLE `%s`.`%s` %s;
EOS

  def self.migrate_to_v2(tables, mysql_opts, sync_fm, position_file, context)
    database = mysql_opts[:database]
    mysql_tabledefs = nil
    original_binlog_file = nil
    binlog_pos = nil
    event_size = 0 # so that the next binlog position becomes the master binlog position
    tables.each do |table|
      # check the current ddl version
      contents = sync_fm.load_generated_ddl([table])
      version = contents.first.to_i
      # return if no need to migrate
      next if version >= V2_TARGET_VERSION

      if mysql_tabledefs.nil?
        FlydataCore::Mysql::CommandGenerator.each_mysql_tabledef(tables, mysql_opts) do |mysql_tabledef, error|
          raise error if error

          mysql_tabledefs ||= {}
          mysql_tabledefs[mysql_tabledef.table_name] = mysql_tabledef
        end
      end
      mysql_tabledef = mysql_tabledefs[table]
      if binlog_pos.nil?
        # get binlog position
        binlog_pos = BinLogPosition.new(File.open(position_file){|f| f.read })
        original_binlog_file = context.current_binlog_file
        context.current_binlog_file = binlog_pos.file
      end
      # get charset
      charset = mysql_tabledef.default_charset_mysql
      # construct queries
      # column charset
      column_event = nil
      at_subquery = mysql_tabledef.column_def.select{|col, coldef| /CHARACTER SET/.match(coldef) }.collect{|col, coldef| CHANGE_COLUMN_SQL % [col, coldef]}.join(",")
      unless at_subquery.empty?
        column_query = ALTER_TABLE_SQL % [database, table, at_subquery]
        column_event = QueryEvent.new(EVENT_TYPE, database, table,
                                      binlog_pos.pos, event_size, column_query,
                                      Time.now.to_i)
        yield column_event
      end
      # table charset
      table_query = ALTER_TABLE_CHARSET_SQL % [database, table, charset]
      # create events and yield
      table_event = QueryEvent.new(EVENT_TYPE, database, table, binlog_pos.pos,
                                   event_size, table_query, Time.now.to_i)
      yield table_event
      $log.info "migrating table `#{table}` from version #{version} to version #{V2_TARGET_VERSION}.  Table event #{table_event} Column event #{column_event}"

      # update generated_ddl
      sync_fm.save_generated_ddl([table], V2_TARGET_VERSION.to_s)
    end
    context.current_binlog_file = original_binlog_file if binlog_pos
  end
end

# mimics RubyBinlog::QueryEvent
class QueryEvent
  def initialize(event_type, database_name, event_table_name, next_position,
                 event_length, query, timestamp)
    @event_type = event_type
    @database_name = database_name
    @event_table_name = event_table_name
    @next_position = next_position
    @event_length = event_length
    @query = query
    @timestamp = timestamp
  end
  attr_reader :event_type, :database_name, :event_table_name, :next_position,
              :event_length, :query, :timestamp

  def to_s
    <<EOS
event_type;#{event_type} database_name:#{database_name} event_table_name:#{event_table_name} next_position:#{next_position} event_length:#{event_length} timestamp:#{timestamp} query:#{query}
EOS
  end
end

end
end