require 'fluent/plugin/in_mysql_binlog'
require 'binlog'
require_relative 'binlog_position'

module Mysql
  class BinlogRecordHandler
    TABLE_NAME = :table_name # A Flydata JSON tag to specify a table name
    TYPE = :type
    SEQ = :seq
    RESPECT_ORDER = :respect_order
    SRC_POS = :src_pos
    TABLE_REV = :table_rev

    def initialize(context)
      @context = context
      @first_empty_binlog = true

      # Load per-table binlog position
      @table_binlog_pos = {}
      @context.tables.each do |table_name|
        table_binlog_content = @context.sync_fm.get_table_binlog_pos(table_name)
        if table_binlog_content
          @table_binlog_pos[table_name] = BinLogPosition.new(table_binlog_content)
        end
      end
    end

    private

    def supported_database
      @context.database
    end

    def acceptable_db?(record)
      supported_database == record["db_name"]
    end

    def acceptable_table?(record, table)
      acceptable = @context.tables.include?(table)

      if acceptable and @table_binlog_pos[record['table_name']]
        if @table_binlog_pos[record['table_name']] >= BinLogPosition.new(
          "#{@context.current_binlog_file}\t#{record['next_position'] - record['event_length']}")
          acceptable = false
        else
          @context.sync_fm.delete_table_binlog_pos(record['table_name'])
          @table_binlog_pos.delete(record['table_name'])
        end
      end
      acceptable
    end

    def emit_record(type, record, opt = {})
      return unless acceptable_db?(record)
      return unless record["table_name"].nil? or acceptable_table?(record, record["table_name"])

      check_empty_binlog

      records = yield
      return if records.nil? # skip
      records = [records] unless records.kind_of?(Array)

      table = records.first[TABLE_NAME] || record['table_name']
      raise "Missing table name. #{record}" if table.to_s.empty?
      return unless acceptable_table?(record, table)

      table_rev = @context.sync_fm.table_rev(table)
      position = record['next_position'] - record['event_length']

      # Add common information to each record
      records.each do |r|
        if opt[:increment_table_rev]
          table_rev = @context.sync_fm.increment_table_rev(table, table_rev)
        end
        r[TYPE] = type
        r[RESPECT_ORDER] = true
        r[TABLE_NAME] = table
        r[SRC_POS] = "#{@context.current_binlog_file}\t#{position}"
        r[TABLE_REV] = table_rev
      end

      # Use binlog's timestamp
      timestamp = record["timestamp"].to_i
      records.each do |row|
        @context.sync_fm.increment_and_save_table_position(row[TABLE_NAME]) do |seq|
          row[SEQ] = seq
          Fluent::Engine.emit(@context.tag, timestamp, row)
        end
      end
    end

    def check_empty_binlog
      #Log one warning per consecutive records that have empty binlog filename
      if @context.current_binlog_file.to_s.empty?
        if @first_empty_binlog
          $log.warn "Binlog file name is empty. Rotate event not received!"
          @first_empty_binlog = false
        end
      else
        @first_empty_binlog = true
      end
    end
  end
end