module ActiveRecord::Import::MysqlAdapter

def add_column_for_on_duplicate_key_update( column, options={} ) # :nodoc:
  if options.include?(:on_duplicate_key_update)
    columns = options[:on_duplicate_key_update]
    case columns
    when Array then columns << column.to_sym unless columns.include?(column.to_sym)
    when Hash then columns[column.to_sym] = column.to_sym
    end
  else
    options[:on_duplicate_key_update] = [ column.to_sym ]
  end
end

def duplicate_key_update_error?(exception)# :nodoc:
  exception.is_a?(ActiveRecord::StatementInvalid) && exception.to_s.include?('Duplicate entry')
end

def insert_many( sql, values, *args ) # :nodoc:
  # the number of inserts default
  number_of_inserts = 0
  base_sql,post_sql = if sql.is_a?( String )
    [ sql, '' ]
  elsif sql.is_a?( Array )
    [ sql.shift, sql.join( ' ' ) ]
  end
  sql_size = QUERY_OVERHEAD + base_sql.size + post_sql.size
  # the number of bytes the requested insert statement values will take up
  values_in_bytes = values.sum {|value| value.bytesize }
  # the number of bytes (commas) it will take to comma separate our values
  comma_separated_bytes = values.size-1
  # the total number of bytes required if this statement is one statement
  total_bytes = sql_size + values_in_bytes + comma_separated_bytes
  max = max_allowed_packet
  # if we can insert it all as one statement
  if NO_MAX_PACKET == max or total_bytes < max
    number_of_inserts += 1
    sql2insert = base_sql + values.join( ',' ) + post_sql
    insert( sql2insert, *args )
  else
    value_sets = ::ActiveRecord::Import::ValueSetsBytesParser.parse(values,
      :reserved_bytes => sql_size,
      :max_bytes => max)
    value_sets.each do |values|
      number_of_inserts += 1
      sql2insert = base_sql + values.join( ',' ) + post_sql
      insert( sql2insert, *args )
    end
  end
  [number_of_inserts,[]]
end

def max_allowed_packet # :nodoc:
  @max_allowed_packet ||= begin
    result = execute( "SHOW VARIABLES like 'max_allowed_packet';" )
    # original Mysql gem responds to #fetch_row while Mysql2 responds to #first
    val = result.respond_to?(:fetch_row) ? result.fetch_row[1] : result.first[1]
    val.to_i
  end
end

def sql_for_on_duplicate_key_update( table_name, *args ) # :nodoc:
  sql = ' ON DUPLICATE KEY UPDATE '
  arg = args.first
  if arg.is_a?( Array )
    sql << sql_for_on_duplicate_key_update_as_array( table_name, arg )
  elsif arg.is_a?( Hash )
    sql << sql_for_on_duplicate_key_update_as_hash( table_name, arg )
  elsif arg.is_a?( String )
    sql << arg
  else
    raise ArgumentError.new( "Expected Array or Hash" )
  end
  sql
end

def sql_for_on_duplicate_key_update_as_array( table_name, arr )  # :nodoc:
  results = arr.map do |column|
    qc = quote_column_name( column )
    "#{table_name}.#{qc}=VALUES(#{qc})"
  end
  results.join( ',' )
end

def sql_for_on_duplicate_key_update_as_hash( table_name, hsh ) # :nodoc:
  results = hsh.map do |column1, column2|
    qc1 = quote_column_name( column1 )
    qc2 = quote_column_name( column2 )
    "#{table_name}.#{qc1}=VALUES( #{qc2} )"
  end
  results.join( ',')
end