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# Copyright (c) 2018 Uber Technologies, Inc.
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# Copyright (c) 2013-2017 Uber Technologies, Inc.
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"""
RowDescription message

RowDescription message describes the column layout of the rows that will be
returned in response to a SELECT, FETCH, etc query.
"""

from __future__ import print_function, division, absolute_import

from struct import unpack, unpack_from, calcsize

from six.moves import range

from ..message import BackendMessage
from ....datatypes import getTypeName


class RowDescription(BackendMessage):
    message_id = b'T'

    def __init__(self, data):
        BackendMessage.__init__(self)
        self.fields = []
        field_count = unpack('!H', data[0:2])[0]

        if field_count == 0:
            return

        # read type pool
        # used for special types e.g. GEOMETRY, GEOGRAPHY
        user_types = []
        type_pool_count = unpack('!I', data[2:6])[0]
        pos = 6
        for _ in range(type_pool_count):
            base_type_oid = unpack('!I', data[pos:(pos + 4)])[0]
            pos += 4
            type_name = unpack_from("!{0}sx".format(data.find(b'\x00', pos) - pos), data, pos)[0]
            pos += len(type_name) + 1
            user_types.append((base_type_oid, type_name))

        # read info of each field
        offset = calcsize("!HBIHHHiH")
        for _ in range(field_count):
            field_name = unpack_from("!{0}sx".format(data.find(b'\x00', pos) - pos), data, pos)[0]
            pos += len(field_name) + 1

            table_oid = unpack('!Q', data[pos:(pos + 8)])[0]
            pos += 8

            schema_name, table_name = None, None
            if table_oid != 0:
                schema_name = unpack_from("!{0}sx".format(data.find(b'\x00', pos) - pos), data, pos)[0]
                pos += len(schema_name) + 1
                table_name = unpack_from("!{0}sx".format(data.find(b'\x00', pos) - pos), data, pos)[0]
                pos += len(table_name) + 1

            field_info = unpack_from("!HBIHHHiH", data, pos)
            pos += offset

            if field_info[1] == 1:
                data_type_oid, data_type_name = user_types[field_info[2]]
            else:
                data_type_oid = field_info[2]
                data_type_name = getTypeName(data_type_oid, field_info[6])

            self.fields.append({
                'name': field_name,
                'table_oid': table_oid,
                'schema_name': schema_name,
                'table_name': table_name,
                'attribute_number': field_info[0],
                'data_type_oid': data_type_oid,
                'data_type_size': field_info[3],
                'data_type_name': data_type_name,
                'null_ok': field_info[4] == 1,
                'is_identity': field_info[5] == 1,
                'type_modifier': field_info[6],
                'format_code': field_info[7],
            })

    def __str__(self):
        return "RowDescription: {}".format(self.fields)


BackendMessage.register(RowDescription)