#
# Copyright 2022 Google LLC
#
# Licensed to the Apache Software Foundation (ASF) under one or more
# contributor license agreements.  See the NOTICE file distributed with
# this work for additional information regarding copyright ownership.
# The ASF licenses this file to You under the Apache License, Version 2.0
# (the "License"); you may not use this file except in compliance with
# the License.  You may obtain a copy of the License at
#
#    http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#

import logging
from typing import Any, Dict, Optional

# Indicates the metadata types that can be mapped - Informational only
metadata_to_map = {
    "doc_id",
    "file_name",
    "doc_status",
    "doc_type",
    "doc_event_id",
    "doc_group_id",
    "hitl_operation_id",
    "created_at",
    "updated_at",
}


class BqMetadataMappingInfo:
    """
    Class holding information about how to map a specific metadata type

    Attributes
    ----
    bq_column_name: str
        The column in BigQuery this metadata will be mapped to
    metadata_value: Any
        If set, this value will be used for the column. If not set, a default value will be used if possible
    skip_map: bool
        If set this particular metadata will NOT be mapped into a BQ column
    """

    def __init__(
        self,
        bq_column_name: str,
        metadata_value: Optional[Any] = None,
        skip_map: bool = False,
    ):
        """
        Initializer for the class

        Parameters
        ----
        bq_column_name: str
            The column in BigQuery this metadata will be mapped to
        metadata_value: Any
            If set, this value will be used for the column. If not set, a default value will be used if possible
        skip_map: bool
            If set this particular metadata will NOT be mapped into a BQ column
        """
        self.bq_column_name = bq_column_name
        self.metadata_value = metadata_value
        self.skip_map = skip_map

    def __str__(self):
        return f"bq_column_name={self.bq_column_name}, metadata_value={self.metadata_value}, skip_map = {self.skip_map}"

    def set_metadata_value_if_not_already_set(self, metadata_value):
        """
        Adds a value to be written to BigQuery, only if it has not previously been set
        """
        if self.metadata_value is None:
            self.metadata_value = metadata_value

    def map_to_bq_col_and_value(self):
        """
        Returns
        -----
        bq_column_name: str
            The BigQuery Column name the metadata will be written to
        metadata_value: Any
            The value that will be written into the BigQuery Column
        """
        if not self.skip_map:
            return self.bq_column_name, self.metadata_value
        else:
            return None, None


# This mapper class allows flexibility in schema column names for metadata to be added in BQ
class BqMetadataMapper:
    def __init__(
        self,
        mapping_info: Dict[str, BqMetadataMappingInfo],
    ):
        self.mapping_info = mapping_info
        # Add default mappings for any missing metadata, using the same name for the BigQuery column
        for cur_metadata in metadata_to_map:
            if cur_metadata not in self.mapping_info:
                logging.debug(f"Adding default mapping for metadata = {cur_metadata}")
                self.mapping_info[cur_metadata] = BqMetadataMappingInfo(
                    bq_column_name=cur_metadata
                )

    def __str__(self):
        out_str = ""
        for k, v in self.mapping_info.items():
            out_str = f"{out_str} metadata = {k} - mapping_info = {v}"
        return out_str

    def get_value_for_metadata(self, metadata_name):
        mapping_info = self.mapping_info.get(metadata_name)
        if mapping_info is not None:
            return mapping_info.metadata_value
        return None

    def set_default_value_for_metadata_if_not_set(
        self, metadata_name, new_default_value
    ):
        mapping_info = self.mapping_info.get(metadata_name)
        if mapping_info is not None:
            mapping_info.set_metadata_value_if_not_already_set(new_default_value)

    # Return an array of column name and value
    def map_metadata(self):
        response = []
        for cur_metadata_name, cur_mapping_info_config in self.mapping_info.items():
            mapping_for_cur_metadata = {}
            (
                bq_col_name,
                bq_col_value,
            ) = cur_mapping_info_config.map_to_bq_col_and_value()
            if not bq_col_name:
                continue

            mapping_for_cur_metadata["bq_column_name"] = bq_col_name
            mapping_for_cur_metadata["bq_column_value"] = bq_col_value
            response.append(mapping_for_cur_metadata)

        return response