# Copyright 2023 The Matrix.org Foundation C.I.C
#
#  Licensed 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
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from synapse.config.homeserver import HomeServerConfig
from synapse.storage.database import LoggingTransaction
from synapse.storage.engines import BaseDatabaseEngine, PostgresEngine


def run_upgrade(
    cur: LoggingTransaction,
    database_engine: BaseDatabaseEngine,
    config: HomeServerConfig,
) -> None:
    """
    Part 3 of a multi-step migration to drop the column `user_id` and replace it with
    `full_user_id`. See the database schema docs for more information on the full
    migration steps.
    """
    hostname = config.server.server_name

    if isinstance(database_engine, PostgresEngine):
        # check if the constraint can be validated
        check_sql = """
        SELECT user_id from user_filters WHERE full_user_id IS NULL
        """
        cur.execute(check_sql)
        res = cur.fetchall()

        if res:
            # there are rows the background job missed, finish them here before we validate constraint
            process_rows_sql = """
            UPDATE user_filters
            SET full_user_id = '@' || user_id || ?
            WHERE user_id IN (
                SELECT user_id FROM user_filters WHERE full_user_id IS NULL
            )
            """
            cur.execute(process_rows_sql, (f":{hostname}",))

        # Now we can validate
        validate_sql = """
        ALTER TABLE user_filters VALIDATE CONSTRAINT full_user_id_not_null
        """
        cur.execute(validate_sql)

    else:
        cur.execute("DROP TABLE IF EXISTS temp_user_filters")
        create_sql = """
        CREATE TABLE temp_user_filters (
            full_user_id text NOT NULL,
            user_id text NOT NULL,
            filter_id bigint NOT NULL,
            filter_json bytea NOT NULL
        )
        """
        cur.execute(create_sql)

        index_sql = """
        CREATE UNIQUE INDEX IF NOT EXISTS user_filters_unique ON
            temp_user_filters (user_id, filter_id)
        """
        cur.execute(index_sql)

        copy_sql = """
        INSERT INTO temp_user_filters (
            user_id,
            filter_id,
            filter_json,
            full_user_id)
            SELECT user_id, filter_id, filter_json, '@' || user_id || ':' || ? FROM user_filters
        """
        cur.execute(copy_sql, (f"{hostname}",))

        drop_sql = """
        DROP TABLE user_filters
        """
        cur.execute(drop_sql)

        rename_sql = """
        ALTER TABLE temp_user_filters RENAME to user_filters
        """
        cur.execute(rename_sql)