# Copyright 2019 3YOURMIND GmbH

# 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
# limitations under the License.

import re
import logging

logger = logging.getLogger(__name__)


def has_default(sql, **kwargs):
    if re.search("SET DEFAULT", sql) and kwargs["errors"]:
        err = next((err for err in kwargs["errors"] if err["code"] == "NOT_NULL"), None)
        if err:
            logger.info(
                (
                    "Found a NOT_NULL error in migration, "
                    "but it has a default value added: {}"
                ).format(err)
            )
            kwargs["errors"].remove(err)

    return False  # Never fails


migration_tests = (
    {
        "code": "NOT_NULL",
        "fn": lambda sql, **kw: re.search("(?<!DROP )NOT NULL", sql)
        and not re.search("CREATE TABLE", sql),
        "err_msg": "NOT NULL constraint on columns",
    },
    {
        "code": "DROP_COLUMN",
        "fn": lambda sql, **kw: re.search("DROP COLUMN", sql),
        "err_msg": "DROPPING columns",
    },
    {
        "code": "RENAME_COLUMN",
        "fn": lambda sql, **kw: re.search("ALTER TABLE .* CHANGE", sql)
        or re.search("ALTER TABLE .* RENAME COLUMN", sql),
        "err_msg": "RENAMING columns",
    },
    {
        "code": "RENAME_TABLE",
        "fn": lambda sql, **kw: re.search("RENAME TABLE", sql)
        or re.search("ALTER TABLE .* RENAME TO", sql),
        "err_msg": "RENAMING tables",
    },
    {
        "code": "ALTER_COLUMN",
        "fn": lambda sql, **kw: re.search("ALTER TABLE .* MODIFY", sql)
        or re.search("ALTER TABLE .* ALTER COLUMN .* TYPE", sql),
        "err_msg": (
            "ALTERING columns (Could be backward compatible. "
            "You may ignore this migration.)"
        ),
    },
    {"code": "", "fn": has_default, "err_msg": ""},
)


def build_error_dict(migration_test, sql_statement):
    table_search = re.search("TABLE `([^`]*)`", sql_statement, re.IGNORECASE)
    col_search = re.search("COLUMN `([^`]*)`", sql_statement, re.IGNORECASE)
    return {
        "err_msg": migration_test["err_msg"],
        "code": migration_test["code"],
        "table": table_search.group(1) if table_search else None,
        "column": col_search.group(1) if col_search else None,
    }


def analyse_sql_statements(sql_statements, exclude_migration_tests):
    errors, ignored = [], []
    for statement in sql_statements:
        for test in migration_tests:
            if test["fn"](statement, errors=errors):
                if test["code"] in exclude_migration_tests:
                    logger.debug("Testing {0} -- IGNORED".format(statement))
                    err = build_error_dict(migration_test=test, sql_statement=statement)
                    ignored.append(err)
                else:
                    logger.debug("Testing {0} -- ERROR".format(statement))
                    err = build_error_dict(migration_test=test, sql_statement=statement)
                    errors.append(err)
            else:
                logger.debug("Testing {0} -- PASSED".format(statement))
    return errors, ignored