# coding=utf-8
#
# Copyright © Cloud Linux GmbH & Cloud Linux Software, Inc 2010-2019 All Rights Reserved
#
# Licensed under CLOUD LINUX LICENSE AGREEMENT
# http://cloudlinux.com/docs/LICENSE.TXT

import logging
import pathlib

import sqlalchemy.engine
import sqlalchemy.exc
from sqlalchemy import delete, event, func
from sqlalchemy.engine.reflection import Inspector
from sqlalchemy.engine.url import make_url
from sqlalchemy.ext.declarative.clsregistry import _ModuleMarker
from sqlalchemy.orm import RelationshipProperty, sessionmaker

from clcommon import mysql_lib
from clcommon.clexception import FormattedException
from lvestats.orm import Base, history
from lvestats.orm import LVE_STATS_2_TABLENAME_PREFIX
from lvestats.utils.dbmigrator import alembic_migrate

DEFAULT_DB_PATH = "/var/lve/lvestats2.db"
# Set the SQLite busy timeout explicitly instead of relying on the pysqlite
# driver default: a writer then waits this long for a transient lock (e.g. a
# concurrent VACUUM/ANALYZE or snapshot write) before failing with SQLITE_BUSY
# and losing a data-collection cycle.
SQLITE_BUSY_TIMEOUT_MS = 5000
MYSQL, POSTGRESQL, SQLITE = "mysql", "postgresql", "sqlite"
SUPPORTED_DATABASES = [MYSQL, POSTGRESQL, SQLITE]
DB_CLIENT_LIBRARY_MAP = {
    MYSQL: "pymysql",
    POSTGRESQL: "psycopg2",
}

__author__ = "shaman"


def find_not_existing_tables_or_views(engine, names):
    """
    Checks if views exist.
    :param sqlalchemy.engine.base.Engine engine:
    :return:
    """
    inspector = Inspector.from_engine(engine)
    existing = set(inspector.get_view_names())
    not_existing = {LVE_STATS_2_TABLENAME_PREFIX + n for n in names} - existing
    return tuple(x.replace(LVE_STATS_2_TABLENAME_PREFIX, "") for x in tuple(not_existing))


def get_list_of_tables_without_views():
    """
    Used to call engine.create_all() without views that are described as Table()
    :return:
    """
    tables = dict(Base.metadata.tables).values()
    tables_for_disabled_features = []

    burstable_limits_feature_flag = "/opt/cloudlinux/flags/enabled-flags.d/burstable-limits.flag"
    if not pathlib.Path(burstable_limits_feature_flag).exists():
        tables_for_disabled_features.append(LVE_STATS_2_TABLENAME_PREFIX + "bursting_events")

    return [t for t in tables if t.name not in tables_for_disabled_features]


class MakeDbException(FormattedException):
    pass


class DatabaseConfigError(FormattedException):
    pass


def cfg_get_uri(cfg, check_support=True):
    """
    Extract and validate database connection uri from config
    :param dict cfg:
    :param bool check_support:
    :return str:
    """
    # check present "db_type"
    db_type = cfg.get("db_type")
    if db_type is None:
        raise DatabaseConfigError(
            {"message": '"%(config_variable)s" not in config', "context": {"config_variable": "db_type"}}
        )

    # check supported databases
    if check_support and db_type not in SUPPORTED_DATABASES:
        raise DatabaseConfigError(
            {
                "message": "Incorrect database type %(database_type)s. You should only use %(database_types)s. "
                'The correct db_type for mariadb is "mysql"',
                "context": {"database_type": db_type, "database_types": '", "'.join(SUPPORTED_DATABASES)},
            }
        )

    # check present "connect_string"
    connect_string = cfg.get("connect_string")
    if db_type != SQLITE and connect_string is None:
        raise DatabaseConfigError(
            {"message": '"%(config_variable)s" not in config', "context": {"config_variable": "connect_string"}}
        )

    # generate database uri
    if db_type == SQLITE:
        uri = f"{db_type}:///{cfg.get('sqlite_db_path', DEFAULT_DB_PATH)}"
    else:
        client_library = get_db_client_library_name(db_type)
        uri = f"{db_type}+{client_library}://{connect_string}"
        uri = get_fixed_uri(db_type, uri)
    return uri


def make_db_engine(cfg, just_print=False, debug=False, pool_class=None, check_support=True):
    """
    Create sqlalchemy database engine
    :param dict cfg:
    :param bool just_print:
    :param bool debug:
    :param pool_class:
    :param bool check_support:
    :return:
    """
    log = logging.getLogger("init_db_engine")

    try:
        connect_string = cfg_get_uri(cfg, check_support=check_support)
    except DatabaseConfigError as e:
        msg = "Unable to configure database connection. %(error)s"
        context = {"error": str(e)}
        log.error(msg, context)
        raise MakeDbException({"message": msg, "context": context}) from e

    log.info("Connecting to database: %s", cfg["db_type"])

    if debug is False and "debug" in cfg:
        debug = cfg["debug"]

    if just_print:

        def dump(sql, *multiparams, **params):
            print(sql)

        engine = sqlalchemy.engine.create_engine(connect_string, strategy="mock", executor=dump)
    else:
        engine = sqlalchemy.engine.create_engine(connect_string, echo=debug, poolclass=pool_class)
        if engine.url.get_backend_name() == SQLITE:
            event.listen(engine, "connect", _set_sqlite_busy_timeout)

    return engine


def _set_sqlite_busy_timeout(dbapi_connection, connection_record):  # pylint: disable=unused-argument
    """Apply SQLITE_BUSY_TIMEOUT_MS to every new SQLite DBAPI connection."""
    cursor = dbapi_connection.cursor()
    try:
        cursor.execute(f"PRAGMA busy_timeout={SQLITE_BUSY_TIMEOUT_MS}")
    finally:
        cursor.close()


def normalize_sqlite_journal_mode(engine, log=None):
    """
    Reset a SQLite lvestats2 database from WAL back to DELETE journal mode.

    lve-stats has a single privileged (root) writer -- the daemon -- and many
    unprivileged, CageFS-isolated consumers that read the database read-only
    (cloudlinux-statistics, lveinfo, charts, bursting info). In WAL mode SQLite
    must write the root-owned ``-shm`` sidecar even for ``SELECT``; non-root
    consumers cannot, so reads fail with "attempt to write a readonly database".
    WAL is therefore unsupported (see doc/design/sqlite-journal-mode.md).

    The daemon -- the sole writer -- calls this on startup so a customer-applied
    WAL database self-heals back to DELETE on ``service lvestats restart``.
    No-op for non-SQLite backends and for databases already in a non-WAL mode,
    preserving the default DELETE behaviour. Non-fatal: a read-only or locked
    database is left untouched.
    """
    log = log or logging.getLogger("init_db_engine")
    if engine.url.get_backend_name() != SQLITE:
        return
    try:
        with engine.connect() as conn:
            current_mode = conn.execute("PRAGMA journal_mode").scalar()
            if current_mode is None or current_mode.lower() != "wal":
                return
            new_mode = conn.execute("PRAGMA journal_mode=DELETE").scalar()
    except sqlalchemy.exc.OperationalError as e:
        # Switching out of WAL needs an exclusive lock; another open connection
        # (e.g. a root-run reader or a manual sqlite3/VACUUM session) blocks it
        # and SQLite raises "database is locked" after busy_timeout. Leave the
        # database as-is -- it will be retried on the next non-locked startup.
        log.warning(
            "lvestats2 database is in unsupported WAL journal mode and could not be reset "
            "(another connection holds the database); retry on a restart with no other "
            "connections active: %s",
            e,
        )
        return
    if new_mode is not None and new_mode.lower() == "delete":
        log.warning("lvestats2 database was in unsupported WAL journal mode; reset to DELETE")
    else:
        # Defensive: some SQLite builds may return the unchanged mode instead of raising.
        log.warning(
            "lvestats2 database is in unsupported WAL journal mode and could not be reset "
            '(result: "%s"); non-root readers may fail until it can be reset on restart',
            new_mode,
        )


def validate_database(engine, hide_logging=False, base=Base):
    log = logging.getLogger("validate_database")
    if hide_logging:
        log.propagate = False
        log.addHandler(logging.NullHandler())
    result = {"table_error": False, "column_error": False, "missing_tables": [], "orm_tables": []}
    database_inspection = Inspector.from_engine(engine)
    real_tables = database_inspection.get_table_names()
    for _, _class in list(base._decl_class_registry.items()):  # pylint: disable=protected-access
        if isinstance(_class, _ModuleMarker):
            continue
        table = _class.__tablename__
        result["orm_tables"].append(table)
        if table in real_tables:
            real_columns = [c["name"] for c in database_inspection.get_columns(table)]
            mapper = sqlalchemy.inspect(_class)
            for column_prop in mapper.attrs:
                if isinstance(column_prop, RelationshipProperty):
                    # We have no relationships
                    pass
                else:
                    for column in column_prop.columns:
                        if column.key not in real_columns:
                            log.critical(
                                "Model %s declares column %s which does not exist in database %s",
                                _class,
                                column.key,
                                engine,
                            )
                            result["column_error"] = True
        else:
            log.critical("Model %s declares table %s which does not exist in database %s", _class, table, engine)
            result["table_error"] = True
            result["missing_tables"].append(table)
    if result["table_error"]:
        log.critical("You can run 'lve-create-db --create-missing-tables' command to recreate missing tables.")
    if result["column_error"]:
        log.critical("You can try to recreate malformed table, or ask CloudLinux support for help.")
    return result


def check_need_create_db(engine):
    inspect_result = validate_database(engine, hide_logging=True)
    return inspect_result["missing_tables"] == inspect_result["orm_tables"]


def create_db(engine):
    Base.metadata.create_all(engine, tables=get_list_of_tables_without_views())
    # write revision version to database only after create all tables
    alembic_migrate(engine, stamp=True)


def setup_db(engine, create_missing_tables=False, cfg=None):
    if create_missing_tables or check_need_create_db(engine):
        create_db(engine)
    else:
        alembic_migrate(engine, lve_stats_cfg=cfg)


def drop_tables(engine):
    Base.metadata.drop_all(engine)


def clear_rows(engine, server_id=None):
    conn_ = engine.connect()
    trans = conn_.begin()  # delete all rows in one transaction
    try:
        for _, table_object in list(Base.metadata.tables.items()):
            if server_id is None:
                delete_query = delete(table_object)
            elif isinstance(server_id, (list, tuple)):
                delete_query = delete(table_object, table_object.c.server_id in server_id)
            else:
                delete_query = delete(table_object, table_object.c.server_id == server_id)
            conn_.execute(delete_query)
        trans.commit()
    except Exception:
        trans.rollback()
        raise


def recreate_db(engine):
    drop_tables(engine)
    create_db(engine)


def find_lost_keep_alive(session, server_id, from_timestmp=None, to_timestamp=None):
    # query for find timestmps with lost keepalive records
    # SELECT created FROM lve_stats2_history WHERE server_id = 'server_id'
    # GROUP BY created HAVING max(id) > 0 AND min(id) > 0
    lost_keepalive = (
        session.query(history.created)
        .filter(history.server_id == server_id)
        .group_by(history.created)
        .having(func.max(history.id) > 0)
        .having(func.min(history.id) > 0)
    )
    if to_timestamp is not None:
        lost_keepalive = lost_keepalive.filter(history.created <= to_timestamp)
    if from_timestmp is not None:
        lost_keepalive = lost_keepalive.filter(history.created >= from_timestmp)
    return [record_[0] for record_ in lost_keepalive]


def fix_lost_keep_alive(session, server_id, from_timestmp=None, to_timestamp=None, log_=None):
    lost_keep_alive = find_lost_keep_alive(session, server_id, from_timestmp, to_timestamp)
    if not lost_keep_alive:
        return
    # add losted keep alive records
    v2_keepalive_row = {col: 0 for col in list(history.__table__.columns.keys())}
    v2_keepalive_row[history.server_id.key] = server_id

    for timestamp in lost_keep_alive:
        history_keepalive = history(**v2_keepalive_row)
        history_keepalive.created = timestamp  # setup timestamp
        session.add(history_keepalive)
    session.commit()
    if log_:
        log_.info("Was fixed %s losted keep alive records: %s", len(lost_keep_alive), lost_keep_alive)


def fix_db(engine, cfg, from_timestmp=None, to_timestamp=None, log_=None):
    # autocommit=True using for clear cache in mariadb between queries
    session = sessionmaker(bind=engine)()
    fix_lost_keep_alive(session, cfg["server_id"], from_timestmp=from_timestmp, to_timestamp=to_timestamp, log_=log_)
    session.close()


def get_db_client_library_name(db_type):
    """
    Get database Python client library name
    :param str db_type:
    :return str:
    """
    client_library = DB_CLIENT_LIBRARY_MAP.get(db_type)
    if client_library is None:
        raise DatabaseConfigError(
            {
                "message": 'The client library to connect to the "%(database_type)s" database cannot be detected',
                "context": {
                    "database_type": db_type,
                },
            }
        )
    return client_library


def get_fixed_uri(db_type, uri):
    """
    Get fixed URI for the specified database
    :param str db_type:
    :param str uri:
    :return str:
    """
    if db_type != MYSQL:
        return uri

    u = make_url(uri)
    return str(mysql_lib.get_rfc1738_db_uri(u))