"""
Base database connectors
"""

import logging
import os
import shlex
from importlib import import_module
from subprocess import Popen
from tempfile import SpooledTemporaryFile

from django.core.files.base import File

from dbbackup import settings, utils

from . import exceptions

logger = logging.getLogger("dbbackup.command")
logger.setLevel(logging.DEBUG)


CONNECTOR_MAPPING = {
    "django.db.backends.sqlite3": "dbbackup.db.sqlite.SqliteConnector",
    "django.db.backends.mysql": "dbbackup.db.mysql.MysqlDumpConnector",
    "django.db.backends.postgresql": "dbbackup.db.postgresql.PgDumpBinaryConnector",
    "django.db.backends.postgresql_psycopg2": "dbbackup.db.postgresql.PgDumpBinaryConnector",
    "django.db.backends.oracle": None,
    "django_mongodb_engine": "dbbackup.db.mongodb.MongoDumpConnector",
    "djongo": "dbbackup.db.mongodb.MongoDumpConnector",
    "django.contrib.gis.db.backends.postgis": "dbbackup.db.postgresql.PgDumpGisConnector",
    "django.contrib.gis.db.backends.mysql": "dbbackup.db.mysql.MysqlDumpConnector",
    "django.contrib.gis.db.backends.oracle": None,
    "django.contrib.gis.db.backends.spatialite": "dbbackup.db.sqlite.SqliteConnector",
    "django_prometheus.db.backends.postgresql": "dbbackup.db.postgresql.PgDumpBinaryConnector",
    "django_prometheus.db.backends.sqlite3": "dbbackup.db.sqlite.SqliteConnector",
    "django_prometheus.db.backends.mysql": "dbbackup.db.mysql.MysqlDumpConnector",
    "django_prometheus.db.backends.postgis": "dbbackup.db.postgresql.PgDumpGisConnector",
    "django_s3_sqlite": "dbbackup.db.sqlite.SqliteConnector",
}

if settings.CUSTOM_CONNECTOR_MAPPING:
    CONNECTOR_MAPPING.update(settings.CUSTOM_CONNECTOR_MAPPING)


def get_connector(database_name=None):
    """
    Get a connector from its database key in settings.
    """
    from django.db import DEFAULT_DB_ALIAS, connections

    # Get DB
    database_name = database_name or DEFAULT_DB_ALIAS
    connection = connections[database_name]
    engine = connection.settings_dict["ENGINE"]
    connector_settings = settings.CONNECTORS.get(database_name, {})
    connector_path = connector_settings.get("CONNECTOR", CONNECTOR_MAPPING[engine])
    connector_module_path = ".".join(connector_path.split(".")[:-1])
    module = import_module(connector_module_path)
    connector_name = connector_path.split(".")[-1]
    connector = getattr(module, connector_name)
    return connector(database_name, **connector_settings)


class BaseDBConnector:
    """
    Base class for create database connector. This kind of object creates
    interaction with database and allow backup and restore operations.
    """

    extension = "dump"
    exclude = []

    def __init__(self, database_name=None, **kwargs):
        from django.db import DEFAULT_DB_ALIAS, connections

        self.database_name = database_name or DEFAULT_DB_ALIAS
        self.connection = connections[self.database_name]
        for attr, value in kwargs.items():
            setattr(self, attr.lower(), value)

    @property
    def settings(self):
        """Mix of database and connector settings."""
        if not hasattr(self, "_settings"):
            sett = self.connection.settings_dict.copy()
            sett.update(settings.CONNECTORS.get(self.database_name, {}))
            self._settings = sett
        return self._settings

    def generate_filename(self, server_name=None):
        return utils.filename_generate(self.extension, self.database_name, server_name)

    def create_dump(self):
        return self._create_dump()

    def _create_dump(self):
        """
        Override this method to define dump creation.
        """
        raise NotImplementedError("_create_dump not implemented")

    def restore_dump(self, dump):
        """
        :param dump: Dump file
        :type dump: file
        """
        return self._restore_dump(dump)

    def _restore_dump(self, dump):
        """
        Override this method to define dump creation.
        :param dump: Dump file
        :type dump: file
        """
        raise NotImplementedError("_restore_dump not implemented")


class BaseCommandDBConnector(BaseDBConnector):
    """
    Base class for create database connector based on command line tools.
    """

    dump_prefix = ""
    dump_suffix = ""
    restore_prefix = ""
    restore_suffix = ""

    use_parent_env = True
    env = {}
    dump_env = {}
    restore_env = {}

    def run_command(self, command, stdin=None, env=None):
        """
        Launch a shell command line.

        :param command: Command line to launch
        :type command: str
        :param stdin: Standard input of command
        :type stdin: file
        :param env: Environment variable used in command
        :type env: dict
        :return: Standard output of command
        :rtype: file
        """
        logger.debug(command)
        cmd = shlex.split(command)
        stdout = SpooledTemporaryFile(
            max_size=settings.TMP_FILE_MAX_SIZE, dir=settings.TMP_DIR
        )
        stderr = SpooledTemporaryFile(
            max_size=settings.TMP_FILE_MAX_SIZE, dir=settings.TMP_DIR
        )
        full_env = os.environ.copy() if self.use_parent_env else {}
        full_env.update(self.env)
        full_env.update(env or {})
        try:
            if isinstance(stdin, File):
                process = Popen(
                    cmd,
                    stdin=stdin.open("rb"),
                    stdout=stdout,
                    stderr=stderr,
                    env=full_env,
                )
            else:
                process = Popen(
                    cmd, stdin=stdin, stdout=stdout, stderr=stderr, env=full_env
                )
            process.wait()
            if process.poll():
                stderr.seek(0)
                raise exceptions.CommandConnectorError(
                    "Error running: {}\n{}".format(
                        command, stderr.read().decode("utf-8")
                    )
                )
            stdout.seek(0)
            stderr.seek(0)
            return stdout, stderr
        except OSError as err:
            raise exceptions.CommandConnectorError(
                f"Error running: {command}\n{str(err)}"
            )