from enum import Enum
from importlib import import_module
from typing import Any, Callable, Dict, Union, get_type_hints

from pypika import Query
from pypika.queries import Column
from pypika.terms import PseudoColumn

import frappe
from frappe.query_builder.terms import NamedParameterWrapper

from .builder import MariaDB, Postgres


class db_type_is(Enum):
	MARIADB = "mariadb"
	POSTGRES = "postgres"


class ImportMapper:
	def __init__(self, func_map: Dict[db_type_is, Callable]) -> None:
		self.func_map = func_map

	def __call__(self, *args: Any, **kwds: Any) -> Callable:
		db = db_type_is(frappe.conf.db_type or "mariadb")
		return self.func_map[db](*args, **kwds)


class BuilderIdentificationFailed(Exception):
	def __init__(self):
		super().__init__("Couldn't guess builder")


def get_query_builder(type_of_db: str) -> Union[Postgres, MariaDB]:
	"""[return the query builder object]

	Args:
	        type_of_db (str): [string value of the db used]

	Returns:
	        Query: [Query object]
	"""
	db = db_type_is(type_of_db)
	picks = {db_type_is.MARIADB: MariaDB, db_type_is.POSTGRES: Postgres}
	return picks[db]


def get_attr(method_string):
	modulename = ".".join(method_string.split(".")[:-1])
	methodname = method_string.split(".")[-1]
	return getattr(import_module(modulename), methodname)


def DocType(*args, **kwargs):
	return frappe.qb.DocType(*args, **kwargs)


def patch_query_execute():
	"""Patch the Query Builder with helper execute method
	This excludes the use of `frappe.db.sql` method while
	executing the query object
	"""
	from frappe.utils.safe_exec import check_safe_sql_query

	def execute_query(query, *args, **kwargs):
		query, params = prepare_query(query)
		return frappe.db.sql(query, params, *args, **kwargs)  # nosemgrep

	def prepare_query(query):
		import inspect

		param_collector = NamedParameterWrapper()
		query = query.get_sql(param_wrapper=param_collector)
		if frappe.flags.in_safe_exec and not check_safe_sql_query(query, throw=False):
			callstack = inspect.stack()
			if len(callstack) >= 3 and ".py" in callstack[2].filename:
				# ignore any query builder methods called from python files
				# assumption is that those functions are whitelisted already.

				# since query objects are patched everywhere any query.run()
				# will have callstack like this:
				# frame0: this function prepare_query()
				# frame1: execute_query()
				# frame2: frame that called `query.run()`
				#
				# if frame2 is server script it wont have a filename and hence
				# it shouldn't be allowed.
				# p.s. stack() returns `"<unknown>"` as filename if not a file.
				pass
			else:
				raise frappe.PermissionError("Only SELECT SQL allowed in scripting")
		return query, param_collector.get_parameters()

	query_class = get_attr(str(frappe.qb).split("'")[1])
	builder_class = get_type_hints(query_class._builder).get("return")

	if not builder_class:
		raise BuilderIdentificationFailed

	builder_class.run = execute_query
	builder_class.walk = prepare_query


def patch_query_aggregation():
	"""Patch aggregation functions to frappe.qb"""
	from frappe.query_builder.functions import _avg, _max, _min, _sum

	frappe.qb.max = _max
	frappe.qb.min = _min
	frappe.qb.avg = _avg
	frappe.qb.sum = _sum