import itertools
import re
from ast import literal_eval
from types import BuiltinFunctionType
from typing import TYPE_CHECKING

import sqlparse
from pypika.queries import QueryBuilder, Table

import frappe
from frappe import _
from frappe.database.operator_map import OPERATOR_MAP
from frappe.database.utils import get_doctype_name
from frappe.query_builder import Criterion, Field, Order, functions
from frappe.query_builder.functions import Function, SqlFunctions
from frappe.query_builder.utils import PseudoColumnMapper
from frappe.utils.data import MARIADB_SPECIFIC_COMMENT

if TYPE_CHECKING:
	from frappe.query_builder import DocType

TAB_PATTERN = re.compile("^tab")
WORDS_PATTERN = re.compile(r"\w+")
BRACKETS_PATTERN = re.compile(r"\(.*?\)|$")
SQL_FUNCTIONS = [sql_function.value for sql_function in SqlFunctions]
COMMA_PATTERN = re.compile(r",\s*(?![^()]*\))")


class Engine:
	def get_query(
		self,
		table: str | Table,
		fields: list | tuple | None = None,
		filters: dict[str, str | int] | str | int | list[list | str | int] | None = None,
		order_by: str | None = None,
		group_by: str | None = None,
		limit: int | None = None,
		offset: int | None = None,
		distinct: bool = False,
		for_update: bool = False,
		update: bool = False,
		into: bool = False,
		delete: bool = False,
	) -> QueryBuilder:
		self.is_mariadb = frappe.db.db_type == "mariadb"
		self.is_postgres = frappe.db.db_type == "postgres"

		if isinstance(table, Table):
			self.table = table
			self.doctype = get_doctype_name(table.get_sql())
		else:
			self.doctype = table
			self.table = frappe.qb.DocType(table)

		if update:
			self.query = frappe.qb.update(self.table)
		elif into:
			self.query = frappe.qb.into(self.table)
		elif delete:
			self.query = frappe.qb.from_(self.table).delete()
		else:
			self.query = frappe.qb.from_(self.table)
			self.apply_fields(fields)

		self.apply_filters(filters)
		self.apply_order_by(order_by)

		if limit:
			self.query = self.query.limit(limit)

		if offset:
			self.query = self.query.offset(offset)

		if distinct:
			self.query = self.query.distinct()

		if for_update:
			self.query = self.query.for_update()

		if group_by:
			self.query = self.query.groupby(group_by)

		return self.query

	def apply_fields(self, fields):
		# add fields
		self.fields = self.parse_fields(fields)
		if not self.fields:
			self.fields = [getattr(self.table, "name")]

		for field in self.fields:
			if isinstance(field, DynamicTableField):
				self.query = field.apply_select(self.query)
			else:
				self.query = self.query.select(field)

	def apply_filters(
		self,
		filters: dict[str, str | int] | str | int | list[list | str | int] | None = None,
	):
		if filters is None:
			return

		if isinstance(filters, (str, int)):
			filters = {"name": str(filters)}

		if isinstance(filters, Criterion):
			self.query = self.query.where(filters)

		elif isinstance(filters, dict):
			self.apply_dict_filters(filters)

		elif isinstance(filters, (list, tuple)):
			if all(isinstance(d, (str, int)) for d in filters) and len(filters) > 0:
				self.apply_dict_filters({"name": ("in", filters)})
			else:
				for filter in filters:
					if isinstance(filter, (str, int, Criterion, dict)):
						self.apply_filters(filter)
					elif isinstance(filter, (list, tuple)):
						self.apply_list_filters(filter)

	def apply_list_filters(self, filter: list):
		if len(filter) == 2:
			field, value = filter
			self._apply_filter(field, value)
		elif len(filter) == 3:
			field, operator, value = filter
			self._apply_filter(field, value, operator)
		elif len(filter) == 4:
			doctype, field, operator, value = filter
			self._apply_filter(field, value, operator, doctype)

	def apply_dict_filters(self, filters: dict[str, str | int | list]):
		for key in filters:
			value = filters.get(key)
			self._apply_filter(key, value)

	def _apply_filter(
		self, field: str, value: str | int | list | None, operator: str = "=", doctype: str | None = None
	):
		_field = field
		_value = value
		_operator = operator

		if isinstance(_field, Field):
			pass
		elif dynamic_field := DynamicTableField.parse(field, self.doctype):
			# apply implicit join if link field's field is referenced
			self.query = dynamic_field.apply_join(self.query)
			_field = dynamic_field.field
		elif has_function(field):
			_field = self.get_function_object(field)
		elif not doctype or doctype == self.doctype:
			_field = self.table[field]
		elif doctype:
			_field = frappe.qb.DocType(doctype)[field]

		# apply implicit join if child table is referenced
		if doctype and doctype != self.doctype:
			meta = frappe.get_meta(doctype)
			table = frappe.qb.DocType(doctype)
			if meta.istable and not self.query.is_joined(table):
				self.query = self.query.left_join(table).on(
					(table.parent == self.table.name) & (table.parenttype == self.doctype)
				)

		if isinstance(_value, (list, tuple)):
			_operator, _value = _value
		elif isinstance(_value, bool):
			_value = int(_value)

		if isinstance(_value, str) and has_function(_value):
			_value = self.get_function_object(_value)

		if isinstance(_value, (list, tuple)) and not _value:
			_value = ("",)

		# Nested set
		if _operator in OPERATOR_MAP["nested_set"]:
			hierarchy = _operator
			docname = _value
			result = get_nested_set_hierarchy_result(self.doctype, docname, hierarchy)
			operator_fn = (
				OPERATOR_MAP["not in"]
				if hierarchy in ("not ancestors of", "not descendants of")
				else OPERATOR_MAP["in"]
			)
			if result:
				result = list(itertools.chain.from_iterable(result))
				self.query = self.query.where(operator_fn(_field, result))
			else:
				self.query = self.query.where(operator_fn(_field, ("",)))
			return

		operator_fn = OPERATOR_MAP[_operator.casefold()]
		if _value is None and isinstance(_field, Field):
			self.query = self.query.where(_field.isnull())
		else:
			self.query = self.query.where(operator_fn(_field, _value))

	def get_function_object(self, field: str) -> "Function":
		"""Expects field to look like 'SUM(*)' or 'name' or something similar. Returns PyPika Function object"""
		func = field.split("(", maxsplit=1)[0].capitalize()
		args_start, args_end = len(func) + 1, field.index(")")
		args = field[args_start:args_end].split(",")

		_, alias = field.split(" as ") if " as " in field else (None, None)

		to_cast = "*" not in args
		_args = []

		for arg in args:
			initial_fields = literal_eval_(arg.strip())
			if to_cast:
				has_primitive_operator = False
				for _operator in OPERATOR_MAP.keys():
					if _operator in initial_fields:
						operator_mapping = OPERATOR_MAP[_operator]
						# Only perform this if operator is of primitive type.
						if isinstance(operator_mapping, BuiltinFunctionType):
							has_primitive_operator = True
							field = operator_mapping(
								*map(
									lambda field: Field(field.strip())
									if "`" not in field
									else PseudoColumnMapper(field.strip()),
									arg.split(_operator),
								),
							)

				field = (
					(Field(initial_fields) if "`" not in initial_fields else PseudoColumnMapper(initial_fields))
					if not has_primitive_operator
					else field
				)
			else:
				field = initial_fields

			_args.append(field)

		if alias and "`" in alias:
			alias = alias.replace("`", "")
		try:
			if func.casefold() == "now":
				return getattr(functions, func)()
			return getattr(functions, func)(*_args, alias=alias or None)
		except AttributeError:
			# Fall back for functions not present in `SqlFunctions``
			return Function(func, *_args, alias=alias or None)

	def sanitize_fields(self, fields: str | list | tuple):
		def _sanitize_field(field: str):
			if not isinstance(field, str):
				return field
			stripped_field = sqlparse.format(field, strip_comments=True, keyword_case="lower")
			if self.is_mariadb:
				return MARIADB_SPECIFIC_COMMENT.sub("", stripped_field)
			return stripped_field

		if isinstance(fields, (list, tuple)):
			return [_sanitize_field(field) for field in fields]
		elif isinstance(fields, str):
			return _sanitize_field(fields)

		return fields

	def parse_string_field(self, field: str):
		if field == "*":
			return self.table.star
		alias = None
		if " as " in field:
			field, alias = field.split(" as ")
		if "`" in field:
			if alias:
				return PseudoColumnMapper(f"{field} {alias}")
			return PseudoColumnMapper(field)
		if alias:
			return self.table[field].as_(alias)
		return self.table[field]

	def parse_fields(self, fields: str | list | tuple | None) -> list:
		if not fields:
			return []
		fields = self.sanitize_fields(fields)
		if isinstance(fields, (list, tuple, set)) and None in fields and Field not in fields:
			return []

		if not isinstance(fields, (list, tuple)):
			fields = [fields]

		def parse_field(field: str):
			if has_function(field):
				return self.get_function_object(field)
			elif parsed := DynamicTableField.parse(field, self.doctype):
				return parsed
			else:
				return self.parse_string_field(field)

		_fields = []
		for field in fields:
			if isinstance(field, Criterion):
				_fields.append(field)
			elif isinstance(field, str):
				if "," in field:
					field = field.casefold() if "`" not in field else field
					field_list = COMMA_PATTERN.split(field)
					for field in field_list:
						if _field := field.strip():
							_fields.append(parse_field(_field))
				else:
					_fields.append(parse_field(field))

		return _fields

	def apply_order_by(self, order_by: str | None):
		if not order_by or order_by == "KEEP_DEFAULT_ORDERING":
			return
		for declaration in order_by.split(","):
			if _order_by := declaration.strip():
				parts = _order_by.split(" ")
				order_field, order_direction = parts[0], parts[1] if len(parts) > 1 else "desc"
				order_direction = Order.asc if order_direction.lower() == "asc" else Order.desc
				self.query = self.query.orderby(order_field, order=order_direction)


class Permission:
	@classmethod
	def check_permissions(cls, query, **kwargs):
		if not isinstance(query, str):
			query = query.get_sql()

		doctype = cls.get_tables_from_query(query)
		if isinstance(doctype, str):
			doctype = [doctype]

		for dt in doctype:
			dt = TAB_PATTERN.sub("", dt)
			if not frappe.has_permission(
				dt,
				"select",
				user=kwargs.get("user"),
				parent_doctype=kwargs.get("parent_doctype"),
			) and not frappe.has_permission(
				dt,
				"read",
				user=kwargs.get("user"),
				parent_doctype=kwargs.get("parent_doctype"),
			):
				frappe.throw(_("Insufficient Permission for {0}").format(frappe.bold(dt)))

	@staticmethod
	def get_tables_from_query(query: str):
		return [table for table in WORDS_PATTERN.findall(query) if table.startswith("tab")]


class DynamicTableField:
	def __init__(
		self,
		doctype: str,
		fieldname: str,
		parent_doctype: str,
		alias: str | None = None,
	) -> None:
		self.doctype = doctype
		self.fieldname = fieldname
		self.alias = alias
		self.parent_doctype = parent_doctype

	def __str__(self) -> str:
		table_name = f"`tab{self.doctype}`"
		fieldname = f"`{self.fieldname}`"
		if frappe.db.db_type == "postgres":
			table_name = table_name.replace("`", '"')
			fieldname = fieldname.replace("`", '"')
		alias = f"AS {self.alias}" if self.alias else ""
		return f"{table_name}.{fieldname} {alias}".strip()

	@staticmethod
	def parse(field: str, doctype: str):
		if "." in field:
			alias = None
			if " as " in field:
				field, alias = field.split(" as ")
			if field.startswith("`tab") or field.startswith('"tab'):
				_, child_doctype, child_field = re.search(r'([`"])tab(.+?)\1.\1(.+)\1', field).groups()
				if child_doctype == doctype:
					return
				return ChildTableField(child_doctype, child_field, doctype, alias=alias)
			else:
				linked_fieldname, fieldname = field.split(".")
				linked_field = frappe.get_meta(doctype).get_field(linked_fieldname)
				linked_doctype = linked_field.options
				if linked_field.fieldtype == "Link":
					return LinkTableField(linked_doctype, fieldname, doctype, linked_fieldname, alias=alias)
				elif linked_field.fieldtype in frappe.model.table_fields:
					return ChildTableField(linked_doctype, fieldname, doctype, alias=alias)

	def apply_select(self, query: QueryBuilder) -> QueryBuilder:
		raise NotImplementedError


class ChildTableField(DynamicTableField):
	def __init__(
		self,
		doctype: str,
		fieldname: str,
		parent_doctype: str,
		alias: str | None = None,
	) -> None:
		self.doctype = doctype
		self.fieldname = fieldname
		self.alias = alias
		self.parent_doctype = parent_doctype
		self.table = frappe.qb.DocType(self.doctype)
		self.field = self.table[self.fieldname]

	def apply_select(self, query: QueryBuilder) -> QueryBuilder:
		table = frappe.qb.DocType(self.doctype)
		query = self.apply_join(query)
		return query.select(getattr(table, self.fieldname).as_(self.alias or None))

	def apply_join(self, query: QueryBuilder) -> QueryBuilder:
		table = frappe.qb.DocType(self.doctype)
		main_table = frappe.qb.DocType(self.parent_doctype)
		if not query.is_joined(table):
			query = query.left_join(table).on(
				(table.parent == main_table.name) & (table.parenttype == self.parent_doctype)
			)
		return query


class LinkTableField(DynamicTableField):
	def __init__(
		self,
		doctype: str,
		fieldname: str,
		parent_doctype: str,
		link_fieldname: str,
		alias: str | None = None,
	) -> None:
		super().__init__(doctype, fieldname, parent_doctype, alias=alias)
		self.link_fieldname = link_fieldname
		self.table = frappe.qb.DocType(self.doctype)
		self.field = self.table[self.fieldname]

	def apply_select(self, query: QueryBuilder) -> QueryBuilder:
		table = frappe.qb.DocType(self.doctype)
		query = self.apply_join(query)
		return query.select(getattr(table, self.fieldname).as_(self.alias or None))

	def apply_join(self, query: QueryBuilder) -> QueryBuilder:
		table = frappe.qb.DocType(self.doctype)
		main_table = frappe.qb.DocType(self.parent_doctype)
		if not query.is_joined(table):
			query = query.left_join(table).on(table.name == getattr(main_table, self.link_fieldname))
		return query


def literal_eval_(literal):
	try:
		return literal_eval(literal)
	except (ValueError, SyntaxError):
		return literal


def has_function(field):
	_field = field.casefold() if (isinstance(field, str) and "`" not in field) else field
	if not issubclass(type(_field), Criterion):
		if any([f"{func}(" in _field for func in SQL_FUNCTIONS]):
			return True


def get_nested_set_hierarchy_result(doctype: str, name: str, hierarchy: str):
	table = frappe.qb.DocType(doctype)
	try:
		lft, rgt = frappe.qb.from_(table).select("lft", "rgt").where(table.name == name).run()[0]
	except IndexError:
		lft, rgt = None, None

	if hierarchy in ("descendants of", "not descendants of"):
		result = (
			frappe.qb.from_(table)
			.select(table.name)
			.where(table.lft > lft)
			.where(table.rgt < rgt)
			.orderby(table.lft, order=Order.asc)
			.run()
		)
	else:
		# Get ancestor elements of a DocType with a tree structure
		result = (
			frappe.qb.from_(table)
			.select(table.name)
			.where(table.lft < lft)
			.where(table.rgt > rgt)
			.orderby(table.lft, order=Order.desc)
			.run()
		)
	return result