from .response import text
from traceback import format_exc

class SanicException(Exception):
	def __init__(self, message, status_code=None):
		super().__init__(message)
		if status_code is not None:
			self.status_code = status_code

class NotFound(SanicException):
	status_code = 404
class InvalidUsage(SanicException):
	status_code = 400
class ServerError(SanicException):
	status_code = 500

class Handler:
	handlers = None
	def __init__(self, sanic):
		self.handlers = {}
		self.sanic = sanic

	def add(self, exception, handler):
		self.handlers[exception] = handler

	def response(self, request, exception):
		"""
		Fetches and executes an exception handler and returns a reponse object
		:param request: Request
		:param exception: Exception to handle
		:return: Response object
		"""
		handler = self.handlers.get(type(exception), self.default)
		response = handler(request=request, exception=exception)
		return response

	def default(self, request, exception):
		if issubclass(type(exception), SanicException):
			return text("Error: {}".format(exception), status=getattr(exception, 'status_code', 500))
		elif self.sanic.debug:
			return text("Error: {}\nException: {}".format(exception, format_exc()), status=500)
		else:
			return text("An error occurred while generating the request", status=500)