sanic/sanic/views.py

from __future__ import annotations

from typing import (
    TYPE_CHECKING,
    Any,
    Callable,
    Iterable,
    List,
    Optional,
    Union,
)
from warnings import warn

from sanic.constants import HTTP_METHODS
from sanic.exceptions import InvalidUsage


if TYPE_CHECKING:
    from sanic import Sanic
    from sanic.blueprints import Blueprint


class HTTPMethodView:
    """Simple class based implementation of view for the sanic.
    You should implement methods (get, post, put, patch, delete) for the class
    to every HTTP method you want to support.

    For example:

    .. code-block:: python

        class DummyView(HTTPMethodView):
            def get(self, request, *args, **kwargs):
                return text('I am get method')
            def put(self, request, *args, **kwargs):
                return text('I am put method')

    If someone tries to use a non-implemented method, there will be a
    405 response.

    If you need any url params just mention them in method definition:

    .. code-block:: python

        class DummyView(HTTPMethodView):
            def get(self, request, my_param_here, *args, **kwargs):
                return text('I am get method with %s' % my_param_here)

    To add the view into the routing you could use

        1) ``app.add_route(DummyView.as_view(), '/')``, OR
        2) ``app.route('/')(DummyView.as_view())``

    To add any decorator you could set it into decorators variable
    """

    decorators: List[Callable[[Callable[..., Any]], Callable[..., Any]]] = []

    def __init_subclass__(
        cls,
        attach: Optional[Union[Sanic, Blueprint]] = None,
        uri: str = "",
        methods: Iterable[str] = frozenset({"GET"}),
        host: Optional[str] = None,
        strict_slashes: Optional[bool] = None,
        version: Optional[int] = None,
        name: Optional[str] = None,
        stream: bool = False,
        version_prefix: str = "/v",
    ) -> None:
        if attach:
            cls.attach(
                attach,
                uri=uri,
                methods=methods,
                host=host,
                strict_slashes=strict_slashes,
                version=version,
                name=name,
                stream=stream,
                version_prefix=version_prefix,
            )

    def dispatch_request(self, request, *args, **kwargs):
        handler = getattr(self, request.method.lower(), None)
        return handler(request, *args, **kwargs)

    @classmethod
    def as_view(cls, *class_args, **class_kwargs):
        """Return view function for use with the routing system, that
        dispatches request to appropriate handler method.
        """

        def view(*args, **kwargs):
            self = view.view_class(*class_args, **class_kwargs)
            return self.dispatch_request(*args, **kwargs)

        if cls.decorators:
            view.__module__ = cls.__module__
            for decorator in cls.decorators:
                view = decorator(view)

        view.view_class = cls
        view.__doc__ = cls.__doc__
        view.__module__ = cls.__module__
        view.__name__ = cls.__name__
        return view

    @classmethod
    def attach(
        cls,
        to: Union[Sanic, Blueprint],
        uri: str,
        methods: Iterable[str] = frozenset({"GET"}),
        host: Optional[str] = None,
        strict_slashes: Optional[bool] = None,
        version: Optional[int] = None,
        name: Optional[str] = None,
        stream: bool = False,
        version_prefix: str = "/v",
    ) -> None:
        to.add_route(
            cls.as_view(),
            uri=uri,
            methods=methods,
            host=host,
            strict_slashes=strict_slashes,
            version=version,
            name=name,
            stream=stream,
            version_prefix=version_prefix,
        )


def stream(func):
    func.is_stream = True
    return func


class CompositionView:
    """Simple method-function mapped view for the sanic.
    You can add handler functions to methods (get, post, put, patch, delete)
    for every HTTP method you want to support.

    For example:

    .. code-block:: python

        view = CompositionView()
        view.add(['GET'], lambda request: text('I am get method'))
        view.add(['POST', 'PUT'], lambda request: text('I am post/put method'))

    If someone tries to use a non-implemented method, there will be a
    405 response.
    """

    def __init__(self):
        self.handlers = {}
        self.name = self.__class__.__name__
        warn(
            "CompositionView has been deprecated and will be removed in "
            "v21.12. Please update your view to HTTPMethodView.",
            DeprecationWarning,
        )

    def __name__(self):
        return self.name

    def add(self, methods, handler, stream=False):
        if stream:
            handler.is_stream = stream
        for method in methods:
            if method not in HTTP_METHODS:
                raise InvalidUsage(f"{method} is not a valid HTTP method.")

            if method in self.handlers:
                raise InvalidUsage(f"Method {method} is already registered.")
            self.handlers[method] = handler

    def __call__(self, request, *args, **kwargs):
        handler = self.handlers[request.method.upper()]
        return handler(request, *args, **kwargs)