from dataclasses import dataclass import flask import pystache from typing import Optional, TypeVar, Type import lc.config as c import lc.error as e import lc.model as m import lc.request as r import lc.view as v T = TypeVar("T", bound=r.Request) @dataclass class ApiOK: response: dict class Endpoint: def __init__(self): self.user = None # try finding the token token = None # first check the HTTP headers if (auth := flask.request.headers.get("Authorization", None)) : token = auth.split()[1] # if that fails, check the session elif flask.session.get("auth", None): token = flask.session["auth"] # if that exists and we can deserialize it, then make sure # it contains a valid user password, too if token and (payload := c.serializer.loads(token)): if "name" not in payload or "password" not in payload: return try: u = m.User.by_slug(payload["name"]) except e.LCException: return if u.authenticate(payload["password"]): self.user = u def api_ok(self, redirect: str, data: dict = {"status": "ok"}) -> ApiOK: if flask.request.content_type == "application/json": return ApiOK(response=data) elif flask.request.content_type == "application/x-www-form-urlencoded": raise e.LCRedirect(redirect) else: raise e.BadContentType(flask.request.content_type or "unknown") def request_data(self, cls: Type[T]) -> T: """Construct a Request model from either a JSON payload or a urlencoded payload""" if flask.request.content_type == "application/json": try: return cls.from_json(flask.request.data) except KeyError as exn: raise e.BadPayload(key=exn.args[0]) elif flask.request.content_type == "application/x-www-form-urlencoded": return cls.from_form(flask.request.form) else: raise e.BadContentType(flask.request.content_type or "unknown") def require_authentication(self, name: str) -> m.User: """ Check that the currently logged-in user exists and is the same as the user whose username is given. Raises an exception otherwise. """ if not self.user or name != self.user.name: raise e.BadPermissions() return self.user def route(self, *args, **kwargs): """Forward to the appropriate routing method""" try: if flask.request.method == "POST": # all POST methods are "API methods": if we want to # display information in response to a post, then we # should redirect to the page where that information # can be viewed instead of returning that # information. (I think.) api_ok = self.api_post(*args, **kwargs) assert isinstance(api_ok, ApiOK) return flask.jsonify(api_ok.response) elif ( flask.request.method in ["GET", "HEAD"] and flask.request.content_type == "application/json" ): # Here we're distinguishing between an API GET (i.e. a # client trying to get JSON data about an endpoint) # versus a user-level GET (i.e. a user in a browser.) # I like using the HTTP headers to distinguish these # cases, while other APIs tend to have a separate /api # endpoint to do this. return flask.jsonify(self.api_get(*args, **kwargs)) # if an exception arose from an "API method", then we should # report it as JSON except e.LCException as exn: if flask.request.content_type == "application/json": return ({"status": exn.http_code(), "error": str(exn)}, exn.http_code()) else: page = render( "main", title="error", content=f"shit's fucked yo: {exn}", user=None, ) return (page, exn.http_code()) # also maybe we tried to redirect, so just do that except e.LCRedirect as exn: return flask.redirect(exn.to_path()) # if we're here, it means we're just trying to get a typical # HTML request. try: return self.html(*args, **kwargs) except e.LCException as exn: page = render( "main", title="error", content=f"shit's fucked yo: {exn}", user=None, ) return (page, exn.http_code()) except e.LCRedirect as exn: return flask.redirect(exn.to_path()) # Decorators result in some weird code in Python, especially 'cause it # doesn't make higher-order functions terse. Let's break this down a # bit. This out method, `endpoint`, takes the route... def endpoint(route: str): """Route an endpoint using our semi-smart routing machinery""" # but `endpoint` returns another function which is going to be # called with the result of the definition after it. The argument # to what we're calling `do_endpoint` here is going to be the # class object defined afterwards. def do_endpoint(endpoint_class: Type[Endpoint]): # we'll just make that explicit here assert Endpoint in endpoint_class.__bases__ # finally, we need a function that we'll give to Flask in # order to actually dispatch to. This is the actual routing # function, which is why it just creates an instance of the # endpoint provided above and calls the `route` method on it def func(*args, **kwargs): return endpoint_class().route(*args, **kwargs) # use reflection over the methods defined by the endpoint # class to decide if it needs to accept POST requests or not. methods = ["GET"] if "api_post" in dir(endpoint_class): methods.append("POST") # this is just for making error messages nicer func.__name__ = endpoint_class.__name__ # finally, use the Flask routing machinery to register our callback return c.app.route(route, methods=methods)(func) return do_endpoint LOADER = pystache.loader.Loader(extension="mustache", search_dirs=["templates"]) def render(name: str, data: Optional[v.View] = None) -> str: """Load and use a Mustache template from the project root""" template = LOADER.load_name(name) renderer = pystache.Renderer(missing_tags="strict", search_dirs=["templates"]) return renderer.render(template, data or {})