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For further +-- documentation, see http://haskell.org/cabal/users-guide/ + +name: scotty-resource +version: 0.1.0.0 +synopsis: A Better way of modeling web resources. +description: + Allows users of the Scotty web framework to model + resources more like the HTTP standard models them. +homepage: https://github.com/taphu/scotty-resource +license: Apache-2.0 +license-file: LICENSE +author: Rick Owens +maintainer: rick@owenssoftware.com +copyright: 2016 - Rick Owens +category: Web +build-type: Simple +-- extra-source-files: +cabal-version: >=1.10 + +library + exposed-modules: + Web.Scotty.Resource.Trans + -- other-modules: + other-extensions: + OverloadedStrings + build-depends: + base >= 4.7 && < 4.8, + containers >= 0.1.0.0 && < 0.6, + http-types >= 0.8.2 && < 0.10, + scotty >= 0.11.0 && < 0.12, + text >= 0.11.3.1 && < 1.3, + transformers >= 0.3.0.0 && < 0.5, + wai >= 3.0.0 && < 3.3 + hs-source-dirs: src + default-language: Haskell2010 + +source-repository head + type: git + location: git://github.com/taphu/scotty-resource.git + diff --git a/src/Web/Scotty/Resource/Trans.hs b/src/Web/Scotty/Resource/Trans.hs new file mode 100644 --- /dev/null +++ b/src/Web/Scotty/Resource/Trans.hs @@ -0,0 +1,248 @@ +{-# LANGUAGE OverloadedStrings #-} +{- | + This module defines better resource routing for Scotty. + + Scotty is defined in terms of "routes", whereas HTTP is defined in + terms of "resources". This package adds a "resource" abstraction to + the scotty ecosystem. + + (note: All examples probably require -XOverloadedStrings) + + Scotty comes out of the box with a way to model "routes". The problem + is that "routes" is not the abstraction used by the HTTP standard and + it can sometimes be tricky to write a perfectly correct HTTP service + using the routes model (where "correct" is judged against rfc-2616). + The most blatant, (and who knows, maybe the only) example of this problem + is shown by the scotty code: + + > import Web.Scotty.Trans (get, scottyT, text) + > + > ... + > + > scottyT 8080 id $ do + > get "/hello" $ do + > text "world" + + If a client requests something like @DELETE /hello@, this scotty application + will return @404 Not Found@, which conflicts with section 5.1.1 of rfc-2616. + A better response would be @405 Method Not Allowed@, and it would include an + automatically generated @Allow@ response header. + + This library gives users a way to model "resources" which is closer to the + abstractions used in the HTTP standard. + + We can re-write the above example like this: + + > import Web.Scotty.Trans (scottyT, text) + > import Web.Scotty.Resource.Trans (resource, get) + > + > ... + > + > scottyT 8080 id $ do + > resource "/hello" $ do + > get $ do + > text "world" + + Given a request: + + > DELETE /hello HTTP/1.1 + > Host: localhost:8080 + + The resource-based scotty application will produce something like: + + > HTTP/1.1 405 Method Not Allowed + > Allow: GET + + Each resource is described by a `WebResource` value, which happens to + be a `Monad`. The only reason `WebResource` implements `Monad` to fit + in with the do-notation coding style of `ScottyT`. This is an abuse of + `Monad`, but, you know, whatever. The `Monoid` typeclass more correctly + represents what a `WebResource` really is. The `Monad` and `Monoid` + typeclasses are used to compose instances of `WebResource`. + + Here is another more complex example, with multiple resources. + + > import Data.Aeson (decode) + > import Network.HTTP.Types (notFound404, badRequest400, noContent204) + > import Web.Scotty.Resource.Trans (resource, get, post) + > import Web.Scotty.Trans (scottyT, text, body, raw, status, param) + > + > import MyApplication (lookupPerson, storePerson) + > + > ... + > + > scottyT 8080 id $ do + > + > -- an "echo" resource + > resource "/echo" $ do + > get $ do + > text "hello world" + > post $ do + > -- echo the request body back to the user + > raw =<< body + > + > -- A resource that represents a kind of a RESTful database of people. + > -- This resource supports GET and PUT. + > resource "/people/:personId" $ do + > get $ do + > personId <- param "personId" + > maybePerson <- lookupPerson personId + > case maybePerson of + > Nothing -> + > status notFound404 + > Just person -> + > json person + > put $ do + > personId <- param "personId" + > maybePerson <- decode <$> body + > case maybePerson of + > Nothing -> do + > status badRequest400 + > text "Invalid person JSON" + > Just person -> + > storePerson personId person + > status noContent204 +-} +module Web.Scotty.Resource.Trans ( + resource, + WebResource, + options, + get, + head, + post, + put, + delete, + patch, + method +) where + +import Prelude hiding (head) + +import Control.Monad (liftM) +import Control.Monad.IO.Class (MonadIO) +import Data.List (intersperse) +import Data.Maybe (fromMaybe) +import Data.Monoid (mconcat, (<>), mempty, Monoid, mappend) +import Data.Set (fromList, toList) +import Data.Text.Encoding (decodeUtf8) +import Data.Text.Lazy (fromStrict) +import Network.HTTP.Types (Method, methodNotAllowed405) +import Network.Wai (requestMethod) +import Web.Scotty.Trans (ActionT, RoutePattern, ScottyT, matchAny, + request, ScottyError, setHeader, status) + +{- | + Add a resource whose uri matches the route pattern. +-} +resource :: (MonadIO m, ScottyError e) + => RoutePattern + -> WebResource e m () + -> ScottyT e m () +resource uri (W methods ()) = matchAny uri $ + getMethod `liftM` request >>= fromMaybe notAllowed + where + getMethod = (`lookup` methods) . requestMethod + notAllowed = do + setHeader "Allow" allowed + status methodNotAllowed405 + + {- + Build a list of allowed methods. + -} + allowed = + ( + fromStrict + . decodeUtf8 + . mconcat + . intersperse ", " + . dedupe + . fmap fst + ) methods + + +{- | + An opaque representation of an http resource. Use `get`, `post`, etc. to + create one of these. Use the `Monad` or `Monoid` instances to compose them. +-} +data WebResource e m a = W [(Method, ActionT e m ())] a +instance Monad (WebResource e m) where + return = W [] + W methods a >>= f = + let W newMethods b = f a + in W (methods <> newMethods) b +instance Monoid (WebResource e m a) where + mempty = W mempty undefined + mappend (W a _) (W b _) = W (a <> b) undefined + + +{- | + Create a `WebResource` that handles OPTIONS requests using the given + scotty action. +-} +options :: ActionT e m () -> WebResource e m () +options action = W [("OPTIONS", action)] () + + +{- | + Create a `WebResource` that handles GET requests using the given + scotty action. +-} +get :: ActionT e m () -> WebResource e m () +get action = W [("GET", action)] () + + +{- | + Create a `WebResource` that handles HEAD requests using the given + scotty action. +-} +head :: ActionT e m () -> WebResource e m () +head action = W [("HEAD", action)] () + + +{- | + Create a `WebResource` that handles POST requests using the given + scotty action. +-} +post :: ActionT e m () -> WebResource e m () +post action = W [("POST", action)] () + + +{- | + Create a `WebResource` that handles PUT requests using the given + scotty action. +-} +put :: ActionT e m () -> WebResource e m () +put action = W [("PUT", action)] () + + +{- | + Create a `WebResource` that handles DELETE requests using the given + scotty action. +-} +delete :: ActionT e m () -> WebResource e m () +delete action = W [("DELETE", action)] () + + +{- | + Create a `WebResource` that handles PATCH requests using the given + scotty action. +-} +patch :: ActionT e m () -> WebResource e m () +patch action = W [("PATCH", action)] () + + +{- | + Create a `WebResource` that handles the specific method using the given + scotty action. +-} +method :: Method -> ActionT e m () -> WebResource e m () +method m action = W [(m, action)] () + + +{- | + A helper function that removes duplicates from a list. +-} +dedupe :: (Ord a, Eq a) => [a] -> [a] +dedupe = toList . fromList + +