unitym (empty) → 0.1.0.0

raw patch · 5 files changed

+140/−0 lines, 5 filesdep +basedep +textdep +transformerssetup-changed

Dependencies added: base, text, transformers

Files

• LICENSE +30/−0
• README.md +0/−0
• Setup.hs +2/−0
• src/Network/UnityM.hs +84/−0
• unitym.cabal +24/−0

@@ -0,0 +1,30 @@+Copyright Brian (c) 2017++All rights reserved.++Redistribution and use in source and binary forms, with or without+modification, are permitted provided that the following conditions are met:++    * Redistributions of source code must retain the above copyright+      notice, this list of conditions and the following disclaimer.++    * Redistributions in binary form must reproduce the above+      copyright notice, this list of conditions and the following+      disclaimer in the documentation and/or other materials provided+      with the distribution.++    * Neither the name of Author name here nor the names of other+      contributors may be used to endorse or promote products derived+      from this software without specific prior written permission.++THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

@@ -0,0 +1,2 @@+import Distribution.Simple+main = defaultMain

@@ -0,0 +1,84 @@+{-# LANGUAGE FlexibleInstances      #-}+{-# LANGUAGE FunctionalDependencies #-}+{-# LANGUAGE MultiParamTypeClasses  #-}+{-# LANGUAGE UndecidableInstances   #-}++{- |+Module          : Network.UnityM+Description     : The Unity Monad- share code between Yesod and Servant, etc.+Copyright       : (c) Brian Hurt, 2017+License         : BSD3+Maintainer      : bhurt42@gmail.com+Stability       : experimental+Portability     : Haskell++One of the nice things about WAI is that it allows us to combine multiple+different server frameworks in a single web server- allowing us to use+(for example) Yesod to develop the server-side rendered HTML part of the+website, and Servant to develop the REST API part.  But this gives rise+to a desire to share code between the different frameworks.  This is+where UnityM comes in.++UnityM is a type class for monad transformer stacks for web servers.+The assumption, in addition to being in some monad, is that we are+responding to some HTTP request, and can thus assume three things:++1. That we have read-only access to some global environment data,+generally a structure of some sort.++2. That the containing framework will catch all exceptions and+convert them into 500 (internal server error) status codes.  And that+thus the low level code does not have to capture and handle exceptions,+and that a workable way to return 500 would be to just throw an exception.++3. That we have the ability to "short-circuit" the evaluation on+errors, and return 403 (permission denied) status codes from+the request.++The type class is a multi-parameter type class, with the first parameter+being the type of the environment variable that can be gotten.  This allows+code to constrain this type with further type class constaints, and thus+work with multiple different environments, for example:++>   class HasFoo a where+>       getFoo :: a -> Foo+>+>   bar :: (Monad m, HasFoo c, UnityM c m) => Something -> m Whatever+>   bar x = do+>       myFoo <- getFoo <$> getContext+>       ...++Note that this type class assumes the code is "low-level", away from the+web request- buisness logic, database access, etc.   And thus a rich+API for different status responses is not needed.  Only two error results+are supported- the generic 500 Internal Server error, and the 403 Permission+Denied error.  The second is only supported so that access grants can+be generalized.  Error checking code that needs different status results+should be written in a framework-specific way.++The different implementations of the unity monad are in separate projects,+so you don't get unnecessary dependencies.++-}+module Network.UnityM where++    import Control.Monad.Trans.Class+    import Data.Text (Text)++    {- | The Unity Monad type class.++        For code that executes in multiple different web contexts.+    -}+    class UnityM c m | m -> c where+        {- | Get the context, the global read-only data object -}+        getContext :: m c+        {- | Short circuit the request with a 403 (Forbidden) status. -}+        permissionDenied :: Text -> m a++    {- | Support monad transformers on top of a Unity monad. -}+    instance {-# OVERLAPPABLE #-} (Monad m, UnityM c m, MonadTrans t) =>+        UnityM c (t m)+        where+            getContext = lift getContext+            permissionDenied = lift . permissionDenied+

@@ -0,0 +1,24 @@+name:                unitym+version:             0.1.0.0+synopsis:            Initial project template from stack+description:         Please see README.md+homepage:            https://github.com/githubuser/unitym#readme+license:             BSD3+license-file:        LICENSE+author:              Author name here+maintainer:          example@example.com+copyright:           2017 Author name here+category:            Web+build-type:          Simple+extra-source-files:  README.md+cabal-version:       >=1.10++library+  hs-source-dirs:      src+  exposed-modules:     Network.UnityM+  build-depends:       base >= 4.7 && < 5+                        , text >= 1.2 && < 1.3+                        , transformers >= 0.5 && < 0.6+  default-language:    Haskell2010+  ghc-options:         -W -Wall -O2+