Use this library to auto-generate an API service that parses a typed value. This library uses Haskell's support for generic programming to customize the API to the type of value that you request.

For example, the following program:

{-# LANGUAGE DeriveGeneric #-} import Server.Generic import System.Directory (removeFile) data Command = Create { filepath :: FilePath, contents :: String } | Delete { filepath :: FilePath } deriving (Generic) instance ParseRecord Command handler :: Command -> IO String handler (Create file text) = do writeFile file text return "File created" handler (Delete file) = do removeFile file return "File deleted" main :: IO () main = serveJSON 8080 handler

... generates two API endpoints which /create and /delete files:

$ curl 'localhost:8080/create?filepath=test.txt&contents=ABC' "File created" $ cat test.txt ABC $ curl 'localhost:8080/delete?filepath=test.txt' "File deleted" $ cat test.txt cat: test.txt: No such file or directory

If we don't provide field labels

{-# LANGUAGE DeriveGeneric #-} import Server.Generic data Command = Add Double Double | Multiply Double Double deriving (Generic) instance ParseRecord Command handler :: Command -> IO Double handler (Add x y) = return (x + y) handler (Multiply x y) = return (x * y) main :: IO () main = serveJSON 8080 handler

... then the arguments become path tokens instead of query parameters:

$ curl 'localhost:8080/add/2/3' 5 $ curl 'localhost:8080/multiply/2/3' 6

This library tries to be as intelligent as possible:

• Labeled fields are read from query parameters
• Unlabeled fields are read from path tokens
• Every constructor generates an API endpoint of the same name (lowercased)
• The Maybe type constructor translates to an optional token/parameter
• The [] type constructor translates to a repeated token/parameter
• Any/All/First/Last/Sum/Product also translate to repeated tokens/parameters, but with different behaviors (i.e. First will return the first token/parameter that matches and Sum will sum them all)

For the full tutorial, read the Hackage documentation.

This library will still be in some flux since I'm not really a web developer and I probably got some design decisions wrong. Most changes will be either:

• Improving idioms to better match what web developers expect
• Improving error messages when the client supplies an invalid route
• Finding out a way to specify how to handle the request method in the type

Copyright (c) 2016 Gabriella Gonzalez
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.
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