From 0897ae55ff1ec961641d4bfe39a291002199082e Mon Sep 17 00:00:00 2001
From: Seongjun Kim <isair.zun@gmail.com>
Date: Tue, 11 Apr 2017 01:02:58 +0900
Subject: [PATCH] Add QueryParamForm to API

---
 servant/src/Servant/API.hs            |  2 +-
 servant/src/Servant/API/QueryParam.hs | 14 +++++++++++++-
 servant/src/Servant/API/TypeLevel.hs  |  4 +++-
 3 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/servant/src/Servant/API.hs b/servant/src/Servant/API.hs
index 08594137..075c3c13 100644
--- a/servant/src/Servant/API.hs
+++ b/servant/src/Servant/API.hs
@@ -71,7 +71,7 @@ import           Servant.API.Header          (Header (..))
 import           Servant.API.HttpVersion     (HttpVersion (..))
 import           Servant.API.IsSecure        (IsSecure (..))
 import           Servant.API.QueryParam      (QueryFlag, QueryParam,
-                                              QueryParams)
+                                              QueryParams, QueryParamForm)
 import           Servant.API.Raw             (Raw)
 import           Servant.API.RemoteHost      (RemoteHost)
 import           Servant.API.ReqBody         (ReqBody)
diff --git a/servant/src/Servant/API/QueryParam.hs b/servant/src/Servant/API/QueryParam.hs
index ca913e17..531528fd 100644
--- a/servant/src/Servant/API/QueryParam.hs
+++ b/servant/src/Servant/API/QueryParam.hs
@@ -3,7 +3,7 @@
 {-# LANGUAGE TypeOperators      #-}
 {-# LANGUAGE PolyKinds          #-}
 {-# OPTIONS_HADDOCK not-home    #-}
-module Servant.API.QueryParam (QueryFlag, QueryParam, QueryParams) where
+module Servant.API.QueryParam (QueryFlag, QueryParam, QueryParams, QueryParamForm) where
 
 import           Data.Typeable (Typeable)
 import           GHC.TypeLits (Symbol)
@@ -42,9 +42,21 @@ data QueryParams (sym :: Symbol) a
 -- >>> type MyApi = "books" :> QueryFlag "published" :> Get '[JSON] [Book]
 data QueryFlag (sym :: Symbol)
 
+-- | Lookup the values associated to the query string parameter
+-- and try to extract it as a value of type @a@.
+--
+-- Example:
+--
+-- >>> -- /books?title=<title>&authors[]=<author1>&authors[]=<author2>&...
+-- >>> type MyApi = "books" :> QueryParamForm BookSearchParams :> Get '[JSON] [Book]
+data QueryParamForm a
+    deriving Typeable
+
 -- $setup
 -- >>> import Servant.API
 -- >>> import Data.Aeson
 -- >>> import Data.Text
+-- >>> import Web.FormUrlEncoded (FromForm)
 -- >>> data Book
 -- >>> instance ToJSON Book where { toJSON = undefined }
+-- >>> data BookSearchParams
diff --git a/servant/src/Servant/API/TypeLevel.hs b/servant/src/Servant/API/TypeLevel.hs
index 3cb8076b..90a7afca 100644
--- a/servant/src/Servant/API/TypeLevel.hs
+++ b/servant/src/Servant/API/TypeLevel.hs
@@ -51,7 +51,8 @@ import           GHC.Exts                (Constraint)
 import           Servant.API.Alternative (type (:<|>))
 import           Servant.API.Capture     (Capture, CaptureAll)
 import           Servant.API.Header      (Header)
-import           Servant.API.QueryParam  (QueryFlag, QueryParam, QueryParams)
+import           Servant.API.QueryParam  (QueryFlag, QueryParam,
+                                          QueryParams, QueryParamForm)
 import           Servant.API.ReqBody     (ReqBody)
 import           Servant.API.Sub         (type (:>))
 import           Servant.API.Verbs       (Verb)
@@ -123,6 +124,7 @@ type family IsElem endpoint api :: Constraint where
                                           = IsElem sa sb
   IsElem sa (QueryParam x y :> sb)        = IsElem sa sb
   IsElem sa (QueryParams x y :> sb)       = IsElem sa sb
+  IsElem sa (QueryParamForm x :> sb)      = IsElem sa sb
   IsElem sa (QueryFlag x :> sb)           = IsElem sa sb
   IsElem (Verb m s ct typ) (Verb m s ct' typ)
                                           = IsSubList ct ct'