From f35e1f949ab3ee718ab773baf9f38ac411d49a28 Mon Sep 17 00:00:00 2001
From: Danny Navarro <j@dannynavarro.net>
Date: Sun, 29 Jan 2017 12:53:15 -0300
Subject: [PATCH] Define Schema using Core AST

Also, temporarily remove error reporting to simplify execution. This should be
restored once the new execution model is nailed.
---
 Data/GraphQL/Execute.hs       | 32 +++++++++++----
 Data/GraphQL/Schema.hs        | 74 +++++++++++++++++------------------
 tests/Test/StarWars/Schema.hs | 12 +++---
 3 files changed, 67 insertions(+), 51 deletions(-)

diff --git a/Data/GraphQL/Execute.hs b/Data/GraphQL/Execute.hs
index 4dab56c..561bf20 100644
--- a/Data/GraphQL/Execute.hs
+++ b/Data/GraphQL/Execute.hs
@@ -3,15 +3,23 @@
 module Data.GraphQL.Execute (execute) where
 
 import Control.Applicative (Alternative)
-import Data.Maybe (catMaybes)
+import qualified Data.List.NonEmpty as NE
+import Data.List.NonEmpty (NonEmpty((:|)))
 
 import qualified Data.Aeson as Aeson
 
-import Data.GraphQL.AST
-import Data.GraphQL.Schema (Schema(..))
+import qualified Data.GraphQL.AST as AST
+import qualified Data.GraphQL.AST.Core as AST.Core
+import Data.GraphQL.Schema (Schema)
 import qualified Data.GraphQL.Schema as Schema
 
-import Data.GraphQL.Error
+
+
+core :: Schema.Subs -> AST.Document -> AST.Core.Document
+core subs ((AST.DefinitionOperation opDef) :| []) = error "Not implemented yet"
+core _    ((AST.DefinitionFragment fragDef) :| []) =
+  error "Fragment definitions not supported yet"
+core _ _ = error "Multiple definitions not supported yet"
 
 -- | Takes a 'Schema', a variable substitution function ('Schema.Subs'), and a
 --   @GraphQL@ 'document'. The substitution is applied to the document using
@@ -19,9 +27,19 @@ import Data.GraphQL.Error
 --
 --   Returns the result of the query against the 'Schema' wrapped in a /data/ field, or
 --   errors wrapped in an /errors/ field.
-execute :: Alternative f
-  => Schema.Schema f -> Schema.Subs -> Document -> f Aeson.Value
-execute resolvers subs doc = undefined -- resolver resolvs $ rootFields subs doc
+execute
+  :: Alternative f
+  => Schema f -> Schema.Subs -> AST.Document -> f Aeson.Value
+execute schema subs doc = document schema $ core subs doc
+
+document :: Alternative f => Schema f -> AST.Core.Document -> f Aeson.Value
+document schema (op :| [])= operation schema op
+document _ _ = error "Multiple operations not supported yet"
+
+operation :: Alternative f => Schema f -> AST.Core.Operation -> f Aeson.Value
+operation schema (AST.Core.Query flds) =
+  Schema.resolve (NE.toList schema) (NE.toList flds)
+operation _ _ = error "Mutations not supported yet"
 
 -- | Takes a variable substitution function and a @GraphQL@ document.
 --   If the document contains one query (and no other definitions)
diff --git a/Data/GraphQL/Schema.hs b/Data/GraphQL/Schema.hs
index 2198362..aa25046 100644
--- a/Data/GraphQL/Schema.hs
+++ b/Data/GraphQL/Schema.hs
@@ -1,4 +1,3 @@
-{-# LANGUAGE OverloadedStrings #-}
 {-# LANGUAGE LambdaCase #-}
 -- | This module provides a representation of a @GraphQL@ Schema in addition to
 --   functions for defining and manipulating Schemas.
@@ -14,15 +13,14 @@ module Data.GraphQL.Schema
   , arrayA
   , enum
   , enumA
-  , resolvers
+  , resolve
   -- * AST Reexports
   , Field
   , Argument(..)
   , Value(..)
   ) where
 
-import Control.Applicative (Alternative((<|>), empty))
-import Data.Bifunctor (first)
+import Control.Applicative (Alternative( empty))
 import Data.Foldable (fold)
 import Data.List.NonEmpty (NonEmpty)
 import Data.Maybe (fromMaybe)
@@ -32,10 +30,8 @@ import qualified Data.Aeson as Aeson
 import Data.HashMap.Strict (HashMap)
 import qualified Data.HashMap.Strict as HashMap
 import Data.Text (Text)
-import qualified Data.Text as T (unwords)
 
 import Data.GraphQL.AST.Core
-import Data.GraphQL.Error
 
 -- | A GraphQL schema.
 --   @f@ is usually expected to be an instance of 'Alternative'.
@@ -43,24 +39,31 @@ type Schema f = NonEmpty (Resolver f)
 
 -- | Resolves a 'Field' into an @Aeson.@'Aeson.Object' with error information
 --   (or 'empty'). @f@ is usually expected to be an instance of 'Alternative'.
-type Resolver f = Field -> CollectErrsT f Aeson.Object
+type Resolver f = Field -> f Aeson.Object
+
+type Resolvers f = [Resolver f]
+
+type Fields = [Field]
+
+type Arguments = [Argument]
 
 -- | Variable substitution function.
 type Subs = Text -> Maybe Text
 
-object :: Alternative f => Name -> [Resolver f] -> Resolver f
-object name resolvs = objectA name $ \case
-      [] -> resolvs
-      _  -> empty
+-- | Create a new 'Resolver' with the given 'Name' from the given 'Resolver's.
+object :: Alternative f => Name -> Resolvers f -> Resolver f
+object name resolvers = objectA name $ \case
+  [] -> resolvers
+  _  -> empty
 
 -- | Like 'object' but also taking 'Argument's.
 objectA
   :: Alternative f
-  => Name -> ([Argument] -> [Resolver f]) -> Resolver f
-objectA name f fld@(Field _ _ args sels) = withField name (resolvers (f args) sels) fld
+  => Name -> (Arguments -> Resolvers f) -> Resolver f
+objectA name f fld@(Field _ _ args flds) = withField name (resolve (f args) flds) fld
 
 -- | A scalar represents a primitive value, like a string or an integer.
-scalar :: (Alternative f, Aeson.ToJSON a) => Text -> a -> Resolver f
+scalar :: (Alternative f, Aeson.ToJSON a) => Name -> a -> Resolver f
 scalar name s = scalarA name $ \case
     [] -> pure s
     _  -> empty
@@ -68,21 +71,21 @@ scalar name s = scalarA name $ \case
 -- | Like 'scalar' but also taking 'Argument's.
 scalarA
   :: (Alternative f, Aeson.ToJSON a)
-  => Name -> ([Argument] -> f a) -> Resolver f
-scalarA name f fld@(Field _ _ args []) = withField name (errWrap $ f args) fld
+  => Name -> (Arguments -> f a) -> Resolver f
+scalarA name f fld@(Field _ _ args []) = withField name (f args) fld
 scalarA _ _ _ = empty
 
-array :: Alternative f => Text -> [[Resolver f]] -> Resolver f
-array name resolvs = arrayA name $ \case
-    [] -> resolvs
+array :: Alternative f => Name -> [Resolvers f] -> Resolver f
+array name resolvers = arrayA name $ \case
+    [] -> resolvers
     _  -> empty
 
 -- | Like 'array' but also taking 'Argument's.
 arrayA
   :: Alternative f
-  => Text -> ([Argument] -> [[Resolver f]]) -> Resolver f
+  => Text -> (Arguments -> [Resolvers f]) -> Resolver f
 arrayA name f fld@(Field _ _ args sels) =
-     withField name (joinErrs $ traverse (`resolvers` sels) $ f args) fld
+     withField name (traverse (`resolve` sels) $ f args) fld
 
 -- | Represents one of a finite set of possible values.
 --   Used in place of a 'scalar' when the possible responses are easily enumerable.
@@ -93,30 +96,25 @@ enum name enums = enumA name $ \case
 
 -- | Like 'enum' but also taking 'Argument's.
 enumA :: Alternative f => Text -> ([Argument] -> f [Text]) -> Resolver f
-enumA name f fld@(Field _ _ args []) = withField name (errWrap $ f args) fld
+enumA name f fld@(Field _ _ args []) = withField name (f args) fld
 enumA _ _ _ = empty
 
 -- | Helper function to facilitate 'Argument' handling.
 withField
   :: (Alternative f, Aeson.ToJSON a)
-  => Name -> CollectErrsT f a -> Field -> CollectErrsT f (HashMap Text Aeson.Value)
+  => Name -> f a -> Field -> f (HashMap Text Aeson.Value)
 withField name f (Field alias name' _ _) =
-     if name == name'
-        then fmap (first $ HashMap.singleton aliasOrName . Aeson.toJSON) f
-        else empty
-     where
-       aliasOrName = fromMaybe name' alias
+  if name == name'
+    then fmap (HashMap.singleton aliasOrName . Aeson.toJSON) f
+    else empty
+  where
+    aliasOrName = fromMaybe name alias
+
 
 -- | Takes a list of 'Resolver's and a list of 'Field's and applies each
 --   'Resolver' to each 'Field'. Resolves into a value containing the
 --   resolved 'Field', or a null value and error information.
-resolvers :: Alternative f => [Resolver f] -> [Field] -> CollectErrsT f Aeson.Value
-resolvers resolvs =
-    fmap (first Aeson.toJSON . fold)
-  . traverse (\fld -> getAlt (foldMap (Alt . ($ fld)) resolvs) <|> errmsg fld)
-  where
-    errmsg (Field alias name _ _) = addErrMsg msg $ (errWrap . pure) val
-       where
-         val = HashMap.singleton aliasOrName Aeson.Null
-         msg = T.unwords ["field", name, "not resolved."]
-         aliasOrName = fromMaybe name alias
+resolve :: Alternative f => Resolvers f -> Fields -> f Aeson.Value
+resolve resolvers =
+    fmap (Aeson.toJSON . fold)
+  . traverse (\fld -> getAlt (foldMap (Alt . ($ fld)) resolvers))
diff --git a/tests/Test/StarWars/Schema.hs b/tests/Test/StarWars/Schema.hs
index 29c123e..e816d63 100644
--- a/tests/Test/StarWars/Schema.hs
+++ b/tests/Test/StarWars/Schema.hs
@@ -19,7 +19,7 @@ schema = hero :| [human, droid]
 hero :: Alternative f => Resolver f
 hero = Schema.objectA "hero" $ \case
   [] -> character artoo
-  [Argument "episode" (ValueInt n)] -> character $ getHero (fromIntegral n)
+  [Argument "episode" (ValueInt n)] -> character . getHero $ fromIntegral n
   _ -> empty
 
 human :: Alternative f => Resolver f
@@ -34,10 +34,10 @@ droid = Schema.objectA "droid" $ \case
 
 character :: Alternative f => Character -> [Resolver f]
 character char =
-  [ Schema.scalar "id"        $ id_ char
-  , Schema.scalar "name"      $ name char
-  , Schema.array  "friends"   $ character <$> getFriends char
-  , Schema.enum   "appearsIn" . traverse getEpisode $ appearsIn char
+  [ Schema.scalar "id"              $ id_ char
+  , Schema.scalar "name"            $ name char
+  , Schema.array  "friends"         $ character <$> getFriends char
+  , Schema.enum   "appearsIn"       . traverse getEpisode $ appearsIn char
   , Schema.scalar "secretBackstory" $ secretBackstory char
-  , Schema.scalar "homePlanet" $ either mempty homePlanet char
+  , Schema.scalar "homePlanet"      $ either mempty homePlanet char
   ]