Split part of Utils.hs into JSON.hs

Utils is a bit big, let's split the JSON stuff (not all of it) into a
separate module that doesn't have any other dependencies.

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Agata Murawska <agatamurawska@google.com>

Makefile.am

@@ -347,6 +347,7 @@ HS_LIB_SRCS = \
 	htools/Ganeti/HTools/Group.hs \
 	htools/Ganeti/HTools/IAlloc.hs \
 	htools/Ganeti/HTools/Instance.hs \
+	htools/Ganeti/HTools/JSON.hs \
 	htools/Ganeti/HTools/Loader.hs \
 	htools/Ganeti/HTools/Luxi.hs \
 	htools/Ganeti/HTools/Node.hs \

htools/Ganeti/HTools/JSON.hs

+{-| JSON utility functions. -}
+
+{-
+
+Copyright (C) 2009, 2010, 2011 Google Inc.
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program; if not, write to the Free Software
+Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+02110-1301, USA.
+
+-}
+
+module Ganeti.HTools.JSON
+    ( fromJResult
+    , readEitherString
+    , JSRecord
+    , loadJSArray
+    , fromObj
+    , maybeFromObj
+    , fromObjWithDefault
+    , fromJVal
+    , asJSObject
+    , asObjectList
+    )
+    where
+
+import Control.Monad (liftM)
+import Data.Maybe (fromMaybe)
+import Text.Printf (printf)
+
+import qualified Text.JSON as J
+
+-- * JSON-related functions
+
+-- | A type alias for the list-based representation of J.JSObject.
+type JSRecord = [(String, J.JSValue)]
+
+-- | Converts a JSON Result into a monadic value.
+fromJResult :: Monad m => String -> J.Result a -> m a
+fromJResult s (J.Error x) = fail (s ++ ": " ++ x)
+fromJResult _ (J.Ok x) = return x
+
+-- | Tries to read a string from a JSON value.
+--
+-- In case the value was not a string, we fail the read (in the
+-- context of the current monad.
+readEitherString :: (Monad m) => J.JSValue -> m String
+readEitherString v =
+    case v of
+      J.JSString s -> return $ J.fromJSString s
+      _ -> fail "Wrong JSON type"
+
+-- | Converts a JSON message into an array of JSON objects.
+loadJSArray :: (Monad m)
+               => String -- ^ Operation description (for error reporting)
+               -> String -- ^ Input message
+               -> m [J.JSObject J.JSValue]
+loadJSArray s = fromJResult s . J.decodeStrict
+
+-- | Reads the value of a key in a JSON object.
+fromObj :: (J.JSON a, Monad m) => JSRecord -> String -> m a
+fromObj o k =
+    case lookup k o of
+      Nothing -> fail $ printf "key '%s' not found, object contains only %s"
+                 k (show (map fst o))
+      Just val -> fromKeyValue k val
+
+-- | Reads the value of an optional key in a JSON object.
+maybeFromObj :: (J.JSON a, Monad m) =>
+                JSRecord -> String -> m (Maybe a)
+maybeFromObj o k =
+    case lookup k o of
+      Nothing -> return Nothing
+      Just val -> liftM Just (fromKeyValue k val)
+
+-- | Reads the value of a key in a JSON object with a default if missing.
+fromObjWithDefault :: (J.JSON a, Monad m) =>
+                      JSRecord -> String -> a -> m a
+fromObjWithDefault o k d = liftM (fromMaybe d) $ maybeFromObj o k
+
+-- | Reads a JValue, that originated from an object key.
+fromKeyValue :: (J.JSON a, Monad m)
+              => String     -- ^ The key name
+              -> J.JSValue  -- ^ The value to read
+              -> m a
+fromKeyValue k val =
+  fromJResult (printf "key '%s', value '%s'" k (show val)) (J.readJSON val)
+
+-- | Small wrapper over readJSON.
+fromJVal :: (Monad m, J.JSON a) => J.JSValue -> m a
+fromJVal v =
+    case J.readJSON v of
+      J.Error s -> fail ("Cannot convert value '" ++ show v ++
+                         "', error: " ++ s)
+      J.Ok x -> return x
+
+-- | Converts a JSON value into a JSON object.
+asJSObject :: (Monad m) => J.JSValue -> m (J.JSObject J.JSValue)
+asJSObject (J.JSObject a) = return a
+asJSObject _ = fail "not an object"
+
+-- | Coneverts a list of JSON values into a list of JSON objects.
+asObjectList :: (Monad m) => [J.JSValue] -> m [J.JSObject J.JSValue]
+asObjectList = mapM asJSObject

htools/Ganeti/HTools/Utils.hs

@@ -49,16 +49,15 @@ module Ganeti.HTools.Utils
     , parseUnit
     ) where
 
-import Control.Monad (liftM)
 import Data.Char (toUpper)
 import Data.List
-import Data.Maybe (fromMaybe)
 import qualified Text.JSON as J
-import Text.Printf (printf)
 
 import Debug.Trace
 
 import Ganeti.HTools.Types
+-- we will re-export these for our existing users
+import Ganeti.HTools.JSON
 
 -- * Debug functions
 
@@ -131,61 +130,6 @@ select :: a            -- ^ default result
        -> a            -- ^ first result which has a True condition, or default
 select def = maybe def snd . find fst
 
--- * JSON-related functions
-
--- | A type alias for the list-based representation of J.JSObject.
-type JSRecord = [(String, J.JSValue)]
-
--- | Converts a JSON Result into a monadic value.
-fromJResult :: Monad m => String -> J.Result a -> m a
-fromJResult s (J.Error x) = fail (s ++ ": " ++ x)
-fromJResult _ (J.Ok x) = return x
-
--- | Tries to read a string from a JSON value.
---
--- In case the value was not a string, we fail the read (in the
--- context of the current monad.
-readEitherString :: (Monad m) => J.JSValue -> m String
-readEitherString v =
-    case v of
-      J.JSString s -> return $ J.fromJSString s
-      _ -> fail "Wrong JSON type"
-
--- | Converts a JSON message into an array of JSON objects.
-loadJSArray :: (Monad m)
-               => String -- ^ Operation description (for error reporting)
-               -> String -- ^ Input message
-               -> m [J.JSObject J.JSValue]
-loadJSArray s = fromJResult s . J.decodeStrict
-
--- | Reads the value of a key in a JSON object.
-fromObj :: (J.JSON a, Monad m) => JSRecord -> String -> m a
-fromObj o k =
-    case lookup k o of
-      Nothing -> fail $ printf "key '%s' not found, object contains only %s"
-                 k (show (map fst o))
-      Just val -> fromKeyValue k val
-
--- | Reads the value of an optional key in a JSON object.
-maybeFromObj :: (J.JSON a, Monad m) =>
-                JSRecord -> String -> m (Maybe a)
-maybeFromObj o k =
-    case lookup k o of
-      Nothing -> return Nothing
-      Just val -> liftM Just (fromKeyValue k val)
-
--- | Reads the value of a key in a JSON object with a default if missing.
-fromObjWithDefault :: (J.JSON a, Monad m) =>
-                      JSRecord -> String -> a -> m a
-fromObjWithDefault o k d = liftM (fromMaybe d) $ maybeFromObj o k
-
--- | Reads a JValue, that originated from an object key.
-fromKeyValue :: (J.JSON a, Monad m)
-              => String     -- ^ The key name
-              -> J.JSValue  -- ^ The value to read
-              -> m a
-fromKeyValue k val =
-  fromJResult (printf "key '%s', value '%s'" k (show val)) (J.readJSON val)
 
 -- | Annotate a Result with an ownership information.
 annotateResult :: String -> Result a -> Result a
@@ -201,22 +145,6 @@ tryFromObj :: (J.JSON a) =>
            -> Result a
 tryFromObj t o = annotateResult t . fromObj o
 
--- | Small wrapper over readJSON.
-fromJVal :: (Monad m, J.JSON a) => J.JSValue -> m a
-fromJVal v =
-    case J.readJSON v of
-      J.Error s -> fail ("Cannot convert value '" ++ show v ++
-                         "', error: " ++ s)
-      J.Ok x -> return x
-
--- | Converts a JSON value into a JSON object.
-asJSObject :: (Monad m) => J.JSValue -> m (J.JSObject J.JSValue)
-asJSObject (J.JSObject a) = return a
-asJSObject _ = fail "not an object"
-
--- | Coneverts a list of JSON values into a list of JSON objects.
-asObjectList :: (Monad m) => [J.JSValue] -> m [J.JSObject J.JSValue]
-asObjectList = mapM asJSObject
 
 -- * Parsing utility functions