root / htools / Ganeti / HTools / JSON.hs @ d575c755
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1 | f047f90f | Iustin Pop | {-| JSON utility functions. -} |
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2 | f047f90f | Iustin Pop | |
3 | f047f90f | Iustin Pop | {- |
4 | f047f90f | Iustin Pop | |
5 | f047f90f | Iustin Pop | Copyright (C) 2009, 2010, 2011 Google Inc. |
6 | f047f90f | Iustin Pop | |
7 | f047f90f | Iustin Pop | This program is free software; you can redistribute it and/or modify |
8 | f047f90f | Iustin Pop | it under the terms of the GNU General Public License as published by |
9 | f047f90f | Iustin Pop | the Free Software Foundation; either version 2 of the License, or |
10 | f047f90f | Iustin Pop | (at your option) any later version. |
11 | f047f90f | Iustin Pop | |
12 | f047f90f | Iustin Pop | This program is distributed in the hope that it will be useful, but |
13 | f047f90f | Iustin Pop | WITHOUT ANY WARRANTY; without even the implied warranty of |
14 | f047f90f | Iustin Pop | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
15 | f047f90f | Iustin Pop | General Public License for more details. |
16 | f047f90f | Iustin Pop | |
17 | f047f90f | Iustin Pop | You should have received a copy of the GNU General Public License |
18 | f047f90f | Iustin Pop | along with this program; if not, write to the Free Software |
19 | f047f90f | Iustin Pop | Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA |
20 | f047f90f | Iustin Pop | 02110-1301, USA. |
21 | f047f90f | Iustin Pop | |
22 | f047f90f | Iustin Pop | -} |
23 | f047f90f | Iustin Pop | |
24 | f047f90f | Iustin Pop | module Ganeti.HTools.JSON |
25 | ebf38064 | Iustin Pop | ( fromJResult |
26 | ebf38064 | Iustin Pop | , readEitherString |
27 | ebf38064 | Iustin Pop | , JSRecord |
28 | ebf38064 | Iustin Pop | , loadJSArray |
29 | ebf38064 | Iustin Pop | , fromObj |
30 | ebf38064 | Iustin Pop | , maybeFromObj |
31 | ebf38064 | Iustin Pop | , fromObjWithDefault |
32 | 706f7f51 | Iustin Pop | , fromKeyValue |
33 | ebf38064 | Iustin Pop | , fromJVal |
34 | ebf38064 | Iustin Pop | , asJSObject |
35 | ebf38064 | Iustin Pop | , asObjectList |
36 | f3f76ccc | Iustin Pop | , tryFromObj |
37 | ebf38064 | Iustin Pop | ) |
38 | ebf38064 | Iustin Pop | where |
39 | f047f90f | Iustin Pop | |
40 | f047f90f | Iustin Pop | import Control.Monad (liftM) |
41 | f047f90f | Iustin Pop | import Data.Maybe (fromMaybe) |
42 | f047f90f | Iustin Pop | import Text.Printf (printf) |
43 | f047f90f | Iustin Pop | |
44 | f047f90f | Iustin Pop | import qualified Text.JSON as J |
45 | f047f90f | Iustin Pop | |
46 | f3f76ccc | Iustin Pop | import Ganeti.BasicTypes |
47 | f3f76ccc | Iustin Pop | |
48 | f047f90f | Iustin Pop | -- * JSON-related functions |
49 | f047f90f | Iustin Pop | |
50 | f047f90f | Iustin Pop | -- | A type alias for the list-based representation of J.JSObject. |
51 | f047f90f | Iustin Pop | type JSRecord = [(String, J.JSValue)] |
52 | f047f90f | Iustin Pop | |
53 | f047f90f | Iustin Pop | -- | Converts a JSON Result into a monadic value. |
54 | f047f90f | Iustin Pop | fromJResult :: Monad m => String -> J.Result a -> m a |
55 | f047f90f | Iustin Pop | fromJResult s (J.Error x) = fail (s ++ ": " ++ x) |
56 | f047f90f | Iustin Pop | fromJResult _ (J.Ok x) = return x |
57 | f047f90f | Iustin Pop | |
58 | f047f90f | Iustin Pop | -- | Tries to read a string from a JSON value. |
59 | f047f90f | Iustin Pop | -- |
60 | f047f90f | Iustin Pop | -- In case the value was not a string, we fail the read (in the |
61 | f047f90f | Iustin Pop | -- context of the current monad. |
62 | f047f90f | Iustin Pop | readEitherString :: (Monad m) => J.JSValue -> m String |
63 | f047f90f | Iustin Pop | readEitherString v = |
64 | ebf38064 | Iustin Pop | case v of |
65 | ebf38064 | Iustin Pop | J.JSString s -> return $ J.fromJSString s |
66 | ebf38064 | Iustin Pop | _ -> fail "Wrong JSON type" |
67 | f047f90f | Iustin Pop | |
68 | f047f90f | Iustin Pop | -- | Converts a JSON message into an array of JSON objects. |
69 | f047f90f | Iustin Pop | loadJSArray :: (Monad m) |
70 | f047f90f | Iustin Pop | => String -- ^ Operation description (for error reporting) |
71 | f047f90f | Iustin Pop | -> String -- ^ Input message |
72 | f047f90f | Iustin Pop | -> m [J.JSObject J.JSValue] |
73 | f047f90f | Iustin Pop | loadJSArray s = fromJResult s . J.decodeStrict |
74 | f047f90f | Iustin Pop | |
75 | f047f90f | Iustin Pop | -- | Reads the value of a key in a JSON object. |
76 | f047f90f | Iustin Pop | fromObj :: (J.JSON a, Monad m) => JSRecord -> String -> m a |
77 | f047f90f | Iustin Pop | fromObj o k = |
78 | ebf38064 | Iustin Pop | case lookup k o of |
79 | ebf38064 | Iustin Pop | Nothing -> fail $ printf "key '%s' not found, object contains only %s" |
80 | ebf38064 | Iustin Pop | k (show (map fst o)) |
81 | ebf38064 | Iustin Pop | Just val -> fromKeyValue k val |
82 | f047f90f | Iustin Pop | |
83 | f047f90f | Iustin Pop | -- | Reads the value of an optional key in a JSON object. |
84 | f047f90f | Iustin Pop | maybeFromObj :: (J.JSON a, Monad m) => |
85 | f047f90f | Iustin Pop | JSRecord -> String -> m (Maybe a) |
86 | f047f90f | Iustin Pop | maybeFromObj o k = |
87 | ebf38064 | Iustin Pop | case lookup k o of |
88 | ebf38064 | Iustin Pop | Nothing -> return Nothing |
89 | ebf38064 | Iustin Pop | Just val -> liftM Just (fromKeyValue k val) |
90 | f047f90f | Iustin Pop | |
91 | f047f90f | Iustin Pop | -- | Reads the value of a key in a JSON object with a default if missing. |
92 | f047f90f | Iustin Pop | fromObjWithDefault :: (J.JSON a, Monad m) => |
93 | f047f90f | Iustin Pop | JSRecord -> String -> a -> m a |
94 | f047f90f | Iustin Pop | fromObjWithDefault o k d = liftM (fromMaybe d) $ maybeFromObj o k |
95 | f047f90f | Iustin Pop | |
96 | f047f90f | Iustin Pop | -- | Reads a JValue, that originated from an object key. |
97 | f047f90f | Iustin Pop | fromKeyValue :: (J.JSON a, Monad m) |
98 | f047f90f | Iustin Pop | => String -- ^ The key name |
99 | f047f90f | Iustin Pop | -> J.JSValue -- ^ The value to read |
100 | f047f90f | Iustin Pop | -> m a |
101 | f047f90f | Iustin Pop | fromKeyValue k val = |
102 | 706f7f51 | Iustin Pop | fromJResult (printf "key '%s'" k) (J.readJSON val) |
103 | f047f90f | Iustin Pop | |
104 | f047f90f | Iustin Pop | -- | Small wrapper over readJSON. |
105 | f047f90f | Iustin Pop | fromJVal :: (Monad m, J.JSON a) => J.JSValue -> m a |
106 | f047f90f | Iustin Pop | fromJVal v = |
107 | ebf38064 | Iustin Pop | case J.readJSON v of |
108 | ebf38064 | Iustin Pop | J.Error s -> fail ("Cannot convert value '" ++ show v ++ |
109 | ebf38064 | Iustin Pop | "', error: " ++ s) |
110 | ebf38064 | Iustin Pop | J.Ok x -> return x |
111 | f047f90f | Iustin Pop | |
112 | f047f90f | Iustin Pop | -- | Converts a JSON value into a JSON object. |
113 | f047f90f | Iustin Pop | asJSObject :: (Monad m) => J.JSValue -> m (J.JSObject J.JSValue) |
114 | f047f90f | Iustin Pop | asJSObject (J.JSObject a) = return a |
115 | f047f90f | Iustin Pop | asJSObject _ = fail "not an object" |
116 | f047f90f | Iustin Pop | |
117 | f047f90f | Iustin Pop | -- | Coneverts a list of JSON values into a list of JSON objects. |
118 | f047f90f | Iustin Pop | asObjectList :: (Monad m) => [J.JSValue] -> m [J.JSObject J.JSValue] |
119 | f047f90f | Iustin Pop | asObjectList = mapM asJSObject |
120 | f3f76ccc | Iustin Pop | |
121 | f3f76ccc | Iustin Pop | -- | Try to extract a key from a object with better error reporting |
122 | f3f76ccc | Iustin Pop | -- than fromObj. |
123 | f3f76ccc | Iustin Pop | tryFromObj :: (J.JSON a) => |
124 | f3f76ccc | Iustin Pop | String -- ^ Textual "owner" in error messages |
125 | f3f76ccc | Iustin Pop | -> JSRecord -- ^ The object array |
126 | f3f76ccc | Iustin Pop | -> String -- ^ The desired key from the object |
127 | f3f76ccc | Iustin Pop | -> Result a |
128 | f3f76ccc | Iustin Pop | tryFromObj t o = annotateResult t . fromObj o |