root / htools / Ganeti / THH.hs @ 92678b3c
History | View | Annotate | Download (17.6 kB)
1 |
{-# LANGUAGE TemplateHaskell, QuasiQuotes #-} |
---|---|
2 |
|
3 |
{-| TemplateHaskell helper for HTools. |
4 |
|
5 |
As TemplateHaskell require that splices be defined in a separate |
6 |
module, we combine all the TemplateHaskell functionality that HTools |
7 |
needs in this module (except the one for unittests). |
8 |
|
9 |
-} |
10 |
|
11 |
{- |
12 |
|
13 |
Copyright (C) 2011 Google Inc. |
14 |
|
15 |
This program is free software; you can redistribute it and/or modify |
16 |
it under the terms of the GNU General Public License as published by |
17 |
the Free Software Foundation; either version 2 of the License, or |
18 |
(at your option) any later version. |
19 |
|
20 |
This program is distributed in the hope that it will be useful, but |
21 |
WITHOUT ANY WARRANTY; without even the implied warranty of |
22 |
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
23 |
General Public License for more details. |
24 |
|
25 |
You should have received a copy of the GNU General Public License |
26 |
along with this program; if not, write to the Free Software |
27 |
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA |
28 |
02110-1301, USA. |
29 |
|
30 |
-} |
31 |
|
32 |
module Ganeti.THH ( Store(..) |
33 |
, declareSADT |
34 |
, makeJSONInstance |
35 |
, genOpID |
36 |
, genOpCode |
37 |
, noDefault |
38 |
, genStrOfOp |
39 |
, genStrOfKey |
40 |
, genLuxiOp |
41 |
) where |
42 |
|
43 |
import Control.Monad (liftM, liftM2) |
44 |
import Data.Char |
45 |
import Data.List |
46 |
import Language.Haskell.TH |
47 |
|
48 |
import qualified Text.JSON as JSON |
49 |
|
50 |
-- * Helper functions |
51 |
|
52 |
-- | Ensure first letter is lowercase. |
53 |
-- |
54 |
-- Used to convert type name to function prefix, e.g. in @data Aa -> |
55 |
-- aaToString@. |
56 |
ensureLower :: String -> String |
57 |
ensureLower [] = [] |
58 |
ensureLower (x:xs) = toLower x:xs |
59 |
|
60 |
-- | Helper for quoted expressions. |
61 |
varNameE :: String -> Q Exp |
62 |
varNameE = varE . mkName |
63 |
|
64 |
-- | showJSON as an expression, for reuse. |
65 |
showJSONE :: Q Exp |
66 |
showJSONE = varNameE "showJSON" |
67 |
|
68 |
-- | ToString function name. |
69 |
toStrName :: String -> Name |
70 |
toStrName = mkName . (++ "ToString") . ensureLower |
71 |
|
72 |
-- | FromString function name. |
73 |
fromStrName :: String -> Name |
74 |
fromStrName = mkName . (++ "FromString") . ensureLower |
75 |
|
76 |
-- | Converts a name to it's varE/litE representations. |
77 |
-- |
78 |
reprE :: Either String Name -> Q Exp |
79 |
reprE = either stringE varE |
80 |
|
81 |
-- | Smarter function application. |
82 |
-- |
83 |
-- This does simply f x, except that if is 'id', it will skip it, in |
84 |
-- order to generate more readable code when using -ddump-splices. |
85 |
appFn :: Exp -> Exp -> Exp |
86 |
appFn f x | f == VarE 'id = x |
87 |
| otherwise = AppE f x |
88 |
|
89 |
-- * Template code for simple string-equivalent ADTs |
90 |
|
91 |
-- | Generates a data type declaration. |
92 |
-- |
93 |
-- The type will have a fixed list of instances. |
94 |
strADTDecl :: Name -> [String] -> Dec |
95 |
strADTDecl name constructors = |
96 |
DataD [] name [] |
97 |
(map (flip NormalC [] . mkName) constructors) |
98 |
[''Show, ''Read, ''Eq, ''Enum, ''Bounded, ''Ord] |
99 |
|
100 |
-- | Generates a toString function. |
101 |
-- |
102 |
-- This generates a simple function of the form: |
103 |
-- |
104 |
-- @ |
105 |
-- nameToString :: Name -> String |
106 |
-- nameToString Cons1 = var1 |
107 |
-- nameToString Cons2 = \"value2\" |
108 |
-- @ |
109 |
genToString :: Name -> Name -> [(String, Either String Name)] -> Q [Dec] |
110 |
genToString fname tname constructors = do |
111 |
sigt <- [t| $(conT tname) -> String |] |
112 |
-- the body clauses, matching on the constructor and returning the |
113 |
-- string value |
114 |
clauses <- mapM (\(c, v) -> clause [recP (mkName c) []] |
115 |
(normalB (reprE v)) []) constructors |
116 |
return [SigD fname sigt, FunD fname clauses] |
117 |
|
118 |
-- | Generates a fromString function. |
119 |
-- |
120 |
-- The function generated is monadic and can fail parsing the |
121 |
-- string. It is of the form: |
122 |
-- |
123 |
-- @ |
124 |
-- nameFromString :: (Monad m) => String -> m Name |
125 |
-- nameFromString s | s == var1 = Cons1 |
126 |
-- | s == \"value2\" = Cons2 |
127 |
-- | otherwise = fail /.../ |
128 |
-- @ |
129 |
genFromString :: Name -> Name -> [(String, Name)] -> Q [Dec] |
130 |
genFromString fname tname constructors = do |
131 |
-- signature of form (Monad m) => String -> m $name |
132 |
sigt <- [t| (Monad m) => String -> m $(conT tname) |] |
133 |
-- clauses for a guarded pattern |
134 |
let varp = mkName "s" |
135 |
varpe = varE varp |
136 |
clauses <- mapM (\(c, v) -> do |
137 |
-- the clause match condition |
138 |
g <- normalG [| $varpe == $(varE v) |] |
139 |
-- the clause result |
140 |
r <- [| return $(conE (mkName c)) |] |
141 |
return (g, r)) constructors |
142 |
-- the otherwise clause (fallback) |
143 |
oth_clause <- do |
144 |
g <- normalG [| otherwise |] |
145 |
r <- [|fail ("Invalid string value for type " ++ |
146 |
$(litE (stringL (nameBase tname))) ++ ": " ++ $varpe) |] |
147 |
return (g, r) |
148 |
let fun = FunD fname [Clause [VarP varp] |
149 |
(GuardedB (clauses++[oth_clause])) []] |
150 |
return [SigD fname sigt, fun] |
151 |
|
152 |
-- | Generates a data type from a given string format. |
153 |
-- |
154 |
-- The format is expected to multiline. The first line contains the |
155 |
-- type name, and the rest of the lines must contain two words: the |
156 |
-- constructor name and then the string representation of the |
157 |
-- respective constructor. |
158 |
-- |
159 |
-- The function will generate the data type declaration, and then two |
160 |
-- functions: |
161 |
-- |
162 |
-- * /name/ToString, which converts the type to a string |
163 |
-- |
164 |
-- * /name/FromString, which (monadically) converts from a string to the type |
165 |
-- |
166 |
-- Note that this is basically just a custom show/read instance, |
167 |
-- nothing else. |
168 |
declareSADT :: String -> [(String, Name)] -> Q [Dec] |
169 |
declareSADT sname cons = do |
170 |
let name = mkName sname |
171 |
ddecl = strADTDecl name (map fst cons) |
172 |
-- process cons in the format expected by genToString |
173 |
cons' = map (\(a, b) -> (a, Right b)) cons |
174 |
tostr <- genToString (toStrName sname) name cons' |
175 |
fromstr <- genFromString (fromStrName sname) name cons |
176 |
return $ ddecl:tostr ++ fromstr |
177 |
|
178 |
|
179 |
-- | Creates the showJSON member of a JSON instance declaration. |
180 |
-- |
181 |
-- This will create what is the equivalent of: |
182 |
-- |
183 |
-- @ |
184 |
-- showJSON = showJSON . /name/ToString |
185 |
-- @ |
186 |
-- |
187 |
-- in an instance JSON /name/ declaration |
188 |
genShowJSON :: String -> Q [Dec] |
189 |
genShowJSON name = [d| showJSON = JSON.showJSON . $(varE (toStrName name)) |] |
190 |
|
191 |
-- | Creates the readJSON member of a JSON instance declaration. |
192 |
-- |
193 |
-- This will create what is the equivalent of: |
194 |
-- |
195 |
-- @ |
196 |
-- readJSON s = case readJSON s of |
197 |
-- Ok s' -> /name/FromString s' |
198 |
-- Error e -> Error /description/ |
199 |
-- @ |
200 |
-- |
201 |
-- in an instance JSON /name/ declaration |
202 |
genReadJSON :: String -> Q Dec |
203 |
genReadJSON name = do |
204 |
let s = mkName "s" |
205 |
body <- [| case JSON.readJSON $(varE s) of |
206 |
JSON.Ok s' -> $(varE (fromStrName name)) s' |
207 |
JSON.Error e -> |
208 |
JSON.Error $ "Can't parse string value for type " ++ |
209 |
$(stringE name) ++ ": " ++ e |
210 |
|] |
211 |
return $ FunD (mkName "readJSON") [Clause [VarP s] (NormalB body) []] |
212 |
|
213 |
-- | Generates a JSON instance for a given type. |
214 |
-- |
215 |
-- This assumes that the /name/ToString and /name/FromString functions |
216 |
-- have been defined as by the 'declareSADT' function. |
217 |
makeJSONInstance :: Name -> Q [Dec] |
218 |
makeJSONInstance name = do |
219 |
let base = nameBase name |
220 |
showJ <- genShowJSON base |
221 |
readJ <- genReadJSON base |
222 |
return [InstanceD [] (AppT (ConT ''JSON.JSON) (ConT name)) (readJ:showJ)] |
223 |
|
224 |
-- * Template code for opcodes |
225 |
|
226 |
-- | Transforms a CamelCase string into an_underscore_based_one. |
227 |
deCamelCase :: String -> String |
228 |
deCamelCase = |
229 |
intercalate "_" . map (map toUpper) . groupBy (\_ b -> not $ isUpper b) |
230 |
|
231 |
-- | Computes the name of a given constructor. |
232 |
constructorName :: Con -> Q Name |
233 |
constructorName (NormalC name _) = return name |
234 |
constructorName (RecC name _) = return name |
235 |
constructorName x = fail $ "Unhandled constructor " ++ show x |
236 |
|
237 |
-- | Builds the generic constructor-to-string function. |
238 |
-- |
239 |
-- This generates a simple function of the following form: |
240 |
-- |
241 |
-- @ |
242 |
-- fname (ConStructorOne {}) = trans_fun("ConStructorOne") |
243 |
-- fname (ConStructorTwo {}) = trans_fun("ConStructorTwo") |
244 |
-- @ |
245 |
-- |
246 |
-- This builds a custom list of name/string pairs and then uses |
247 |
-- 'genToString' to actually generate the function |
248 |
genConstrToStr :: (String -> String) -> Name -> String -> Q [Dec] |
249 |
genConstrToStr trans_fun name fname = do |
250 |
TyConI (DataD _ _ _ cons _) <- reify name |
251 |
cnames <- mapM (liftM nameBase . constructorName) cons |
252 |
let svalues = map (Left . trans_fun) cnames |
253 |
genToString (mkName fname) name $ zip cnames svalues |
254 |
|
255 |
-- | Constructor-to-string for OpCode. |
256 |
genOpID :: Name -> String -> Q [Dec] |
257 |
genOpID = genConstrToStr deCamelCase |
258 |
|
259 |
-- | OpCode parameter (field) type. |
260 |
type OpParam = (String, Q Type, Q Exp) |
261 |
|
262 |
-- | Generates the OpCode data type. |
263 |
-- |
264 |
-- This takes an opcode logical definition, and builds both the |
265 |
-- datatype and the JSON serialisation out of it. We can't use a |
266 |
-- generic serialisation since we need to be compatible with Ganeti's |
267 |
-- own, so we have a few quirks to work around. |
268 |
-- |
269 |
-- There are three things to be defined for each parameter: |
270 |
-- |
271 |
-- * name |
272 |
-- |
273 |
-- * type; if this is 'Maybe', will only be serialised if it's a |
274 |
-- 'Just' value |
275 |
-- |
276 |
-- * default; if missing, won't raise an exception, but will instead |
277 |
-- use the default |
278 |
-- |
279 |
genOpCode :: String -- ^ Type name to use |
280 |
-> [(String, [OpParam])] -- ^ Constructor name and parameters |
281 |
-> Q [Dec] |
282 |
genOpCode name cons = do |
283 |
decl_d <- mapM (\(cname, fields) -> do |
284 |
-- we only need the type of the field, without Q |
285 |
fields' <- mapM (\(_, qt, _) -> |
286 |
qt >>= \t -> return (NotStrict, t)) |
287 |
fields |
288 |
return $ NormalC (mkName cname) fields') |
289 |
cons |
290 |
let declD = DataD [] (mkName name) [] decl_d [''Show, ''Read, ''Eq] |
291 |
|
292 |
(savesig, savefn) <- genSaveOpCode cons |
293 |
(loadsig, loadfn) <- genLoadOpCode cons |
294 |
return [declD, loadsig, loadfn, savesig, savefn] |
295 |
|
296 |
-- | Checks whether a given parameter is options. |
297 |
-- |
298 |
-- This requires that it's a 'Maybe'. |
299 |
isOptional :: Type -> Bool |
300 |
isOptional (AppT (ConT dt) _) | dt == ''Maybe = True |
301 |
isOptional _ = False |
302 |
|
303 |
-- | Generates the \"save\" expression for a single opcode parameter. |
304 |
-- |
305 |
-- There is only one special handling mode: if the parameter is of |
306 |
-- 'Maybe' type, then we only save it if it's a 'Just' value, |
307 |
-- otherwise we skip it. |
308 |
saveField :: Name -- ^ The name of variable that contains the value |
309 |
-> OpParam -- ^ Parameter definition |
310 |
-> Q Exp |
311 |
saveField fvar (fname, qt, _) = do |
312 |
t <- qt |
313 |
let fnexp = stringE fname |
314 |
fvare = varE fvar |
315 |
(if isOptional t |
316 |
then [| case $fvare of |
317 |
Just v' -> [( $fnexp, $showJSONE v')] |
318 |
Nothing -> [] |
319 |
|] |
320 |
else [| [( $fnexp, $showJSONE $fvare )] |]) |
321 |
|
322 |
-- | Generates the \"save\" clause for an entire opcode constructor. |
323 |
-- |
324 |
-- This matches the opcode with variables named the same as the |
325 |
-- constructor fields (just so that the spliced in code looks nicer), |
326 |
-- and passes those name plus the parameter definition to 'saveField'. |
327 |
saveConstructor :: String -- ^ The constructor name |
328 |
-> [OpParam] -- ^ The parameter definitions for this |
329 |
-- constructor |
330 |
-> Q Clause -- ^ Resulting clause |
331 |
saveConstructor sname fields = do |
332 |
let cname = mkName sname |
333 |
let fnames = map (\(n, _, _) -> mkName n) fields |
334 |
let pat = conP cname (map varP fnames) |
335 |
let felems = map (uncurry saveField) (zip fnames fields) |
336 |
-- now build the OP_ID serialisation |
337 |
opid = [| [( $(stringE "OP_ID"), |
338 |
$showJSONE $(stringE . deCamelCase $ sname) )] |] |
339 |
flist = listE (opid:felems) |
340 |
-- and finally convert all this to a json object |
341 |
flist' = [| $(varNameE "makeObj") (concat $flist) |] |
342 |
clause [pat] (normalB flist') [] |
343 |
|
344 |
-- | Generates the main save opcode function. |
345 |
-- |
346 |
-- This builds a per-constructor match clause that contains the |
347 |
-- respective constructor-serialisation code. |
348 |
genSaveOpCode :: [(String, [OpParam])] -> Q (Dec, Dec) |
349 |
genSaveOpCode opdefs = do |
350 |
cclauses <- mapM (uncurry saveConstructor) opdefs |
351 |
let fname = mkName "saveOpCode" |
352 |
sigt <- [t| $(conT (mkName "OpCode")) -> JSON.JSValue |] |
353 |
return $ (SigD fname sigt, FunD fname cclauses) |
354 |
|
355 |
-- | Generates the \"load\" field for a single parameter. |
356 |
-- |
357 |
-- There is custom handling, depending on how the parameter is |
358 |
-- specified. For a 'Maybe' type parameter, we allow that it is not |
359 |
-- present (via 'Utils.maybeFromObj'). Otherwise, if there is a |
360 |
-- default value, we allow the parameter to be abset, and finally if |
361 |
-- there is no default value, we require its presence. |
362 |
loadField :: OpParam -> Q (Name, Stmt) |
363 |
loadField (fname, qt, qdefa) = do |
364 |
let fvar = mkName fname |
365 |
t <- qt |
366 |
defa <- qdefa |
367 |
-- these are used in all patterns below |
368 |
let objvar = varNameE "o" |
369 |
objfield = stringE fname |
370 |
bexp <- if isOptional t |
371 |
then [| $((varNameE "maybeFromObj")) $objvar $objfield |] |
372 |
else case defa of |
373 |
AppE (ConE dt) defval | dt == 'Just -> |
374 |
-- but has a default value |
375 |
[| $(varNameE "fromObjWithDefault") |
376 |
$objvar $objfield $(return defval) |] |
377 |
ConE dt | dt == 'Nothing -> |
378 |
[| $(varNameE "fromObj") $objvar $objfield |] |
379 |
s -> fail $ "Invalid default value " ++ show s ++ |
380 |
", expecting either 'Nothing' or a 'Just defval'" |
381 |
return (fvar, BindS (VarP fvar) bexp) |
382 |
|
383 |
loadConstructor :: String -> [OpParam] -> Q Exp |
384 |
loadConstructor sname fields = do |
385 |
let name = mkName sname |
386 |
fbinds <- mapM loadField fields |
387 |
let (fnames, fstmts) = unzip fbinds |
388 |
let cval = foldl (\accu fn -> AppE accu (VarE fn)) (ConE name) fnames |
389 |
fstmts' = fstmts ++ [NoBindS (AppE (VarE 'return) cval)] |
390 |
return $ DoE fstmts' |
391 |
|
392 |
genLoadOpCode :: [(String, [OpParam])] -> Q (Dec, Dec) |
393 |
genLoadOpCode opdefs = do |
394 |
let fname = mkName "loadOpCode" |
395 |
arg1 = mkName "v" |
396 |
objname = mkName "o" |
397 |
opid = mkName "op_id" |
398 |
st1 <- bindS (varP objname) [| liftM JSON.fromJSObject |
399 |
(JSON.readJSON $(varE arg1)) |] |
400 |
st2 <- bindS (varP opid) [| $(varNameE "fromObj") |
401 |
$(varE objname) $(stringE "OP_ID") |] |
402 |
-- the match results (per-constructor blocks) |
403 |
mexps <- mapM (uncurry loadConstructor) opdefs |
404 |
fails <- [| fail $ "Unknown opcode " ++ $(varE opid) |] |
405 |
let mpats = map (\(me, c) -> |
406 |
let mp = LitP . StringL . deCamelCase . fst $ c |
407 |
in Match mp (NormalB me) [] |
408 |
) $ zip mexps opdefs |
409 |
defmatch = Match WildP (NormalB fails) [] |
410 |
cst = NoBindS $ CaseE (VarE opid) $ mpats++[defmatch] |
411 |
body = DoE [st1, st2, cst] |
412 |
sigt <- [t| JSON.JSValue -> JSON.Result $(conT (mkName "OpCode")) |] |
413 |
return $ (SigD fname sigt, FunD fname [Clause [VarP arg1] (NormalB body) []]) |
414 |
|
415 |
-- | No default type. |
416 |
noDefault :: Q Exp |
417 |
noDefault = conE 'Nothing |
418 |
|
419 |
-- * Template code for luxi |
420 |
|
421 |
-- | Constructor-to-string for LuxiOp. |
422 |
genStrOfOp :: Name -> String -> Q [Dec] |
423 |
genStrOfOp = genConstrToStr id |
424 |
|
425 |
-- | Constructor-to-string for MsgKeys. |
426 |
genStrOfKey :: Name -> String -> Q [Dec] |
427 |
genStrOfKey = genConstrToStr ensureLower |
428 |
|
429 |
-- | LuxiOp parameter type. |
430 |
type LuxiParam = (String, Q Type, Q Exp) |
431 |
|
432 |
-- | Storage options for JSON. |
433 |
data Store = SList | SDict |
434 |
|
435 |
-- | Generates the LuxiOp data type. |
436 |
-- |
437 |
-- This takes a Luxi operation definition and builds both the |
438 |
-- datatype and the function trnasforming the arguments to JSON. |
439 |
-- We can't use anything less generic, because the way different |
440 |
-- operations are serialized differs on both parameter- and top-level. |
441 |
-- |
442 |
-- There are three things to be defined for each parameter: |
443 |
-- |
444 |
-- * name |
445 |
-- |
446 |
-- * type |
447 |
-- |
448 |
-- * operation; this is the operation performed on the parameter before |
449 |
-- serialization |
450 |
-- |
451 |
genLuxiOp :: String -> [(String, [LuxiParam], Store)] -> Q [Dec] |
452 |
genLuxiOp name cons = do |
453 |
decl_d <- mapM (\(cname, fields, _) -> do |
454 |
fields' <- mapM (\(_, qt, _) -> |
455 |
qt >>= \t -> return (NotStrict, t)) |
456 |
fields |
457 |
return $ NormalC (mkName cname) fields') |
458 |
cons |
459 |
let declD = DataD [] (mkName name) [] decl_d [''Show, ''Read] |
460 |
(savesig, savefn) <- genSaveLuxiOp cons |
461 |
return [declD, savesig, savefn] |
462 |
|
463 |
-- | Generates a Q Exp for an element, depending of the JSON return type. |
464 |
helperLuxiField :: Store -> String -> Q Exp -> Q Exp |
465 |
helperLuxiField SList name val = [| [ JSON.showJSON $val ] |] |
466 |
helperLuxiField SDict name val = [| [(name, JSON.showJSON $val)] |] |
467 |
|
468 |
-- | Generates the \"save\" expression for a single luxi parameter. |
469 |
saveLuxiField :: Store -> Name -> LuxiParam -> Q Exp |
470 |
saveLuxiField store fvar (fname, qt, fn) = do |
471 |
t <- qt |
472 |
let fvare = varE fvar |
473 |
(if isOptional t |
474 |
then [| case $fvare of |
475 |
Just v' -> |
476 |
$(helperLuxiField store fname $ liftM2 appFn fn [| v' |]) |
477 |
Nothing -> [] |
478 |
|] |
479 |
else helperLuxiField store fname $ liftM2 appFn fn fvare) |
480 |
|
481 |
-- | Generates final JSON Q Exp for constructor. |
482 |
helperLuxiConstructor :: Store -> Q Exp -> Q Exp |
483 |
helperLuxiConstructor SDict val = [| JSON.showJSON $ JSON.makeObj $val |] |
484 |
helperLuxiConstructor SList val = [| JSON.JSArray $val |] |
485 |
|
486 |
-- | Generates the \"save\" clause for entire LuxiOp constructor. |
487 |
saveLuxiConstructor :: (String, [LuxiParam], Store) -> Q Clause |
488 |
saveLuxiConstructor (sname, fields, store) = do |
489 |
let cname = mkName sname |
490 |
fnames = map (\(nm, _, _) -> mkName nm) fields |
491 |
pat = conP cname (map varP fnames) |
492 |
flist = map (uncurry $ saveLuxiField store) (zip fnames fields) |
493 |
flist' = appE [| concat |] (listE flist) |
494 |
finval = helperLuxiConstructor store flist' |
495 |
clause [pat] (normalB finval) [] |
496 |
|
497 |
-- | Generates the main save LuxiOp function. |
498 |
genSaveLuxiOp :: [(String, [LuxiParam], Store)]-> Q (Dec, Dec) |
499 |
genSaveLuxiOp opdefs = do |
500 |
sigt <- [t| $(conT (mkName "LuxiOp")) -> JSON.JSValue |] |
501 |
let fname = mkName "opToArgs" |
502 |
cclauses <- mapM saveLuxiConstructor opdefs |
503 |
return $ (SigD fname sigt, FunD fname cclauses) |