1 {-# LANGUAGE TemplateHaskell, QuasiQuotes #-}
3 {-| TemplateHaskell helper for HTools.
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).
13 Copyright (C) 2011 Google Inc.
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.
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.
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
32 module Ganeti.THH ( declareSADT
52 , buildObjectSerialisation
58 import Control.Monad (liftM, liftM2)
61 import qualified Data.Map as M
62 import Language.Haskell.TH
64 import qualified Text.JSON as JSON
68 type Container = M.Map String
70 -- | Serialised field data type.
71 data Field = Field { fieldName :: String
73 , fieldRead :: Maybe (Q Exp)
74 , fieldShow :: Maybe (Q Exp)
75 , fieldDefault :: Maybe (Q Exp)
76 , fieldConstr :: Maybe String
77 , fieldIsContainer :: Bool
78 , fieldIsOptional :: Bool
81 -- | Generates a simple field.
82 simpleField :: String -> Q Type -> Field
83 simpleField fname ftype =
84 Field { fieldName = fname
88 , fieldDefault = Nothing
89 , fieldConstr = Nothing
90 , fieldIsContainer = False
91 , fieldIsOptional = False
94 -- | Sets the renamed constructor field.
95 renameField :: String -> Field -> Field
96 renameField constrName field = field { fieldConstr = Just constrName }
98 -- | Sets the default value on a field (makes it optional with a
100 defaultField :: Q Exp -> Field -> Field
101 defaultField defval field = field { fieldDefault = Just defval }
103 -- | Marks a field optional (turning its base type into a Maybe).
104 optionalField :: Field -> Field
105 optionalField field = field { fieldIsOptional = True }
107 -- | Marks a field as a container.
108 containerField :: Field -> Field
109 containerField field = field { fieldIsContainer = True }
111 -- | Sets custom functions on a field.
112 customField :: Q Exp -> Q Exp -> Field -> Field
113 customField readfn showfn field =
114 field { fieldRead = Just readfn, fieldShow = Just showfn }
116 fieldRecordName :: Field -> String
117 fieldRecordName (Field { fieldName = name, fieldConstr = alias }) =
118 maybe (camelCase name) id alias
120 fieldVariable :: Field -> String
121 fieldVariable = map toLower . fieldRecordName
123 actualFieldType :: Field -> Q Type
124 actualFieldType f | fieldIsContainer f = [t| Container $t |]
125 | fieldIsOptional f = [t| Maybe $t |]
127 where t = fieldType f
129 checkNonOptDef :: (Monad m) => Field -> m ()
130 checkNonOptDef (Field { fieldIsOptional = True, fieldName = name }) =
131 fail $ "Optional field " ++ name ++ " used in parameter declaration"
132 checkNonOptDef (Field { fieldDefault = (Just _), fieldName = name }) =
133 fail $ "Default field " ++ name ++ " used in parameter declaration"
134 checkNonOptDef _ = return ()
136 loadFn :: Field -> Q Exp -> Q Exp
137 loadFn (Field { fieldIsContainer = True }) expr = [| $expr >>= readContainer |]
138 loadFn (Field { fieldRead = Just readfn }) expr = [| $expr >>= $readfn |]
141 saveFn :: Field -> Q Exp -> Q Exp
142 saveFn (Field { fieldIsContainer = True }) expr = [| showContainer $expr |]
143 saveFn (Field { fieldRead = Just readfn }) expr = [| $readfn $expr |]
146 -- * Common field declarations
148 timeStampFields :: [Field]
150 [ defaultField [| 0::Double |] $ simpleField "ctime" [t| Double |]
151 , defaultField [| 0::Double |] $ simpleField "mtime" [t| Double |]
154 serialFields :: [Field]
156 [ renameField "Serial" $ simpleField "serial_no" [t| Int |] ]
158 uuidFields :: [Field]
159 uuidFields = [ simpleField "uuid" [t| String |] ]
161 -- * Helper functions
163 -- | Ensure first letter is lowercase.
165 -- Used to convert type name to function prefix, e.g. in @data Aa ->
167 ensureLower :: String -> String
169 ensureLower (x:xs) = toLower x:xs
171 -- | Ensure first letter is uppercase.
173 -- Used to convert constructor name to component
174 ensureUpper :: String -> String
176 ensureUpper (x:xs) = toUpper x:xs
178 -- | Helper for quoted expressions.
179 varNameE :: String -> Q Exp
180 varNameE = varE . mkName
182 -- | showJSON as an expression, for reuse.
184 showJSONE = varNameE "showJSON"
186 -- | ToRaw function name.
187 toRawName :: String -> Name
188 toRawName = mkName . (++ "ToRaw") . ensureLower
190 -- | FromRaw function name.
191 fromRawName :: String -> Name
192 fromRawName = mkName . (++ "FromRaw") . ensureLower
194 -- | Converts a name to it's varE/litE representations.
196 reprE :: Either String Name -> Q Exp
197 reprE = either stringE varE
199 -- | Smarter function application.
201 -- This does simply f x, except that if is 'id', it will skip it, in
202 -- order to generate more readable code when using -ddump-splices.
203 appFn :: Exp -> Exp -> Exp
204 appFn f x | f == VarE 'id = x
205 | otherwise = AppE f x
207 -- | Container loader
208 readContainer :: (Monad m) => JSON.JSObject a -> m (Container a)
209 readContainer = return . M.fromList . JSON.fromJSObject
211 -- | Container dumper
212 showContainer :: (JSON.JSON a) => Container a -> JSON.JSValue
213 showContainer = JSON.makeObj . map (second JSON.showJSON) . M.toList
215 -- * Template code for simple raw type-equivalent ADTs
217 -- | Generates a data type declaration.
219 -- The type will have a fixed list of instances.
220 strADTDecl :: Name -> [String] -> Dec
221 strADTDecl name constructors =
223 (map (flip NormalC [] . mkName) constructors)
224 [''Show, ''Read, ''Eq, ''Enum, ''Bounded, ''Ord]
226 -- | Generates a toRaw function.
228 -- This generates a simple function of the form:
231 -- nameToRaw :: Name -> /traw/
232 -- nameToRaw Cons1 = var1
233 -- nameToRaw Cons2 = \"value2\"
235 genToRaw :: Name -> Name -> Name -> [(String, Either String Name)] -> Q [Dec]
236 genToRaw traw fname tname constructors = do
237 sigt <- [t| $(conT tname) -> $(conT traw) |]
238 -- the body clauses, matching on the constructor and returning the
240 clauses <- mapM (\(c, v) -> clause [recP (mkName c) []]
241 (normalB (reprE v)) []) constructors
242 return [SigD fname sigt, FunD fname clauses]
244 -- | Generates a fromRaw function.
246 -- The function generated is monadic and can fail parsing the
247 -- raw value. It is of the form:
250 -- nameFromRaw :: (Monad m) => /traw/ -> m Name
251 -- nameFromRaw s | s == var1 = Cons1
252 -- | s == \"value2\" = Cons2
253 -- | otherwise = fail /.../
255 genFromRaw :: Name -> Name -> Name -> [(String, Name)] -> Q [Dec]
256 genFromRaw traw fname tname constructors = do
257 -- signature of form (Monad m) => String -> m $name
258 sigt <- [t| (Monad m) => $(conT traw) -> m $(conT tname) |]
259 -- clauses for a guarded pattern
260 let varp = mkName "s"
262 clauses <- mapM (\(c, v) -> do
263 -- the clause match condition
264 g <- normalG [| $varpe == $(varE v) |]
266 r <- [| return $(conE (mkName c)) |]
267 return (g, r)) constructors
268 -- the otherwise clause (fallback)
270 g <- normalG [| otherwise |]
271 r <- [|fail ("Invalid string value for type " ++
272 $(litE (stringL (nameBase tname))) ++ ": " ++ show $varpe) |]
274 let fun = FunD fname [Clause [VarP varp]
275 (GuardedB (clauses++[oth_clause])) []]
276 return [SigD fname sigt, fun]
278 -- | Generates a data type from a given raw format.
280 -- The format is expected to multiline. The first line contains the
281 -- type name, and the rest of the lines must contain two words: the
282 -- constructor name and then the string representation of the
283 -- respective constructor.
285 -- The function will generate the data type declaration, and then two
288 -- * /name/ToRaw, which converts the type to a raw type
290 -- * /name/FromRaw, which (monadically) converts from a raw type to the type
292 -- Note that this is basically just a custom show/read instance,
294 declareADT :: Name -> String -> [(String, Name)] -> Q [Dec]
295 declareADT traw sname cons = do
296 let name = mkName sname
297 ddecl = strADTDecl name (map fst cons)
298 -- process cons in the format expected by genToRaw
299 cons' = map (\(a, b) -> (a, Right b)) cons
300 toraw <- genToRaw traw (toRawName sname) name cons'
301 fromraw <- genFromRaw traw (fromRawName sname) name cons
302 return $ ddecl:toraw ++ fromraw
304 declareIADT :: String -> [(String, Name)] -> Q [Dec]
305 declareIADT = declareADT ''Int
307 declareSADT :: String -> [(String, Name)] -> Q [Dec]
308 declareSADT = declareADT ''String
310 -- | Creates the showJSON member of a JSON instance declaration.
312 -- This will create what is the equivalent of:
315 -- showJSON = showJSON . /name/ToRaw
318 -- in an instance JSON /name/ declaration
319 genShowJSON :: String -> Q [Dec]
320 genShowJSON name = [d| showJSON = JSON.showJSON . $(varE (toRawName name)) |]
322 -- | Creates the readJSON member of a JSON instance declaration.
324 -- This will create what is the equivalent of:
327 -- readJSON s = case readJSON s of
328 -- Ok s' -> /name/FromRaw s'
329 -- Error e -> Error /description/
332 -- in an instance JSON /name/ declaration
333 genReadJSON :: String -> Q Dec
334 genReadJSON name = do
336 body <- [| case JSON.readJSON $(varE s) of
337 JSON.Ok s' -> $(varE (fromRawName name)) s'
339 JSON.Error $ "Can't parse raw value for type " ++
340 $(stringE name) ++ ": " ++ e
342 return $ FunD (mkName "readJSON") [Clause [VarP s] (NormalB body) []]
344 -- | Generates a JSON instance for a given type.
346 -- This assumes that the /name/ToRaw and /name/FromRaw functions
347 -- have been defined as by the 'declareSADT' function.
348 makeJSONInstance :: Name -> Q [Dec]
349 makeJSONInstance name = do
350 let base = nameBase name
351 showJ <- genShowJSON base
352 readJ <- genReadJSON base
353 return [InstanceD [] (AppT (ConT ''JSON.JSON) (ConT name)) (readJ:showJ)]
355 -- * Template code for opcodes
357 -- | Transforms a CamelCase string into an_underscore_based_one.
358 deCamelCase :: String -> String
360 intercalate "_" . map (map toUpper) . groupBy (\_ b -> not $ isUpper b)
362 -- | Transform an underscore_name into a CamelCase one.
363 camelCase :: String -> String
364 camelCase = concatMap (ensureUpper . drop 1) .
365 groupBy (\_ b -> b /= '_') . ('_':)
367 -- | Computes the name of a given constructor.
368 constructorName :: Con -> Q Name
369 constructorName (NormalC name _) = return name
370 constructorName (RecC name _) = return name
371 constructorName x = fail $ "Unhandled constructor " ++ show x
373 -- | Builds the generic constructor-to-string function.
375 -- This generates a simple function of the following form:
378 -- fname (ConStructorOne {}) = trans_fun("ConStructorOne")
379 -- fname (ConStructorTwo {}) = trans_fun("ConStructorTwo")
382 -- This builds a custom list of name/string pairs and then uses
383 -- 'genToRaw' to actually generate the function
384 genConstrToStr :: (String -> String) -> Name -> String -> Q [Dec]
385 genConstrToStr trans_fun name fname = do
386 TyConI (DataD _ _ _ cons _) <- reify name
387 cnames <- mapM (liftM nameBase . constructorName) cons
388 let svalues = map (Left . trans_fun) cnames
389 genToRaw ''String (mkName fname) name $ zip cnames svalues
391 -- | Constructor-to-string for OpCode.
392 genOpID :: Name -> String -> Q [Dec]
393 genOpID = genConstrToStr deCamelCase
395 -- | OpCode parameter (field) type.
396 type OpParam = (String, Q Type, Q Exp)
398 -- | Generates the OpCode data type.
400 -- This takes an opcode logical definition, and builds both the
401 -- datatype and the JSON serialisation out of it. We can't use a
402 -- generic serialisation since we need to be compatible with Ganeti's
403 -- own, so we have a few quirks to work around.
405 -- There are three things to be defined for each parameter:
409 -- * type; if this is 'Maybe', will only be serialised if it's a
412 -- * default; if missing, won't raise an exception, but will instead
415 genOpCode :: String -- ^ Type name to use
416 -> [(String, [OpParam])] -- ^ Constructor name and parameters
418 genOpCode name cons = do
419 decl_d <- mapM (\(cname, fields) -> do
420 -- we only need the type of the field, without Q
421 fields' <- mapM (\(_, qt, _) ->
422 qt >>= \t -> return (NotStrict, t))
424 return $ NormalC (mkName cname) fields')
426 let declD = DataD [] (mkName name) [] decl_d [''Show, ''Read, ''Eq]
428 (savesig, savefn) <- genSaveOpCode cons
429 (loadsig, loadfn) <- genLoadOpCode cons
430 return [declD, loadsig, loadfn, savesig, savefn]
432 -- | Checks whether a given parameter is options.
434 -- This requires that it's a 'Maybe'.
435 isOptional :: Type -> Bool
436 isOptional (AppT (ConT dt) _) | dt == ''Maybe = True
439 -- | Generates the \"save\" expression for a single opcode parameter.
441 -- There is only one special handling mode: if the parameter is of
442 -- 'Maybe' type, then we only save it if it's a 'Just' value,
443 -- otherwise we skip it.
444 saveField :: Name -- ^ The name of variable that contains the value
445 -> OpParam -- ^ Parameter definition
447 saveField fvar (fname, qt, _) = do
449 let fnexp = stringE fname
452 then [| case $fvare of
453 Just v' -> [( $fnexp, $showJSONE v')]
456 else [| [( $fnexp, $showJSONE $fvare )] |])
458 -- | Generates the \"save\" clause for an entire opcode constructor.
460 -- This matches the opcode with variables named the same as the
461 -- constructor fields (just so that the spliced in code looks nicer),
462 -- and passes those name plus the parameter definition to 'saveField'.
463 saveConstructor :: String -- ^ The constructor name
464 -> [OpParam] -- ^ The parameter definitions for this
466 -> Q Clause -- ^ Resulting clause
467 saveConstructor sname fields = do
468 let cname = mkName sname
469 let fnames = map (\(n, _, _) -> mkName n) fields
470 let pat = conP cname (map varP fnames)
471 let felems = map (uncurry saveField) (zip fnames fields)
472 -- now build the OP_ID serialisation
473 opid = [| [( $(stringE "OP_ID"),
474 $showJSONE $(stringE . deCamelCase $ sname) )] |]
475 flist = listE (opid:felems)
476 -- and finally convert all this to a json object
477 flist' = [| $(varNameE "makeObj") (concat $flist) |]
478 clause [pat] (normalB flist') []
480 -- | Generates the main save opcode function.
482 -- This builds a per-constructor match clause that contains the
483 -- respective constructor-serialisation code.
484 genSaveOpCode :: [(String, [OpParam])] -> Q (Dec, Dec)
485 genSaveOpCode opdefs = do
486 cclauses <- mapM (uncurry saveConstructor) opdefs
487 let fname = mkName "saveOpCode"
488 sigt <- [t| $(conT (mkName "OpCode")) -> JSON.JSValue |]
489 return $ (SigD fname sigt, FunD fname cclauses)
491 -- | Generates the \"load\" field for a single parameter.
493 -- There is custom handling, depending on how the parameter is
494 -- specified. For a 'Maybe' type parameter, we allow that it is not
495 -- present (via 'Utils.maybeFromObj'). Otherwise, if there is a
496 -- default value, we allow the parameter to be abset, and finally if
497 -- there is no default value, we require its presence.
498 loadField :: OpParam -> Q (Name, Stmt)
499 loadField (fname, qt, qdefa) = do
500 let fvar = mkName fname
503 -- these are used in all patterns below
504 let objvar = varNameE "o"
505 objfield = stringE fname
506 bexp <- if isOptional t
507 then [| $((varNameE "maybeFromObj")) $objvar $objfield |]
509 AppE (ConE dt) defval | dt == 'Just ->
510 -- but has a default value
511 [| $(varNameE "fromObjWithDefault")
512 $objvar $objfield $(return defval) |]
513 ConE dt | dt == 'Nothing ->
514 [| $(varNameE "fromObj") $objvar $objfield |]
515 s -> fail $ "Invalid default value " ++ show s ++
516 ", expecting either 'Nothing' or a 'Just defval'"
517 return (fvar, BindS (VarP fvar) bexp)
519 loadConstructor :: String -> [OpParam] -> Q Exp
520 loadConstructor sname fields = do
521 let name = mkName sname
522 fbinds <- mapM loadField fields
523 let (fnames, fstmts) = unzip fbinds
524 let cval = foldl (\accu fn -> AppE accu (VarE fn)) (ConE name) fnames
525 fstmts' = fstmts ++ [NoBindS (AppE (VarE 'return) cval)]
528 genLoadOpCode :: [(String, [OpParam])] -> Q (Dec, Dec)
529 genLoadOpCode opdefs = do
530 let fname = mkName "loadOpCode"
533 opid = mkName "op_id"
534 st1 <- bindS (varP objname) [| liftM JSON.fromJSObject
535 (JSON.readJSON $(varE arg1)) |]
536 st2 <- bindS (varP opid) [| $(varNameE "fromObj")
537 $(varE objname) $(stringE "OP_ID") |]
538 -- the match results (per-constructor blocks)
539 mexps <- mapM (uncurry loadConstructor) opdefs
540 fails <- [| fail $ "Unknown opcode " ++ $(varE opid) |]
541 let mpats = map (\(me, c) ->
542 let mp = LitP . StringL . deCamelCase . fst $ c
543 in Match mp (NormalB me) []
545 defmatch = Match WildP (NormalB fails) []
546 cst = NoBindS $ CaseE (VarE opid) $ mpats++[defmatch]
547 body = DoE [st1, st2, cst]
548 sigt <- [t| JSON.JSValue -> JSON.Result $(conT (mkName "OpCode")) |]
549 return $ (SigD fname sigt, FunD fname [Clause [VarP arg1] (NormalB body) []])
551 -- | No default type.
553 noDefault = conE 'Nothing
555 -- * Template code for luxi
557 -- | Constructor-to-string for LuxiOp.
558 genStrOfOp :: Name -> String -> Q [Dec]
559 genStrOfOp = genConstrToStr id
561 -- | Constructor-to-string for MsgKeys.
562 genStrOfKey :: Name -> String -> Q [Dec]
563 genStrOfKey = genConstrToStr ensureLower
565 -- | LuxiOp parameter type.
566 type LuxiParam = (String, Q Type, Q Exp)
568 -- | Generates the LuxiOp data type.
570 -- This takes a Luxi operation definition and builds both the
571 -- datatype and the function trnasforming the arguments to JSON.
572 -- We can't use anything less generic, because the way different
573 -- operations are serialized differs on both parameter- and top-level.
575 -- There are three things to be defined for each parameter:
581 -- * operation; this is the operation performed on the parameter before
584 genLuxiOp :: String -> [(String, [LuxiParam])] -> Q [Dec]
585 genLuxiOp name cons = do
586 decl_d <- mapM (\(cname, fields) -> do
587 fields' <- mapM (\(_, qt, _) ->
588 qt >>= \t -> return (NotStrict, t))
590 return $ NormalC (mkName cname) fields')
592 let declD = DataD [] (mkName name) [] decl_d [''Show, ''Read]
593 (savesig, savefn) <- genSaveLuxiOp cons
594 return [declD, savesig, savefn]
596 -- | Generates the \"save\" expression for a single luxi parameter.
597 saveLuxiField :: Name -> LuxiParam -> Q Exp
598 saveLuxiField fvar (_, qt, fn) =
599 [| JSON.showJSON ( $(liftM2 appFn fn $ varE fvar) ) |]
601 -- | Generates the \"save\" clause for entire LuxiOp constructor.
602 saveLuxiConstructor :: (String, [LuxiParam]) -> Q Clause
603 saveLuxiConstructor (sname, fields) = do
604 let cname = mkName sname
605 fnames = map (\(nm, _, _) -> mkName nm) fields
606 pat = conP cname (map varP fnames)
607 flist = map (uncurry saveLuxiField) (zip fnames fields)
608 finval = if null flist
609 then [| JSON.showJSON () |]
610 else [| JSON.showJSON $(listE flist) |]
611 clause [pat] (normalB finval) []
613 -- | Generates the main save LuxiOp function.
614 genSaveLuxiOp :: [(String, [LuxiParam])]-> Q (Dec, Dec)
615 genSaveLuxiOp opdefs = do
616 sigt <- [t| $(conT (mkName "LuxiOp")) -> JSON.JSValue |]
617 let fname = mkName "opToArgs"
618 cclauses <- mapM saveLuxiConstructor opdefs
619 return $ (SigD fname sigt, FunD fname cclauses)
621 -- * "Objects" functionality
623 -- | Extract the field's declaration from a Field structure.
624 fieldTypeInfo :: String -> Field -> Q (Name, Strict, Type)
625 fieldTypeInfo field_pfx fd = do
626 t <- actualFieldType fd
627 let n = mkName . (field_pfx ++) . fieldRecordName $ fd
628 return (n, NotStrict, t)
630 -- | Build an object declaration.
631 buildObject :: String -> String -> [Field] -> Q [Dec]
632 buildObject sname field_pfx fields = do
633 let name = mkName sname
634 fields_d <- mapM (fieldTypeInfo field_pfx) fields
635 let decl_d = RecC name fields_d
636 let declD = DataD [] name [] [decl_d] [''Show, ''Read]
637 ser_decls <- buildObjectSerialisation sname fields
638 return $ declD:ser_decls
640 buildObjectSerialisation :: String -> [Field] -> Q [Dec]
641 buildObjectSerialisation sname fields = do
642 let name = mkName sname
643 savedecls <- genSaveObject saveObjectField sname fields
644 (loadsig, loadfn) <- genLoadObject loadObjectField sname fields
645 shjson <- objectShowJSON sname
646 rdjson <- objectReadJSON sname
647 let instdecl = InstanceD [] (AppT (ConT ''JSON.JSON) (ConT name))
649 return $ savedecls ++ [loadsig, loadfn, instdecl]
651 genSaveObject :: (Name -> Field -> Q Exp)
652 -> String -> [Field] -> Q [Dec]
653 genSaveObject save_fn sname fields = do
654 let name = mkName sname
655 let fnames = map (mkName . fieldVariable) fields
656 let pat = conP name (map varP fnames)
657 let tdname = mkName ("toDict" ++ sname)
658 tdsigt <- [t| $(conT name) -> [(String, JSON.JSValue)] |]
660 let felems = map (uncurry save_fn) (zip fnames fields)
662 -- and finally convert all this to a json object
663 tdlist = [| concat $flist |]
665 tclause <- clause [pat] (normalB tdlist) []
666 cclause <- [| $(varNameE "makeObj") . $(varE tdname) |]
667 let fname = mkName ("save" ++ sname)
668 sigt <- [t| $(conT name) -> JSON.JSValue |]
669 return [SigD tdname tdsigt, FunD tdname [tclause],
670 SigD fname sigt, ValD (VarP fname) (NormalB cclause) []]
672 saveObjectField :: Name -> Field -> Q Exp
673 saveObjectField fvar field
674 | isContainer = [| [( $nameE , $showJSONE . showContainer $ $fvarE)] |]
675 | fisOptional = [| case $(varE fvar) of
677 Just v -> [( $nameE, $showJSONE v)]
679 | otherwise = case fieldShow field of
680 Nothing -> [| [( $nameE, $showJSONE $fvarE)] |]
681 Just fn -> [| [( $nameE, $showJSONE . $fn $ $fvarE)] |]
682 where isContainer = fieldIsContainer field
683 fisOptional = fieldIsOptional field
684 nameE = stringE (fieldName field)
687 objectShowJSON :: String -> Q [Dec]
688 objectShowJSON name =
689 [d| showJSON = JSON.showJSON . $(varE . mkName $ "save" ++ name) |]
691 genLoadObject :: (Field -> Q (Name, Stmt))
692 -> String -> [Field] -> Q (Dec, Dec)
693 genLoadObject load_fn sname fields = do
694 let name = mkName sname
695 funname = mkName $ "load" ++ sname
698 opid = mkName "op_id"
699 st1 <- bindS (varP objname) [| liftM JSON.fromJSObject
700 (JSON.readJSON $(varE arg1)) |]
701 fbinds <- mapM load_fn fields
702 let (fnames, fstmts) = unzip fbinds
703 let cval = foldl (\accu fn -> AppE accu (VarE fn)) (ConE name) fnames
704 fstmts' = st1:fstmts ++ [NoBindS (AppE (VarE 'return) cval)]
705 sigt <- [t| JSON.JSValue -> JSON.Result $(conT name) |]
706 return $ (SigD funname sigt,
707 FunD funname [Clause [VarP arg1] (NormalB (DoE fstmts')) []])
709 loadObjectField :: Field -> Q (Name, Stmt)
710 loadObjectField field = do
711 let name = fieldVariable field
713 -- these are used in all patterns below
714 let objvar = varNameE "o"
715 objfield = stringE (fieldName field)
717 if fieldIsOptional field
718 then [| $(varNameE "maybeFromObj") $objvar $objfield |]
719 else case fieldDefault field of
721 [| $(varNameE "fromObjWithDefault") $objvar
723 Nothing -> [| $(varNameE "fromObj") $objvar $objfield |]
724 bexp <- loadFn field loadexp
726 return (fvar, BindS (VarP fvar) bexp)
728 objectReadJSON :: String -> Q Dec
729 objectReadJSON name = do
731 body <- [| case JSON.readJSON $(varE s) of
732 JSON.Ok s' -> $(varE .mkName $ "load" ++ name) s'
734 JSON.Error $ "Can't parse value for type " ++
735 $(stringE name) ++ ": " ++ e
737 return $ FunD (mkName "readJSON") [Clause [VarP s] (NormalB body) []]
739 -- * Inheritable parameter tables implementation
741 -- | Compute parameter type names.
742 paramTypeNames :: String -> (String, String)
743 paramTypeNames root = ("Filled" ++ root ++ "Params",
744 "Partial" ++ root ++ "Params")
746 -- | Compute information about the type of a parameter field.
747 paramFieldTypeInfo :: String -> Field -> Q (Name, Strict, Type)
748 paramFieldTypeInfo field_pfx fd = do
749 t <- actualFieldType fd
750 let n = mkName . (++ "P") . (field_pfx ++) .
752 return (n, NotStrict, AppT (ConT ''Maybe) t)
754 -- | Build a parameter declaration.
756 -- This function builds two different data structures: a /filled/ one,
757 -- in which all fields are required, and a /partial/ one, in which all
758 -- fields are optional. Due to the current record syntax issues, the
759 -- fields need to be named differrently for the two structures, so the
760 -- partial ones get a /P/ suffix.
761 buildParam :: String -> String -> [Field] -> Q [Dec]
762 buildParam sname field_pfx fields = do
763 let (sname_f, sname_p) = paramTypeNames sname
764 name_f = mkName sname_f
765 name_p = mkName sname_p
766 fields_f <- mapM (fieldTypeInfo field_pfx) fields
767 fields_p <- mapM (paramFieldTypeInfo field_pfx) fields
768 let decl_f = RecC name_f fields_f
769 decl_p = RecC name_p fields_p
770 let declF = DataD [] name_f [] [decl_f] [''Show, ''Read]
771 declP = DataD [] name_p [] [decl_p] [''Show, ''Read]
772 ser_decls_f <- buildObjectSerialisation sname_f fields
773 ser_decls_p <- buildPParamSerialisation sname_p fields
774 fill_decls <- fillParam sname field_pfx fields
775 return $ [declF, declP] ++ ser_decls_f ++ ser_decls_p ++ fill_decls
777 buildPParamSerialisation :: String -> [Field] -> Q [Dec]
778 buildPParamSerialisation sname fields = do
779 let name = mkName sname
780 savedecls <- genSaveObject savePParamField sname fields
781 (loadsig, loadfn) <- genLoadObject loadPParamField sname fields
782 shjson <- objectShowJSON sname
783 rdjson <- objectReadJSON sname
784 let instdecl = InstanceD [] (AppT (ConT ''JSON.JSON) (ConT name))
786 return $ savedecls ++ [loadsig, loadfn, instdecl]
788 savePParamField :: Name -> Field -> Q Exp
789 savePParamField fvar field = do
791 let actualVal = mkName "v"
792 normalexpr <- saveObjectField actualVal field
793 -- we have to construct the block here manually, because we can't
795 return $ CaseE (VarE fvar) [ Match (ConP 'Nothing [])
796 (NormalB (ConE '[])) []
797 , Match (ConP 'Just [VarP actualVal])
798 (NormalB normalexpr) []
800 loadPParamField :: Field -> Q (Name, Stmt)
801 loadPParamField field = do
803 let name = fieldName field
805 -- these are used in all patterns below
806 let objvar = varNameE "o"
807 objfield = stringE name
808 loadexp = [| $(varNameE "maybeFromObj") $objvar $objfield |]
809 bexp <- loadFn field loadexp
810 return (fvar, BindS (VarP fvar) bexp)
812 -- | Builds a simple declaration of type @n_x = fromMaybe f_x p_x@.
813 buildFromMaybe :: String -> Q Dec
814 buildFromMaybe fname =
815 valD (varP (mkName $ "n_" ++ fname))
816 (normalB [| $(varNameE "fromMaybe")
817 $(varNameE $ "f_" ++ fname)
818 $(varNameE $ "p_" ++ fname) |]) []
820 fillParam :: String -> String -> [Field] -> Q [Dec]
821 fillParam sname field_pfx fields = do
822 let fnames = map (\fd -> field_pfx ++ fieldRecordName fd) fields
823 (sname_f, sname_p) = paramTypeNames sname
826 name_f = mkName sname_f
827 name_p = mkName sname_p
828 fun_name = mkName $ "fill" ++ sname ++ "Params"
829 le_full = ValD (ConP name_f (map (VarP . mkName . ("f_" ++)) fnames))
830 (NormalB . VarE . mkName $ oname_f) []
831 le_part = ValD (ConP name_p (map (VarP . mkName . ("p_" ++)) fnames))
832 (NormalB . VarE . mkName $ oname_p) []
833 obj_new = foldl (\accu vname -> AppE accu (VarE vname)) (ConE name_f)
834 $ map (mkName . ("n_" ++)) fnames
835 le_new <- mapM buildFromMaybe fnames
836 funt <- [t| $(conT name_f) -> $(conT name_p) -> $(conT name_f) |]
837 let sig = SigD fun_name funt
838 fclause = Clause [VarP (mkName oname_f), VarP (mkName oname_p)]
839 (NormalB $ LetE (le_full:le_part:le_new) obj_new) []
840 fun = FunD fun_name [fclause]