1 {-# LANGUAGE TemplateHaskell #-}
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, 2012 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
56 import Control.Monad (liftM)
59 import Data.Maybe (fromMaybe)
60 import qualified Data.Set as Set
61 import Language.Haskell.TH
63 import qualified Text.JSON as JSON
67 -- | Serialised field data type.
68 data Field = Field { fieldName :: String
70 , fieldRead :: Maybe (Q Exp)
71 , fieldShow :: Maybe (Q Exp)
72 , fieldDefault :: Maybe (Q Exp)
73 , fieldConstr :: Maybe String
74 , fieldIsOptional :: Bool
77 -- | Generates a simple field.
78 simpleField :: String -> Q Type -> Field
79 simpleField fname ftype =
80 Field { fieldName = fname
84 , fieldDefault = Nothing
85 , fieldConstr = Nothing
86 , fieldIsOptional = False
89 -- | Sets the renamed constructor field.
90 renameField :: String -> Field -> Field
91 renameField constrName field = field { fieldConstr = Just constrName }
93 -- | Sets the default value on a field (makes it optional with a
95 defaultField :: Q Exp -> Field -> Field
96 defaultField defval field = field { fieldDefault = Just defval }
98 -- | Marks a field optional (turning its base type into a Maybe).
99 optionalField :: Field -> Field
100 optionalField field = field { fieldIsOptional = True }
102 -- | Sets custom functions on a field.
103 customField :: Name -- ^ The name of the read function
104 -> Name -- ^ The name of the show function
105 -> Field -- ^ The original field
106 -> Field -- ^ Updated field
107 customField readfn showfn field =
108 field { fieldRead = Just (varE readfn), fieldShow = Just (varE showfn) }
110 -- | Computes the record name for a given field, based on either the
111 -- string value in the JSON serialisation or the custom named if any
113 fieldRecordName :: Field -> String
114 fieldRecordName (Field { fieldName = name, fieldConstr = alias }) =
115 fromMaybe (camelCase name) alias
117 -- | Computes the preferred variable name to use for the value of this
118 -- field. If the field has a specific constructor name, then we use a
119 -- first-letter-lowercased version of that; otherwise, we simply use
120 -- the field name. See also 'fieldRecordName'.
121 fieldVariable :: Field -> String
123 case (fieldConstr f) of
124 Just name -> ensureLower name
125 _ -> map (\c -> if c == '-' then '_' else c) $ fieldName f
127 actualFieldType :: Field -> Q Type
128 actualFieldType f | fieldIsOptional f = [t| Maybe $t |]
130 where t = fieldType f
132 checkNonOptDef :: (Monad m) => Field -> m ()
133 checkNonOptDef (Field { fieldIsOptional = True, fieldName = name }) =
134 fail $ "Optional field " ++ name ++ " used in parameter declaration"
135 checkNonOptDef (Field { fieldDefault = (Just _), fieldName = name }) =
136 fail $ "Default field " ++ name ++ " used in parameter declaration"
137 checkNonOptDef _ = return ()
139 -- | Produces the expression that will de-serialise a given
140 -- field. Since some custom parsing functions might need to use the
141 -- entire object, we do take and pass the object to any custom read
143 loadFn :: Field -- ^ The field definition
144 -> Q Exp -- ^ The value of the field as existing in the JSON message
145 -> Q Exp -- ^ The entire object in JSON object format
146 -> Q Exp -- ^ Resulting expression
147 loadFn (Field { fieldRead = Just readfn }) expr o = [| $expr >>= $readfn $o |]
148 loadFn _ expr _ = expr
150 -- * Common field declarations
152 -- | Timestamp fields description.
153 timeStampFields :: [Field]
155 [ defaultField [| 0::Double |] $ simpleField "ctime" [t| Double |]
156 , defaultField [| 0::Double |] $ simpleField "mtime" [t| Double |]
159 -- | Serial number fields description.
160 serialFields :: [Field]
162 [ renameField "Serial" $ simpleField "serial_no" [t| Int |] ]
164 -- | UUID fields description.
165 uuidFields :: [Field]
166 uuidFields = [ simpleField "uuid" [t| String |] ]
168 -- | Tag field description.
169 tagsFields :: [Field]
170 tagsFields = [ defaultField [| Set.empty |] $
171 simpleField "tags" [t| Set.Set String |] ]
173 -- * Helper functions
175 -- | Ensure first letter is lowercase.
177 -- Used to convert type name to function prefix, e.g. in @data Aa ->
179 ensureLower :: String -> String
181 ensureLower (x:xs) = toLower x:xs
183 -- | Ensure first letter is uppercase.
185 -- Used to convert constructor name to component
186 ensureUpper :: String -> String
188 ensureUpper (x:xs) = toUpper x:xs
190 -- | Helper for quoted expressions.
191 varNameE :: String -> Q Exp
192 varNameE = varE . mkName
194 -- | showJSON as an expression, for reuse.
196 showJSONE = varNameE "showJSON"
198 -- | ToRaw function name.
199 toRawName :: String -> Name
200 toRawName = mkName . (++ "ToRaw") . ensureLower
202 -- | FromRaw function name.
203 fromRawName :: String -> Name
204 fromRawName = mkName . (++ "FromRaw") . ensureLower
206 -- | Converts a name to it's varE\/litE representations.
207 reprE :: Either String Name -> Q Exp
208 reprE = either stringE varE
210 -- | Smarter function application.
212 -- This does simply f x, except that if is 'id', it will skip it, in
213 -- order to generate more readable code when using -ddump-splices.
214 appFn :: Exp -> Exp -> Exp
215 appFn f x | f == VarE 'id = x
216 | otherwise = AppE f x
218 -- * Template code for simple raw type-equivalent ADTs
220 -- | Generates a data type declaration.
222 -- The type will have a fixed list of instances.
223 strADTDecl :: Name -> [String] -> Dec
224 strADTDecl name constructors =
226 (map (flip NormalC [] . mkName) constructors)
227 [''Show, ''Read, ''Eq, ''Enum, ''Bounded, ''Ord]
229 -- | Generates a toRaw function.
231 -- This generates a simple function of the form:
234 -- nameToRaw :: Name -> /traw/
235 -- nameToRaw Cons1 = var1
236 -- nameToRaw Cons2 = \"value2\"
238 genToRaw :: Name -> Name -> Name -> [(String, Either String Name)] -> Q [Dec]
239 genToRaw traw fname tname constructors = do
240 let sigt = AppT (AppT ArrowT (ConT tname)) (ConT traw)
241 -- the body clauses, matching on the constructor and returning the
243 clauses <- mapM (\(c, v) -> clause [recP (mkName c) []]
244 (normalB (reprE v)) []) constructors
245 return [SigD fname sigt, FunD fname clauses]
247 -- | Generates a fromRaw function.
249 -- The function generated is monadic and can fail parsing the
250 -- raw value. It is of the form:
253 -- nameFromRaw :: (Monad m) => /traw/ -> m Name
254 -- nameFromRaw s | s == var1 = Cons1
255 -- | s == \"value2\" = Cons2
256 -- | otherwise = fail /.../
258 genFromRaw :: Name -> Name -> Name -> [(String, Name)] -> Q [Dec]
259 genFromRaw traw fname tname constructors = do
260 -- signature of form (Monad m) => String -> m $name
261 sigt <- [t| (Monad m) => $(conT traw) -> m $(conT tname) |]
262 -- clauses for a guarded pattern
263 let varp = mkName "s"
265 clauses <- mapM (\(c, v) -> do
266 -- the clause match condition
267 g <- normalG [| $varpe == $(varE v) |]
269 r <- [| return $(conE (mkName c)) |]
270 return (g, r)) constructors
271 -- the otherwise clause (fallback)
273 g <- normalG [| otherwise |]
274 r <- [|fail ("Invalid string value for type " ++
275 $(litE (stringL (nameBase tname))) ++ ": " ++ show $varpe) |]
277 let fun = FunD fname [Clause [VarP varp]
278 (GuardedB (clauses++[oth_clause])) []]
279 return [SigD fname sigt, fun]
281 -- | Generates a data type from a given raw format.
283 -- The format is expected to multiline. The first line contains the
284 -- type name, and the rest of the lines must contain two words: the
285 -- constructor name and then the string representation of the
286 -- respective constructor.
288 -- The function will generate the data type declaration, and then two
291 -- * /name/ToRaw, which converts the type to a raw type
293 -- * /name/FromRaw, which (monadically) converts from a raw type to the type
295 -- Note that this is basically just a custom show\/read instance,
297 declareADT :: Name -> String -> [(String, Name)] -> Q [Dec]
298 declareADT traw sname cons = do
299 let name = mkName sname
300 ddecl = strADTDecl name (map fst cons)
301 -- process cons in the format expected by genToRaw
302 cons' = map (\(a, b) -> (a, Right b)) cons
303 toraw <- genToRaw traw (toRawName sname) name cons'
304 fromraw <- genFromRaw traw (fromRawName sname) name cons
305 return $ ddecl:toraw ++ fromraw
307 declareIADT :: String -> [(String, Name)] -> Q [Dec]
308 declareIADT = declareADT ''Int
310 declareSADT :: String -> [(String, Name)] -> Q [Dec]
311 declareSADT = declareADT ''String
313 -- | Creates the showJSON member of a JSON instance declaration.
315 -- This will create what is the equivalent of:
318 -- showJSON = showJSON . /name/ToRaw
321 -- in an instance JSON /name/ declaration
322 genShowJSON :: String -> Q Dec
323 genShowJSON name = do
324 body <- [| JSON.showJSON . $(varE (toRawName name)) |]
325 return $ FunD (mkName "showJSON") [Clause [] (NormalB body) []]
327 -- | Creates the readJSON member of a JSON instance declaration.
329 -- This will create what is the equivalent of:
332 -- readJSON s = case readJSON s of
333 -- Ok s' -> /name/FromRaw s'
334 -- Error e -> Error /description/
337 -- in an instance JSON /name/ declaration
338 genReadJSON :: String -> Q Dec
339 genReadJSON name = do
341 body <- [| case JSON.readJSON $(varE s) of
342 JSON.Ok s' -> $(varE (fromRawName name)) s'
344 JSON.Error $ "Can't parse raw value for type " ++
345 $(stringE name) ++ ": " ++ e ++ " from " ++
348 return $ FunD (mkName "readJSON") [Clause [VarP s] (NormalB body) []]
350 -- | Generates a JSON instance for a given type.
352 -- This assumes that the /name/ToRaw and /name/FromRaw functions
353 -- have been defined as by the 'declareSADT' function.
354 makeJSONInstance :: Name -> Q [Dec]
355 makeJSONInstance name = do
356 let base = nameBase name
357 showJ <- genShowJSON base
358 readJ <- genReadJSON base
359 return [InstanceD [] (AppT (ConT ''JSON.JSON) (ConT name)) [readJ,showJ]]
361 -- * Template code for opcodes
363 -- | Transforms a CamelCase string into an_underscore_based_one.
364 deCamelCase :: String -> String
366 intercalate "_" . map (map toUpper) . groupBy (\_ b -> not $ isUpper b)
368 -- | Transform an underscore_name into a CamelCase one.
369 camelCase :: String -> String
370 camelCase = concatMap (ensureUpper . drop 1) .
371 groupBy (\_ b -> b /= '_' && b /= '-') . ('_':)
373 -- | Computes the name of a given constructor.
374 constructorName :: Con -> Q Name
375 constructorName (NormalC name _) = return name
376 constructorName (RecC name _) = return name
377 constructorName x = fail $ "Unhandled constructor " ++ show x
379 -- | Extract all constructor names from a given type.
380 reifyConsNames :: Name -> Q [String]
381 reifyConsNames name = do
382 reify_result <- reify name
384 TyConI (DataD _ _ _ cons _) -> mapM (liftM nameBase . constructorName) cons
385 o -> fail $ "Unhandled name passed to reifyConsNames, expected\
386 \ type constructor but got '" ++ show o ++ "'"
388 -- | Builds the generic constructor-to-string function.
390 -- This generates a simple function of the following form:
393 -- fname (ConStructorOne {}) = trans_fun("ConStructorOne")
394 -- fname (ConStructorTwo {}) = trans_fun("ConStructorTwo")
397 -- This builds a custom list of name\/string pairs and then uses
398 -- 'genToRaw' to actually generate the function.
399 genConstrToStr :: (String -> String) -> Name -> String -> Q [Dec]
400 genConstrToStr trans_fun name fname = do
401 cnames <- reifyConsNames name
402 let svalues = map (Left . trans_fun) cnames
403 genToRaw ''String (mkName fname) name $ zip cnames svalues
405 -- | Constructor-to-string for OpCode.
406 genOpID :: Name -> String -> Q [Dec]
407 genOpID = genConstrToStr deCamelCase
409 -- | Builds a list with all defined constructor names for a type.
416 -- Where the actual values of the string are the constructor names
417 -- mapped via @trans_fun@.
418 genAllConstr :: (String -> String) -> Name -> String -> Q [Dec]
419 genAllConstr trans_fun name vstr = do
420 cnames <- reifyConsNames name
421 let svalues = sort $ map trans_fun cnames
423 sig = SigD vname (AppT ListT (ConT ''String))
424 body = NormalB (ListE (map (LitE . StringL) svalues))
425 return $ [sig, ValD (VarP vname) body []]
427 -- | Generates a list of all defined opcode IDs.
428 genAllOpIDs :: Name -> String -> Q [Dec]
429 genAllOpIDs = genAllConstr deCamelCase
431 -- | OpCode parameter (field) type.
432 type OpParam = (String, Q Type, Q Exp)
434 -- | Generates the OpCode data type.
436 -- This takes an opcode logical definition, and builds both the
437 -- datatype and the JSON serialisation out of it. We can't use a
438 -- generic serialisation since we need to be compatible with Ganeti's
439 -- own, so we have a few quirks to work around.
440 genOpCode :: String -- ^ Type name to use
441 -> [(String, [Field])] -- ^ Constructor name and parameters
443 genOpCode name cons = do
444 decl_d <- mapM (\(cname, fields) -> do
445 -- we only need the type of the field, without Q
446 fields' <- mapM actualFieldType fields
447 let fields'' = zip (repeat NotStrict) fields'
448 return $ NormalC (mkName cname) fields'')
450 let declD = DataD [] (mkName name) [] decl_d [''Show, ''Read, ''Eq]
452 (savesig, savefn) <- genSaveOpCode cons
453 (loadsig, loadfn) <- genLoadOpCode cons
454 return [declD, loadsig, loadfn, savesig, savefn]
456 -- | Checks whether a given parameter is options.
458 -- This requires that it's a 'Maybe'.
459 isOptional :: Type -> Bool
460 isOptional (AppT (ConT dt) _) | dt == ''Maybe = True
463 -- | Generates the \"save\" clause for an entire opcode constructor.
465 -- This matches the opcode with variables named the same as the
466 -- constructor fields (just so that the spliced in code looks nicer),
467 -- and passes those name plus the parameter definition to 'saveObjectField'.
468 saveConstructor :: String -- ^ The constructor name
469 -> [Field] -- ^ The parameter definitions for this
471 -> Q Clause -- ^ Resulting clause
472 saveConstructor sname fields = do
473 let cname = mkName sname
474 fnames <- mapM (newName . fieldVariable) fields
475 let pat = conP cname (map varP fnames)
476 let felems = map (uncurry saveObjectField) (zip fnames fields)
477 -- now build the OP_ID serialisation
478 opid = [| [( $(stringE "OP_ID"),
479 JSON.showJSON $(stringE . deCamelCase $ sname) )] |]
480 flist = listE (opid:felems)
481 -- and finally convert all this to a json object
482 flist' = [| $(varNameE "makeObj") (concat $flist) |]
483 clause [pat] (normalB flist') []
485 -- | Generates the main save opcode function.
487 -- This builds a per-constructor match clause that contains the
488 -- respective constructor-serialisation code.
489 genSaveOpCode :: [(String, [Field])] -> Q (Dec, Dec)
490 genSaveOpCode opdefs = do
491 cclauses <- mapM (uncurry saveConstructor) opdefs
492 let fname = mkName "saveOpCode"
493 sigt <- [t| $(conT (mkName "OpCode")) -> JSON.JSValue |]
494 return $ (SigD fname sigt, FunD fname cclauses)
496 -- | Generates load code for a single constructor of the opcode data type.
497 loadConstructor :: String -> [Field] -> Q Exp
498 loadConstructor sname fields = do
499 let name = mkName sname
500 fbinds <- mapM loadObjectField fields
501 let (fnames, fstmts) = unzip fbinds
502 let cval = foldl (\accu fn -> AppE accu (VarE fn)) (ConE name) fnames
503 fstmts' = fstmts ++ [NoBindS (AppE (VarE 'return) cval)]
506 -- | Generates the loadOpCode function.
507 genLoadOpCode :: [(String, [Field])] -> Q (Dec, Dec)
508 genLoadOpCode opdefs = do
509 let fname = mkName "loadOpCode"
512 opid = mkName "op_id"
513 st1 <- bindS (varP objname) [| liftM JSON.fromJSObject
514 (JSON.readJSON $(varE arg1)) |]
515 st2 <- bindS (varP opid) [| $(varNameE "fromObj")
516 $(varE objname) $(stringE "OP_ID") |]
517 -- the match results (per-constructor blocks)
518 mexps <- mapM (uncurry loadConstructor) opdefs
519 fails <- [| fail $ "Unknown opcode " ++ $(varE opid) |]
520 let mpats = map (\(me, c) ->
521 let mp = LitP . StringL . deCamelCase . fst $ c
522 in Match mp (NormalB me) []
524 defmatch = Match WildP (NormalB fails) []
525 cst = NoBindS $ CaseE (VarE opid) $ mpats++[defmatch]
526 body = DoE [st1, st2, cst]
527 sigt <- [t| JSON.JSValue -> JSON.Result $(conT (mkName "OpCode")) |]
528 return $ (SigD fname sigt, FunD fname [Clause [VarP arg1] (NormalB body) []])
530 -- * Template code for luxi
532 -- | Constructor-to-string for LuxiOp.
533 genStrOfOp :: Name -> String -> Q [Dec]
534 genStrOfOp = genConstrToStr id
536 -- | Constructor-to-string for MsgKeys.
537 genStrOfKey :: Name -> String -> Q [Dec]
538 genStrOfKey = genConstrToStr ensureLower
540 -- | LuxiOp parameter type.
541 type LuxiParam = (String, Q Type)
543 -- | Generates the LuxiOp data type.
545 -- This takes a Luxi operation definition and builds both the
546 -- datatype and the function trnasforming the arguments to JSON.
547 -- We can't use anything less generic, because the way different
548 -- operations are serialized differs on both parameter- and top-level.
550 -- There are two things to be defined for each parameter:
556 genLuxiOp :: String -> [(String, [LuxiParam])] -> Q [Dec]
557 genLuxiOp name cons = do
558 decl_d <- mapM (\(cname, fields) -> do
559 fields' <- mapM (\(_, qt) ->
560 qt >>= \t -> return (NotStrict, t))
562 return $ NormalC (mkName cname) fields')
564 let declD = DataD [] (mkName name) [] decl_d [''Show, ''Read, ''Eq]
565 (savesig, savefn) <- genSaveLuxiOp cons
566 req_defs <- declareSADT "LuxiReq" .
567 map (\(str, _) -> ("Req" ++ str, mkName ("luxiReq" ++ str))) $
569 return $ [declD, savesig, savefn] ++ req_defs
571 -- | Generates the \"save\" expression for a single luxi parameter.
572 saveLuxiField :: Name -> LuxiParam -> Q Exp
573 saveLuxiField fvar (_, qt) =
574 [| JSON.showJSON $(varE fvar) |]
576 -- | Generates the \"save\" clause for entire LuxiOp constructor.
577 saveLuxiConstructor :: (String, [LuxiParam]) -> Q Clause
578 saveLuxiConstructor (sname, fields) = do
579 let cname = mkName sname
580 fnames = map (mkName . fst) fields
581 pat = conP cname (map varP fnames)
582 flist = map (uncurry saveLuxiField) (zip fnames fields)
583 finval = if null flist
584 then [| JSON.showJSON () |]
585 else [| JSON.showJSON $(listE flist) |]
586 clause [pat] (normalB finval) []
588 -- | Generates the main save LuxiOp function.
589 genSaveLuxiOp :: [(String, [LuxiParam])]-> Q (Dec, Dec)
590 genSaveLuxiOp opdefs = do
591 sigt <- [t| $(conT (mkName "LuxiOp")) -> JSON.JSValue |]
592 let fname = mkName "opToArgs"
593 cclauses <- mapM saveLuxiConstructor opdefs
594 return $ (SigD fname sigt, FunD fname cclauses)
596 -- * "Objects" functionality
598 -- | Extract the field's declaration from a Field structure.
599 fieldTypeInfo :: String -> Field -> Q (Name, Strict, Type)
600 fieldTypeInfo field_pfx fd = do
601 t <- actualFieldType fd
602 let n = mkName . (field_pfx ++) . fieldRecordName $ fd
603 return (n, NotStrict, t)
605 -- | Build an object declaration.
606 buildObject :: String -> String -> [Field] -> Q [Dec]
607 buildObject sname field_pfx fields = do
608 let name = mkName sname
609 fields_d <- mapM (fieldTypeInfo field_pfx) fields
610 let decl_d = RecC name fields_d
611 let declD = DataD [] name [] [decl_d] [''Show, ''Read, ''Eq]
612 ser_decls <- buildObjectSerialisation sname fields
613 return $ declD:ser_decls
615 -- | Generates an object definition: data type and its JSON instance.
616 buildObjectSerialisation :: String -> [Field] -> Q [Dec]
617 buildObjectSerialisation sname fields = do
618 let name = mkName sname
619 savedecls <- genSaveObject saveObjectField sname fields
620 (loadsig, loadfn) <- genLoadObject loadObjectField sname fields
621 shjson <- objectShowJSON sname
622 rdjson <- objectReadJSON sname
623 let instdecl = InstanceD [] (AppT (ConT ''JSON.JSON) (ConT name))
625 return $ savedecls ++ [loadsig, loadfn, instdecl]
627 -- | Generates the save object functionality.
628 genSaveObject :: (Name -> Field -> Q Exp)
629 -> String -> [Field] -> Q [Dec]
630 genSaveObject save_fn sname fields = do
631 let name = mkName sname
632 fnames <- mapM (newName . fieldVariable) fields
633 let pat = conP name (map varP fnames)
634 let tdname = mkName ("toDict" ++ sname)
635 tdsigt <- [t| $(conT name) -> [(String, JSON.JSValue)] |]
637 let felems = map (uncurry save_fn) (zip fnames fields)
639 -- and finally convert all this to a json object
640 tdlist = [| concat $flist |]
642 tclause <- clause [pat] (normalB tdlist) []
643 cclause <- [| $(varNameE "makeObj") . $(varE tdname) |]
644 let fname = mkName ("save" ++ sname)
645 sigt <- [t| $(conT name) -> JSON.JSValue |]
646 return [SigD tdname tdsigt, FunD tdname [tclause],
647 SigD fname sigt, ValD (VarP fname) (NormalB cclause) []]
649 -- | Generates the code for saving an object's field, handling the
650 -- various types of fields that we have.
651 saveObjectField :: Name -> Field -> Q Exp
652 saveObjectField fvar field
653 | fisOptional = [| case $(varE fvar) of
655 Just v -> [( $nameE, JSON.showJSON v)]
657 | otherwise = case fieldShow field of
658 Nothing -> [| [( $nameE, JSON.showJSON $fvarE)] |]
659 Just fn -> [| let (actual, extra) = $fn $fvarE
660 in extra ++ [( $nameE, JSON.showJSON actual)]
662 where fisOptional = fieldIsOptional field
663 nameE = stringE (fieldName field)
666 -- | Generates the showJSON clause for a given object name.
667 objectShowJSON :: String -> Q Dec
668 objectShowJSON name = do
669 body <- [| JSON.showJSON . $(varE . mkName $ "save" ++ name) |]
670 return $ FunD (mkName "showJSON") [Clause [] (NormalB body) []]
672 -- | Generates the load object functionality.
673 genLoadObject :: (Field -> Q (Name, Stmt))
674 -> String -> [Field] -> Q (Dec, Dec)
675 genLoadObject load_fn sname fields = do
676 let name = mkName sname
677 funname = mkName $ "load" ++ sname
680 opid = mkName "op_id"
681 st1 <- bindS (varP objname) [| liftM JSON.fromJSObject
682 (JSON.readJSON $(varE arg1)) |]
683 fbinds <- mapM load_fn fields
684 let (fnames, fstmts) = unzip fbinds
685 let cval = foldl (\accu fn -> AppE accu (VarE fn)) (ConE name) fnames
686 fstmts' = st1:fstmts ++ [NoBindS (AppE (VarE 'return) cval)]
687 sigt <- [t| JSON.JSValue -> JSON.Result $(conT name) |]
688 return $ (SigD funname sigt,
689 FunD funname [Clause [VarP arg1] (NormalB (DoE fstmts')) []])
691 -- | Generates code for loading an object's field.
692 loadObjectField :: Field -> Q (Name, Stmt)
693 loadObjectField field = do
694 let name = fieldVariable field
696 -- these are used in all patterns below
697 let objvar = varNameE "o"
698 objfield = stringE (fieldName field)
700 if fieldIsOptional field
701 then [| $(varNameE "maybeFromObj") $objvar $objfield |]
702 else case fieldDefault field of
704 [| $(varNameE "fromObjWithDefault") $objvar
706 Nothing -> [| $(varNameE "fromObj") $objvar $objfield |]
707 bexp <- loadFn field loadexp objvar
709 return (fvar, BindS (VarP fvar) bexp)
711 -- | Builds the readJSON instance for a given object name.
712 objectReadJSON :: String -> Q Dec
713 objectReadJSON name = do
715 body <- [| case JSON.readJSON $(varE s) of
716 JSON.Ok s' -> $(varE .mkName $ "load" ++ name) s'
718 JSON.Error $ "Can't parse value for type " ++
719 $(stringE name) ++ ": " ++ e
721 return $ FunD (mkName "readJSON") [Clause [VarP s] (NormalB body) []]
723 -- * Inheritable parameter tables implementation
725 -- | Compute parameter type names.
726 paramTypeNames :: String -> (String, String)
727 paramTypeNames root = ("Filled" ++ root ++ "Params",
728 "Partial" ++ root ++ "Params")
730 -- | Compute information about the type of a parameter field.
731 paramFieldTypeInfo :: String -> Field -> Q (Name, Strict, Type)
732 paramFieldTypeInfo field_pfx fd = do
733 t <- actualFieldType fd
734 let n = mkName . (++ "P") . (field_pfx ++) .
736 return (n, NotStrict, AppT (ConT ''Maybe) t)
738 -- | Build a parameter declaration.
740 -- This function builds two different data structures: a /filled/ one,
741 -- in which all fields are required, and a /partial/ one, in which all
742 -- fields are optional. Due to the current record syntax issues, the
743 -- fields need to be named differrently for the two structures, so the
744 -- partial ones get a /P/ suffix.
745 buildParam :: String -> String -> [Field] -> Q [Dec]
746 buildParam sname field_pfx fields = do
747 let (sname_f, sname_p) = paramTypeNames sname
748 name_f = mkName sname_f
749 name_p = mkName sname_p
750 fields_f <- mapM (fieldTypeInfo field_pfx) fields
751 fields_p <- mapM (paramFieldTypeInfo field_pfx) fields
752 let decl_f = RecC name_f fields_f
753 decl_p = RecC name_p fields_p
754 let declF = DataD [] name_f [] [decl_f] [''Show, ''Read, ''Eq]
755 declP = DataD [] name_p [] [decl_p] [''Show, ''Read, ''Eq]
756 ser_decls_f <- buildObjectSerialisation sname_f fields
757 ser_decls_p <- buildPParamSerialisation sname_p fields
758 fill_decls <- fillParam sname field_pfx fields
759 return $ [declF, declP] ++ ser_decls_f ++ ser_decls_p ++ fill_decls
761 -- | Generates the serialisation for a partial parameter.
762 buildPParamSerialisation :: String -> [Field] -> Q [Dec]
763 buildPParamSerialisation sname fields = do
764 let name = mkName sname
765 savedecls <- genSaveObject savePParamField sname fields
766 (loadsig, loadfn) <- genLoadObject loadPParamField sname fields
767 shjson <- objectShowJSON sname
768 rdjson <- objectReadJSON sname
769 let instdecl = InstanceD [] (AppT (ConT ''JSON.JSON) (ConT name))
771 return $ savedecls ++ [loadsig, loadfn, instdecl]
773 -- | Generates code to save an optional parameter field.
774 savePParamField :: Name -> Field -> Q Exp
775 savePParamField fvar field = do
777 let actualVal = mkName "v"
778 normalexpr <- saveObjectField actualVal field
779 -- we have to construct the block here manually, because we can't
781 return $ CaseE (VarE fvar) [ Match (ConP 'Nothing [])
782 (NormalB (ConE '[])) []
783 , Match (ConP 'Just [VarP actualVal])
784 (NormalB normalexpr) []
787 -- | Generates code to load an optional parameter field.
788 loadPParamField :: Field -> Q (Name, Stmt)
789 loadPParamField field = do
791 let name = fieldName field
793 -- these are used in all patterns below
794 let objvar = varNameE "o"
795 objfield = stringE name
796 loadexp = [| $(varNameE "maybeFromObj") $objvar $objfield |]
797 bexp <- loadFn field loadexp objvar
798 return (fvar, BindS (VarP fvar) bexp)
800 -- | Builds a simple declaration of type @n_x = fromMaybe f_x p_x@.
801 buildFromMaybe :: String -> Q Dec
802 buildFromMaybe fname =
803 valD (varP (mkName $ "n_" ++ fname))
804 (normalB [| $(varNameE "fromMaybe")
805 $(varNameE $ "f_" ++ fname)
806 $(varNameE $ "p_" ++ fname) |]) []
808 -- | Builds a function that executes the filling of partial parameter
809 -- from a full copy (similar to Python's fillDict).
810 fillParam :: String -> String -> [Field] -> Q [Dec]
811 fillParam sname field_pfx fields = do
812 let fnames = map (\fd -> field_pfx ++ fieldRecordName fd) fields
813 (sname_f, sname_p) = paramTypeNames sname
816 name_f = mkName sname_f
817 name_p = mkName sname_p
818 fun_name = mkName $ "fill" ++ sname ++ "Params"
819 le_full = ValD (ConP name_f (map (VarP . mkName . ("f_" ++)) fnames))
820 (NormalB . VarE . mkName $ oname_f) []
821 le_part = ValD (ConP name_p (map (VarP . mkName . ("p_" ++)) fnames))
822 (NormalB . VarE . mkName $ oname_p) []
823 obj_new = foldl (\accu vname -> AppE accu (VarE vname)) (ConE name_f)
824 $ map (mkName . ("n_" ++)) fnames
825 le_new <- mapM buildFromMaybe fnames
826 funt <- [t| $(conT name_f) -> $(conT name_p) -> $(conT name_f) |]
827 let sig = SigD fun_name funt
828 fclause = Clause [VarP (mkName oname_f), VarP (mkName oname_p)]
829 (NormalB $ LetE (le_full:le_part:le_new) obj_new) []
830 fun = FunD fun_name [fclause]