+-- * "Objects" functionality
+
+-- | Extract the field's declaration from a Field structure.
+fieldTypeInfo :: String -> Field -> Q (Name, Strict, Type)
+fieldTypeInfo field_pfx fd = do
+ t <- actualFieldType fd
+ let n = mkName . (field_pfx ++) . fieldRecordName $ fd
+ return (n, NotStrict, t)
+
+-- | Build an object declaration.
+buildObject :: String -> String -> [Field] -> Q [Dec]
+buildObject sname field_pfx fields = do
+ let name = mkName sname
+ fields_d <- mapM (fieldTypeInfo field_pfx) fields
+ let decl_d = RecC name fields_d
+ let declD = DataD [] name [] [decl_d] [''Show, ''Read, ''Eq]
+ ser_decls <- buildObjectSerialisation sname fields
+ return $ declD:ser_decls
+
+-- | Generates an object definition: data type and its JSON instance.
+buildObjectSerialisation :: String -> [Field] -> Q [Dec]
+buildObjectSerialisation sname fields = do
+ let name = mkName sname
+ savedecls <- genSaveObject saveObjectField sname fields
+ (loadsig, loadfn) <- genLoadObject loadObjectField sname fields
+ shjson <- objectShowJSON sname
+ rdjson <- objectReadJSON sname
+ let instdecl = InstanceD [] (AppT (ConT ''JSON.JSON) (ConT name))
+ [rdjson, shjson]
+ return $ savedecls ++ [loadsig, loadfn, instdecl]
+
+-- | The toDict function name for a given type.
+toDictName :: String -> Name
+toDictName sname = mkName ("toDict" ++ sname)
+
+-- | Generates the save object functionality.
+genSaveObject :: (Name -> Field -> Q Exp)
+ -> String -> [Field] -> Q [Dec]
+genSaveObject save_fn sname fields = do
+ let name = mkName sname
+ fnames <- mapM (newName . fieldVariable) fields
+ let pat = conP name (map varP fnames)
+ let tdname = toDictName sname
+ tdsigt <- [t| $(conT name) -> [(String, JSON.JSValue)] |]
+
+ let felems = map (uncurry save_fn) (zip fnames fields)
+ flist = listE felems
+ -- and finally convert all this to a json object
+ tdlist = [| concat $flist |]
+ iname = mkName "i"
+ tclause <- clause [pat] (normalB tdlist) []
+ cclause <- [| $(varNameE "makeObj") . $(varE tdname) |]
+ let fname = mkName ("save" ++ sname)
+ sigt <- [t| $(conT name) -> JSON.JSValue |]
+ return [SigD tdname tdsigt, FunD tdname [tclause],
+ SigD fname sigt, ValD (VarP fname) (NormalB cclause) []]
+
+-- | Generates the code for saving an object's field, handling the
+-- various types of fields that we have.
+saveObjectField :: Name -> Field -> Q Exp
+saveObjectField fvar field =
+ case fieldIsOptional field of
+ OptionalOmitNull -> [| case $(varE fvar) of
+ Nothing -> []
+ Just v -> [( $nameE, JSON.showJSON v )]
+ |]
+ OptionalSerializeNull -> [| case $(varE fvar) of
+ Nothing -> [( $nameE, JSON.JSNull )]
+ Just v -> [( $nameE, JSON.showJSON v )]
+ |]
+ NotOptional ->
+ case fieldShow field of
+ Nothing -> [| [( $nameE, JSON.showJSON $fvarE)] |]
+ Just fn -> [| let (actual, extra) = $fn $fvarE
+ in extra ++ [( $nameE, JSON.showJSON actual)]
+ |]
+ where nameE = stringE (fieldName field)
+ fvarE = varE fvar
+
+-- | Generates the showJSON clause for a given object name.
+objectShowJSON :: String -> Q Dec
+objectShowJSON name = do
+ body <- [| JSON.showJSON . $(varE . mkName $ "save" ++ name) |]
+ return $ FunD (mkName "showJSON") [Clause [] (NormalB body) []]
+
+-- | Generates the load object functionality.
+genLoadObject :: (Field -> Q (Name, Stmt))
+ -> String -> [Field] -> Q (Dec, Dec)
+genLoadObject load_fn sname fields = do
+ let name = mkName sname
+ funname = mkName $ "load" ++ sname
+ arg1 = mkName "v"
+ objname = mkName "o"
+ opid = mkName "op_id"
+ st1 <- bindS (varP objname) [| liftM JSON.fromJSObject
+ (JSON.readJSON $(varE arg1)) |]
+ fbinds <- mapM load_fn fields
+ let (fnames, fstmts) = unzip fbinds
+ let cval = foldl (\accu fn -> AppE accu (VarE fn)) (ConE name) fnames
+ fstmts' = st1:fstmts ++ [NoBindS (AppE (VarE 'return) cval)]
+ sigt <- [t| JSON.JSValue -> JSON.Result $(conT name) |]
+ return $ (SigD funname sigt,
+ FunD funname [Clause [VarP arg1] (NormalB (DoE fstmts')) []])
+
+-- | Generates code for loading an object's field.
+loadObjectField :: Field -> Q (Name, Stmt)
+loadObjectField field = do
+ let name = fieldVariable field
+ fvar <- newName name
+ -- these are used in all patterns below
+ let objvar = varNameE "o"
+ objfield = stringE (fieldName field)
+ loadexp =
+ if fieldIsOptional field /= NotOptional
+ -- we treat both optional types the same, since
+ -- 'maybeFromObj' can deal with both missing and null values
+ -- appropriately (the same)
+ then [| $(varNameE "maybeFromObj") $objvar $objfield |]
+ else case fieldDefault field of
+ Just defv ->
+ [| $(varNameE "fromObjWithDefault") $objvar
+ $objfield $defv |]
+ Nothing -> [| $(varNameE "fromObj") $objvar $objfield |]
+ bexp <- loadFn field loadexp objvar
+
+ return (fvar, BindS (VarP fvar) bexp)
+
+-- | Builds the readJSON instance for a given object name.
+objectReadJSON :: String -> Q Dec
+objectReadJSON name = do
+ let s = mkName "s"
+ body <- [| case JSON.readJSON $(varE s) of
+ JSON.Ok s' -> $(varE .mkName $ "load" ++ name) s'
+ JSON.Error e ->
+ JSON.Error $ "Can't parse value for type " ++
+ $(stringE name) ++ ": " ++ e
+ |]
+ return $ FunD (mkName "readJSON") [Clause [VarP s] (NormalB body) []]
+
+-- * Inheritable parameter tables implementation
+
+-- | Compute parameter type names.
+paramTypeNames :: String -> (String, String)
+paramTypeNames root = ("Filled" ++ root ++ "Params",
+ "Partial" ++ root ++ "Params")
+
+-- | Compute information about the type of a parameter field.
+paramFieldTypeInfo :: String -> Field -> Q (Name, Strict, Type)
+paramFieldTypeInfo field_pfx fd = do
+ t <- actualFieldType fd
+ let n = mkName . (++ "P") . (field_pfx ++) .
+ fieldRecordName $ fd
+ return (n, NotStrict, AppT (ConT ''Maybe) t)
+
+-- | Build a parameter declaration.
+--
+-- This function builds two different data structures: a /filled/ one,
+-- in which all fields are required, and a /partial/ one, in which all
+-- fields are optional. Due to the current record syntax issues, the
+-- fields need to be named differrently for the two structures, so the
+-- partial ones get a /P/ suffix.
+buildParam :: String -> String -> [Field] -> Q [Dec]
+buildParam sname field_pfx fields = do
+ let (sname_f, sname_p) = paramTypeNames sname
+ name_f = mkName sname_f
+ name_p = mkName sname_p
+ fields_f <- mapM (fieldTypeInfo field_pfx) fields
+ fields_p <- mapM (paramFieldTypeInfo field_pfx) fields
+ let decl_f = RecC name_f fields_f
+ decl_p = RecC name_p fields_p
+ let declF = DataD [] name_f [] [decl_f] [''Show, ''Read, ''Eq]
+ declP = DataD [] name_p [] [decl_p] [''Show, ''Read, ''Eq]
+ ser_decls_f <- buildObjectSerialisation sname_f fields
+ ser_decls_p <- buildPParamSerialisation sname_p fields
+ fill_decls <- fillParam sname field_pfx fields
+ return $ [declF, declP] ++ ser_decls_f ++ ser_decls_p ++ fill_decls ++
+ buildParamAllFields sname fields ++
+ buildDictObjectInst name_f sname_f
+
+-- | Builds a list of all fields of a parameter.
+buildParamAllFields :: String -> [Field] -> [Dec]
+buildParamAllFields sname fields =
+ let vname = mkName ("all" ++ sname ++ "ParamFields")
+ sig = SigD vname (AppT ListT (ConT ''String))
+ val = ListE $ map (LitE . StringL . fieldName) fields
+ in [sig, ValD (VarP vname) (NormalB val) []]
+
+-- | Builds the 'DictObject' instance for a filled parameter.
+buildDictObjectInst :: Name -> String -> [Dec]
+buildDictObjectInst name sname =
+ [InstanceD [] (AppT (ConT ''DictObject) (ConT name))
+ [ValD (VarP 'toDict) (NormalB (VarE (toDictName sname))) []]]
+
+-- | Generates the serialisation for a partial parameter.
+buildPParamSerialisation :: String -> [Field] -> Q [Dec]
+buildPParamSerialisation sname fields = do
+ let name = mkName sname
+ savedecls <- genSaveObject savePParamField sname fields
+ (loadsig, loadfn) <- genLoadObject loadPParamField sname fields
+ shjson <- objectShowJSON sname
+ rdjson <- objectReadJSON sname
+ let instdecl = InstanceD [] (AppT (ConT ''JSON.JSON) (ConT name))
+ [rdjson, shjson]
+ return $ savedecls ++ [loadsig, loadfn, instdecl]
+
+-- | Generates code to save an optional parameter field.
+savePParamField :: Name -> Field -> Q Exp
+savePParamField fvar field = do
+ checkNonOptDef field
+ let actualVal = mkName "v"
+ normalexpr <- saveObjectField actualVal field
+ -- we have to construct the block here manually, because we can't
+ -- splice-in-splice
+ return $ CaseE (VarE fvar) [ Match (ConP 'Nothing [])
+ (NormalB (ConE '[])) []
+ , Match (ConP 'Just [VarP actualVal])
+ (NormalB normalexpr) []
+ ]
+
+-- | Generates code to load an optional parameter field.
+loadPParamField :: Field -> Q (Name, Stmt)
+loadPParamField field = do
+ checkNonOptDef field
+ let name = fieldName field
+ fvar <- newName name
+ -- these are used in all patterns below
+ let objvar = varNameE "o"
+ objfield = stringE name
+ loadexp = [| $(varNameE "maybeFromObj") $objvar $objfield |]
+ bexp <- loadFn field loadexp objvar
+ return (fvar, BindS (VarP fvar) bexp)
+
+-- | Builds a simple declaration of type @n_x = fromMaybe f_x p_x@.
+buildFromMaybe :: String -> Q Dec
+buildFromMaybe fname =
+ valD (varP (mkName $ "n_" ++ fname))
+ (normalB [| $(varNameE "fromMaybe")
+ $(varNameE $ "f_" ++ fname)
+ $(varNameE $ "p_" ++ fname) |]) []
+
+-- | Builds a function that executes the filling of partial parameter
+-- from a full copy (similar to Python's fillDict).
+fillParam :: String -> String -> [Field] -> Q [Dec]
+fillParam sname field_pfx fields = do
+ let fnames = map (\fd -> field_pfx ++ fieldRecordName fd) fields
+ (sname_f, sname_p) = paramTypeNames sname
+ oname_f = "fobj"
+ oname_p = "pobj"
+ name_f = mkName sname_f
+ name_p = mkName sname_p
+ fun_name = mkName $ "fill" ++ sname ++ "Params"
+ le_full = ValD (ConP name_f (map (VarP . mkName . ("f_" ++)) fnames))
+ (NormalB . VarE . mkName $ oname_f) []
+ le_part = ValD (ConP name_p (map (VarP . mkName . ("p_" ++)) fnames))
+ (NormalB . VarE . mkName $ oname_p) []
+ obj_new = foldl (\accu vname -> AppE accu (VarE vname)) (ConE name_f)
+ $ map (mkName . ("n_" ++)) fnames
+ le_new <- mapM buildFromMaybe fnames
+ funt <- [t| $(conT name_f) -> $(conT name_p) -> $(conT name_f) |]
+ let sig = SigD fun_name funt
+ fclause = Clause [VarP (mkName oname_f), VarP (mkName oname_p)]
+ (NormalB $ LetE (le_full:le_part:le_new) obj_new) []
+ fun = FunD fun_name [fclause]
+ return [sig, fun]
+
+-- * Template code for exceptions
+
+-- | Exception simple error message field.
+excErrMsg :: (String, Q Type)
+excErrMsg = ("errMsg", [t| String |])
+
+-- | Builds an exception type definition.
+genException :: String -- ^ Name of new type
+ -> SimpleObject -- ^ Constructor name and parameters
+ -> Q [Dec]
+genException name cons = do
+ let tname = mkName name
+ declD <- buildSimpleCons tname cons
+ (savesig, savefn) <- genSaveSimpleObj tname ("save" ++ name) cons $
+ uncurry saveExcCons
+ (loadsig, loadfn) <- genLoadExc tname ("load" ++ name) cons
+ return [declD, loadsig, loadfn, savesig, savefn]
+
+-- | Generates the \"save\" clause for an entire exception constructor.
+--
+-- This matches the exception with variables named the same as the
+-- constructor fields (just so that the spliced in code looks nicer),
+-- and calls showJSON on it.
+saveExcCons :: String -- ^ The constructor name
+ -> [SimpleField] -- ^ The parameter definitions for this
+ -- constructor
+ -> Q Clause -- ^ Resulting clause
+saveExcCons sname fields = do
+ let cname = mkName sname
+ fnames <- mapM (newName . fst) fields
+ let pat = conP cname (map varP fnames)
+ felems = if null fnames
+ then conE '() -- otherwise, empty list has no type
+ else listE $ map (\f -> [| JSON.showJSON $(varE f) |]) fnames
+ let tup = tupE [ litE (stringL sname), felems ]
+ clause [pat] (normalB [| JSON.showJSON $tup |]) []
+
+-- | Generates load code for a single constructor of an exception.
+--
+-- Generates the code (if there's only one argument, we will use a
+-- list, not a tuple:
+--
+-- @
+-- do
+-- (x1, x2, ...) <- readJSON args
+-- return $ Cons x1 x2 ...
+-- @
+loadExcConstructor :: Name -> String -> [SimpleField] -> Q Exp
+loadExcConstructor inname sname fields = do
+ let name = mkName sname
+ f_names <- mapM (newName . fst) fields
+ let read_args = AppE (VarE 'JSON.readJSON) (VarE inname)
+ let binds = case f_names of
+ [x] -> BindS (ListP [VarP x])
+ _ -> BindS (TupP (map VarP f_names))
+ cval = foldl (\accu fn -> AppE accu (VarE fn)) (ConE name) f_names
+ return $ DoE [binds read_args, NoBindS (AppE (VarE 'return) cval)]
+
+{-| Generates the loadException function.
+
+This generates a quite complicated function, along the lines of:
+
+@
+loadFn (JSArray [JSString name, args]) = case name of
+ "A1" -> do
+ (x1, x2, ...) <- readJSON args
+ return $ A1 x1 x2 ...
+ "a2" -> ...
+ s -> fail $ "Unknown exception" ++ s
+loadFn v = fail $ "Expected array but got " ++ show v
+@
+-}
+genLoadExc :: Name -> String -> SimpleObject -> Q (Dec, Dec)
+genLoadExc tname sname opdefs = do
+ let fname = mkName sname
+ exc_name <- newName "name"
+ exc_args <- newName "args"
+ exc_else <- newName "s"
+ arg_else <- newName "v"
+ fails <- [| fail $ "Unknown exception '" ++ $(varE exc_else) ++ "'" |]
+ -- default match for unknown exception name
+ let defmatch = Match (VarP exc_else) (NormalB fails) []
+ -- the match results (per-constructor blocks)
+ str_matches <-
+ mapM (\(s, params) -> do
+ body_exp <- loadExcConstructor exc_args s params
+ return $ Match (LitP (StringL s)) (NormalB body_exp) [])
+ opdefs
+ -- the first function clause; we can't use [| |] due to TH
+ -- limitations, so we have to build the AST by hand
+ let clause1 = Clause [ConP 'JSON.JSArray
+ [ListP [ConP 'JSON.JSString [VarP exc_name],
+ VarP exc_args]]]
+ (NormalB (CaseE (AppE (VarE 'JSON.fromJSString)
+ (VarE exc_name))
+ (str_matches ++ [defmatch]))) []
+ -- the fail expression for the second function clause
+ fail_type <- [| fail $ "Invalid exception: expected '(string, [args])' " ++
+ " but got " ++ show (pp_value $(varE arg_else)) ++ "'"
+ |]
+ -- the second function clause
+ let clause2 = Clause [VarP arg_else] (NormalB fail_type) []
+ sigt <- [t| JSON.JSValue -> JSON.Result $(conT tname) |]
+ return $ (SigD fname sigt, FunD fname [clause1, clause2])