{-# LANGUAGE TemplateHaskell #-}
-{-| TemplateHaskell helper for HTools.
+{-| TemplateHaskell helper for Ganeti Haskell code.
As TemplateHaskell require that splices be defined in a separate
module, we combine all the TemplateHaskell functionality that HTools
, uuidFields
, serialFields
, tagsFields
+ , TagSet
, buildObject
, buildObjectSerialisation
, buildParam
, DictObject(..)
+ , genException
+ , excErrMsg
) where
import Control.Monad (liftM)
import Language.Haskell.TH
import qualified Text.JSON as JSON
+import Text.JSON.Pretty (pp_value)
-- * Exported types
uuidFields :: [Field]
uuidFields = [ simpleField "uuid" [t| String |] ]
+-- | Tag set type alias.
+type TagSet = Set.Set String
+
-- | Tag field description.
tagsFields :: [Field]
tagsFields = [ defaultField [| Set.empty |] $
- simpleField "tags" [t| Set.Set String |] ]
+ simpleField "tags" [t| TagSet |] ]
+
+-- * Internal types
+
+-- | A simple field, in constrast to the customisable 'Field' type.
+type SimpleField = (String, Q Type)
+
+-- | A definition for a single constructor for a simple object.
+type SimpleConstructor = (String, [SimpleField])
+
+-- | A definition for ADTs with simple fields.
+type SimpleObject = [SimpleConstructor]
-- * Helper functions
appFn f x | f == VarE 'id = x
| otherwise = AppE f x
+-- | Builds a field for a normal constructor.
+buildConsField :: Q Type -> StrictTypeQ
+buildConsField ftype = do
+ ftype' <- ftype
+ return (NotStrict, ftype')
+
+-- | Builds a constructor based on a simple definition (not field-based).
+buildSimpleCons :: Name -> SimpleObject -> Q Dec
+buildSimpleCons tname cons = do
+ decl_d <- mapM (\(cname, fields) -> do
+ fields' <- mapM (buildConsField . snd) fields
+ return $ NormalC (mkName cname) fields') cons
+ return $ DataD [] tname [] decl_d [''Show, ''Read, ''Eq]
+
+-- | Generate the save function for a given type.
+genSaveSimpleObj :: Name -- ^ Object type
+ -> String -- ^ Function name
+ -> SimpleObject -- ^ Object definition
+ -> (SimpleConstructor -> Q Clause) -- ^ Constructor save fn
+ -> Q (Dec, Dec)
+genSaveSimpleObj tname sname opdefs fn = do
+ let sigt = AppT (AppT ArrowT (ConT tname)) (ConT ''JSON.JSValue)
+ fname = mkName sname
+ cclauses <- mapM fn opdefs
+ return $ (SigD fname sigt, FunD fname cclauses)
+
-- * Template code for simple raw type-equivalent ADTs
-- | Generates a data type declaration.
genStrOfKey :: Name -> String -> Q [Dec]
genStrOfKey = genConstrToStr ensureLower
--- | LuxiOp parameter type.
-type LuxiParam = (String, Q Type)
-
-- | Generates the LuxiOp data type.
--
-- This takes a Luxi operation definition and builds both the
--
-- * type
--
-genLuxiOp :: String -> [(String, [LuxiParam])] -> Q [Dec]
+genLuxiOp :: String -> SimpleObject -> Q [Dec]
genLuxiOp name cons = do
- decl_d <- mapM (\(cname, fields) -> do
- fields' <- mapM (\(_, qt) ->
- qt >>= \t -> return (NotStrict, t))
- fields
- return $ NormalC (mkName cname) fields')
- cons
- let declD = DataD [] (mkName name) [] decl_d [''Show, ''Read, ''Eq]
- (savesig, savefn) <- genSaveLuxiOp cons
+ let tname = mkName name
+ declD <- buildSimpleCons tname cons
+ (savesig, savefn) <- genSaveSimpleObj tname "opToArgs"
+ cons saveLuxiConstructor
req_defs <- declareSADT "LuxiReq" .
map (\(str, _) -> ("Req" ++ str, mkName ("luxiReq" ++ str))) $
cons
return $ [declD, savesig, savefn] ++ req_defs
-- | Generates the \"save\" expression for a single luxi parameter.
-saveLuxiField :: Name -> LuxiParam -> Q Exp
+saveLuxiField :: Name -> SimpleField -> Q Exp
saveLuxiField fvar (_, qt) =
[| JSON.showJSON $(varE fvar) |]
-- | Generates the \"save\" clause for entire LuxiOp constructor.
-saveLuxiConstructor :: (String, [LuxiParam]) -> Q Clause
+saveLuxiConstructor :: SimpleConstructor -> Q Clause
saveLuxiConstructor (sname, fields) = do
let cname = mkName sname
fnames = map (mkName . fst) fields
else [| JSON.showJSON $(listE flist) |]
clause [pat] (normalB finval) []
--- | Generates the main save LuxiOp function.
-genSaveLuxiOp :: [(String, [LuxiParam])]-> Q (Dec, Dec)
-genSaveLuxiOp opdefs = do
- sigt <- [t| $(conT (mkName "LuxiOp")) -> JSON.JSValue |]
- let fname = mkName "opToArgs"
- cclauses <- mapM saveLuxiConstructor opdefs
- return $ (SigD fname sigt, FunD fname cclauses)
-
-- * "Objects" functionality
-- | Extract the field's declaration from a Field structure.
(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])
projects / ganeti-local / blobdiff