------------------------------------------------------------------------
--- A transformation from a Curry program with pre/postconditions and/or
--- specification into a Curry program where these conditions are integrated
--- into the code as run-time assertions.
---
--- The general idea of contracts and this transformation is described in:
---
--- > S. Antoy, M. Hanus:
--- > Contracts and Specifications for Functional Logic Programming
--- > Proc. 14th International Symposium on Practical Aspects of
--- > Declarative Languages (PADL 2012), pp. 33-47, Springer LNCS 7149, 2012
---
--- @author Michael Hanus
--- @version October 2016
------------------------------------------------------------------------

module TransContracts(main,transContracts) where

import AbstractCurry.Types
import AbstractCurry.Files
import AbstractCurry.Pretty
import AbstractCurry.Build
import AbstractCurry.Select
import AbstractCurry.Transform
import Char
import ContractUsage
import Directory
import Distribution
import FilePath          (takeDirectory)
import List
import Maybe             (fromJust, isNothing)
import System

-- in order to use the determinism analysis:
import Analysis.ProgInfo      (ProgInfo, lookupProgInfo)
import Analysis.Deterministic (Deterministic(..), nondetAnalysis)
import CASS.Server            (analyzeGeneric)

import SimplifyPostConds
import TheoremUsage

------------------------------------------------------------------------

banner :: String
banner = unlines [bannerLine,bannerText,bannerLine]
 where
   bannerText = "Contract Transformation Tool (Version of 12/08/16)"
   bannerLine = take (length bannerText) (repeat '=')

------------------------------------------------------------------------
--- Execute the contract wrapper in "preprocessor mode".
--- The Curry program must be read with `readCurry` (and not
--- `readUntypedCurry`) in order to correctly process arities
--- based on function types!
--- The result is `Nothing` if no transformation was applied or `Just` the
--- transformed program.
transContracts :: Int -> [String] -> String -> CurryProg -> IO (Maybe CurryProg)
transContracts verb moreopts srcprog inputProg = do
  when (verb>1) $ putStr banner
  opts <- processOpts defaultOptions moreopts
  transformCProg verb opts srcprog inputProg (progName inputProg)
 where
  processOpts opts ppopts = case ppopts of
    []          -> return opts
    ("-e":more) -> processOpts (opts { withEncapsulate   = True }) more
    ("-t":more) -> processOpts (opts { topLevelContracts = True }) more
    _           -> showError
   where
    showError = do
      putStrLn $ "Unknown options (ignored): " ++ show (unwords ppopts)
      return opts

------------------------------------------------------------------------
-- Data type for transformation parameters
data Options = Options
  { -- encapsulate assertion checking by set functions?
    withEncapsulate   :: Bool
    -- should contracts be asserted only to top-level entries of an operation
    -- or also to all (recursive) calls?
  , topLevelContracts :: Bool
    -- load and execute transformed program?
  , executeProg       :: Bool
  }

defaultOptions :: Options
defaultOptions = Options
  { withEncapsulate   = False
  , topLevelContracts = False
  , executeProg       = False
  }

------------------------------------------------------------------------
-- Start the contract wrapper in "stand-alone mode":
main :: IO ()
main = do
  putStrLn banner
  args <- getArgs
  processArgs defaultOptions args
 where
  processArgs opts args = case args of
     ("-e":margs) -> processArgs (opts { withEncapsulate   = True }) margs
     ("-t":margs) -> processArgs (opts { topLevelContracts = True }) margs
     ("-r":margs) -> processArgs (opts { executeProg       = True }) margs
     [mnamec]        -> let mname = stripCurrySuffix mnamec
                         in transformStandalone opts mname
                                      (transformedModName mname ++ ".curry")

     _ -> putStrLn $ unlines $
           ["ERROR: Illegal arguments for transformation: " ++ unwords args
           ,""
           ,"Usage: cwrapper [-e] [-t] [-r] <module_name>"
           ,"-e   : encapsulate nondeterminism of assertions"
           ,"-t   : assert contracts only to top-level (not recursive) calls"
           ,"-r   : load the transformed program into Curry system"
           ]

-- Prepare to call the main transformation for stand-alone mode:
transformStandalone :: Options -> String -> String -> IO ()
transformStandalone opts modname outfile = do
  mmodsrc <- lookupModuleSourceInLoadPath modname
  srcprog <- case mmodsrc of
               Nothing -> error $
                            "Source code of module '"++modname++"' not found!"
               Just (_,progname) -> readFile progname
  let acyfile = abstractCurryFileName modname
  doesFileExist acyfile >>= \b -> if b then removeFile acyfile else done
  prog <- readCurry modname
  doesFileExist acyfile >>= \b -> if b then done
                                       else error "Source program incorrect"
  let outmodname = transformedModName modname
  newprog <- transformCProg 1 opts srcprog prog outmodname
  writeFile outfile (showCProg (maybe prog id newprog) ++ "\n")
  when (executeProg opts) $ loadIntoCurry outmodname

-- Specifies how the name of the transformed module is built from the
-- name of the original module.
transformedModName :: String -> String
transformedModName m = m++"C"

-- start Curry system (PAKCS, KiCS2) and load a module:
loadIntoCurry :: String -> IO ()
loadIntoCurry m = do
  putStrLn $ "\nStarting Curry system and loading module '"++m++"'..."
  system $ installDir++"/bin/curry :l "++m
  done

------------------------------------------------------------------------
--- The main transformation operation with parameters:
--- * verbosity level
--- * options
--- * source text of the module
--- * AbstractCurry representation of the module
--- * name of the output module (if it should be renamed)
--- The result is Nothing if no transformation was applied or Just the
--- transformed program.
transformCProg :: Int -> Options -> String -> CurryProg -> String
               -> IO (Maybe CurryProg)
transformCProg verb opts srctxt orgprog outmodname = do
  let -- to avoid constructor CFunc and references to Test.Prop
      prog = addCmtFuncInProg (renameProp2EasyCheck orgprog)
      usageerrors = checkContractUse prog
  unless (null usageerrors) $ do
    putStr (unlines $ "ERROR: ILLEGAL USE OF CONTRACTS:" :
               map (\ ((mn,fn),err) -> fn ++ " (module " ++ mn ++ "): " ++ err)
                   usageerrors)
    error "Contract transformation aborted"
  let funposs      = linesOfFDecls srctxt prog
      fdecls       = functions prog
      funspecs     = getFunDeclsWith isSpecName prog
      specnames    = map (fromSpecName . snd . funcName) funspecs
      preconds     = getFunDeclsWith isPreCondName prog
      prenames     = map (fromPreCondName  . snd . funcName) preconds
      opostconds   = getFunDeclsWith isPostCondName prog
  -- filter theorems which have a proof file:
  theofuncs <- getTheoremFunctions
                (takeDirectory (modNameToPath (progName prog))) prog
  postconds <- simplifyPostConditionsWithTheorems verb theofuncs opostconds
  let postnames = map (fromPostCondName  . snd . funcName) postconds
      checkfuns = union specnames (union prenames postnames)
  if null checkfuns
   then do
     when (verb>1) $
       putStrLn "Contract transformation not required since no contracts found!"
     return Nothing
   else do
     when (verb>0) $
       putStrLn $ "Adding contract checking to: " ++ unwords checkfuns
     detinfo <- analyzeGeneric nondetAnalysis (progName prog)
                                              >>= return . either id error
     let newprog = transformProgram opts funposs fdecls detinfo
                                    funspecs preconds postconds prog
     return (Just (renameCurryModule outmodname newprog))

-- Get functions from a Curry module with a name satisfying the predicate:
getFunDeclsWith :: (String -> Bool) -> CurryProg -> [CFuncDecl]
getFunDeclsWith pred prog = filter (pred . snd . funcName) (functions prog)

------------------------------------------------------------------------
-- Transform a given program w.r.t. given specifications and pre/postconditions
transformProgram :: Options -> [(QName,Int)]-> [CFuncDecl]
                 -> ProgInfo Deterministic -> [CFuncDecl]
                 -> [CFuncDecl] -> [CFuncDecl] -> CurryProg -> CurryProg
transformProgram opts funposs allfdecls detinfo specdecls predecls postdecls
  (CurryProg mname imps dfltdecl clsdecls instdecls tdecls orgfdecls opdecls) =
 let -- replace in program old postconditions by new simplified postconditions:
     fdecls = filter (\fd -> funcName fd `notElem` map funcName postdecls)
                     orgfdecls ++ postdecls
     newpostconds = concatMap
                      (genPostCond4Spec opts allfdecls detinfo postdecls)
                      specdecls
     newfunnames  = map (snd . funcName) newpostconds
     -- remove old postconditions which are transformed into postconditions
     -- with specification checking:
     wonewfuns    = filter (\fd -> snd (funcName fd) `notElem` newfunnames)
                           fdecls
     -- compute postconditions actually used for contract checking:
     contractpcs  = postdecls++newpostconds
  in CurryProg mname
               (nub ("Test.Contract":"SetFunctions":imps))
               dfltdecl clsdecls instdecls tdecls
               (map deleteCmtIfEmpty
                  (concatMap
                     (addContract opts funposs allfdecls predecls contractpcs)
                     wonewfuns ++
                   newpostconds))
               opdecls

-- Add an empty comment to each function which has no comment
addCmtFuncInProg :: CurryProg -> CurryProg
addCmtFuncInProg
  (CurryProg mname imps dfltdecl clsdecls instdecls tdecls fdecls opdecls) =
   CurryProg mname imps dfltdecl clsdecls instdecls tdecls
             (map addCmtFunc fdecls) opdecls
 where
  addCmtFunc (CFunc qn ar vis texp rs) = CmtFunc "" qn ar vis texp rs
  addCmtFunc (CmtFunc cmt qn ar vis texp rs) = CmtFunc cmt qn ar vis texp rs

-- Generate a postcondition from a specification that is parameterized
-- by an "observation function".
-- If the specification is deterministic, generate an equality check,
-- otherwise generate a set containment check.
genPostCond4Spec :: Options -> [CFuncDecl] -> ProgInfo Deterministic
                 -> [CFuncDecl] -> CFuncDecl -> [CFuncDecl]
genPostCond4Spec _ _ _ _ (CFunc _ _ _ _ _) = error "genPostCond4Spec"
genPostCond4Spec _ allfdecls detinfo postdecls
               (CmtFunc _ (m,f) ar vis (CQualType (CContext clscons) texp) _) =
 let fname     = fromSpecName f
     -- is the specification deterministic?
     detspec   = maybe False (== Det) (lookupProgInfo (m,f) detinfo)
     fpostname = toPostCondName fname
     fpgenname = fpostname++"'generic"
     oldfpostc = filter (\fd -> snd (funcName fd) == fpostname) postdecls
     oldcmt    = if null oldfpostc then ""
                                   else '\n' : funcComment (head oldfpostc)
     varg      = (0,"g")
     argvars   = map (\i -> (i,"x"++show i)) [1..(ar+1)]
     spargvars = take ar argvars
     resultvar = last argvars
     gtype     = CTVar (0,"grt") -- result type of observation function
     varz      = (ar+2,"z")
     obsfun    = maybe (pre "id")
                       funcName
                       (find (\fd -> snd (funcName fd) == fpostname++"'observe")
                             allfdecls)
     gspecname = (m,f++"'g")
     gspec     = cfunc gspecname ar Private
                  (CQualType (CContext ((pre "Eq", gtype) : clscons))
                   ((resultType texp ~> gtype) ~> replaceResultType texp gtype))
                  [let gsargvars = map (\i -> (i,"x"++show i)) [1..ar]
                   in  simpleRule (CPVar varg : map CPVar gsargvars)
                                  (CApply (CVar varg)
                                          (applyF (m,f) (map CVar gsargvars)))]
     postcheck = CLetDecl
                  [CLocalPat (CPVar varz)
                     (CSimpleRhs (CApply (CVar varg) (CVar resultvar)) [])]
                  (if detspec
                   then applyF (pre "==")
                          [CVar varz,
                           applyF gspecname (map CVar (varg : spargvars))]
                   else applyF (pre "&&")
                         [applyF (pre "==") [CVar varz, CVar varz],
                          applyF (sfMod "valueOf")
                           [CVar varz,
                            applyF (sfMod $ "set"++show (ar+1))
                             (constF gspecname : map CVar (varg :spargvars))]])
     rename qf = if qf==(m,fpostname) then (m,fpostname++"'org") else qf
  in [cmtfunc
       ("Parametric postcondition for '"++fname++
        "' (generated from specification). "++oldcmt)
       (m,fpgenname) (ar+2) Private
       (CQualType (CContext ((pre "Eq", gtype) : clscons))
                  ((resultType texp ~> gtype) ~> extendFuncType texp boolType))
       [if null oldfpostc
        then simpleRule (map CPVar (varg:argvars)) postcheck
        else simpleRuleWithLocals
                (map CPVar (varg:argvars))
                (applyF (pre "&&")
                             [applyF (rename (funcName (head oldfpostc)))
                                     (map CVar argvars),
                              postcheck])
                [updQNamesInCLocalDecl rename
                        (CLocalFunc (deleteCmt (head oldfpostc)))]]
     ,gspec
     ,cmtfunc
       ("Postcondition for '"++fname++"' (generated from specification). "++
        oldcmt)
       (m,fpostname) (ar+1) vis
       (CQualType
          (CContext (union (type2EqConstraints (resultType texp)) clscons))
          (extendFuncType texp boolType))
       [simpleRule (map CPVar argvars)
                   (applyF (m,fpgenname)
                           (constF obsfun : map CVar argvars))]
     ]

-- Transform a type into Eq constraints for all type variables occurring
-- in this type. Note: this is not sufficient since one needs also be
-- sure that each type constructor has an Eq instance.
type2EqConstraints :: CTypeExpr -> [CConstraint]
type2EqConstraints texp =
  map (\tv -> (pre "Eq",CTVar tv)) (nub (tvarsOfType texp))

-- Transform a type into Eq constraints for all type variables occurring
-- in this type. Note: this is not sufficient since one needs also be
-- sure that each type constructor has an Eq instance.
type2ShowConstraints :: CTypeExpr -> [CConstraint]
type2ShowConstraints texp =
  map (\tv -> (pre "Show",CTVar tv)) (nub (tvarsOfType texp))

-- adds contract checking to a function if it has a pre- or postcondition
addContract :: Options -> [(QName,Int)] -> [CFuncDecl] -> [CFuncDecl]
            -> [CFuncDecl] -> CFuncDecl -> [CFuncDecl]
addContract _ _ _ _ _ (CFunc _ _ _ _ _) =
  error "Internal error in addContract: CFunc occurred"
addContract opts funposs allfdecls predecls postdecls
   fdecl@(CmtFunc cmt qn@(m,f) ar vis (CQualType (CContext clscons) texp) _) =
 let argvars   = map (\i -> (i,"x"++show i)) [1..ar]
     encapsSuf = if withEncapsulate opts then "ND" else ""
     encaps fn n = if withEncapsulate opts then setFun n fn [] else constF fn

     -- Textual comment about function source:
     fref      = string2ac $ "'" ++ f ++ "' (module " ++ m ++
                             maybe ")"
                                   (\l -> ", line " ++ show l ++ ")")
                                   (lookup qn funposs)

     -- call to observation function (if provided):
     obsfunexp = constF $
                  maybe (pre "id")
                       funcName
                       (find (\fd -> snd (funcName fd) == f++"'post'observe")
                             allfdecls)

     ctexp = CQualType (CContext
                         (union (type2EqConstraints (resultType texp))
                                (union (type2ShowConstraints texp) clscons)))
                       texp

     -- Construct function with precondition added and a function without prec.:
     (precheck,woprefdecl) =
        maybe ([],fdecl)
          (\predecl ->
            let prename = funcName predecl
                rename = updateFunc id qn (withSuffix qn "'WithoutPreCondCheck")
            in ([cmtfunc cmt (m,f) ar vis ctexp
                   [simpleRule (map CPVar argvars)
                      (applyF (cMod $ "withPreContract" ++ show ar ++ encapsSuf)
                         ([fref, encaps prename ar, constF (rename qn)] ++
                          map CVar argvars))]],
                addCmtLine "Without precondition checking!" $
                           rnmFDecl rename fdecl))
          (find (\fd -> fromPreCondName (snd (funcName fd)) == f) predecls)

     -- Construct function with postcond. added and a function without postc.:
     (postcheck,wopostfdecl) =
        maybe ([],woprefdecl)
          (\postdecl ->
            let postname = funcName postdecl
                qnp      = funcName woprefdecl
                rename   = updateFunc id qnp
                                      (withSuffix qnp "'WithoutPostCondCheck")
            in ([cmtfunc (funcComment woprefdecl) qnp ar vis ctexp
                 [simpleRule (map CPVar argvars)
                    (applyF (cMod $ "withPostContract" ++ show ar ++ encapsSuf)
                      ([fref, encaps postname (ar+1), obsfunexp,
                        constF (rename qnp)] ++
                       map CVar argvars))]],
                 setPrivate $ addCmtLine "Without postcondition checking!" $
                              rnmFDecl rename woprefdecl))
          (find (\fd-> fromPostCondName (snd (funcName fd)) == f) postdecls)

     rnmFDecl rnm fdcl = if topLevelContracts opts
                           then updQNamesInCFuncDecl rnm fdcl
                           else renameFDecl rnm fdcl

  in precheck ++ postcheck ++ [wopostfdecl]

--- Updates a function at some point.
updateFunc :: Eq a => (a -> b) -> a -> b -> (a -> b)
updateFunc f x v y = if y==x then v else f y

--- Define a function as private.
setPrivate :: CFuncDecl -> CFuncDecl
setPrivate = updCFuncDecl id id id (const Private) id id

--- Adds a suffix to  qualified name.
withSuffix :: QName -> String -> QName
withSuffix (m,f) s = (m, f ++ s)

-- An operation of the module Test.Contract:
cMod :: String -> QName
cMod f = ("Test.Contract",f)

-- An operation of the module SetFunctions:
sfMod :: String -> QName
sfMod f = ("SetFunctions",f)

-- Set function for a function name with given arity and arguments:
setFun :: Int -> QName -> [CExpr] -> CExpr
setFun n qn args = applyF (sfMod $ "set"++show n) (constF qn : args)

------------------------------------------------------------------------
-- Auxiliary operations:

-- Replaces a result type of a function type by a new type
replaceResultType :: CTypeExpr -> CTypeExpr -> CTypeExpr
replaceResultType texp ntype =
  case texp of CFuncType t1 t2 -> CFuncType t1 (replaceResultType t2 ntype)
               _               -> ntype

-- Transform a n-ary function type into a (n+1)-ary function type with
-- a given new result type
extendFuncType :: CTypeExpr -> CTypeExpr -> CTypeExpr
extendFuncType t texp = case t of
  CFuncType t1 t2 -> t1 ~> (extendFuncType t2 texp)
  _               -> t ~> texp

--- Renames a function declaration (but not the body).
renameFDecl :: (QName -> QName) -> CFuncDecl -> CFuncDecl
renameFDecl rn (CFunc qn ar vis texp rules) = CFunc (rn qn) ar vis texp rules
renameFDecl rn (CmtFunc cmt qn ar vis texp rules) =
  CmtFunc cmt (rn qn) ar vis texp rules

--- Adds a line to the comment in a function declaration.
addCmtLine :: String -> CFuncDecl -> CFuncDecl
addCmtLine s (CFunc     qn ar vis texp rules) =
  CmtFunc s qn ar vis texp rules
addCmtLine s (CmtFunc cmt qn ar vis texp rules) =
  CmtFunc (if null cmt then s else unlines [cmt,s]) qn ar vis texp rules

--- Deletes the comment in a function declaration.
deleteCmt :: CFuncDecl -> CFuncDecl
deleteCmt (CFunc     qn ar vis texp rules) = CFunc qn ar vis texp rules
deleteCmt (CmtFunc _ qn ar vis texp rules) = CFunc qn ar vis texp rules

--- Deletes the comment in a function declaration if it is the empty string.
deleteCmtIfEmpty :: CFuncDecl -> CFuncDecl
deleteCmtIfEmpty (CFunc qn ar vis texp rules)     = CFunc qn ar vis texp rules
deleteCmtIfEmpty (CmtFunc cmt qn ar vis texp rules) =
  if null cmt then CFunc qn ar vis texp rules
              else CmtFunc cmt qn ar vis texp rules

------------------------------------------------------------------------
-- Compute names and lines numbers of all top-level operations in a program.
linesOfFDecls :: String -> CurryProg -> [(QName,Int)]
linesOfFDecls srctxt prog =
  map (addSourceLineNumber (map firstId (lines srctxt)))
      (map funcName (functions prog))
 where
  addSourceLineNumber ids qn = (qn, maybe 0 (+1) (elemIndex (snd qn) ids))

-- Compute the first identifier (name or operator in brackets) in a string:
firstId :: String -> String
firstId [] = ""
firstId (c:cs)
  | isAlpha c = takeWhile isIdChar (c:cs)
  | c == '('  = let bracketid = takeWhile (/=')') cs
                 in if all (`elem` infixIDs) bracketid
                    then bracketid
                    else ""
  | otherwise = ""

-- Is this an alphanumeric character, underscore, or apostroph?
isIdChar :: Char -> Bool
isIdChar c = isAlphaNum c || c == '_' || c == '\''

-- All characters occurring in infix operators.
infixIDs :: String
infixIDs =  "~!@#$%^&*+-=<>?./|\\:"

------------------------------------------------------------------------
-- Auxiliaries

-- Rename all module references to "Test.Prog" into "Test.EasyCheck"
renameProp2EasyCheck :: CurryProg -> CurryProg
renameProp2EasyCheck prog =
  updCProg id (map rnmMod) id id id id id id
           (updQNamesInCProg (\ (mod,n) -> (rnmMod mod,n)) prog)
 where
  rnmMod mod | mod == propModule = easyCheckModule
             | otherwise         = mod

--- Name of the Test.Prop module (the clone of the EasyCheck module).
propModule :: String
propModule = "Test.Prop"

--- Name of the EasyCheck module.
easyCheckModule :: String
easyCheckModule = "Test.EasyCheck"

------------------------------------------------------------------------