{- |
Module      : Language.Scheme.Compiler
Copyright   : Justin Ethier
Licence     : MIT (see LICENSE in the distribution)

Maintainer  : github.com/justinethier
Stability   : experimental
Portability : portable

This module contains a Scheme to Haskell compiler which performs the following 
transformations:

> Scheme AST (LispVal) => Haskell AST (HaskAST) => Compiled Code (String)

The GHC compiler is then used to create a native executable. At present, the 
focus has just been on creating a compiler that will generate correct, working 
code. Many optimizations could and need to be made for time and space...

Note the following type is used for all functions generated by the compiler: 

> compiledFunc :: 
>   Env ->                  -- Runtime Environment
>   LispVal ->              -- Continuation
>   LispVal ->              -- Value
>   Maybe [LispVal] ->      -- Additional arguments
>   IOThrowsError LispVal   -- Result

-}

module Language.Scheme.Compiler 
    (
      compile
    , compileApply
    , compileBlock
    , compileDivertedVars 
    , compileExpr
    , compileLambdaList
    , compileLisp
    , compileScalar
    , compileSpecialForm
    , compileSpecialFormBody
    , compileSpecialFormEntryPoint
    , defineLambdaVars
    , defineTopLevelVars
    , divertVars 
    , initializeCompiler
    , isPrim
    , mcompile
    , mfunc
    )
where 
import Language.Scheme.Compiler.Libraries as LSCL
import Language.Scheme.Compiler.Types
import qualified Language.Scheme.Core as LSC 
    (apply, evalLisp, findFileOrLib)
import qualified Language.Scheme.Macro
import Language.Scheme.Primitives
import Language.Scheme.Types
import Language.Scheme.Variables
import Control.Monad.Error
import Data.Complex
import qualified Data.List
import Data.Ratio
-- import Debug.Trace

-- |Perform one-time initialization of the compiler's environment
initializeCompiler :: Env -> IOThrowsError [HaskAST]
initializeCompiler env = do
  -- Define imports var here as an empty list.
  -- This list is appended to by (load-ffi) instances,
  -- and the imports are explicitly added later on...
  _ <- defineNamespacedVar env 't' {-"internal"-} "imports" $ List []
  return []

-- | Compile a file containing scheme code
compileLisp 
    :: Env  -- ^ Compiler environment 
    -> String -- ^ Filename
    -> String -- ^ Function entry point (code calls into this function)
    -> Maybe String -- ^ Function exit point, if any
    -> IOThrowsError [HaskAST]
compileLisp env filename entryPoint exitPoint = do
    filename' <- LSC.findFileOrLib filename 
    load filename' >>= compileBlock entryPoint exitPoint env []

-- |Compile a list (block) of Scheme code
compileBlock :: String -> Maybe String -> Env -> [HaskAST] -> [LispVal] 
             -> IOThrowsError [HaskAST]
compileBlock symThisFunc symLastFunc env result lisps = do
  _ <- defineTopLevelVars env lisps
  _compileBlock symThisFunc symLastFunc env result lisps

_compileBlock :: String -> Maybe String -> Env -> [HaskAST] -> [LispVal] 
              -> IOThrowsError [HaskAST]
_compileBlock symThisFunc symLastFunc env result [c] = do
  compiled <- mcompile env c $ CompileOptions symThisFunc False False symLastFunc 
  return $ result ++ compiled
_compileBlock symThisFunc symLastFunc env result (c:cs) = do
  Atom symNextFunc <- _gensym "f"
  compiled <- mcompile env c $ 
                       CompileOptions symThisFunc False False (Just symNextFunc)
  _compileBlock symNextFunc symLastFunc env (result ++ compiled) cs
_compileBlock _ _ _ result [] = return result

-- TODO: could everything just be regular function calls except when a continuation is 'added to the stack' via a makeCPS(makeCPSWArgs ...) ?? I think this could be made more efficient

-- |Helper function to compile expressions consisting of a scalar
compileScalar :: String -> CompOpts -> IOThrowsError [HaskAST]
compileScalar val copts = do 
  f <- return $ AstAssignM "x1" $ AstValue val 
  c <- return $ createAstCont copts "x1" ""
  return [createAstFunc copts [f, c]]

-- |Compile the list of arguments for a function
compileLambdaList :: [LispVal] -> IOThrowsError String
compileLambdaList l = do
  serialized <- mapM serialize l 
  return $ "[" ++ concat (Data.List.intersperse "," serialized) ++ "]"
 where serialize (Atom a) = return $ (show a)
       serialize a = throwError $ Default $ 
                         "invalid parameter to lambda list: " ++ show a

-- |Add lambda variables to the compiler's environment
defineLambdaVars :: Env -> [LispVal] -> IOThrowsError LispVal
defineLambdaVars env (Atom v : vs) = do
    _ <- defineVar env v $ Number 0 -- For now, actual value does not matter
    defineLambdaVars env vs
defineLambdaVars env (_ : vs) = defineLambdaVars env vs
defineLambdaVars _ [] = return $ Nil ""

-- |Find all variables defined at "this" level and load their symbols into
--  the environment. This allows the compiler validation to work even 
--  though a variable is used in a sub-form before it is defined further
--  on down in the program
defineTopLevelVars :: Env -> [LispVal] -> IOThrowsError LispVal
defineTopLevelVars env (List [Atom "define", Atom var, _] : ls) = do
    _ <- defineTopLevelVar env var
    defineTopLevelVars env ls
defineTopLevelVars env ((List (Atom "define" : List (Atom var : _) : _)) : ls) = do
    _ <- defineTopLevelVar env var
    defineTopLevelVars env ls
defineTopLevelVars env ((List (Atom "define" : DottedList (Atom var : _) _ : _)) : ls) = do
    _ <- defineTopLevelVar env var
    defineTopLevelVars env ls
defineTopLevelVars env (_ : ls) = defineTopLevelVars env ls
defineTopLevelVars _ _ = return nullLisp 

defineTopLevelVar :: Env -> String -> IOThrowsError LispVal
defineTopLevelVar env var = do
  defineVar env var $ Number 0 -- Actual value not loaded at the moment 

-- |Compile a Lisp expression to Haskell. Note this function does
--  not expand macros; mcompile should be used instead if macros
--  may appear in the expression.
compile :: Env -> LispVal -> CompOpts -> IOThrowsError [HaskAST]
-- Experimenting with r7rs library support
compile env 
        (List (Atom "import" : mods)) 
        copts@(CompileOptions _ _ _ _) = do
    LispEnv meta <- getVar env "*meta-env*"
    LSCL.importAll env 
                   meta 
                   mods 
                  (CompileLibraryOptions compileBlock compileLisp) 
                   copts
compile _ (Nil n) copts = compileScalar ("  return $ Nil " ++ (show n)) copts
compile _ (String s) copts = compileScalar ("  return $ String " ++ (show s)) copts
compile _ (Char c) copts = compileScalar ("  return $ Char " ++ (show c)) copts
compile _ (Complex c) copts = compileScalar ("  return $ Complex $ (" ++ (show $ realPart c) ++ ") :+ (" ++ (show $ imagPart c) ++ ")") copts
compile _ (Float f) copts = compileScalar ("  return $ Float (" ++ (show f) ++ ")") copts
compile _ (Rational r) copts = compileScalar ("  return $ Rational $ (" ++ (show $ numerator r) ++ ") % (" ++ (show $ denominator r) ++ ")") copts 
compile _ (Number n) copts = compileScalar ("  return $ Number (" ++ (show n) ++ ")") copts
compile _ (Bool b) copts = compileScalar ("  return $ Bool " ++ (show b)) copts
compile _ v@(Vector _) copts = compileScalar (" return $ " ++ ast2Str v) copts
compile _ v@(ByteVector _) copts = compileScalar (" return $ " ++ ast2Str v) copts
compile _ ht@(HashTable _) copts = compileScalar (" return $ " ++ ast2Str ht) copts
compile env (Atom a) copts = do
 isDefined <- liftIO $ isRecBound env a
 case isDefined of
   True -> do
     return [createAstFunc copts [
               AstValue $ "  val <- getRTVar env \"" ++ a ++ "\""], 
               createAstCont copts "val" ""]
   False -> throwError $ UnboundVar "Variable is not defined" a

compile _ (List [Atom "quote", val]) copts = 
  compileScalar (" return $ " ++ ast2Str val) copts

compile env ast@(List [Atom "expand",  _body]) copts = do
  compileSpecialFormBody env ast copts (\ _ -> do
    val <- Language.Scheme.Macro.expand env False _body LSC.apply
    compileScalar (" return $ " ++ ast2Str val) copts)

compile env ast@(List (Atom "let-syntax" : List _bindings : _body)) copts = do
  compileSpecialFormBody env ast copts (\ _ -> do
    bodyEnv <- liftIO $ extendEnv env []
    _ <- Language.Scheme.Macro.loadMacros env bodyEnv Nothing False _bindings
    -- Expand whole body as a single continuous macro, to ensure hygiene
    expanded <- Language.Scheme.Macro.expand bodyEnv False (List _body) LSC.apply
    divertVars bodyEnv expanded copts compexp)
 where 
     -- Pick up execution here after expansion
     compexp bodyEnv' expanded' copts' = do
       case expanded' of
         List e -> compile bodyEnv' (List $ Atom "begin" : e) copts'
         e -> compile bodyEnv' e copts'

compile env ast@(List (Atom "letrec-syntax" : List _bindings : _body)) copts = do
  compileSpecialFormBody env ast copts (\ _ -> do
    bodyEnv <- liftIO $ extendEnv env []
    _ <- Language.Scheme.Macro.loadMacros bodyEnv bodyEnv Nothing False _bindings
    -- Expand whole body as a single continuous macro, to ensure hygiene
    expanded <- Language.Scheme.Macro.expand bodyEnv False (List _body) LSC.apply
    divertVars bodyEnv expanded copts compexp)
  where 
     -- Pick up execution here after expansion
     compexp bodyEnv' expanded' copts' = do
       case expanded' of
         List e -> compile bodyEnv' (List $ Atom "begin" : e) copts'
         e -> compile bodyEnv' e copts'

-- A non-standard way to rebind a macro to another keyword
compile env 
        (List [Atom "define-syntax", 
                   Atom newKeyword,
                   Atom keyword]) 
        copts = do
  bound <- getNamespacedVar' env macroNamespace keyword
  case bound of
    Just m -> do
        _ <- defineNamespacedVar env macroNamespace newKeyword m
        compFunc <- return $ [
          AstValue $ "  bound <- getNamespacedVar' env macroNamespace \"" ++ 
                          keyword ++ "\"",
          AstValue $ "  case bound of ",
          AstValue $ "    Just m -> ",
          AstValue $ "      defineNamespacedVar env macroNamespace \"" ++ 
                              newKeyword ++ "\" m",
          AstValue $ "    Nothing -> throwError $ TypeMismatch \"macro\" $ " ++ 
                             "Atom \"" ++ keyword ++ "\"",
          createAstCont copts "(Nil \"\")" ""]
        return $ [createAstFunc copts compFunc]
    Nothing -> throwError $ TypeMismatch "macro" $ Atom keyword

compile env ast@(List [Atom "define-syntax", Atom keyword,
  (List [Atom "er-macro-transformer", 
    (List (Atom "lambda" : List fparams : fbody))])])
  copts = do
  _ <- validateFuncParams fparams (Just 3)
  compileSpecialFormBody env ast copts (\ _ -> do
    let fparamsStr = asts2Str fparams
        fbodyStr = asts2Str fbody
  
    f <- makeNormalFunc env fparams fbody 
    _ <- defineNamespacedVar env macroNamespace keyword $ SyntaxExplicitRenaming f
  
    compFunc <- return $ [
      AstValue $ "  f <- makeNormalFunc env " ++ fparamsStr ++ " " ++ fbodyStr, 
      AstValue $ "  defineNamespacedVar env macroNamespace \"" ++ keyword ++ 
                      "\" $ SyntaxExplicitRenaming f",
      createAstCont copts "(Nil \"\")" ""]
    return $ [createAstFunc copts compFunc])

compile env lisp@(List [Atom "define-syntax", Atom keyword, 
    (List (Atom "syntax-rules" : Atom ellipsis : (List identifiers : rules)))]) copts = do
  compileSpecialFormBody env lisp copts (\ _ -> do
    let idStr = asts2Str identifiers
        ruleStr = asts2Str rules
  
    -- Make macro available at compile time
    _ <- defineNamespacedVar env macroNamespace keyword $ 
           Syntax (Just env) Nothing False ellipsis identifiers rules
  
    -- And load it at runtime as well
    -- Env should be identical to the one loaded at compile time...
    compileScalar 
      ("  defineNamespacedVar env macroNamespace \"" ++ keyword ++ 
       "\" $ Syntax (Just env) Nothing False \"" ++ ellipsis ++ "\" " ++ idStr ++ " " ++ ruleStr) copts)

compile env lisp@(List [Atom "define-syntax", Atom keyword, 
    (List (Atom "syntax-rules" : (List identifiers : rules)))]) copts = do
  compileSpecialFormBody env lisp copts (\ _ -> do
    let idStr = asts2Str identifiers
        ruleStr = asts2Str rules
  
    -- Make macro available at compile time
    _ <- defineNamespacedVar env macroNamespace keyword $ 
           Syntax (Just env) Nothing False "..." identifiers rules
  
    -- And load it at runtime as well
    -- Env should be identical to the one loaded at compile time...
    compileScalar 
      ("  defineNamespacedVar env macroNamespace \"" ++ keyword ++ 
       "\" $ Syntax (Just env) Nothing False \"...\" " ++ idStr ++ " " ++ ruleStr) copts)

compile env ast@(List [Atom "if", predic, conseq]) copts = 
  compileSpecialFormBody env ast copts (\ _ -> do
    compile env (List [Atom "if", predic, conseq, Nil ""]) copts)

compile env ast@(List [Atom "if", predic, conseq, alt]) copts = do
  compileSpecialFormBody env ast copts (\ nextFunc -> do
    Atom symPredicate <- _gensym "ifPredic"
    Atom symCheckPredicate <- _gensym "compiledIfPredicate"
    Atom symConsequence <- _gensym "compiledConsequence"
    Atom symAlternate <- _gensym "compiledAlternative"

    -- Entry point; ensure if is not rebound
    f <- return [AstValue $ "  " ++ symPredicate ++
                            " env (makeCPSWArgs env cont " ++ symCheckPredicate ++ " []) " ++ 
                            " (Nil \"\") (Just []) "]
    -- Compile expression for if's args
    compPredicate <- compileExpr env predic symPredicate Nothing      -- Do not want to call into nextFunc in the middle of (if)
    compConsequence <- compileExpr env conseq symConsequence nextFunc -- pick up at nextFunc after consequence
    compAlternate <- compileExpr env alt symAlternate nextFunc        -- or...pick up at nextFunc after alternate
    -- Special case because we need to check the predicate's value
    compCheckPredicate <- return $ AstFunction symCheckPredicate " env cont result _ " [
       AstValue $ "  case result of ",
       AstValue $ "    Bool False -> " ++ symAlternate ++ " env cont (Nil \"\") (Just []) ",
       AstValue $ "    _ -> " ++ symConsequence ++ " env cont (Nil \"\") (Just []) "]
    
    -- Join compiled code together
    return $ [createAstFunc copts f] ++ compPredicate ++ [compCheckPredicate] ++ 
              compConsequence ++ compAlternate)

compile env ast@(List [Atom "set!", Atom var, form]) copts@(CompileOptions _ _ _ _) = do
  compileSpecialFormBody env ast copts (\ _ -> do
    Atom symDefine <- _gensym "setFunc"
    Atom symMakeDefine <- _gensym "setFuncMakeSet"

    -- Store var in huskc's env for macro processing
    _ <- setVar env var form

    entryPt <- compileSpecialFormEntryPoint "set!" symDefine copts
    compDefine <- compileExpr env form symDefine $ Just symMakeDefine
    compMakeDefine <- return $ AstFunction symMakeDefine " env cont result _ " [
       AstValue $ "  _ <- setVar env \"" ++ var ++ "\" result",
       createAstCont copts "result" ""]
    return $ [entryPt] ++ compDefine ++ [compMakeDefine])

compile env ast@(List [Atom "set!", nonvar, _]) copts = do 
  compileSpecialFormBody env ast copts (\ _ -> do
    f <- compileSpecialForm "set!" ("throwError $ TypeMismatch \"variable\"" ++
                            " $ String \"" ++ (show nonvar) ++ "\"")  copts
    return [f])
compile env ast@(List (Atom "set!" : args)) copts = do
  compileSpecialFormBody env ast copts (\ _ -> do
    f <- compileSpecialForm "set!" ("throwError $ NumArgs 2 $ [String \"" ++ 
            (show args) ++ "\"]") copts -- Cheesy to use a string, but fine for now...
    return [f])

compile env ast@(List [Atom "define", Atom var, form]) copts@(CompileOptions _ _ _ _) = do
  compileSpecialFormBody env ast copts (\ _ -> do
    Atom symDefine <- _gensym "defineFuncDefine"
    Atom symMakeDefine <- _gensym "defineFuncMakeDef"
   
    -- Store var in huskc's env for macro processing (and same for other vers of define)
    _ <- defineVar env var form


    -- WORKAROUND #1
    -- Special case to support require-extension
    _ <- case form of
        List [Atom "current-environment"] -> 
            defineVar env var $ LispEnv env
        _ -> return $ Nil "" 
    -- End special case

   
    -- Entry point; ensure var is not rebound
    f <- return $ [
          AstValue $ "  " ++ symDefine ++ " env cont (Nil \"\") (Just [])" ]
    compDefine <- compileExpr env form symDefine $ Just symMakeDefine
    compMakeDefine <- return $ AstFunction symMakeDefine " env cont result _ " [
       AstValue $ "  _ <- defineVar env \"" ++ var ++ "\" result",
       createAstCont copts "result" ""]
    return $ [createAstFunc copts f] ++ compDefine ++ [compMakeDefine])

compile env ast@(List (Atom "define" : List (Atom var : fparams) : fbody)) 
        copts@(CompileOptions _ _ _ _) = do
  _ <- validateFuncParams fparams Nothing
  compileSpecialFormBody env ast copts (\ _ -> do
    bodyEnv <- liftIO $ extendEnv env []
    -- bind lambda params in the extended env
    _ <- defineLambdaVars bodyEnv (Atom var : fparams)
   
    Atom symCallfunc <- _gensym "defineFuncEntryPt"
    compiledParams <- compileLambdaList fparams
    compiledBody <- compileBlock symCallfunc Nothing bodyEnv [] fbody
   
    -- Cache macro expansions within function body
    ebody <- mapM (\ lisp -> Language.Scheme.Macro.macroEval env lisp LSC.apply) fbody
    -- Store var in huskc's env for macro processing (and same for other vers of define)
    _ <- makeNormalFunc env fparams ebody >>= defineVar env var
   
    -- Entry point; ensure var is not rebound
    f <- return $ [
          AstValue $ "  result <- makeNormalHFunc env (" ++ compiledParams ++ 
                     ") " ++ symCallfunc,
          AstValue $ "  _ <- defineVar env \"" ++ var ++ "\" result ",
          createAstCont copts "result" ""
          ]
    return $ [createAstFunc copts f] ++ compiledBody)

compile env 
        ast@(List (Atom "define" : DottedList (Atom var : fparams) varargs : fbody)) 
        copts@(CompileOptions _ _ _ _) = do
  _ <- validateFuncParams (fparams ++ [varargs]) Nothing
  compileSpecialFormBody env ast copts (\ _ -> do
    bodyEnv <- liftIO $ extendEnv env []
    -- bind lambda params in the extended env
    _ <- defineLambdaVars bodyEnv $ (Atom var : fparams) ++ [varargs]
   
    Atom symCallfunc <- _gensym "defineFuncEntryPt"
    compiledParams <- compileLambdaList fparams
    compiledBody <- compileBlock symCallfunc Nothing bodyEnv [] fbody
   
    -- Store var in huskc's env for macro processing (and same for other vers of define)
    ebody <- mapM (\ lisp -> Language.Scheme.Macro.macroEval env lisp LSC.apply) fbody
    _ <- makeVarargs varargs env fparams ebody >>= defineVar env var
   
    -- Entry point; ensure var is not rebound
    f <- return $ [
      AstValue $ "  result <- makeHVarargs (" ++ ast2Str varargs ++ ") env (" ++ 
                       compiledParams ++ ") " ++ symCallfunc,
      AstValue $ "  _ <- defineVar env \"" ++ var ++ "\" result ",
      createAstCont copts "result" "" ]
    return $ [createAstFunc copts f] ++ compiledBody)

compile env ast@(List (Atom "lambda" : List fparams : fbody)) 
        copts@(CompileOptions _ _ _ _) = do
  _ <- validateFuncParams fparams Nothing
  compileSpecialFormBody env ast copts (\ _ -> do
    Atom symCallfunc <- _gensym "lambdaFuncEntryPt"
    compiledParams <- compileLambdaList fparams
   
    bodyEnv <- liftIO $ extendEnv env []
    -- bind lambda params in the extended env
    _ <- defineLambdaVars bodyEnv fparams
   
    compiledBody <- compileBlock symCallfunc Nothing bodyEnv [] fbody
   
    -- Entry point; ensure var is not rebound
    f <- return $ [
          AstValue $ "  result <- makeNormalHFunc env (" ++ compiledParams ++ 
                     ") " ++ symCallfunc,
          createAstCont copts "result" ""
          ]
    return $ [createAstFunc copts f] ++ compiledBody)

compile env ast@(List (Atom "lambda" : DottedList fparams varargs : fbody)) 
        copts@(CompileOptions _ _ _ _) = do
  _ <- validateFuncParams (fparams ++ [varargs]) Nothing
  compileSpecialFormBody env ast copts (\ _ -> do
    Atom symCallfunc <- _gensym "lambdaFuncEntryPt"
    compiledParams <- compileLambdaList fparams
   
    bodyEnv <- liftIO $ extendEnv env []
    -- bind lambda params in the extended env
    _ <- defineLambdaVars bodyEnv $ fparams ++ [varargs]
   
    compiledBody <- compileBlock symCallfunc Nothing bodyEnv [] fbody
   
    -- Entry point; ensure var is not rebound
    f <- return $ [
      AstValue $ "  result <- makeHVarargs (" ++ ast2Str varargs ++ ") env (" ++ 
         compiledParams ++ ") " ++ symCallfunc,
      createAstCont copts "result" "" ]
    return $ [createAstFunc copts f] ++ compiledBody)

compile env ast@(List (Atom "lambda" : varargs@(Atom _) : fbody)) 
        copts@(CompileOptions _ _ _ _) = do
  compileSpecialFormBody env ast copts (\ _ -> do
    Atom symCallfunc <- _gensym "lambdaFuncEntryPt"
   
    bodyEnv <- liftIO $ extendEnv env []
    -- bind lambda params in the extended env
    _ <- defineLambdaVars bodyEnv [varargs]
   
    compiledBody <- compileBlock symCallfunc Nothing bodyEnv [] fbody
   
    -- Entry point; ensure var is not rebound
    f <- return $ [
          AstValue $ "  result <- makeHVarargs (" ++ ast2Str varargs ++ ") env [] " ++ symCallfunc,
          createAstCont copts "result" ""
          ]
    return $ [createAstFunc copts f] ++ compiledBody)

compile env ast@(List [Atom "string-set!", Atom var, i, character]) copts = do
  compileSpecialFormBody env ast copts (\ _ -> do
    Atom symDefine <- _gensym "stringSetFunc"
    Atom symMakeDefine <- _gensym "stringSetFuncMakeSet"
    Atom symChr <- _gensym "stringSetChar"
    Atom symCompiledI <- _gensym "stringI"
   
    entryPt <- compileSpecialFormEntryPoint "string-set!" symChr copts
    compChr <- compileExpr env character symChr $ Just symDefine
    compDefine <- return $ AstFunction symDefine " env cont chr _ " [
        AstValue $ "  " ++ symCompiledI ++ " env (makeCPSWArgs env cont " ++ 
          symMakeDefine ++ " [chr]) (Nil \"\") (Just []) " ]
    compI <- compileExpr env i symCompiledI Nothing
    compMakeDefine <- return $ AstFunction symMakeDefine " env cont idx (Just [chr]) " [
       AstValue $ "  tmp <- getVar env \"" ++ var ++ "\"",
       AstValue $ "  derefValue <- recDerefPtrs tmp",
       AstValue $ "  result <- substr (derefValue, chr, idx)",
       AstValue $ "  _ <- updateObject env \"" ++ var ++ "\" result",
       createAstCont copts "result" ""]
    return $ [entryPt, compDefine, compMakeDefine] ++ compI ++ compChr)

compile env ast@(List [Atom "string-set!", nonvar, _, _]) copts = do 
  compileSpecialFormBody env ast copts (\ _ -> do
    f <- compileSpecialForm "string-set!" ("throwError $ TypeMismatch \"variable\"" ++
                            " $ String \"" ++ (show nonvar) ++ "\"")  copts
    return [f])
compile env ast@(List (Atom "string-set!" : args)) copts = do
  compileSpecialFormBody env ast copts (\ _ -> do
    f <- compileSpecialForm "string-set!" ("throwError $ NumArgs 3 $ [String \"" ++ 
            (show args) ++ "\"]") copts
    return [f])

compile env ast@(List [Atom "set-car!", Atom var, argObj]) copts = do
  compileSpecialFormBody env ast copts (\ _ -> do
    Atom symGetVar <- _gensym "setCarGetVar"
    Atom symCompiledObj <- _gensym "setCarCompiledObj"
    Atom symObj <- _gensym "setCarObj"
    Atom symDoSet <- _gensym "setCarDoSet"
   
    -- Code to all into next continuation from copts, if one exists
    let finalContinuation = case copts of
          (CompileOptions _ _ _ (Just nextFunc)) -> "continueEval e (makeCPSWArgs e c " ++ nextFunc ++ " [])\n"
          _ -> "continueEval e c\n"
   
    -- Entry point that allows set-car! to be redefined
    entryPt <- compileSpecialFormEntryPoint "set-car!" symGetVar copts
   
    -- Function to read existing var
    compGetVar <- return $ AstFunction symGetVar " env cont idx _ " [
       AstValue $ "  result <- getVar env \"" ++ var ++ "\"",
       AstValue $ "  derefValue <- recDerefPtrs result",
       AstValue $ "  " ++ symObj ++ " env cont derefValue (Just []) "]
   
    -- Compiled version of argObj
    compiledObj <- compileExpr env argObj symCompiledObj Nothing 
   
    -- Function to check looked-up var and call into appropriate handlers; 
    -- based on code from Core
    --
    -- This is so verbose because we need to have overloads of symObj to 
    -- deal with many possible inputs.
    -- FUTURE: consider making these functions part of the runtime.
    compObj <- return $ AstValue $ "" ++
      symObj ++ " :: Env -> LispVal -> LispVal -> Maybe [LispVal] -> IOThrowsError LispVal\n" ++
      symObj ++ " _ _ obj@(List []) _ = throwError $ TypeMismatch \"pair\" obj\n" ++
      symObj ++ " e c obj@(List (_ : _)) _ = " ++ symCompiledObj ++ " e (makeCPSWArgs e c " ++ symDoSet ++ " [obj]) (Nil \"\") Nothing\n" ++
      symObj ++ " e c obj@(DottedList _ _) _ = " ++ symCompiledObj ++ " e (makeCPSWArgs e c " ++ symDoSet ++ " [obj]) (Nil \"\") Nothing\n" ++
      symObj ++ " _ _ obj _ = throwError $ TypeMismatch \"pair\" obj\n"
   
    -- Function to do the actual (set!), based on code from Core
    --
    -- This is so verbose because we need to have overloads of symObj to deal 
    -- with many possible inputs.
    -- FUTURE: consider making these functions part of the runtime.
    compDoSet <- return $ AstValue $ "" ++
                 symDoSet ++ " :: Env -> LispVal -> LispVal -> Maybe [LispVal] -> IOThrowsError LispVal\n" ++
                 symDoSet ++ " e c obj (Just [List (_ : ls)]) = updateObject e \"" ++ var ++ "\" (List (obj : ls)) >>= " ++ finalContinuation ++
                 symDoSet ++ " e c obj (Just [DottedList (_ : ls) l]) = updateObject e \"" ++ var ++ "\" (DottedList (obj : ls) l) >>= " ++ finalContinuation ++
                 symDoSet ++ " _ _ _ _ = throwError $ InternalError \"Unexpected argument to " ++ symDoSet ++ "\"\n"
   
    -- Return a list of all the compiled code
    return $ [entryPt, compGetVar, compObj, compDoSet] ++ compiledObj)

compile env ast@(List [Atom "set-car!", nonvar, _]) copts = do 
  compileSpecialFormBody env ast copts (\ _ -> do
    f <- compileSpecialForm "set-car!" ("throwError $ TypeMismatch \"variable\"" ++
                            " $ String \"" ++ (show nonvar) ++ "\"")  copts
    return [f])
compile env ast@(List (Atom "set-car!" : args)) copts = do
  compileSpecialFormBody env ast copts (\ _ -> do
    f <- compileSpecialForm "set-car!" ("throwError $ NumArgs 2 $ [String \"" ++ 
            (show args) ++ "\"]") copts
    return [f])

compile env ast@(List [Atom "set-cdr!", Atom var, argObj]) copts = do
  compileSpecialFormBody env ast copts (\ _ -> do
    Atom symGetVar <- _gensym "setCdrGetVar"
    Atom symCompiledObj <- _gensym "setCdrCompiledObj"
    Atom symObj <- _gensym "setCdrObj"
    Atom symDoSet <- _gensym "setCdrDoSet"
   
    -- Code to all into next continuation from copts, if one exists
    let finalContinuation = case copts of
          (CompileOptions _ _ _ (Just nextFunc)) -> "continueEval e (makeCPSWArgs e c " ++ nextFunc ++ " [])\n"
          _ -> "continueEval e c\n"
   
    -- Entry point that allows set-car! to be redefined
    entryPt <- compileSpecialFormEntryPoint "set-car!" symGetVar copts
   
    -- Function to read existing var
    compGetVar <- return $ AstFunction symGetVar " env cont idx _ " [
       AstValue $ "  result <- getVar env \"" ++ var ++ "\"",
       AstValue $ "  derefValue <- recDerefPtrs result",
       AstValue $ "  " ++ symObj ++ " env cont derefValue (Just []) "]
   
    -- Compiled version of argObj
    compiledObj <- compileExpr env argObj symCompiledObj Nothing 
   
    -- Function to check looked-up var and call into appropriate handlers; based on code from Core
    --
    -- This is so verbose because we need to have overloads of symObj to deal with many possible inputs.
    -- FUTURE: consider making these functions part of the runtime.
    compObj <- return $ AstValue $ "" ++
      symObj ++ " :: Env -> LispVal -> LispVal -> Maybe [LispVal] -> IOThrowsError LispVal\n" ++
      symObj ++ " _ _ obj@(List []) _ = throwError $ TypeMismatch \"pair\" obj\n" ++
   -- TODO: below, we want to make sure obj is of the right type. if so, 
   -- compile obj and call into the "set" 
   --       function below to do the actual set-car
      symObj ++ " e c obj@(List (_ : _)) _ = " ++ symCompiledObj ++ " e (makeCPSWArgs e c " ++ symDoSet ++ " [obj]) (Nil \"\") Nothing\n" ++
      symObj ++ " e c obj@(DottedList _ _) _ = " ++ symCompiledObj ++ " e (makeCPSWArgs e c " ++ symDoSet ++ " [obj]) (Nil \"\") Nothing\n" ++
      symObj ++ " _ _ obj _ = throwError $ TypeMismatch \"pair\" obj\n"
   
    -- Function to do the actual (set!), based on code from Core
    --
    -- This is so verbose because we need to have overloads of symObj 
    -- to deal with many possible inputs.
    -- FUTURE: consider making these functions part of the runtime.
    compDoSet <- return $ AstValue $ "" ++
      symDoSet ++ " :: Env -> LispVal -> LispVal -> Maybe [LispVal] -> IOThrowsError LispVal\n" ++
      symDoSet ++ " e c obj (Just [List (l : _)]) = do\n" ++
                  "   l' <- recDerefPtrs l\n" ++
                  "   obj' <- recDerefPtrs obj\n" ++
                  "   (cons [l', obj']) >>= updateObject e \"" ++ var ++ "\" >>= " ++ finalContinuation ++
      symDoSet ++ " e c obj (Just [DottedList (l : _) _]) = do\n" ++
                  "   l' <- recDerefPtrs l\n" ++
                  "   obj' <- recDerefPtrs obj\n" ++
                  "   (cons [l', obj']) >>= updateObject e \"" ++ var ++ "\" >>= " ++ finalContinuation ++
      symDoSet ++ " _ _ _ _ = throwError $ InternalError \"Unexpected argument to " ++ symDoSet ++ "\"\n"
   
    -- Return a list of all the compiled code
    return $ [entryPt, compGetVar, compObj, compDoSet] ++ compiledObj)

compile env ast@(List [Atom "set-cdr!", nonvar, _]) copts = do 
  compileSpecialFormBody env ast copts (\ _ -> do
    f <- compileSpecialForm "set-cdr!" ("throwError $ TypeMismatch \"variable\"" ++
                            " $ String \"" ++ (show nonvar) ++ "\"")  copts
    return [f])
compile env ast@(List (Atom "set-cdr!" : args)) copts = do
  compileSpecialFormBody env ast copts (\ _ -> do
    f <- compileSpecialForm "set-cdr!" ("throwError $ NumArgs 2 $ [String \"" ++ 
            (show args) ++ "\"]") copts
    return [f])

compile env ast@(List [Atom "list-set!", Atom var, i, object]) copts = do
  compileSpecialFormBody env ast copts (\ _ -> do
    Atom symCompiledIdx <- _gensym "listSetIdx"
    Atom symCompiledObj <- _gensym "listSetObj"
    Atom symUpdateVec <- _gensym "listSetUpdate"
    Atom symIdxWrapper <- _gensym "listSetIdxWrapper"
   
    -- Entry point that allows this form to be redefined
    entryPt <- compileSpecialFormEntryPoint "list-set!" symCompiledIdx copts
    -- Compile index, then use a wrapper to pass it as an arg while compiling obj
    compiledIdx <- compileExpr env i symCompiledIdx (Just symIdxWrapper) 
    compiledIdxWrapper <- return $ AstFunction symIdxWrapper " env cont idx _ " [
       AstValue $ "  " ++ symCompiledObj ++ " env (makeCPSWArgs env cont " ++ symUpdateVec ++ " [idx]) (Nil \"\") (Just []) " ]
    compiledObj <- compileExpr env object symCompiledObj Nothing
    -- Do actual update
    compiledUpdate <- return $ AstFunction symUpdateVec " env cont obj (Just [idx]) " [
       AstValue $ "  vec <- getVar env \"" ++ var ++ "\"",
       AstValue $ "  result <- updateList vec idx obj >>= updateObject env \"" ++ var ++ "\"",
       createAstCont copts "result" ""]
   
    return $ [entryPt, compiledIdxWrapper, compiledUpdate] ++ compiledIdx ++ compiledObj)

compile env ast@(List [Atom "list-set!", nonvar, _, _]) copts = do 
  compileSpecialFormBody env ast copts (\ _ -> do
    f <- compileSpecialForm "list-set!" ("throwError $ TypeMismatch \"variable\"" ++
                            " $ String \"" ++ (show nonvar) ++ "\"")  copts
    return [f])
compile env ast@(List (Atom "list-set!" : args)) copts = do
  compileSpecialFormBody env ast copts (\ _ -> do
    f <- compileSpecialForm "list-set!" ("throwError $ NumArgs 3 $ [String \"" ++ 
            (show args) ++ "\"]") copts
    return [f])

compile env ast@(List [Atom "vector-set!", Atom var, i, object]) copts = do
  compileSpecialFormBody env ast copts (\ _ -> do
    Atom symCompiledIdx <- _gensym "vectorSetIdx"
    Atom symCompiledObj <- _gensym "vectorSetObj"
    Atom symUpdateVec <- _gensym "vectorSetUpdate"
    Atom symIdxWrapper <- _gensym "vectorSetIdxWrapper"
   
    -- Entry point that allows this form to be redefined
    entryPt <- compileSpecialFormEntryPoint "vector-set!" symCompiledIdx copts
    -- Compile index, then use a wrapper to pass it as an arg while compiling obj
    compiledIdx <- compileExpr env i symCompiledIdx (Just symIdxWrapper) 
    compiledIdxWrapper <- return $ AstFunction symIdxWrapper " env cont idx _ " [
       AstValue $ "  " ++ symCompiledObj ++ " env (makeCPSWArgs env cont " ++ symUpdateVec ++ " [idx]) (Nil \"\") (Just []) " ]
    compiledObj <- compileExpr env object symCompiledObj Nothing
    -- Do actual update
    compiledUpdate <- return $ AstFunction symUpdateVec " env cont obj (Just [idx]) " [
       AstValue $ "  vec <- getVar env \"" ++ var ++ "\"",
       AstValue $ "  result <- updateVector vec idx obj >>= updateObject env \"" ++ var ++ "\"",
       createAstCont copts "result" ""]
   
    return $ [entryPt, compiledIdxWrapper, compiledUpdate] ++ compiledIdx ++ compiledObj)

compile env ast@(List [Atom "vector-set!", nonvar, _, _]) copts = do 
  compileSpecialFormBody env ast copts (\ _ -> do
    f <- compileSpecialForm "vector-set!" ("throwError $ TypeMismatch \"variable\"" ++
                            " $ String \"" ++ (show nonvar) ++ "\"")  copts
    return [f])
compile env ast@(List (Atom "vector-set!" : args)) copts = do
  compileSpecialFormBody env ast copts (\ _ -> do
    f <- compileSpecialForm "vector-set!" ("throwError $ NumArgs 3 $ [String \"" ++ 
            (show args) ++ "\"]") copts
    return [f])


compile env ast@(List [Atom "bytevector-u8-set!", Atom var, i, object]) copts = do
  compileSpecialFormBody env ast copts (\ _ -> do
    Atom symCompiledIdx <- _gensym "bytevectorSetIdx"
    Atom symCompiledObj <- _gensym "bytevectorSetObj"
    Atom symUpdateVec <- _gensym "bytevectorSetUpdate"
    Atom symIdxWrapper <- _gensym "bytevectorSetIdxWrapper"
   
    -- Entry point that allows this form to be redefined
    entryPt <- compileSpecialFormEntryPoint "bytevector-u8-set!" symCompiledIdx copts
    -- Compile index, then use a wrapper to pass it as an arg while compiling obj
    compiledIdx <- compileExpr env i symCompiledIdx (Just symIdxWrapper) 
    compiledIdxWrapper <- return $ AstFunction symIdxWrapper " env cont idx _ " [
       AstValue $ "  " ++ symCompiledObj ++ " env (makeCPSWArgs env cont " ++ symUpdateVec ++ " [idx]) (Nil \"\") (Just []) " ]
    compiledObj <- compileExpr env object symCompiledObj Nothing
    -- Do actual update
    compiledUpdate <- return $ AstFunction symUpdateVec " env cont obj (Just [idx]) " [
       AstValue $ "  vec <- getVar env \"" ++ var ++ "\"",
       AstValue $ "  result <- updateByteVector vec idx obj >>= updateObject env \"" ++ var ++ "\"",
       createAstCont copts "result" ""]
   
    return $ [entryPt, compiledIdxWrapper, compiledUpdate] ++ compiledIdx ++ compiledObj)

compile env ast@(List [Atom "bytevector-u8-set!", nonvar, _, _]) copts = do 
  compileSpecialFormBody env ast copts (\ _ -> do
    f <- compileSpecialForm "bytevector-u8-set!" ("throwError $ TypeMismatch \"variable\"" ++
                            " $ String \"" ++ (show nonvar) ++ "\"")  copts
    return [f])
compile env ast@(List (Atom "bytevector-u8-set!" : args)) copts = do
  compileSpecialFormBody env ast copts (\ _ -> do
    f <- compileSpecialForm "bytevector-u8-set!" ("throwError $ NumArgs 3 $ [String \"" ++ 
            (show args) ++ "\"]") copts
    return [f])

compile env ast@(List [Atom "hash-table-set!", Atom var, rkey, rvalue]) copts = do
  compileSpecialFormBody env ast copts (\ _ -> do
    Atom symCompiledIdx <- _gensym "hashTableSetIdx"
    Atom symCompiledObj <- _gensym "hashTableSetObj"
    Atom symUpdateVec <- _gensym "hashTableSetUpdate"
    Atom symIdxWrapper <- _gensym "hashTableSetIdxWrapper"
   
    -- Entry point that allows this form to be redefined
    entryPt <- compileSpecialFormEntryPoint "hash-table-set!" symCompiledIdx copts
    -- Compile index, then use a wrapper to pass it as an arg while compiling obj
    compiledIdx <- compileExpr env rkey symCompiledIdx (Just symIdxWrapper) 
    compiledIdxWrapper <- return $ AstFunction symIdxWrapper " env cont idx _ " [
       AstValue $ "  " ++ symCompiledObj ++ " env (makeCPSWArgs env cont " ++ symUpdateVec ++ " [idx]) (Nil \"\") (Just []) " ]
    compiledObj <- compileExpr env rvalue symCompiledObj Nothing
    -- Do actual update
    compiledUpdate <- return $ AstFunction symUpdateVec " env cont obj (Just [rkey]) " [
       -- TODO: this should be more robust, than just assuming ht is a HashTable
       AstValue $ "  HashTable ht <- getVar env \"" ++ var ++ "\"",
       AstValue $ "  HashTable ht' <- recDerefPtrs $ HashTable ht",
       AstValue $ "  result <- updateObject env \"" ++ var ++ "\" (HashTable $ Data.Map.insert rkey obj ht') ",
       createAstCont copts "result" ""]
   
    return $ [entryPt, compiledIdxWrapper, compiledUpdate] ++ compiledIdx ++ compiledObj)

compile env ast@(List [Atom "hash-table-set!", nonvar, _, _]) copts = do 
  compileSpecialFormBody env ast copts (\ _ -> do
    f <- compileSpecialForm "hash-table-set!" ("throwError $ TypeMismatch \"variable\"" ++
                            " $ String \"" ++ (show nonvar) ++ "\"")  copts
    return [f])
compile env ast@(List (Atom "hash-table-set!" : args)) copts = do
  compileSpecialFormBody env ast copts (\ _ -> do
    f <- compileSpecialForm "hash-table-set!" ("throwError $ NumArgs 3 $ [String \"" ++ 
            (show args) ++ "\"]") copts
    return [f])

compile env ast@(List [Atom "hash-table-delete!", Atom var, rkey]) copts = do
  compileSpecialFormBody env ast copts (\ _ -> do
    Atom symCompiledIdx <- _gensym "hashTableDeleteIdx"
    Atom symDoDelete <- _gensym "hashTableDelete"
   
    -- Entry point that allows this form to be redefined
    entryPt <- compileSpecialFormEntryPoint "hash-table-delete!" symCompiledIdx copts
    -- Compile index, then use a wrapper to pass it as an arg while compiling obj
    compiledIdx <- compileExpr env rkey symCompiledIdx (Just symDoDelete) 
    -- Do actual update
    compiledUpdate <- return $ AstFunction symDoDelete " env cont rkey _ " [
       -- TODO: this should be more robust, than just assuming ht is a HashTable
       AstValue $ "  HashTable ht <- getVar env \"" ++ var ++ "\"",
       AstValue $ "  HashTable ht' <- recDerefPtrs $ HashTable ht",
       AstValue $ "  result <- updateObject env \"" ++ var ++ "\" (HashTable $ Data.Map.delete rkey ht') ",
       createAstCont copts "result" ""]
   
    return $ [entryPt, compiledUpdate] ++ compiledIdx)

compile env ast@(List [Atom "hash-table-delete!", nonvar, _]) copts = do 
  compileSpecialFormBody env ast copts (\ _ -> do
    f <- compileSpecialForm "hash-table-delete!" ("throwError $ TypeMismatch \"variable\"" ++
                            " $ String \"" ++ (show nonvar) ++ "\"")  copts
    return [f])
compile env ast@(List (Atom "hash-table-delete!" : args)) copts = do
  compileSpecialFormBody env ast copts (\ _ -> do
    f <- compileSpecialForm "hash-table-delete!" ("throwError $ NumArgs 2 $ [String \"" ++ 
            (show args) ++ "\"]") copts
    return [f])

compile env ast@(List (Atom "%import" : args)) copts = do
  compileSpecialFormBody env ast copts (\ _ -> do
    throwError $ NotImplemented $ "%import, with args: " ++ show args)

compile env (List [a@(Atom "husk-interpreter?")]) copts = do
    mfunc env (List [a, Bool True]) compile copts 

compile env args@(List [Atom "load", filename, envSpec]) copts = do
  -- Explicitly do NOT call compileSpecialFormBody here, since load is not normally a special form

  -- F*ck it, just run the evaluator here since filename is req'd at compile time
  fname <- LSC.evalLisp env filename
  case fname of
    -- Compile contents of the file
    String fn -> compileFile fn

    -- Unable to get filename at compile time, fall back to loading at runtime
    _ -> mfunc env args compileApply copts

 where 
 compileFile filename' = do
  Atom symEnv <- _gensym "loadEnv"
  Atom symLoad <- _gensym "load"
  compEnv <- compileExpr env envSpec symEnv
                         Nothing -- Return env to our custom func

  -- WORKAROUND #1
  -- Special case to support require-extension
  env' <- case envSpec of
               Atom a -> do
                   v <- getVar env a
                   case v of
                       LispEnv e -> return e
                       _ -> return env
               _ -> return env
  -- End special case

  compLoad <- compileLisp env' filename' symLoad Nothing
 
  -- Entry point
  f <- return $ [
    -- TODO: should do runtime error checking if something else
    --       besides a LispEnv is returned
    AstValue $ "  LispEnv e <- " ++ symEnv ++ " env (makeNullContinuation env) (Nil \"\") (Just []) ",
    AstValue $ "  result <- " ++ symLoad ++ " e (makeNullContinuation e) (Nil \"\") Nothing",
    createAstCont copts "result" ""]
  -- Join compiled code together
  return $ [createAstFunc copts f] ++ compEnv ++ compLoad

compile env (List [Atom "load", filename]) copts = do -- TODO: allow filename from a var, support env optional arg
 -- TODO: error handling for string below
 String filename' <- LSC.evalLisp env filename
 Atom symEntryPt <- _gensym "load"
 result <- compileLisp env filename' symEntryPt Nothing
 return $ result ++ 
   [createAstFunc copts [
    AstValue $ "  result <- " ++ symEntryPt ++ 
               " env (makeNullContinuation env) (Nil \"\") Nothing",
    createAstCont copts "result" ""]]

-- FUTURE: eventually it should be possible to evaluate the args instead of assuming
-- that they are all strings, but lets keep it simple for now
compile env (List [Atom "load-ffi", 
                        String moduleName, 
                        String externalFuncName, 
                        String internalFuncName]) copts = do
--  Atom symLoadFFI <- _gensym "loadFFI"

  -- Only append module again if it is not already in the list
  List l <- getNamespacedVar env 't' {-"internal"-} "imports"
  _ <- if not ((String moduleName) `elem` l)
          then setNamespacedVar env 't' {-"internal"-} "imports" $ 
                                List $ l ++ [String moduleName]
          else return $ String ""

  -- Pass along moduleName as another top-level import
  return [createAstFunc copts [
    AstValue $ "  result <- defineVar env \"" ++ 
        internalFuncName ++ "\" $ IOFunc " ++ 
        moduleName ++ "." ++ externalFuncName,
    createAstCont copts "result" ""]]

compile env args@(List (_ : _)) copts = mfunc env args compileApply copts 
compile _ badForm _ = throwError $ BadSpecialForm "Unrecognized special form" badForm

-- |Expand macros and compile the resulting code
mcompile :: Env -> LispVal -> CompOpts -> IOThrowsError [HaskAST]
mcompile env lisp copts = mfunc env lisp compile copts

-- |Expand macros and then pass control to the given function 
mfunc :: Env
      -> LispVal 
      -> (Env -> LispVal -> CompOpts -> IOThrowsError [HaskAST]) 
      -> CompOpts 
      -> IOThrowsError [HaskAST] 
mfunc env lisp func copts = do
  expanded <- Language.Scheme.Macro.macroEval env lisp LSC.apply
  divertVars env expanded copts func

-- |Do the actual insertion of diverted variables back to the 
--  compiled program.
divertVars 
    :: Env 
    -- ^ Current compile Environment
    -> LispVal
    -- ^ Lisp code after macro expansion
    -> CompOpts
    -- ^ Compiler options
    -> (Env -> LispVal -> CompOpts -> IOThrowsError [HaskAST])
    -- ^ Continuation to call into after vars are diverted
    -> IOThrowsError [HaskAST]
    -- ^ Code generated by the continuation, along with the code
    --   added to divert vars to the compiled program
divertVars env expanded copts@(CompileOptions _ uvar uargs nfnc) func = do
  vars <- Language.Scheme.Macro.getDivertedVars env
  case vars of 
    [] -> func env expanded copts
    _ -> do 
      Atom symNext <- _gensym "afterDivert"
      diverted <- compileDivertedVars symNext env vars copts
      rest <- func env expanded $ CompileOptions symNext uvar uargs nfnc
      return $ [diverted] ++ rest

-- |Take a list of variables diverted into env at compile time, and
--  divert them into the env at runtime
compileDivertedVars :: String -> Env -> [LispVal] -> CompOpts -> IOThrowsError HaskAST
compileDivertedVars 
  formNext _ vars 
  copts@(CompileOptions _ useVal useArgs _) = do
  let val = case useVal of
        True -> "value"
        _ -> "Nil \"\""
      args = case useArgs of
        True -> "(Just args)"
        _ -> "(Just [])"
      comp (List [Atom renamed, Atom orig]) = do
        [AstValue $ "  v <- getVar env \"" ++ orig ++ "\"",
         AstValue $ "  _ <- defineVar env \"" ++ renamed ++ "\" v"]
      comp _ = []
      cvars = map comp vars 
      f = (concat cvars) ++ 
          [AstValue $ "  " ++ formNext ++ " env cont (" ++ val ++ ") " ++ args]
  return $ createAstFunc copts f

-- |Create the function entry point for a special form
compileSpecialFormEntryPoint :: String -> String -> CompOpts -> IOThrowsError HaskAST
compileSpecialFormEntryPoint formName formSym copts = do
 compileSpecialForm formName ("" ++ formSym ++ " env cont (Nil \"\") (Just [])") copts

-- | Helper function for compiling a special form
compileSpecialForm :: String -> String -> CompOpts -> IOThrowsError HaskAST
compileSpecialForm _ formCode copts = do
 f <- return $ [
       AstValue $ "  " ++ formCode]
 return $ createAstFunc copts f

-- |A wrapper for each special form that allows the form variable 
--  (EG: "if") to be redefined at compile time
compileSpecialFormBody :: Env
                       -> LispVal
                       -> CompOpts
                       -> (Maybe String -> ErrorT LispError IO [HaskAST])
                       -> ErrorT LispError IO [HaskAST]
compileSpecialFormBody env 
                       ast@(List (Atom fnc : _)) 
                       copts@(CompileOptions _ _ _ nextFunc) 
                       spForm = do
  isDefined <- liftIO $ isRecBound env fnc
  case isDefined of
    True -> mfunc env ast compileApply copts 
    False -> spForm nextFunc
compileSpecialFormBody _ _ _ _ = throwError $ InternalError "compileSpecialFormBody"

-- | Compile an intermediate expression (such as an arg to if) and 
--   call into the next continuation with it's value
compileExpr :: Env -> LispVal -> String -> Maybe String -> IOThrowsError [HaskAST]
compileExpr env expr symThisFunc fForNextExpr = do
  mcompile env expr (CompileOptions symThisFunc False False fForNextExpr) 

-- |Compile a function call
compileApply :: Env -> LispVal -> CompOpts -> IOThrowsError [HaskAST]
compileApply env (List (func : fparams)) copts@(CompileOptions coptsThis _ _ coptsNext) = do

--
-- TODO: it is probably possible to mix creating conts and not when there are func and non-func args.
--  
--  _ <- case (trace ("calling compileApply: " ++ show (List (func : fparams))) func) of
  _ <- case func of
    List _ -> return $ Nil ""
    Atom _ -> return $ Nil "" 
    _ -> throwError $ BadSpecialForm "Unable to evaluate form" $ List (func : fparams)

  primitive <- isPrim env func
  let literals = collectLiterals fparams 
      nonFunctionCalls = collectLiteralsAndVars fparams

  case (primitive, literals, nonFunctionCalls) of
     -- Primitive (non-I/O) function with literal args, 
     -- evaluate at compile time
     (Just primFunc, Just ls, _) -> do
       result <- LSC.apply 
        (makeNullContinuation env)
        primFunc
        ls

       return $ [createAstFunc copts [
         AstValue $ "  let result = " ++ (ast2Str result),
         createAstCont copts "result" ""]]

     -- Other function with literal args, no need to create a
     -- continuation chain. But this case may include I/O funcs and
     -- variables, so everything must be executed at runtime
     (_, _, Just ls) -> compileFuncLitArgs ls
     
     -- Any other function, do it the hard way...
     --
     -- Compile the function and each argument as a link in
     -- a chain of continuations.
     _ -> compileAllArgs func

 where 
  -- |Compile a function call that contains arguments that are not
  --  function calls executed at runtime.
  compileFuncLitArgs args = do
       -- Keep track of any variables since we need to do a
       -- 'getRtVar' lookup for each of them prior to apply
       let pack (Atom p : ps) strs vars i = do
             let varName = "v" ++ show i
             pack ps 
                  (strs ++ [varName]) 
                  (vars ++ [(p, varName)]) 
                  (i + 1)
           pack (p : ps) strs vars i = 
             pack ps 
                  (strs ++ [ast2Str p]) 
                  vars 
                  i
           pack [] strs vars _ = (strs, vars)
       let (paramStrs, vars) = pack args [] [] (0::Int)
       _compileFuncLitArgs func vars $ "[" ++ joinL paramStrs "," ++ "]"

  _compileFuncLitArgs fnc vars args = do
    Atom stubFunc <- _gensym "applyStubF"
    Atom nextFunc <- _gensym "applyNextF"

    c <- return $ 
      AstFunction coptsThis " env cont _ _ " [
        AstValue $ "  continueEval env (makeCPSWArgs env (makeCPSWArgs env cont " ++ 
                   nextFunc ++ " []) " ++ stubFunc ++ " []) $ Nil\"\""]  
    _comp <- mcompile env fnc $ CompileOptions stubFunc False False Nothing

    -- Haskell variables must be used to retrieve each atom from the env
    let varLines = 
          map (\ (rt, cp) -> 
                  AstValue $ "  " ++ cp ++ " <- getRTVar env \"" ++ rt ++ "\"")
              vars

    rest <- case coptsNext of
             Nothing -> return $ [
               AstFunction nextFunc
                " env cont value _ " $ varLines ++ 
                [AstValue $ "  apply cont value " ++ args]]
             Just fnextExpr -> return $ [
               AstFunction nextFunc 
                " env cont value _ " $ varLines ++ 
                [AstValue $ "  apply (makeCPSWArgs env cont " ++ 
                            fnextExpr ++ " []) value " ++ args]]
    return $ [c] ++ _comp ++ rest

  -- |Compile function and args as a chain of continuations
-- TODO:
  compileAllArgs (Atom fncName) = do
    rest <- case fparams of
    --rest <- case (trace "fncName" fparams) of
              [] -> do
                  throwError $ Default $ " unreachable code in compileAllArgs for " ++ fncName
--                fnc <- compileInlineVar env fncName "fnc"
--                return [AstFunction 
--                          coptsThis
--                          " env cont (Nil _) (Just (a:as)) "
--                          [fnc,
--                           AstValue $ "  apply " ++ applyCont ++ " fnc (a:as) "],
--                        AstFunction 
--                          coptsThis
--                          " env cont value (Just (a:as)) " 
--                          [fnc,
--                           AstValue $ "  apply " ++ applyCont ++ " fnc $ (a:as) ++ [value] "]]
              _ -> compileArgs coptsThis True (Just fncName) fparams -- True, passing fnc as value
    return $ rest
    --return $ [c, wrapper ] ++ _comp ++ rest
  compileAllArgs func' = do
    Atom stubFunc <- _gensym "applyStubF"
    Atom wrapperFunc <- _gensym "applyWrapper"
    Atom nextFunc <- _gensym "applyNextF"

    c <- return $ 
      AstFunction coptsThis " env cont _ _ " [
        AstValue $ "  continueEval env (makeCPSWArgs env (makeCPSWArgs env cont " ++ 
                   wrapperFunc ++ " []) " ++ stubFunc ++ " []) $ Nil\"\""]  
    -- Use wrapper to pass high-order function (func) as an argument to apply
    wrapper <- return $ 
      AstFunction wrapperFunc " env cont value _ " [
          AstValue $ "  continueEval env (makeCPSWArgs env cont " ++ 
                     nextFunc ++ " [value]) $ Nil \"\""]
    _comp <- mcompile env func' $ CompileOptions stubFunc False False Nothing

    rest <- case fparams of
              [] -> do
                return [AstFunction 
                          nextFunc 
                          " env cont (Nil _) (Just (a:as)) "
                          [AstValue $ "  apply " ++ applyCont ++ " a as "],
                        AstFunction 
                          nextFunc 
                          " env cont value (Just (a:as)) " 
                          [AstValue $ "  apply " ++ applyCont ++ " a $ as ++ [value] "]]
              _ -> compileArgs nextFunc False Nothing fparams -- False since no value passed in this time
    return $ [c, wrapper ] ++ _comp ++ rest

  applyCont :: String
  applyCont = case coptsNext of
                Nothing -> "cont"
                Just fnextExpr -> "(makeCPSWArgs env cont " ++ fnextExpr ++ " [])"

  -- |Compile each argument as its own continuation (lambda), and then
  --  call the function using "applyWrapper"
  compileArgs :: String -> Bool -> (Maybe String) -> [LispVal] -> IOThrowsError [HaskAST]
  compileArgs thisFunc thisFuncUseValue maybeFnc args = do
    case args of
      (a:as) -> do
        let (asRest, asLiterals) = (as, []) --TODO: takeLiterals a as
        let lastArg = null asRest
        Atom stubFunc <- _gensym "applyFirstArg" -- Call into compiled stub
        Atom nextFunc <- do
            case lastArg of
                True -> return $ Atom "applyWrapper" -- Use wrapper to call into 'apply'
                _ -> _gensym "applyNextArg" -- Next func argument to execute...
        _comp <- mcompile env a $ CompileOptions stubFunc thisFuncUseValue False Nothing

        -- inline function?
        fnc <- case maybeFnc of
                 Just fncName -> compileInlineVar env fncName "value"
                 _ -> return $ AstValue ""

        -- Flag below means that the expression's value matters, add it to args
        f <- if thisFuncUseValue
                then return $ AstValue $ thisFunc ++ " env cont value (Just args) = do "
                else return $ AstValue $ thisFunc ++ " env cont _ (Just args) = do "
        c <- do
             let nextCont' = case (lastArg, coptsNext) of
                                 (True, Just fnextExpr) -> "(makeCPSWArgs env cont " ++ fnextExpr ++ " [])"
                                 _ -> "cont"
             let literalArgs = asts2Str asLiterals
             let argsCode = case thisFuncUseValue of
                              True -> " $ args ++ [value] ++ " ++ literalArgs ++ ") " 
                              False -> " $ args ++ " ++ literalArgs ++ ") "

             if thisFuncUseValue
                then return $ AstValue $ "  continueEval env (makeCPSWArgs env (makeCPSWArgs env " ++ nextCont' ++ " " ++
                                         nextFunc ++ argsCode ++ stubFunc ++ " []) (Nil \"\") "  
                else return $ AstValue $ "  continueEval env (makeCPSWArgs env (makeCPSWArgs env " ++ nextCont' ++ " " ++
                                         nextFunc ++ argsCode ++ stubFunc ++ " []) $ Nil\"\""  

        rest <- case lastArg of
                     True -> return [] -- Using apply wrapper, so no more code
                     _ -> compileArgs nextFunc True Nothing asRest -- True indicates nextFunc needs to use value arg passed into it
        return $ [ f, fnc, c] ++ _comp ++ rest

      _ -> throwError $ TypeMismatch "nonempty list" $ List args

compileApply _ err _ = do
    throwError $ Default $ "compileApply - Unexpected argument: " ++ show err

-- |Determines if the given lispval is a primitive function
isPrim :: Env -> LispVal -> IOThrowsError (Maybe LispVal)
isPrim env (Atom func) = do
  val <- getVar env func >>= recDerefPtrs
  case val of
      p@(PrimitiveFunc _) -> return $ Just p
      _ -> return Nothing
isPrim _ p@(PrimitiveFunc _) = return $ Just p
isPrim _ _ = return Nothing

-- |Determine if the given list of expressions contains only literal identifiers
--  EG: 1, "2", etc. And return them if that is all that is found.
--
-- Atoms are a special case since they denote variables that will only be
-- available at runtime, so a flag is used to selectively include them.
--
_collectLiterals :: [LispVal] -> [LispVal] -> Bool -> (Maybe [LispVal])
_collectLiterals (List _ : _) _ _ = Nothing
_collectLiterals (Atom _ : _) _ False = Nothing
_collectLiterals (a : as) nfs varFlag = _collectLiterals as (a : nfs) varFlag
_collectLiterals [] nfs _ = Just $ reverse nfs

-- Wrappers for the above function
collectLiterals, collectLiteralsAndVars :: [LispVal] -> (Maybe [LispVal])
collectLiteralsAndVars args = _collectLiterals args [] True
collectLiterals args = _collectLiterals args [] False

-- Take as many literals as possible from the given list, and
-- return those literals and the rest of the list
takeLiterals :: LispVal -> [LispVal] -> ([LispVal], [LispVal])
takeLiterals (List _) ls = (ls, [])
takeLiterals _ ls' = do
  loop ls' []
 where
  loop (l : ls) acc = do
    if isLiteral l
       then loop ls (l : acc)
       else ((l:ls), acc)
  loop [] acc = ([], Data.List.reverse acc)

  isLiteral (List _) = False
  isLiteral (Atom _) = False
  isLiteral _ = True

-- Compile variable as a stand-alone line of code
compileInlineVar :: Env -> String -> String -> IOThrowsError HaskAST
compileInlineVar env a hsName = do
 isDefined <- liftIO $ isRecBound env a
 case isDefined of
   True -> return $ AstValue $ "  " ++ hsName ++ " <- getRTVar env \"" ++ a ++ "\""
   False -> throwError $ UnboundVar "Variable is not defined" a