{-# LANGUAGE GeneralizedNewtypeDeriving, TupleSections #-}
module Codegen(codegen) where

import Control.Monad.State.Strict
import Control.Monad.Except
import Data.Char
import Data.Maybe
import qualified Data.Map.Strict as Map
import qualified LLVM.General.AST.Type as A
import qualified LLVM.General.AST.Global as A.G
import qualified LLVM.General.AST.CallingConvention as A.CC
import qualified LLVM.General.AST.Constant as A.C
import qualified LLVM.General.AST.Float as A.F
-- import qualified LLVM.General.AST.Operand as A
-- import qualified LLVM.General.AST.Name as A
-- import qualified LLVM.General.AST.Instruction as A
import qualified LLVM.General.AST.IntegerPredicate as A.IP
import qualified LLVM.General.AST.FloatingPointPredicate as A.FPP
import qualified LLVM.General.AST.Linkage as A.L
-- import qualified LLVM.General.AST.Visibility as A.V
import qualified LLVM.General.AST as A
import Debug.Trace

import AST
import PShow


type Error a = Either String a

type LLName = String


data GenState
    = GenState {currentBlock :: Maybe LLName
               ,allBlocks :: Map.Map LLName A.BasicBlock
               ,currentFunction :: Declaration
               ,nextId :: Integer
               ,definitions :: [A.Definition]
               ,variables :: Map.Map Name (Type, LLName)
               ,globalVariables :: Map.Map Name (Type, LLName)
               ,globalFunctions :: Map.Map Name (Type, LLName)
               ,stringLiterals :: [(LLName, String)]}
    deriving (Show)

initialGenState :: GenState
initialGenState
    = GenState {currentBlock = Nothing
               ,allBlocks = Map.empty
               ,currentFunction = undefined
               ,nextId = 1
               ,definitions = []
               ,variables = Map.empty
               ,globalVariables = Map.empty
               ,globalFunctions = Map.empty
               ,stringLiterals = []}

newtype CGMonad a = CGMonad {unMon :: ExceptT String (State GenState) a}
    deriving (Functor, Applicative, Monad, MonadState GenState, MonadError String)

runCGMonad :: CGMonad a -> Error (a, GenState)
runCGMonad m = let (e, s) = runState (runExceptT (unMon m)) initialGenState
               in either Left (\x -> Right (x, s)) e

getUniqueId :: CGMonad Integer
getUniqueId = state $ \s -> (nextId s, s {nextId = nextId s + 1})

getNewName :: String -> CGMonad LLName
getNewName base = fmap ((base++) . show) getUniqueId

newBlock :: CGMonad LLName
newBlock = do
    name <- getNewName ".bb"
    state $ \s -> (name, s {
            currentBlock = Just name,
            allBlocks = Map.insert name (A.BasicBlock (A.Name name) [] (A.Do $ A.Unreachable [])) $ allBlocks s
        })

newBlockJump :: LLName -> CGMonad LLName
newBlockJump next = do
    bb <- newBlock
    setTerminator $ A.Br (A.Name next) []
    return bb

changeBlock :: LLName -> CGMonad ()
changeBlock name = state $ \s -> ((), s {currentBlock = Just name})

instrReturnsVoid :: A.Instruction -> Bool
instrReturnsVoid (A.Store {}) = True
instrReturnsVoid (A.Call _ _ _ (Right oper) _ _ _) = case oper of
    (A.LocalReference (A.FunctionType A.VoidType _ _) _) -> True
    (A.ConstantOperand (A.C.GlobalReference (A.FunctionType A.VoidType _ _) _)) -> True
    _ -> False
instrReturnsVoid _ = False

addInstr :: A.Instruction -> CGMonad LLName
addInstr instr
    | instrReturnsVoid instr = addNamedInstr $ A.Do instr
    | otherwise = do
        name <- getNewName ".t"
        addNamedInstr $ A.Name name A.:= instr

addNamedInstr :: A.Named A.Instruction -> CGMonad LLName
addNamedInstr instr@(A.Name name A.:= _) = do
    let append (A.BasicBlock n il t) = A.BasicBlock n (il ++ [instr]) t
    state $ \s -> (name, s {allBlocks = Map.adjust append (fromJust (currentBlock s)) (allBlocks s)})
addNamedInstr instr@(A.Do _) = do
    let append (A.BasicBlock n il t) = A.BasicBlock n (il ++ [instr]) t
    state $ \s -> ("", s {allBlocks = Map.adjust append (fromJust (currentBlock s)) (allBlocks s)})
addNamedInstr _ = undefined

-- addNamedInstrList :: [A.Named A.Instruction] -> CGMonad LLName
-- addNamedInstrList l = mapM addNamedInstr l >>= return . last

setTerminator :: A.Terminator -> CGMonad ()
setTerminator term = do
    let replace (A.BasicBlock n il _) = A.BasicBlock n il (A.Do term)
    state $ \s -> ((), s {allBlocks = Map.adjust replace (fromJust (currentBlock s)) (allBlocks s)})

getTerminator :: CGMonad (A.Named A.Terminator)
getTerminator = do
    s <- get
    let (A.BasicBlock _ _ t) = fromJust $ Map.lookup (fromJust $ currentBlock s) (allBlocks s)
    return t

setCurrentFunction :: Declaration -> CGMonad ()
setCurrentFunction dec = do
    state $ \s -> ((), s {currentFunction = dec})

setVar :: Name -> LLName -> Type -> CGMonad ()
setVar name label t = do
    state $ \s -> ((), s {variables = Map.insert name (t, label) $ variables s})

setGlobalVar :: Name -> LLName -> Type -> CGMonad ()
setGlobalVar name label t = do
    state $ \s -> ((), s {globalVariables = Map.insert name (t, label) $ globalVariables s})

setGlobalFunction :: Name -> LLName -> Type -> CGMonad ()
setGlobalFunction name label t = do
    state $ \s -> ((), s {globalFunctions = Map.insert name (t, label) $ globalFunctions s})

lookupVar :: Name -> CGMonad (Type, LLName)
lookupVar name | trace ("Looking up var " ++ name) False = undefined
lookupVar name = do
    obj <- get
    let locfound = Map.lookup name $ variables obj
        glofound = Map.lookup name $ globalVariables obj
    if isJust locfound
        then return $ fromJust locfound
        else return $ fromJust glofound

lookupGlobalVar :: Name -> CGMonad (Type, LLName)
lookupGlobalVar name = liftM (fromJust . Map.lookup name . globalVariables) get

lookupGlobalFunction :: Name -> CGMonad (Type, LLName)
lookupGlobalFunction name = liftM (fromJust . Map.lookup name . globalFunctions) get

addStringLiteral :: String -> CGMonad (A.Type, LLName)
addStringLiteral str = do
    name <- getNewName ".str"
    state $ \s -> ((A.ptr $ A.ArrayType (fromIntegral (length str + 1)) A.i8, name),
                   s {stringLiterals = (name, str) : stringLiterals s})

variableStoreOperand :: Name -> CGMonad A.Operand
variableStoreOperand name = get >>= (maybe getGlobal getLocal . Map.lookup name . variables)
  where
    getLocal :: (Type, LLName) -> CGMonad A.Operand
    getLocal (t, nm) = return $ A.LocalReference (A.ptr (toLLVMType t)) (A.Name nm)

    getGlobal :: CGMonad A.Operand
    getGlobal = do
        (t, nm) <- lookupGlobalVar name
        return $ A.ConstantOperand $ A.C.GlobalReference (A.ptr (toLLVMType t)) (A.Name nm)

variableOperand :: Name -> CGMonad A.Operand
variableOperand name = get >>= (maybe getGlobal getLocal . Map.lookup name . variables)
  where
    getLocal :: (Type, LLName) -> CGMonad A.Operand
    getLocal (t, nm) = do
        let loadoper = A.LocalReference (A.ptr (toLLVMType t)) (A.Name nm)
        label <- addInstr $ A.Load False loadoper Nothing 0 []
        return $ A.LocalReference (toLLVMType t) (A.Name label)

    getGlobal :: CGMonad A.Operand
    getGlobal = do
        (t, nm) <- lookupGlobalVar name
        let loadoper = A.ConstantOperand $ A.C.GlobalReference (A.ptr (toLLVMType t)) (A.Name nm)
        label <- addInstr $ A.Load False loadoper Nothing 0 []
        return $ A.LocalReference (toLLVMType t) (A.Name label)


-- namedName :: A.Named a -> LLName
-- namedName (A.Name name A.:= _) = name
-- namedName _ = undefined


codegen :: Program  -- Program to compile
        -> String   -- Module name
        -> String   -- File name of source
        -> Error A.Module
codegen prog name fname = do
    (defs, st) <- runCGMonad $ do
                    defs <- generateDefs prog
                    -- traceShow defs $ return ()
                    -- liftM stringLiterals get >>= flip traceShow (return ())
                    return defs

    traceShow st $ return ()

    return $ A.defaultModule {
            A.moduleName = name,
            A.moduleSourceFileName = fname,
            A.moduleDefinitions = defs
        }


generateDefs :: Program -> CGMonad [A.Definition]
generateDefs prog
    = liftM concat $ sequence $ [genGlobalVars prog, genFunctions prog, genStringLiterals]

genGlobalVars :: Program -> CGMonad [A.Definition]
genGlobalVars (Program decs) = liftM (mapMaybe id) $ mapM gen decs
  where
    gen :: Declaration -> CGMonad (Maybe A.Definition)
    gen (DecVariable t n Nothing) = do
        setGlobalVar n n t
        return $ Just $ A.GlobalDefinition $
            A.globalVariableDefaults {
                A.G.name = A.Name n,
                A.G.type' = toLLVMType t,
                A.G.initializer = Just $ initializerFor t
            }
    gen (DecVariable _ _ (Just _)) = throwError $ "Initialised global variables not supported yet"
    gen (DecFunction rt n a _) = do
        setGlobalFunction n n (TypeFunc rt (map fst a))
        return Nothing
    gen (DecExtern t@(TypeFunc rt ats) n) = do
        setGlobalFunction n n t
        argnames <- sequence $ replicate (length ats) (getNewName ".arg")
        return $ Just $ A.GlobalDefinition $
            A.functionDefaults {
                A.G.returnType = toLLVMType rt,
                A.G.name = A.Name n,
                A.G.parameters = ([A.Parameter (toLLVMType at) (A.Name an) [] | (at,an) <- zip ats argnames], False),
                A.G.basicBlocks = []
            }
    gen (DecExtern t n) = do
        setGlobalVar n n t
        return $ Just $ A.GlobalDefinition $
            A.globalVariableDefaults {
                A.G.name = A.Name n,
                A.G.type' = toLLVMType t,
                A.G.initializer = Nothing
            }
    gen (DecTypedef _ _) = return Nothing

genStringLiterals :: CGMonad [A.Definition]
genStringLiterals = liftM stringLiterals get >>= return . map gen
  where
    gen :: (LLName, String) -> A.Definition
    gen (name, str) = A.GlobalDefinition $ A.globalVariableDefaults {
            A.G.name = A.Name name,
            A.G.linkage = A.L.Private,
            A.G.isConstant = True,
            A.G.type' = A.ArrayType (fromIntegral (length str + 1)) A.i8,
            A.G.initializer = Just $ A.C.Array A.i8 $ [A.C.Int 8 (fromIntegral (ord c)) | c <- str] ++ [A.C.Int 8 0]
        }

genFunctions :: Program -> CGMonad [A.Definition]
genFunctions (Program decs) = liftM (mapMaybe id) $ mapM gen decs
  where
    gen :: Declaration -> CGMonad (Maybe A.Definition)
    gen dec@(DecFunction rettype name args body) = do
        setCurrentFunction dec
        state $ \s -> ((), s {
                allBlocks = Map.empty,
                variables = Map.empty
            })
        firstbb <- genFunctionBlock body (rettype, name) args
        cleanupTrampolines firstbb
        blockmap <- liftM allBlocks get
        let bbs' = map snd $ filter (\x -> fst x /= firstbb) $ Map.toList blockmap
            bbs = fromJust (Map.lookup firstbb blockmap) : bbs'
        return $ Just $ A.GlobalDefinition $ A.functionDefaults {
                A.G.returnType = toLLVMType rettype,
                A.G.name = A.Name name,
                A.G.parameters = ([A.Parameter (toLLVMType t) (A.Name (".farg_"++n)) [] | (t,n) <- args], False),
                A.G.basicBlocks = bbs
            }
    gen _ = return Nothing



genFunctionBlock :: Block -> (Type, Name) -> [(Type, Name)] -> CGMonad LLName
genFunctionBlock bl (rettype, fname) args = do
    firstbb <- newBlock
    let prepArg :: (Type,Name) -> CGMonad ()
        prepArg (t,n) = do
            label <- addInstr $ A.Alloca (toLLVMType t) Nothing 0 []
            void $ addInstr $ A.Store False (A.LocalReference (A.ptr (toLLVMType t)) (A.Name label))
                                      (A.LocalReference (toLLVMType t) (A.Name (".farg_"++n)))
                                      Nothing 0 []
            setVar n label t
    sequence_ $ map prepArg args

    termbb <- newBlock
    setTerminator $ if rettype == TypeVoid then A.Ret Nothing [] else A.Unreachable []

    bodybb <- genBlock bl termbb
    changeBlock firstbb
    setTerminator $ A.Br (A.Name bodybb) []

    if rettype /= TypeVoid
        then whenM (bbIsReferenced termbb) $ throwError $
                 "Control reaches end of non-void function '" ++ fname ++ "'"
        else return ()

    if length args > 0
        then return firstbb
        else return bodybb

whenM :: (Monad m) => m Bool -> m a -> m ()
whenM cond value = cond >>= \c -> if c then void value else return ()

genBlock :: Block
         -> LLName  -- name of BasicBlock following this Block
         -> CGMonad LLName  -- name of first BasicBlock
genBlock (Block []) following = genBlock (Block [StEmpty]) following
genBlock (Block [stmt]) following = do
    firstbb <- genSingle stmt following
    return firstbb
genBlock (Block (stmt:rest)) following = do
    interbb <- newBlock
    firstbb <- genSingle stmt interbb
    restbb <- genBlock (Block rest) following
    changeBlock interbb
    setTerminator $ A.Br (A.Name restbb) []
    return firstbb

genSingle :: Statement
          -> LLName  -- name of BasicBlock following this statement
          -> CGMonad LLName  -- name of first BasicBlock
genSingle StEmpty following = return following
genSingle (StBlock block) following = genBlock block following
genSingle (StExpr expr) following = do
    bb <- newBlockJump following
    void $ genExpression expr
    return bb
genSingle (StVarDeclaration t n Nothing) following = do
    bb <- newBlockJump following
    label <- addInstr $ A.Alloca (toLLVMType t) Nothing 0 []
    setVar n label t
    return bb
genSingle (StVarDeclaration _ _ (Just _)) _ = undefined
genSingle (StAssignment name expr) following = do
    bb <- newBlockJump following
    oper <- genExpression expr
    (dsttype, _) <- lookupVar name
    oper' <- castOperand oper dsttype
    ref <- variableStoreOperand name
    void $ addInstr $ A.Store False ref oper' Nothing 0 []
    return bb
genSingle (StReturn Nothing) _ = do
    bb <- newBlock
    setTerminator $ A.Ret Nothing []
    return bb
genSingle (StReturn (Just expr)) _ = do
    bb <- newBlock
    oper <- genExpression expr
    rettype <- liftM (typeOf . currentFunction) get
    oper' <- castOperand oper rettype
    setTerminator $ A.Ret (Just oper') []
    return bb
genSingle (StIf cexpr st1 st2) following = do
    stbb1 <- genSingle st1 following
    stbb2 <- genSingle st2 following
    cbb <- newBlock
    coper <- genExpression cexpr
    coper' <- castToBool coper
    setTerminator $ A.CondBr coper' (A.Name stbb1) (A.Name stbb2) []
    return cbb
genSingle (StWhile cexpr st) following = do
    cbb <- newBlock
    loopbb <- newBlockJump cbb
    stbb <- genSingle st loopbb
    changeBlock cbb
    coper <- genExpression cexpr
    coper' <- castToBool coper
    setTerminator $ A.CondBr coper' (A.Name stbb) (A.Name following) []
    return cbb

genExpression :: Expression -> CGMonad A.Operand
genExpression (ExLit lit (Just t)) = literalToOperand lit t
genExpression (ExBinOp bo e1 e2 (Just t)) = do
    case bo of
        Plus -> do
            e1op <- genExprArgument e1 >>= flip castOperand t
            e2op <- genExprArgument e2 >>= flip castOperand t
            label <- case t of
                (TypeInt _) -> addInstr $ A.Add False False e1op e2op []
                (TypeUInt _) -> addInstr $ A.Add False False e1op e2op []
                TypeFloat -> addInstr $ A.FAdd A.NoFastMathFlags e1op e2op []
                TypeDouble -> addInstr $ A.FAdd A.NoFastMathFlags e1op e2op []
                (TypePtr _) -> throwError $ "Plus '+' operator not defined on pointers"
                (TypeFunc _ _) -> throwError $ "Plus '+' operator not defined on function pointers"
                (TypeName _) -> undefined
                TypeVoid -> undefined
            return $ A.LocalReference (toLLVMType t) (A.Name label)
        Minus -> do
            e1op <- genExprArgument e1 >>= flip castOperand t
            e2op <- genExprArgument e2 >>= flip castOperand t
            label <- case t of
                (TypeInt _) -> addInstr $ A.Sub False False e1op e2op []
                (TypeUInt _) -> addInstr $ A.Sub False False e1op e2op []
                TypeFloat -> addInstr $ A.FSub A.NoFastMathFlags e1op e2op []
                TypeDouble -> addInstr $ A.FSub A.NoFastMathFlags e1op e2op []
                (TypePtr _) -> throwError $ "Minus '-' operator not defined on pointers"
                (TypeFunc _ _) -> throwError $ "Minus '-' operator not defined on function pointers"
                (TypeName _) -> undefined
                TypeVoid -> undefined
            return $ A.LocalReference (toLLVMType t) (A.Name label)
        Times -> do
            e1op <- genExprArgument e1 >>= flip castOperand t
            e2op <- genExprArgument e2 >>= flip castOperand t
            label <- case t of
                (TypeInt _) -> addInstr $ A.Mul False False e1op e2op []
                (TypeUInt _) -> addInstr $ A.Mul False False e1op e2op []
                TypeFloat -> addInstr $ A.FMul A.NoFastMathFlags e1op e2op []
                TypeDouble -> addInstr $ A.FMul A.NoFastMathFlags e1op e2op []
                (TypePtr _) -> throwError $ "Multiply '*' operator not defined on pointers"
                (TypeFunc _ _) -> throwError $ "Multiply '*' operator not defined on function pointers"
                (TypeName _) -> undefined
                TypeVoid -> undefined
            return $ A.LocalReference (toLLVMType t) (A.Name label)
        Divide -> do
            e1op <- genExprArgument e1 >>= flip castOperand t
            e2op <- genExprArgument e2 >>= flip castOperand t
            label <- case t of
                (TypeInt _) -> addInstr $ A.SDiv False e1op e2op []
                (TypeUInt _) -> addInstr $ A.UDiv False e1op e2op []
                TypeFloat -> addInstr $ A.FDiv A.NoFastMathFlags e1op e2op []
                TypeDouble -> addInstr $ A.FDiv A.NoFastMathFlags e1op e2op []
                (TypePtr _) -> throwError $ "Divide '/' operator not defined on pointers"
                (TypeFunc _ _) -> throwError $ "Divide '/' operator not defined on function pointers"
                (TypeName _) -> undefined
                TypeVoid -> undefined
            return $ A.LocalReference (toLLVMType t) (A.Name label)
        Modulo -> do
            e1op <- genExprArgument e1 >>= flip castOperand t
            e2op <- genExprArgument e2 >>= flip castOperand t
            label <- case t of
                (TypeInt _) -> addInstr $ A.SRem e1op e2op []
                (TypeUInt _) -> addInstr $ A.URem e1op e2op []
                TypeFloat -> addInstr $ A.FRem A.NoFastMathFlags e1op e2op []
                TypeDouble -> addInstr $ A.FRem A.NoFastMathFlags e1op e2op []
                (TypePtr _) -> throwError $ "Modulo '%' operator not defined on pointers"
                (TypeFunc _ _) -> throwError $ "Modulo '%' operator not defined on function pointers"
                (TypeName _) -> undefined
                TypeVoid -> undefined
            return $ A.LocalReference (toLLVMType t) (A.Name label)
        Equal -> do
            sharedType <- commonTypeM (fromJust (exTypeOf e1)) (fromJust (exTypeOf e2))
            e1op <- genExprArgument e1 >>= flip castOperand sharedType
            e2op <- genExprArgument e2 >>= flip castOperand sharedType
            label <- case sharedType of
                (TypeInt _) -> addInstr $ A.ICmp A.IP.EQ e1op e2op []
                (TypeUInt _) -> addInstr $ A.ICmp A.IP.EQ e1op e2op []
                TypeFloat -> addInstr $ A.FCmp A.FPP.OEQ e1op e2op []
                TypeDouble -> addInstr $ A.FCmp A.FPP.OEQ e1op e2op []
                (TypePtr _) -> addInstr $ A.ICmp A.IP.EQ e1op e2op []
                (TypeFunc _ _) -> addInstr $ A.ICmp A.IP.EQ e1op e2op []
                (TypeName _) -> undefined
                TypeVoid -> undefined
            return $ A.LocalReference (A.IntegerType 1) (A.Name label)
        Greater -> do
            sharedType <- commonTypeM (fromJust (exTypeOf e1)) (fromJust (exTypeOf e2))
            e1op <- genExprArgument e1 >>= flip castOperand sharedType
            e2op <- genExprArgument e2 >>= flip castOperand sharedType
            label <- case sharedType of
                (TypeInt _) -> addInstr $ A.ICmp A.IP.SGT e1op e2op []
                (TypeUInt _) -> addInstr $ A.ICmp A.IP.UGT e1op e2op []
                TypeFloat -> addInstr $ A.FCmp A.FPP.OGT e1op e2op []
                TypeDouble -> addInstr $ A.FCmp A.FPP.OGT e1op e2op []
                (TypePtr _) -> addInstr $ A.ICmp A.IP.UGT e1op e2op []
                (TypeFunc _ _) -> addInstr $ A.ICmp A.IP.UGT e1op e2op []
                (TypeName _) -> undefined
                TypeVoid -> undefined
            return $ A.LocalReference (A.IntegerType 1) (A.Name label)
        Less -> do
            sharedType <- commonTypeM (fromJust (exTypeOf e1)) (fromJust (exTypeOf e2))
            e1op <- genExprArgument e1 >>= flip castOperand sharedType
            e2op <- genExprArgument e2 >>= flip castOperand sharedType
            label <- case sharedType of
                (TypeInt _) -> addInstr $ A.ICmp A.IP.SLT e1op e2op []
                (TypeUInt _) -> addInstr $ A.ICmp A.IP.ULT e1op e2op []
                TypeFloat -> addInstr $ A.FCmp A.FPP.OLT e1op e2op []
                TypeDouble -> addInstr $ A.FCmp A.FPP.OLT e1op e2op []
                (TypePtr _) -> addInstr $ A.ICmp A.IP.ULT e1op e2op []
                (TypeFunc _ _) -> addInstr $ A.ICmp A.IP.ULT e1op e2op []
                (TypeName _) -> undefined
                TypeVoid -> undefined
            return $ A.LocalReference (A.IntegerType 1) (A.Name label)
        GEqual -> do
            sharedType <- commonTypeM (fromJust (exTypeOf e1)) (fromJust (exTypeOf e2))
            e1op <- genExprArgument e1 >>= flip castOperand sharedType
            e2op <- genExprArgument e2 >>= flip castOperand sharedType
            label <- case sharedType of
                (TypeInt _) -> addInstr $ A.ICmp A.IP.SGE e1op e2op []
                (TypeUInt _) -> addInstr $ A.ICmp A.IP.UGE e1op e2op []
                TypeFloat -> addInstr $ A.FCmp A.FPP.OGE e1op e2op []
                TypeDouble -> addInstr $ A.FCmp A.FPP.OGE e1op e2op []
                (TypePtr _) -> addInstr $ A.ICmp A.IP.UGE e1op e2op []
                (TypeFunc _ _) -> addInstr $ A.ICmp A.IP.UGE e1op e2op []
                (TypeName _) -> undefined
                TypeVoid -> undefined
            return $ A.LocalReference (A.IntegerType 1) (A.Name label)
        LEqual -> do
            sharedType <- commonTypeM (fromJust (exTypeOf e1)) (fromJust (exTypeOf e2))
            e1op <- genExprArgument e1 >>= flip castOperand sharedType
            e2op <- genExprArgument e2 >>= flip castOperand sharedType
            label <- case sharedType of
                (TypeInt _) -> addInstr $ A.ICmp A.IP.SLE e1op e2op []
                (TypeUInt _) -> addInstr $ A.ICmp A.IP.ULE e1op e2op []
                TypeFloat -> addInstr $ A.FCmp A.FPP.OLE e1op e2op []
                TypeDouble -> addInstr $ A.FCmp A.FPP.OLE e1op e2op []
                (TypePtr _) -> addInstr $ A.ICmp A.IP.ULE e1op e2op []
                (TypeFunc _ _) -> addInstr $ A.ICmp A.IP.ULE e1op e2op []
                (TypeName _) -> undefined
                TypeVoid -> undefined
            return $ A.LocalReference (A.IntegerType 1) (A.Name label)
        BoolAnd -> do
            firstbb <- liftM (fromJust . currentBlock) get
            (A.LocalReference (A.IntegerType 1) (A.Name label1)) <- genExprArgument e1 >>= castToBool
            (A.Do origterm) <- getTerminator

            bb2 <- newBlock
            (A.LocalReference (A.IntegerType 1) (A.Name label2)) <- genExprArgument e2 >>= castToBool

            bb3 <- newBlock

            changeBlock firstbb
            setTerminator $ A.CondBr (A.LocalReference A.i1 (A.Name label1)) (A.Name bb2) (A.Name bb3) []

            changeBlock bb2
            setTerminator $ A.Br (A.Name bb3) []

            changeBlock bb3
            setTerminator origterm
            reslabel <- addInstr $ A.Phi A.i1 [(A.ConstantOperand (A.C.Int 1 0), A.Name firstbb),
                                               (A.LocalReference A.i1 (A.Name label2), A.Name bb2)] []
            return $ A.LocalReference A.i1 (A.Name reslabel)
        -- BoolOr -> do
        --     e1op' <- castToBool e1op
        --     e2op' <- castToBool e2op
        --     label <- addInstr $ A.Or e1op' e2op' []
        --     return $ A.LocalReference (A.IntegerType 1) (A.Name label)
        _ -> throwError $ "Binary operator " ++ pshow bo ++ " not implemented"
genExpression (ExUnOp uo e1 (Just t)) = do
    e1op <- genExprArgument e1
    case uo of
        Negate -> do
            label <- case t of
                (TypeInt s) -> addInstr $ A.Sub False False (A.ConstantOperand (A.C.Int (fromIntegral s) 0)) e1op []
                (TypeUInt s) -> addInstr $ A.Sub False False (A.ConstantOperand (A.C.Int (fromIntegral s) 0)) e1op []
                TypeFloat -> addInstr $ A.FSub A.NoFastMathFlags (A.ConstantOperand (A.C.Float (A.F.Single 0))) e1op []
                TypeDouble -> addInstr $ A.FSub A.NoFastMathFlags (A.ConstantOperand (A.C.Float (A.F.Double 0))) e1op []
                (TypePtr _) -> throwError $ "Negate '-' operator not defined on a pointer"
                (TypeName _) -> undefined
                (TypeFunc _ _) -> throwError $ "Negate '-' operator not defined on a function pointer"
                TypeVoid -> undefined
            return $ A.LocalReference (toLLVMType t) (A.Name label)
        Not -> do
            label <- case t of
                (TypeInt s) -> addInstr $ A.ICmp A.IP.EQ (A.ConstantOperand (A.C.Int (fromIntegral s) 0)) e1op []
                (TypeUInt s) -> addInstr $ A.ICmp A.IP.EQ (A.ConstantOperand (A.C.Int (fromIntegral s) 0)) e1op []
                TypeFloat -> addInstr $ A.FCmp A.FPP.OEQ (A.ConstantOperand (A.C.Float (A.F.Single 0))) e1op []
                TypeDouble -> addInstr $ A.FCmp A.FPP.OEQ (A.ConstantOperand (A.C.Float (A.F.Double 0))) e1op []
                (TypePtr _) -> addInstr $ A.ICmp A.IP.EQ (A.ConstantOperand (A.C.Null (toLLVMType t))) e1op []
                (TypeName _) -> undefined
                (TypeFunc _ _) -> throwError $ "Not '!' operator not defined on a function pointer"
                TypeVoid -> undefined
            return $ A.LocalReference (toLLVMType t) (A.Name label)
        Dereference -> do
            label <- case t of
                (TypePtr _) -> addInstr $ A.Load False e1op Nothing 0 []
                _ -> throwError $ "Dereference '*' operator only defined on pointers"
            return $ A.LocalReference (toLLVMType t) (A.Name label)
        _ -> throwError $ "Unary operator " ++ pshow uo ++ " not implemented"
genExpression ex = throwError $ "Expression '" ++ pshow ex ++ "' not implemented"

genExprArgument :: Expression -> CGMonad A.Operand
genExprArgument expr = case expr of
        (ExLit lit (Just t)) -> literalToOperand lit t
        _ -> genExpression expr

literalToOperand :: Literal -> Type -> CGMonad A.Operand
literalToOperand (LitInt i) (TypeInt sz) = return $ A.ConstantOperand (A.C.Int (fromIntegral sz) i)
literalToOperand (LitFloat f) TypeFloat = return $ A.ConstantOperand (A.C.Float (A.F.Single (realToFrac f)))
literalToOperand (LitFloat f) TypeDouble = return $ A.ConstantOperand (A.C.Float (A.F.Double f))
literalToOperand (LitVar n) t = do
    oper <- variableOperand n
    oper' <- castOperand oper t
    return oper'
literalToOperand (LitString s) (TypePtr (TypeInt 8)) = do
    (ty, name) <- addStringLiteral s
    label <- addInstr $ A.GetElementPtr True (A.ConstantOperand $ A.C.GlobalReference ty (A.Name name))
                                        [A.ConstantOperand $ A.C.Int 64 0,
                                         A.ConstantOperand $ A.C.Int 32 0]
                                        []
    return $ A.LocalReference (A.ptr A.i8) (A.Name label)
literalToOperand (LitString _) _ = undefined
literalToOperand (LitCall n args) _ = do
    ((TypeFunc rt ats), lname) <- lookupGlobalFunction n
    let processArgs :: [Expression] -> [Type] -> CGMonad [A.Operand]
        processArgs [] [] = return []
        processArgs [] _ = undefined
        processArgs _ [] = undefined
        processArgs (ex:exs) (t:ts) = do
            first <- genExpression ex >>= flip castOperand t
            rest <- processArgs exs ts
            return $ first : rest
    rargs <- processArgs args ats
    let argpairs = map (\a -> (a,[])) rargs
        foper = A.ConstantOperand $
                    A.C.GlobalReference (A.FunctionType (toLLVMType rt) (map toLLVMType ats) False)
                                        (A.Name lname)
    label <- addInstr $ A.Call Nothing A.CC.C [] (Right foper) argpairs [] []
    return $ A.LocalReference (toLLVMType rt) (A.Name label)
literalToOperand lit _ = throwError $ "Literal '" ++ pshow lit ++ "' not implemented"

castOperand :: A.Operand -> Type -> CGMonad A.Operand
castOperand orig@(A.ConstantOperand (A.C.Int s1 val)) t2@(TypeInt s2)
    | fromIntegral s1 == s2 = return orig
    | fromIntegral s1 < s2 = return $ A.ConstantOperand (A.C.Int (fromIntegral s2) val)
    | fromIntegral s1 > s2 = throwError $ "Integer " ++ show val ++ " too large for type '" ++ pshow t2 ++ "'"
castOperand (A.ConstantOperand (A.C.Int _ val)) TypeFloat = do
    return $ A.ConstantOperand (A.C.Float (A.F.Single (fromIntegral val)))
castOperand (A.ConstantOperand (A.C.Int _ val)) TypeDouble = do
    return $ A.ConstantOperand (A.C.Float (A.F.Double (fromIntegral val)))
castOperand orig@(A.ConstantOperand (A.C.Float (A.F.Single _))) TypeFloat = do
    return orig
castOperand orig@(A.ConstantOperand (A.C.Float (A.F.Double _))) TypeDouble = do
    return orig
castOperand (A.ConstantOperand (A.C.Float (A.F.Single f))) TypeDouble = do
    return $ A.ConstantOperand (A.C.Float (A.F.Double (realToFrac f)))

castOperand orig@(A.LocalReference (A.IntegerType s1) _) t2@(TypeInt s2)
    | fromIntegral s1 == s2 = return orig
    | fromIntegral s1 < s2 = do
        label <- addInstr $ A.SExt orig (toLLVMType t2) []
        return $ A.LocalReference (toLLVMType t2) (A.Name label)
    | fromIntegral s1 > s2 = throwError $ "Cannot implicitly cast '" ++ pshow (TypeInt (fromIntegral s1))
                                          ++ "' to '" ++ pshow t2 ++ "'"
castOperand orig@(A.LocalReference (A.IntegerType s1) _) t2@(TypeUInt s2)
    | fromIntegral s1 == s2 = return orig
    | fromIntegral s1 < s2 = do
        label <- addInstr $ A.ZExt orig (toLLVMType t2) []
        return $ A.LocalReference (toLLVMType t2) (A.Name label)
    | fromIntegral s1 > s2 = throwError $ "Cannot implicitly cast '" ++ pshow (TypeUInt (fromIntegral s1))
                                          ++ "' to '" ++ pshow t2 ++ "'"
castOperand orig@(A.ConstantOperand (A.C.GlobalReference (A.IntegerType s1) _)) t2@(TypeInt s2)
    | fromIntegral s1 == s2 = return orig
    | fromIntegral s1 < s2 = do
        label <- addInstr $ A.SExt orig (toLLVMType t2) []
        return $ A.LocalReference (toLLVMType t2) (A.Name label)
    | fromIntegral s1 > s2 = throwError $ "Cannot implicitly cast '" ++ pshow (TypeInt (fromIntegral s1))
                                          ++ "' to '" ++ pshow t2 ++ "'"
castOperand orig@(A.ConstantOperand (A.C.GlobalReference (A.IntegerType s1) _)) t2@(TypeUInt s2)
    | fromIntegral s1 == s2 = return orig
    | fromIntegral s1 < s2 = do
        label <- addInstr $ A.ZExt orig (toLLVMType t2) []
        return $ A.LocalReference (toLLVMType t2) (A.Name label)
    | fromIntegral s1 > s2 = throwError $ "Cannot implicitly cast '" ++ pshow (TypeUInt (fromIntegral s1))
                                          ++ "' to '" ++ pshow t2 ++ "'"

castOperand orig@(A.LocalReference t _) TypeFloat | t == toLLVMType TypeFloat = do
    return orig
castOperand orig@(A.LocalReference t _) TypeDouble | t == toLLVMType TypeDouble = do
    return orig
castOperand orig@(A.LocalReference t _) TypeDouble | t == toLLVMType TypeFloat = do
    label <- addInstr $ A.FPExt orig (toLLVMType TypeDouble) []
    return $ A.LocalReference (toLLVMType TypeDouble) (A.Name label)

castOperand orig@(A.LocalReference (A.PointerType t1 _) _) (TypePtr t2)
    | toLLVMType t2 == t1 = return orig
    | otherwise = throwError $ "Cannot implicitly cast between pointer to '" ++ show t1
                               ++ "' and '" ++ pshow t2 ++ "'"
castOperand orig@(A.ConstantOperand (A.C.GlobalReference (A.PointerType t1 _) _)) (TypePtr t2)
    | toLLVMType t2 == t1 = return orig
    | otherwise = throwError $ "Cannot implicitly cast between pointer to '" ++ show t1
                               ++ "' and '" ++ pshow t2 ++ "'"
castOperand orig@(A.LocalReference (A.PointerType (A.FunctionType rt1 at1 False) _) _) t2@(TypeFunc rt2 at2)
    | toLLVMType rt2 == rt1 && all (uncurry (==)) (zip at1 (map toLLVMType at2)) = return orig
    | otherwise = throwError $ "Cannot implicitly cast between '" ++ show orig
                               ++ "' and '" ++ pshow t2 ++ "'"

castOperand orig t2 = throwError $ "Cast from '" ++ show orig ++ "' to type '" ++ pshow t2 ++ "' not implemented"


castToBool :: A.Operand -> CGMonad A.Operand
castToBool orig@(A.LocalReference (A.IntegerType 1) _) =
    return orig
castToBool orig@(A.LocalReference (A.IntegerType s1) _) = do
    label <- addInstr $ A.ICmp A.IP.NE orig (A.ConstantOperand (A.C.Int s1 0)) []
    return $ A.LocalReference (A.IntegerType 1) (A.Name label)
castToBool (A.ConstantOperand (A.C.Int _ val)) =
    return $ A.ConstantOperand (A.C.Int 1 (if val == 0 then 1 else 0))
castToBool _ = undefined


commonType :: Type -> Type -> Maybe Type
commonType (TypePtr t1) (TypePtr t2) | t1 == t2 = Just $ TypePtr t1
commonType (TypePtr _) _ = Nothing
commonType _ (TypePtr _) = Nothing

commonType (TypeInt s1) (TypeInt s2) = Just $ TypeInt (max s1 s2)

commonType (TypeUInt s1) (TypeUInt s2) = Just $ TypeUInt (max s1 s2)

commonType TypeFloat (TypeInt _) = Just TypeFloat
commonType (TypeInt _) TypeFloat = Just TypeFloat
commonType TypeDouble (TypeInt _) = Just TypeDouble
commonType (TypeInt _) TypeDouble = Just TypeDouble
commonType TypeFloat TypeFloat = Just TypeFloat
commonType TypeDouble TypeDouble = Just TypeDouble
commonType TypeFloat TypeDouble = Just TypeDouble
commonType TypeDouble TypeFloat = Just TypeDouble

commonType t@(TypeFunc rt1 at1) (TypeFunc rt2 at2)
    | rt1 == rt2 && at1 == at2 = Just t
    | otherwise = Nothing

commonType _ _ = Nothing

commonTypeM :: Type -> Type -> CGMonad Type
commonTypeM t1 t2 = maybe err return $ commonType t1 t2
    where err = throwError $ "Cannot implicitly find common type of '" ++ pshow t1 ++ "' and '" ++ pshow t2 ++ "'"


cleanupTrampolines :: LLName -> CGMonad ()
cleanupTrampolines toskip = do
    state $ \s -> ((), s {allBlocks = go (allBlocks s)})
  where
    go :: Map.Map LLName A.BasicBlock -> Map.Map LLName A.BasicBlock
    go bbs = folder bbs (Map.toList bbs)
      where
        folder :: Map.Map LLName A.BasicBlock -> [(LLName, A.BasicBlock)] -> Map.Map LLName A.BasicBlock
        folder whole [] = whole
        folder whole ((name, (A.BasicBlock (A.Name name2) [] (A.Do (A.Br (A.Name dst) [])))) : _)
            | name /= name2 = error "INTERNAL ERROR: name /= name2"
            | name /= toskip = let res = eliminate name dst $ Map.delete name whole
                               in folder res (Map.toList res)
        folder whole (_:rest) = folder whole rest

    eliminate :: LLName -> LLName -> Map.Map LLName A.BasicBlock -> Map.Map LLName A.BasicBlock
    eliminate name dst bbs = Map.fromList $ map (\(n,bb) -> (n,goBB bb)) $ Map.toList bbs
      where
        goBB :: A.BasicBlock -> A.BasicBlock
        goBB (A.BasicBlock nm instrs (A.Name n A.:= term))
            = A.BasicBlock nm instrs (A.Name n A.:= (goT term))
        goBB (A.BasicBlock _ _ (A.UnName _ A.:= _))
            = undefined
        goBB (A.BasicBlock nm instrs (A.Do term))
            = A.BasicBlock nm instrs (A.Do (goT term))

        goT :: A.Terminator -> A.Terminator
        goT (A.CondBr cond d1 d2 []) = A.CondBr cond (changeName name dst d1)
                                                     (changeName name dst d2) []
        goT (A.Br d []) = A.Br (changeName name dst d) []
        goT (A.Switch op d1 ds []) = A.Switch op (changeName name dst d1)
                                              (map (\(c,n) -> (c, changeName name dst n)) ds) 
                                              []
        goT (A.IndirectBr {}) = undefined
        goT (A.Invoke {}) = undefined
        goT bb = bb

    changeName :: LLName -> LLName -> A.Name -> A.Name
    changeName from to (A.Name x)
        | x == from = A.Name to
        | otherwise = A.Name x
    changeName _ _ (A.UnName _) = undefined

bbIsReferenced :: LLName -> CGMonad Bool
bbIsReferenced bb = do
    bbs <- liftM allBlocks get
    return $ any checkBlock bbs
  where
    checkBlock :: A.BasicBlock -> Bool
    checkBlock (A.BasicBlock name instrs (_ A.:= term)) = checkBlock (A.BasicBlock name instrs (A.Do term))
    checkBlock (A.BasicBlock _ _ (A.Do term)) = case term of
        (A.Ret _ _) -> False
        (A.CondBr _ (A.Name d1) (A.Name d2) _) -> d1 == bb || d2 == bb
        (A.Br (A.Name d) _) -> d == bb
        (A.Unreachable _) -> False
        _ -> undefined


toLLVMType :: Type -> A.Type
toLLVMType (TypeInt s) = A.IntegerType $ fromIntegral s
toLLVMType (TypeUInt s) = A.IntegerType $ fromIntegral s
toLLVMType TypeFloat = A.float
toLLVMType TypeDouble = A.double
toLLVMType (TypePtr t) = A.ptr $ toLLVMType t
toLLVMType (TypeName _) = undefined
toLLVMType (TypeFunc r a) = A.ptr $ A.FunctionType (toLLVMType r) (map toLLVMType a) False
toLLVMType TypeVoid = A.VoidType

initializerFor :: Type -> A.C.Constant
initializerFor (TypeInt s) = A.C.Int (fromIntegral s) 0
initializerFor (TypeUInt s) = A.C.Int (fromIntegral s) 0
initializerFor TypeFloat = A.C.Float (A.F.Single 0)
initializerFor TypeDouble = A.C.Float (A.F.Double 0)
initializerFor _ = undefined