module Codegen(codegen) where

-- import Control.Monad
-- 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.Constant as A.C
-- 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 as A
-- import Debug.Trace

import AST


type Error a = Either String a


codegen :: Program  -- Program to compile
        -> String   -- Module name
        -> String   -- File name of source
        -> Error A.Module
codegen prog name fname = do
    defs <- generateDefs prog
    return $ A.defaultModule {
            A.moduleName = name,
            A.moduleSourceFileName = fname,
            A.moduleDefinitions = defs
        }


generateDefs :: Program -> Error [A.Definition]
generateDefs prog = do
    vardecls <- genGlobalVars prog
    return vardecls

genGlobalVars :: Program -> Error [A.Definition]
genGlobalVars (Program decs) = mapM gen $ filter isDecVariable decs
  where
    gen (DecVariable t n Nothing) = return $ A.GlobalDefinition $
            A.globalVariableDefaults {
                A.G.name = A.Name n,
                A.G.type' = toLLVMType t,
                A.G.initializer = Just $ initializerFor t
            }
    gen (DecVariable _ _ (Just _)) = Left $ "Initialised global variables not supported yet"
    gen _ = 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

initializerFor :: Type -> A.C.Constant
initializerFor (TypeInt s) = A.C.Int (fromIntegral s) 0
initializerFor (TypeUInt s) = A.C.Int (fromIntegral s) 0
initializerFor _ = undefined


isDecVariable :: Declaration -> Bool
isDecVariable (DecVariable {}) = True
isDecVariable _ = False