module Language.Elna.Intermediate
    ( Quadruple(..)
    {- , Label(..)
    , Operand(..)
    , Variable(..) -}
    , intermediate
    ) where

import Data.Vector (Vector)
import qualified Data.Vector as Vector
import qualified Language.Elna.AST as AST
import Language.Elna.SymbolTable (SymbolTable{-, Info(..) -})

data Quadruple
    = StartQuadruple
    | StopQuadruple
    deriving (Eq, Show)

intermediate :: SymbolTable -> AST.Program -> {- HashMap AST.Identifier (-} Vector Quadruple --)
intermediate _globalTable = const $ Vector.fromList [StartQuadruple, StopQuadruple]
    {- = fst
    . flip runState mempty
    . runIntermediate
    . program globalTable -}
{-
import Data.Bifunctor (Bifunctor(..))
import Data.Int (Int32)
import Data.HashMap.Strict (HashMap)
import qualified Data.HashMap.Strict as HashMap
import Data.Text (Text)
import Data.Word (Word32)
import Language.Elna.Types (Type(..))
import qualified Language.Elna.SymbolTable as SymbolTable
import Data.Foldable (Foldable(..), foldrM)
import GHC.Records (HasField(..))
import qualified Data.Text as Text
import qualified Data.Text.Lazy.Builder.Int as Text.Builder
import qualified Data.Text.Lazy.Builder as Text.Builder
import qualified Data.Text.Lazy as Text.Lazy

data Operand
    = VariableOperand Variable
    | IntOperand Int32
    deriving (Eq, Show)

newtype Label = Label Text
    deriving Eq

instance Show Label
  where
    show (Label label) = '.' : Text.unpack label

data Variable = Variable Text | TempVariable Int32
    deriving Eq

instance Show Variable
  where
    show (Variable variable) = '$' : Text.unpack variable
    show (TempVariable variable) = '$' : show variable

data Quadruple
    = StartQuadruple
    | GoToQuadruple Label
    | AssignQuadruple Operand Variable
    | ArrayQuadruple Variable Operand Variable
    | ArrayAssignQuadruple Operand Operand Variable
    | AddQuadruple Operand Operand Variable
    | SubtractionQuadruple Operand Operand Variable
    | ProductQuadruple Operand Operand Variable
    | DivisionQuadruple Operand Operand Variable
    | NegationQuadruple Operand Variable
    | EqualQuadruple Operand Operand Label
    | NonEqualQuadruple Operand Operand Label
    | LessQuadruple Operand Operand Label
    | GreaterQuadruple Operand Operand Label
    | LessOrEqualQuadruple Operand Operand Label
    | GreaterOrEqualQuadruple Operand Operand Label
    | LabelQuadruple Label
    | ParameterQuadruple Operand
    | CallQuadruple Variable Word32
    | StopQuadruple
    deriving (Eq, Show)

createLabel :: Intermediate Label
createLabel = do
    currentCounter <- Intermediate $ gets labelCounter
    Intermediate $ modify' modifier
    pure
        $ Label
        $ Text.Lazy.toStrict
        $ Text.Builder.toLazyText
        $ Text.Builder.decimal currentCounter
  where
    modifier generator = generator
        { labelCounter = getField @"labelCounter" generator + 1
        }

createTemporary :: Intermediate Variable
createTemporary = do
    currentCounter <- Intermediate $ gets temporaryCounter
    Intermediate $ modify' modifier
    pure $ TempVariable currentCounter
  where
    modifier generator = generator
        { temporaryCounter = getField @"temporaryCounter" generator + 1
        }

program
    :: SymbolTable
    -> AST.Program
    -> Intermediate (HashMap AST.Identifier (Vector Quadruple))
program globalTable (AST.Program declarations) =
    foldrM go HashMap.empty declarations
  where
    go (AST.TypeDefinition _ _) accumulator = pure accumulator
    go (AST.ProcedureDefinition procedureName _ _ statements) accumulator = do
        translatedStatements <- Vector.cons StartQuadruple
            . flip Vector.snoc StopQuadruple
            . fold
            <$> traverse (statement globalTable) statements
        pure $ HashMap.insert procedureName translatedStatements accumulator

statement :: SymbolTable -> AST.Statement -> Intermediate (Vector Quadruple)
statement _ AST.EmptyStatement = pure mempty
statement localTable (AST.AssignmentStatement variableAccess' assignee) = do
    (rhsOperand, rhsStatements) <- expression localTable assignee
    let variableType' = variableType variableAccess' localTable
    accessResult <- variableAccess localTable variableAccess' Nothing variableType' mempty
    pure $ rhsStatements <> case accessResult of
            (AST.Identifier identifier, Just accumulatedIndex, accumulatedStatements) ->
                Vector.snoc accumulatedStatements
                    $ ArrayAssignQuadruple rhsOperand accumulatedIndex
                    $ Variable identifier
            (AST.Identifier identifier, Nothing, accumulatedStatements) ->
                Vector.snoc accumulatedStatements
                    $ AssignQuadruple rhsOperand
                    $ Variable identifier
statement localTable (AST.IfStatement ifCondition ifStatement elseStatement) = do
    (conditionStatements, jumpConstructor) <- condition localTable ifCondition
    ifLabel <- createLabel
    endLabel <- createLabel
    ifStatements <- statement localTable ifStatement
    possibleElseStatements <- traverse (statement localTable) elseStatement
    pure $ conditionStatements <> case possibleElseStatements of
        Just elseStatements -> Vector.cons (jumpConstructor ifLabel) elseStatements
            <> Vector.fromList [GoToQuadruple endLabel, LabelQuadruple ifLabel]
            <> Vector.snoc ifStatements (LabelQuadruple endLabel)
        Nothing -> Vector.fromList [jumpConstructor ifLabel, GoToQuadruple endLabel, LabelQuadruple ifLabel]
            <> Vector.snoc ifStatements (LabelQuadruple endLabel)
statement localTable (AST.WhileStatement whileCondition whileStatement) = do
    (conditionStatements, jumpConstructor) <- condition localTable whileCondition
    startLabel <- createLabel
    endLabel <- createLabel
    conditionLabel <- createLabel
    whileStatements <- statement localTable whileStatement
    pure $ Vector.fromList [LabelQuadruple conditionLabel]
        <> conditionStatements
        <> Vector.fromList [jumpConstructor startLabel, GoToQuadruple endLabel, LabelQuadruple startLabel]
        <> whileStatements
        <> Vector.fromList [GoToQuadruple conditionLabel, LabelQuadruple endLabel]
statement localTable (AST.CallStatement (AST.Identifier callName) arguments) = do
    visitedArguments <- traverse (expression localTable) arguments
    let (parameterStatements, argumentStatements)
            = bimap (Vector.fromList . fmap ParameterQuadruple) Vector.concat
            $ unzip visitedArguments
     in pure
        $ Vector.snoc (argumentStatements <> parameterStatements)
        $ CallQuadruple (Variable callName)
        $ fromIntegral
        $ Vector.length argumentStatements
statement localTable (AST.CompoundStatement statements) =
    fold <$> traverse (statement localTable) statements

condition
    :: SymbolTable
    -> AST.Condition
    -> Intermediate (Vector Quadruple, Label -> Quadruple)
condition localTable (AST.EqualCondition lhs rhs) = do
    (lhsOperand, lhsStatements) <- expression localTable lhs
    (rhsOperand, rhsStatements) <- expression localTable rhs
    pure
        ( lhsStatements <> rhsStatements
        , EqualQuadruple lhsOperand rhsOperand
        )
condition localTable (AST.NonEqualCondition lhs rhs) = do
    (lhsOperand, lhsStatements) <- expression localTable lhs
    (rhsOperand, rhsStatements) <- expression localTable rhs
    pure
        ( lhsStatements <> rhsStatements
        , NonEqualQuadruple lhsOperand rhsOperand
        )
condition localTable (AST.LessCondition lhs rhs) = do
    (lhsOperand, lhsStatements) <- expression localTable lhs
    (rhsOperand, rhsStatements) <- expression localTable rhs
    pure (lhsStatements <> rhsStatements, LessQuadruple lhsOperand rhsOperand)
condition localTable (AST.GreaterCondition lhs rhs) = do
    (lhsOperand, lhsStatements) <- expression localTable lhs
    (rhsOperand, rhsStatements) <- expression localTable rhs
    pure
        ( lhsStatements <> rhsStatements
        , GreaterQuadruple lhsOperand rhsOperand
        )
condition localTable (AST.LessOrEqualCondition lhs rhs) = do
    (lhsOperand, lhsStatements) <- expression localTable lhs
    (rhsOperand, rhsStatements) <- expression localTable rhs
    pure
        ( lhsStatements <> rhsStatements
        , LessOrEqualQuadruple lhsOperand rhsOperand
        )
condition localTable (AST.GreaterOrEqualCondition lhs rhs) = do
    (lhsOperand, lhsStatements) <- expression localTable lhs
    (rhsOperand, rhsStatements) <- expression localTable rhs
    pure
        ( lhsStatements <> rhsStatements
        , GreaterOrEqualQuadruple lhsOperand rhsOperand
        )

variableAccess
    :: SymbolTable
    -> AST.VariableAccess
    -> Maybe Operand
    -> Type
    -> Vector Quadruple
    -> Intermediate (AST.Identifier, Maybe Operand, Vector Quadruple)
variableAccess _ (AST.VariableAccess identifier) accumulatedIndex _ accumulatedStatements =
    pure (identifier, accumulatedIndex, accumulatedStatements)
variableAccess localTable (AST.ArrayAccess access1 index1) Nothing (ArrayType _ baseType) _ = do
    (indexPlace, statements) <- expression localTable index1
    variableAccess localTable access1 (Just indexPlace) baseType statements
variableAccess localTable (AST.ArrayAccess arrayAccess' arrayIndex) (Just baseIndex) (ArrayType arraySize baseType) statements = do
    (indexPlace, statements') <- expression localTable arrayIndex
    resultVariable <- createTemporary
    let resultOperand = VariableOperand resultVariable
        indexCalculation = Vector.fromList
            [ ProductQuadruple (IntOperand $ fromIntegral arraySize) baseIndex resultVariable
            , AddQuadruple indexPlace resultOperand resultVariable
            ]
     in variableAccess localTable arrayAccess' (Just resultOperand) baseType
        $ statements <> indexCalculation <> statements'
variableAccess _ _ _ _ _ = error "Array access operator doesn't match the type."

variableType :: AST.VariableAccess -> SymbolTable -> Type
variableType (AST.VariableAccess identifier) symbolTable
    | Just (TypeInfo type') <- SymbolTable.lookup identifier symbolTable = type'
    | otherwise = error "Undefined type."
variableType (AST.ArrayAccess arrayAccess' _) symbolTable =
    variableType arrayAccess' symbolTable

expression :: SymbolTable -> AST.Expression -> Intermediate (Operand, Vector Quadruple)
expression localTable = \case
    (AST.VariableExpression variableExpression) -> do
        let variableType' = variableType variableExpression localTable
        variableAccess' <- variableAccess localTable variableExpression Nothing variableType' mempty
        case variableAccess' of
            (AST.Identifier identifier, Nothing, statements) ->
                pure (VariableOperand (Variable identifier), statements)
            (AST.Identifier identifier, Just operand, statements) -> do
                arrayAddress <- createTemporary
                let arrayStatement = ArrayQuadruple (Variable identifier) operand arrayAddress
                pure
                    ( VariableOperand arrayAddress
                    , Vector.snoc statements arrayStatement
                    )
    (AST.LiteralExpression literal') -> pure (literal literal', mempty)
    (AST.NegationExpression negation) -> do
        (operand, statements) <- expression localTable negation
        tempVariable <- createTemporary
        let negationQuadruple = NegationQuadruple operand tempVariable
        pure
            ( VariableOperand tempVariable
            , Vector.snoc statements negationQuadruple
            )
    (AST.SumExpression lhs rhs) -> binaryExpression AddQuadruple lhs rhs
    (AST.SubtractionExpression lhs rhs) ->
        binaryExpression SubtractionQuadruple lhs rhs
    (AST.ProductExpression lhs rhs) ->
        binaryExpression ProductQuadruple lhs rhs
    (AST.DivisionExpression lhs rhs) ->
        binaryExpression DivisionQuadruple lhs rhs
  where
    binaryExpression f lhs rhs = do
        (lhsOperand, lhsStatements) <- expression localTable lhs
        (rhsOperand, rhsStatements) <- expression localTable rhs
        tempVariable <- createTemporary
        let newQuadruple = f lhsOperand rhsOperand tempVariable
        pure
            ( VariableOperand tempVariable
            , Vector.snoc (lhsStatements <> rhsStatements) newQuadruple
            )

literal :: AST.Literal -> Operand
literal (AST.IntegerLiteral integer) = IntOperand integer
literal (AST.HexadecimalLiteral integer) = IntOperand integer
literal (AST.CharacterLiteral character) = IntOperand $ fromIntegral character
literal (AST.BooleanLiteral boolean)
    | boolean = IntOperand 1
    | otherwise = IntOperand 0
-}