{-# LANGUAGE BlockArguments #-}
{-# LANGUAGE ForeignFunctionInterface #-}
{-# LANGUAGE NamedFieldPuns #-}

module ExpressionTest (tests) where

import Control.Exception (finally)
import Data.Char (toLower)
import Data.IORef (IORef, newIORef, readIORef, writeIORef)
import Data.List (isInfixOf)
import Database.DuckDB.FFI
import Foreign.C.String (peekCString, withCString)
import Foreign.Marshal.Alloc (alloca)
import Foreign.Ptr (castPtr, freeHaskellFunPtr, nullFunPtr, nullPtr)
import Foreign.Storable (peek, poke)
import Test.Tasty (TestTree, testGroup)
import Test.Tasty.HUnit (assertBool, testCase, (@?=))
import Utils (
    destroyDuckValue,
    destroyErrorData,
    destroyLogicalType,
    withConnection,
    withDatabase,
    withLogicalType,
    withResult,
    withScalarFunction,
 )

data ExpressionHarness = ExpressionHarness
    { ehFoldable :: IO (Maybe Bool)
    , ehReturnType :: IO (Maybe DuckDBType)
    , ehFoldedValue :: IO (Maybe String)
    , ehFoldError :: IO (Maybe String)
    }

data ExpressionState = ExpressionState
    { esFoldable :: IORef (Maybe Bool)
    , esReturnType :: IORef (Maybe DuckDBType)
    , esFoldValue :: IORef (Maybe String)
    , esFoldError :: IORef (Maybe String)
    }

tests :: TestTree
tests =
    testGroup
        "Expression Interface"
        [ expressionFoldLiteral
        , expressionNonFoldable
        ]

expressionFoldLiteral :: TestTree
expressionFoldLiteral =
    testCase "folds literal expressions to constant values" $
        withDatabase \db ->
            withConnection db \conn ->
                withExpressionFunction conn "expr_literal" \ExpressionHarness{ehFoldable, ehReturnType, ehFoldedValue, ehFoldError} -> do
                    withResult conn "SELECT expr_literal(42)" \_ -> pure ()
                    ehFoldable >>= (@?= Just True)
                    ehReturnType >>= (@?= Just DuckDBTypeInteger)
                    ehFoldedValue >>= (@?= Just "42")
                    ehFoldError >>= (@?= Nothing)

expressionNonFoldable :: TestTree
expressionNonFoldable =
    testCase "detects non-foldable column references" $
        withDatabase \db ->
            withConnection db \conn ->
                withExpressionFunction conn "expr_non_foldable" \ExpressionHarness{ehFoldable, ehReturnType, ehFoldedValue, ehFoldError} -> do
                    withResult conn "SELECT expr_non_foldable(v) FROM (VALUES (7)) t(v)" \_ -> pure ()
                    ehFoldable >>= (@?= Just False)
                    ehReturnType >>= (@?= Just DuckDBTypeInteger)
                    ehFoldedValue >>= (@?= Nothing)
                    errMsg <- ehFoldError
                    assertBool "expected fold error message" $
                        maybe False (isInfixOf "fold" . map toLower) errMsg

withExpressionFunction :: DuckDBConnection -> String -> (ExpressionHarness -> IO a) -> IO a
withExpressionFunction conn funcName action = do
    foldRef <- newIORef Nothing
    typeRef <- newIORef Nothing
    valueRef <- newIORef Nothing
    errorRef <- newIORef Nothing
    let state = ExpressionState foldRef typeRef valueRef errorRef
    bindPtr <- mkScalarBindFun (expressionBind state)
    execPtr <- mkScalarExecFun expressionExec
    result <-
        withScalarFunction $ \scalarFun -> do
            withCString funcName $ \name -> c_duckdb_scalar_function_set_name scalarFun name
            withLogicalType (c_duckdb_create_logical_type DuckDBTypeInteger) $ \intType -> do
                c_duckdb_scalar_function_add_parameter scalarFun intType
                c_duckdb_scalar_function_set_return_type scalarFun intType
                c_duckdb_scalar_function_set_bind scalarFun bindPtr
                c_duckdb_scalar_function_set_function scalarFun execPtr
                c_duckdb_scalar_function_set_extra_info scalarFun nullPtr nullFunPtr
                c_duckdb_register_scalar_function conn scalarFun >>= (@?= DuckDBSuccess)
                action
                    ExpressionHarness
                        { ehFoldable = readIORef foldRef
                        , ehReturnType = readIORef typeRef
                        , ehFoldedValue = readIORef valueRef
                        , ehFoldError = readIORef errorRef
                        }
    freeHaskellFunPtr bindPtr
    freeHaskellFunPtr execPtr
    pure result

expressionBind :: ExpressionState -> DuckDBBindInfo -> IO ()
expressionBind ExpressionState{esFoldable, esReturnType, esFoldValue, esFoldError} info = do
    argCount <- c_duckdb_scalar_function_bind_get_argument_count info
    argCount @?= 1
    exprHandle <- c_duckdb_scalar_function_bind_get_argument info 0
    finally
        ( do
            foldableFlag <- c_duckdb_expression_is_foldable exprHandle
            let isFoldable = foldableFlag /= 0
            writeIORef esFoldable (Just isFoldable)
            retType <- c_duckdb_expression_return_type exprHandle
            typeId <- c_duckdb_get_type_id retType
            destroyLogicalType retType
            writeIORef esReturnType (Just typeId)
            alloca \ctxPtr -> do
                c_duckdb_scalar_function_get_client_context info ctxPtr
                ctx <- peek ctxPtr
                alloca \valuePtr -> do
                    poke valuePtr nullPtr
                    errData <- c_duckdb_expression_fold ctx exprHandle valuePtr
                    if errData == nullPtr
                        then do
                            valueHandle <- peek valuePtr
                            if valueHandle == nullPtr
                                then do
                                    writeIORef esFoldValue Nothing
                                    writeIORef esFoldError (Just "fold produced null value")
                                else do
                                    rendered <- duckValueToString valueHandle
                                    writeIORef esFoldValue (Just rendered)
                                    writeIORef esFoldError Nothing
                                    destroyDuckValue valueHandle
                        else do
                            msgPtr <- c_duckdb_error_data_message errData
                            msg <- peekCString msgPtr
                            writeIORef esFoldValue Nothing
                            writeIORef esFoldError (Just msg)
                            destroyErrorData errData
        )
        (alloca \exprPtr -> poke exprPtr exprHandle >> c_duckdb_destroy_expression exprPtr)

expressionExec :: DuckDBFunctionInfo -> DuckDBDataChunk -> DuckDBVector -> IO ()
expressionExec _ chunk outVec = do
    inVec <- c_duckdb_data_chunk_get_vector chunk 0
    c_duckdb_vector_reference_vector outVec inVec

-- Helpers ------------------------------------------------------------------

duckValueToString :: DuckDBValue -> IO String
duckValueToString value = do
    strPtr <- c_duckdb_value_to_string value
    text <- peekCString strPtr
    c_duckdb_free (castPtr strPtr)
    pure text

-- Wrapper constructors -----------------------------------------------------

foreign import ccall "wrapper"
    mkScalarBindFun :: (DuckDBBindInfo -> IO ()) -> IO DuckDBScalarFunctionBindFun

foreign import ccall "wrapper"
    mkScalarExecFun :: (DuckDBFunctionInfo -> DuckDBDataChunk -> DuckDBVector -> IO ()) -> IO DuckDBScalarFunctionFun