module Main (main) where

import Control.Arrow
import Control.Applicative
import Control.Concurrent
import Control.Concurrent.STM
import Control.Monad
import Control.Monad.Except
import Control.Monad.Reader

import Data.Map (Map)
import Data.Map qualified as M
import Data.Maybe
import Data.Scientific
import Data.Text (Text)
import qualified Data.Text as T

import Text.Read (readMaybe)

import System.Console.GetOpt
import System.Directory
import System.Environment
import System.Exit
import System.FilePath
import System.IO.Error
import System.Posix.Process
import System.Posix.Signals
import System.Process

import GDB
import Network
import Output
import Parser
import Process
import Test
import Util

data Options = Options
    { optDefaultTool :: String
    , optProcTools :: [(ProcName, String)]
    , optVerbose :: Bool
    , optTimeout :: Scientific
    , optGDB :: Bool
    , optForce :: Bool
    }

defaultOptions :: Options
defaultOptions = Options
    { optDefaultTool = ""
    , optProcTools = []
    , optVerbose = False
    , optTimeout = 1
    , optGDB = False
    , optForce = False
    }

testDir :: FilePath
testDir = "./.test"


data TestEnv = TestEnv
    { teOutput :: Output
    , teFailed :: TVar (Maybe Failed)
    , teOptions :: Options
    , teGDB :: Maybe (MVar GDB)
    }

data TestState = TestState
    { tsNetwork :: Network
    , tsVars :: [(VarName, SomeVarValue)]
    , tsNodePacketLoss :: Map NodeName Scientific
    }

newtype TestRun a = TestRun { fromTestRun :: ReaderT (TestEnv, TestState) (ExceptT Failed IO) a }
    deriving (Functor, Applicative, Monad, MonadReader (TestEnv, TestState), MonadIO)

instance MonadFail TestRun where
    fail str = do
        outLine OutputError Nothing $ T.pack str
        throwError Failed

instance MonadError Failed TestRun where
    throwError failed = do
        failedVar <- asks $ teFailed . fst
        liftIO $ atomically $ modifyTVar failedVar (`mplus` Just failed)

        te <- asks fst
        case failed of
            ProcessCrashed _ | Just mgdb <- teGDB te -> do
                maybe (return ()) gdbSession =<< liftIO (tryTakeMVar mgdb)
            _ -> return ()

        TestRun $ throwError failed

    catchError (TestRun act) handler = TestRun $ catchError act $ fromTestRun . handler

instance MonadEval TestRun where
    lookupVar name = maybe (fail $ "variable not in scope: '" ++ unpackVarName name ++ "'") return =<< asks (lookup name . tsVars . snd)

instance MonadOutput TestRun where
    getOutput = asks $ teOutput . fst

withVar :: ExprType e => VarName -> e -> TestRun a -> TestRun a
withVar name value = local (fmap $ \s -> s { tsVars = (name, SomeVarValue value) : tsVars s })

withNodePacketLoss :: Node -> Scientific -> TestRun a -> TestRun a
withNodePacketLoss node loss inner = do
    x <- local (fmap $ \s -> s { tsNodePacketLoss = M.insertWith (\l l' -> 1 - (1 - l) * (1 - l')) (nodeName node) loss $ tsNodePacketLoss s }) $ do
        resetLoss
        inner
    resetLoss
    return x
  where
    resetLoss = do
        tl <- asks $ fromMaybe 0 . M.lookup (nodeName node) . tsNodePacketLoss . snd
        liftIO $ callOn node $ "tc qdisc replace dev veth0 root netem loss " ++ show (tl * 100) ++ "%"
        liftIO $ putStrLn $ "tc qdisc replace dev veth0 root netem loss " ++ show (tl * 100) ++ "%"

forkTest :: TestRun () -> TestRun ()
forkTest act = do
    tenv <- ask
    void $ liftIO $ forkIO $ do
        runExceptT (flip runReaderT tenv $ fromTestRun act) >>= \case
            Left e -> atomically $ writeTVar (teFailed $ fst tenv) (Just e)
            Right () -> return ()

atomicallyTest :: STM a -> TestRun a
atomicallyTest act = do
    failedVar <- asks $ teFailed . fst
    res <- liftIO $ atomically $ do
        readTVar failedVar >>= \case
            Just e  -> return $ Left e
            Nothing -> Right <$> act
    case res of
        Left e -> throwError e
        Right x -> return x

withNetwork :: (Network -> TestRun a) -> TestRun a
withNetwork inner = do
    net <- liftIO $ do
        callCommand "ip link add name br0 group 1 type bridge"
        callCommand "ip addr add 192.168.0.1/24 broadcast 192.168.0.255 dev br0"
        callCommand "ip link set dev br0 up"
        callCommand "ip link set dev lo up"
        Network <$> newMVar [] <*> newMVar [] <*> pure testDir

    void $ spawnOn (Left net) (ProcNameTcpdump) (Just softwareTermination) $
        "tcpdump -i br0 -w '" ++ testDir ++ "/br0.pcap' -U -Z root"

    useGDB <- asks $ optGDB . teOptions . fst
    mgdb <- if useGDB
        then do
            failedVar <- asks $ teFailed . fst
            gdb <- gdbStart $ atomically . writeTVar failedVar . Just . ProcessCrashed
            liftIO $ modifyMVar_ (netProcesses net) $ return . (gdbProcess gdb:)
            Just <$> liftIO (newMVar gdb)
        else return Nothing

    res <- local ((\te -> te { teGDB = mgdb }) *** (\s -> s { tsNetwork = net })) $ inner net

    processes <- liftIO $ readMVar (netProcesses net)
    forM_ processes $ \p -> do
        closeProcess p `catchError` \_ -> return ()

    liftIO $ do
        callCommand $ "ip -all netns del"
        callCommand $ "ip link del group 1"

    return res

createNode :: TypedVarName Node -> (Node -> TestRun a) -> TestRun a
createNode (TypedVarName vname) inner = do
    net <- asks $ tsNetwork . snd
    node <- liftIO $ do
        node <- modifyMVar (netNodes net) $ \nodes -> do
            let nname = nextNodeName vname $ map nodeName nodes
                ip = "192.168.0." ++ show (11 + length nodes)
                node = Node { nodeName = nname
                            , nodeIp = T.pack ip
                            , nodeNetwork = net
                            , nodeDir = netDir net </> ("erebos_" ++ unpackNodeName nname)
                            }
            return $ (node : nodes, node)

        let name = unpackNodeName $ nodeName node
            dir = nodeDir node

        exists <- doesPathExist dir
        when exists $ ioError $ userError $ dir ++ " exists"
        createDirectoryIfMissing True dir

        callCommand $ "ip netns add \""++ name ++ "\""
        callCommand $ "ip link add \"veth_" ++ name ++ "\" group 1 type veth peer name veth0 netns \"" ++ name ++ "\""
        callCommand $ "ip link set dev \"veth_" ++ name ++ "\" master br0 up"
        callOn node $ "ip addr add " ++ T.unpack (nodeIp node) ++ "/24 broadcast 192.168.0.255 dev veth0"
        callOn node $ "ip link set dev veth0 up"
        callOn node $ "ip link set dev lo up"
        return node

    withVar vname node $ inner node

callOn :: Node -> String -> IO ()
callOn node cmd = callCommand $ "ip netns exec \"" ++ unpackNodeName (nodeName node) ++ "\" " ++ cmd

spawnOn :: Either Network Node -> ProcName -> Maybe Signal -> String -> TestRun Process
spawnOn target pname killWith cmd = do
    let prefix = either (const "") (\node -> "ip netns exec \"" ++ unpackNodeName (nodeName node) ++ "\" ") target
    (Just hin, Just hout, Just herr, handle) <- liftIO $ createProcess (shell $ prefix ++ cmd)
        { std_in = CreatePipe, std_out = CreatePipe, std_err = CreatePipe
        , env = Just [("EREBOS_DIR", either netDir nodeDir target)]
        }
    pout <- liftIO $ newTVarIO []

    let process = Process
            { procName = pname
            , procHandle = handle
            , procStdin = hin
            , procOutput = pout
            , procKillWith = killWith
            , procNode = either (const undefined) id target
            }

    forkTest $ lineReadingLoop process hout $ \line -> do
        outProc OutputChildStdout process line
        liftIO $ atomically $ modifyTVar pout (++[line])
    forkTest $ lineReadingLoop process herr $ \line -> do
        case pname of
             ProcNameTcpdump -> return ()
             _ -> outProc OutputChildStderr process line

    let net = either id nodeNetwork target
    asks (teGDB . fst) >>= maybe (return Nothing) (liftIO . tryReadMVar) >>= \case
        Just gdb -> addInferior gdb process
        Nothing -> return ()

    liftIO $ modifyMVar_ (netProcesses net) $ return . (process:)
    return process

tryMatch :: Regex -> [Text] -> Maybe ((Text, [Text]), [Text])
tryMatch re (x:xs) | Right (Just (_, _, _, capture)) <- regexMatch re x = Just ((x, capture), xs)
                   | otherwise = fmap (x:) <$> tryMatch re xs
tryMatch _ [] = Nothing

exprFailed :: Text -> SourceLine -> Maybe ProcName -> Expr a -> TestRun ()
exprFailed desc (SourceLine sline) pname expr = do
    let prompt = maybe T.empty textProcName pname
    exprVars <- gatherVars expr
    outLine OutputMatchFail (Just prompt) $ T.concat [desc, T.pack " failed on ", sline]
    forM_ exprVars $ \(name, value) ->
        outLine OutputMatchFail (Just prompt) $ T.concat [T.pack "  ", textVarName name, T.pack " = ", textSomeVarValue value]
    throwError Failed

expect :: SourceLine -> Process -> Expr Regex -> [TypedVarName Text] -> TestRun () -> TestRun ()
expect (SourceLine sline) p expr tvars inner = do
    re <- eval expr
    timeout <- asks $ optTimeout . teOptions . fst
    delay <- liftIO $ registerDelay $ ceiling $ 1000000 * timeout
    mbmatch <- atomicallyTest $ (Nothing <$ (check =<< readTVar delay)) <|> do
        line <- readTVar (procOutput p)
        case tryMatch re line of
             Nothing -> retry
             Just (m, out') -> do
                 writeTVar (procOutput p) out'
                 return $ Just m
    case mbmatch of
         Just (line, capture) -> do
             let vars = map (\(TypedVarName n) -> n) tvars

             when (length vars /= length capture) $ do
                 outProc OutputMatchFail p $ T.pack "mismatched number of capture variables on " `T.append` sline
                 throwError Failed

             forM_ vars $ \name -> do
                 cur <- asks (lookup name . tsVars . snd)
                 when (isJust cur) $ do
                     outProc OutputError p $ T.pack "variable '" `T.append` textVarName name `T.append` T.pack "' already exists on " `T.append` sline
                     throwError Failed

             outProc OutputMatch p line
             local (fmap $ \s -> s { tsVars = zip vars (map SomeVarValue capture) ++ tsVars s }) inner

         Nothing -> exprFailed (T.pack "expect") (SourceLine sline) (Just $ procName p) expr

testStepGuard :: SourceLine -> Expr Bool -> TestRun ()
testStepGuard sline expr = do
    x <- eval expr
    when (not x) $ exprFailed (T.pack "guard") sline Nothing expr

finally :: MonadError e m => m a -> m b -> m a
finally act handler = do
    x <- act `catchError` \e -> handler >> throwError e
    void handler
    return x

evalSteps :: [TestStep] -> TestRun ()
evalSteps = mapM_ $ \case
    Let (SourceLine sline) name expr inner -> do
        cur <- asks (lookup name . tsVars . snd)
        when (isJust cur) $ do
            outLine OutputError Nothing $ T.pack "variable '" `T.append` textVarName name `T.append` T.pack "' already exists on " `T.append` sline
            throwError Failed
        value <- eval expr
        withVar name value $ evalSteps inner

    DeclNode name@(TypedVarName vname) inner -> do
        createNode name $ \node -> do
            withVar vname node $ evalSteps inner

    Spawn (TypedVarName vname@(VarName tname)) nname inner -> do
        either createNode ((>>=) . eval) nname $ \node -> do
            let pname = ProcName tname
            opts <- asks $ teOptions . fst
            p <- spawnOn (Right node) pname Nothing $
                fromMaybe (optDefaultTool opts) (lookup pname $ optProcTools opts)
            withVar vname p (evalSteps inner) `finally` do
                net <- asks $ tsNetwork . snd
                ps <- liftIO $ takeMVar (netProcesses net)
                closeProcess p `finally` do
                    liftIO $ putMVar (netProcesses net) $ filter (/=p) ps

    Send pname expr -> do
        p <- eval pname
        line <- eval expr
        outProc OutputChildStdin p line
        send p line

    Expect line pname expr captures inner -> do
        p <- eval pname
        expect line p expr captures $ evalSteps inner

    Guard line expr -> do
        testStepGuard line expr

    PacketLoss loss node inner -> do
        l <- eval loss
        n <- eval node
        withNodePacketLoss n l $ evalSteps inner

    Wait -> do
        outPrompt $ T.pack "Waiting..."
        void $ liftIO $ getLine
        outClearPrompt

runTest :: Output -> Options -> Test -> IO Bool
runTest out opts test = do
    tenv <- TestEnv
        <$> pure out
        <*> newTVarIO Nothing
        <*> pure opts
        <*> pure Nothing
    tstate <- TestState
        <$> pure (error "network not initialized")
        <*> pure []
        <*> pure M.empty

    when (optForce opts) $ removeDirectoryRecursive testDir `catchIOError` \e ->
        if isDoesNotExistError e then return () else ioError e
    exists <- doesPathExist testDir
    when exists $ ioError $ userError $ testDir ++ " exists"
    createDirectoryIfMissing True testDir

    res <- runExceptT $ flip runReaderT (tenv, tstate) $ fromTestRun $ withNetwork $ \net -> do
        let sigHandler SignalInfo { siginfoSpecific = chld } = do
                processes <- readMVar (netProcesses net)
                forM_ processes $ \p -> do
                    mbpid <- getPid (procHandle p)
                    when (mbpid == Just (siginfoPid chld)) $ flip runReaderT out $ do
                        let err detail = outProc OutputChildFail p detail
                        case siginfoStatus chld of
                             Exited ExitSuccess -> outProc OutputChildInfo p $ T.pack $ "child exited successfully"
                             Exited (ExitFailure code) -> do
                                 err $ T.pack $ "child process exited with status " ++ show code
                                 liftIO $ atomically $ writeTVar (teFailed tenv) $ Just Failed
                             Terminated sig _ -> do
                                 err $ T.pack $ "child terminated with signal " ++ show sig
                                 liftIO $ atomically $ writeTVar (teFailed tenv) $ Just $ ProcessCrashed p
                             Stopped sig -> err $ T.pack $ "child stopped with signal " ++ show sig
        oldHandler <- liftIO $ installHandler processStatusChanged (CatchInfo sigHandler) Nothing

        evalSteps (testSteps test) `finally` do
            void $ liftIO $ installHandler processStatusChanged oldHandler Nothing

    failed <- atomically $ readTVar (teFailed tenv)
    case (res, failed) of
        (Right (), Nothing) -> do
            removeDirectoryRecursive testDir
            return True
        _ -> return False


options :: [OptDescr (Options -> Options)]
options =
    [ Option ['T'] ["tool"]
        (ReqArg (\str opts -> case break (==':') str of
                                   (path, []) -> opts { optDefaultTool = path }
                                   (pname, (_:path)) -> opts { optProcTools = (ProcName (T.pack pname), path) : optProcTools opts }
                ) "PATH")
        "test tool to be used"
    , Option ['v'] ["verbose"]
        (NoArg (\opts -> opts { optVerbose = True }))
        "show output of processes and successful tests"
    , Option ['t'] ["timeout"]
        (ReqArg (\str opts -> case readMaybe str of
                                   Just timeout -> opts { optTimeout = timeout }
                                   Nothing -> error "timeout must be a number") "SECONDS")
        "default timeout in seconds with microsecond precision"
    , Option ['g'] ["gdb"]
        (NoArg (\opts -> opts { optGDB = True }))
        "run GDB and attach spawned processes"
    , Option ['f'] ["force"]
        (NoArg (\opts -> opts { optForce = True }))
        "remove test directory if it exists instead of stopping"
    ]

main :: IO ()
main = do
    envtool <- fromMaybe (error "No test tool defined") <$> lookupEnv "EREBOS_TEST_TOOL"
    args <- getArgs
    (opts, files) <- case getOpt Permute options args of
        (o, files, []) -> return (foldl (flip id) defaultOptions { optDefaultTool = envtool } o, files)
        (_, _, errs) -> ioError (userError (concat errs ++ usageInfo header options))
            where header = "Usage: erebos-tester [OPTION...]"

    optDefaultTool opts `seq` return ()

    out <- startOutput $ optVerbose opts
    ok <- flip allM files $ allM (runTest out opts) <=< parseTestFile
    when (not ok) exitFailure