{-# LANGUAGE OverloadedStrings #-}

module Main (main) where

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.FilePath.Glob
import System.IO.Error
import System.Posix.Process
import System.Posix.Signals
import System.Process

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

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

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

data TestEnv = TestEnv
    { teOutput :: Output
    , teFailed :: TVar (Maybe Failed)
    , teOptions :: Options
    , teProcesses :: MVar [Process]
    , 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)
    rootNetwork = asks $ tsNetwork . 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
    testDir <- asks $ optTestDir . teOptions . fst
    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 [] <*> pure testDir

    res <- spawnOn (Left net) (ProcNameTcpdump) (Just softwareTermination)
        ("tcpdump -i br0 -w '" ++ testDir ++ "/br0.pcap' -U -Z root") $ \_ -> do
        local (fmap $ \s -> s { tsNetwork = net }) $ inner net

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

    return res

createNode :: Expr Network -> Either (TypedVarName Node) (TypedVarName Process) -> (Node -> TestRun a) -> TestRun a
createNode netexpr tvname inner = do
    net <- eval netexpr
    node <- liftIO $ do
        node <- modifyMVar (netNodes net) $ \nodes -> do
            let nname = nextNodeName (either fromTypedVarName fromTypedVarName tvname) $ 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

    either (flip withVar node . fromTypedVarName) (const id) tvname $ 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 -> (Process -> TestRun a) -> TestRun a
spawnOn target pname killWith cmd inner = 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

    asks (teGDB . fst) >>= maybe (return Nothing) (liftIO . tryReadMVar) >>= \case
        Just gdb | ProcName _ <- pname -> addInferior gdb process
        _ -> return ()

    procVar <- asks $ teProcesses . fst
    liftIO $ modifyMVar_ procVar $ return . (process:)

    inner process `finally` do
        ps <- liftIO $ takeMVar procVar
        closeProcess process `finally` do
            liftIO $ putMVar procVar $ filter (/=process) ps

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) net inner -> do
        createNode net (Left name) $ \node -> do
            withVar vname node $ evalSteps inner

    Spawn tvname@(TypedVarName vname@(VarName tname)) target inner -> do
        case target of
            Left nname -> createNode RootNetwork (Left nname) go
            Right (Left net) -> createNode net (Right tvname) go
            Right (Right node) -> go =<< eval node
      where
        go node = do
            opts <- asks $ teOptions . fst
            let pname = ProcName tname
                tool = fromMaybe (optDefaultTool opts) (lookup pname $ optProcTools opts)
            spawnOn (Right node) pname Nothing tool $ \p -> do
                withVar vname p (evalSteps inner)

    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
    let testDir = optTestDir opts
    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

    failedVar <- newTVarIO Nothing
    procVar <- newMVar []

    mgdb <- if optGDB opts
        then flip runReaderT out $ do
            gdb <- gdbStart $ atomically . writeTVar failedVar . Just . ProcessCrashed
            Just . (, gdbProcess gdb) <$> liftIO (newMVar gdb)
        else return Nothing

    let tenv = TestEnv
            { teOutput = out
            , teFailed = failedVar
            , teOptions = opts
            , teProcesses = procVar
            , teGDB = fst <$> mgdb
            }
        tstate = TestState
            { tsNetwork = error "network not initialized"
            , tsVars = []
            , tsNodePacketLoss = M.empty
            }

    let sigHandler SignalInfo { siginfoSpecific = chld } = do
            processes <- readMVar procVar
            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 <- installHandler processStatusChanged (CatchInfo sigHandler) Nothing

    res <- runExceptT $ flip runReaderT (tenv, tstate) $ fromTestRun $ do
        withNetwork $ \_ -> evalSteps (testSteps test)

    void $ installHandler processStatusChanged oldHandler Nothing

    Right () <- runExceptT $ flip runReaderT out $ do
        maybe (return ()) (closeProcess . snd) mgdb
    [] <- readMVar procVar

    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
    configPath <- findConfig
    config <- mapM parseConfig configPath
    let baseDir = maybe "." dropFileName configPath

    envtool <- lookupEnv "EREBOS_TEST_TOOL" >>= \mbtool ->
        return $ fromMaybe (error "No test tool defined") $ mbtool `mplus` (return . (baseDir </>) =<< configTool =<< config)

    let initOpts = defaultOptions
            { optDefaultTool = envtool
            , optTestDir = normalise $ baseDir </> optTestDir defaultOptions
            }

    args <- getArgs
    (opts, ofiles) <- case getOpt Permute options args of
        (o, files, []) -> return (foldl (flip id) initOpts o, files)
        (_, _, errs) -> ioError (userError (concat errs ++ usageInfo header options))
            where header = "Usage: erebos-tester [OPTION...]"

    getPermissions (head $ words $ optDefaultTool opts) >>= \perms -> do
        when (not $ executable perms) $ do
            fail $ optDefaultTool opts <> " is not executable"

    files <- if not (null ofiles)
        then return ofiles
        else concat <$> mapM (flip globDir1 baseDir) (maybe [] configTests config)
    when (null files) $ fail $ "No test files"

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