{- git-annex fuzz generator
 -
 - Copyright 2013 Joey Hess <id@joeyh.name>
 -
 - Licensed under the GNU AGPL version 3 or higher.
 -}

{-# LANGUAGE OverloadedStrings #-}

module Command.FuzzTest where

import Command
import qualified Annex
import qualified Git.Config
import Config
import Utility.ThreadScheduler
import Utility.DiskFree
import Git.Types (fromConfigKey)

import Data.Time.Clock
import System.Random (getStdRandom, random, randomR)
import Test.QuickCheck
import Control.Concurrent

cmd :: Command
cmd = notBareRepo $
	command "fuzztest" SectionTesting
		"generates fuzz test files"
		paramNothing (withParams seek)

seek :: CmdParams -> CommandSeek
seek = withNothing (commandAction start)

start :: CommandStart
start = do
	guardTest
	logf <- fromRepo gitAnnexFuzzTestLogFile
	showStart "fuzztest" (toRawFilePath logf)
	logh <- liftIO $ openFile logf WriteMode
	void $ forever $ fuzz logh
	stop

guardTest :: Annex ()
guardTest = unlessM (fromMaybe False . Git.Config.isTrue' <$> getConfig key mempty) $
	giveup $ unlines
		[ "Running fuzz tests *writes* to and *deletes* files in"
		, "this repository, and pushes those changes to other"
		, "repositories! This is a developer tool, not something"
		, "to play with."
		, ""
		, "Refusing to run fuzz tests, since " ++ fromConfigKey key ++ " is not set!"
		]
  where
	key = annexConfig "eat-my-repository"

fuzz :: Handle -> Annex ()
fuzz logh = do
	fuzzer <- genFuzzAction
	record logh $ flip Started fuzzer
	result <- tryNonAsync $ runFuzzAction fuzzer
	record logh $ flip Finished $
		either (const False) (const True) result

record :: Handle -> (UTCTime -> TimeStampedFuzzAction) -> Annex ()
record h tmpl = liftIO $ do
	now <- getCurrentTime
	let s = show $ tmpl now
	print s
	hPrint h s
	hFlush h

{- Delay for either a fraction of a second, or a few seconds, or up
 - to 1 minute.
 -
 - The MinutesDelay is used as an opportunity to do housekeeping tasks.
 -}
randomDelay :: Delay -> Annex ()
randomDelay TinyDelay = liftIO $
	threadDelay =<< getStdRandom (randomR (10000, 1000000))
randomDelay SecondsDelay = liftIO $ 
	threadDelaySeconds =<< Seconds <$> getStdRandom (randomR (1, 10))
randomDelay MinutesDelay = do
	liftIO $ threadDelaySeconds =<< Seconds <$> getStdRandom (randomR (1, 60))
	reserve <- annexDiskReserve <$> Annex.getGitConfig
	free <- liftIO $ getDiskFree "."
	case free of
		Just have | have < reserve -> do
			warning "Low disk space; fuzz test paused."
			liftIO $ threadDelaySeconds (Seconds 60)
			randomDelay MinutesDelay
		_  -> noop

data Delay
	= TinyDelay
	| SecondsDelay
	| MinutesDelay
	deriving (Read, Show, Eq)

instance Arbitrary Delay where
	arbitrary = elements [TinyDelay, SecondsDelay, MinutesDelay]

data FuzzFile = FuzzFile FilePath
	deriving (Read, Show, Eq)

data FuzzDir = FuzzDir FilePath
	deriving (Read, Show, Eq)

instance Arbitrary FuzzFile where
	arbitrary = FuzzFile <$> arbitrary

instance Arbitrary FuzzDir where
	arbitrary = FuzzDir <$> arbitrary

class ToFilePath a where
	toFilePath :: a -> FilePath

instance ToFilePath FuzzFile where
	toFilePath (FuzzFile f) = f

instance ToFilePath FuzzDir where
	toFilePath (FuzzDir d) = d

isFuzzFile :: FilePath -> Bool
isFuzzFile f = "fuzzfile_" `isPrefixOf` takeFileName f

isFuzzDir :: FilePath -> Bool
isFuzzDir d = "fuzzdir_" `isPrefixOf` d

mkFuzzFile :: FilePath -> [FuzzDir] -> FuzzFile
mkFuzzFile file dirs = FuzzFile $ joinPath (map toFilePath dirs) </> ("fuzzfile_" ++ file)

mkFuzzDir :: Int -> FuzzDir
mkFuzzDir n = FuzzDir $ "fuzzdir_" ++ show n

{- File is placed inside a directory hierarchy up to 4 subdirectories deep. -}
genFuzzFile :: IO FuzzFile
genFuzzFile = do
	n <- getStdRandom $ randomR (0, 4)
	dirs <- replicateM n genFuzzDir
	file <- show <$> (getStdRandom random :: IO Int)
	return $ mkFuzzFile file dirs

{- Only 16 distinct subdirectories are used. When nested 4 deep, this
 - yields 69904 total directories max, which is below the default Linux
 - inotify limit of 81920. The goal is not to run the assistant out of
 - inotify descriptors. -}
genFuzzDir :: IO FuzzDir
genFuzzDir = mkFuzzDir <$> (getStdRandom (randomR (1,16)) :: IO Int)

data TimeStampedFuzzAction 
	= Started UTCTime FuzzAction
	| Finished UTCTime Bool
	deriving (Read, Show)

data FuzzAction
	= FuzzAdd FuzzFile
	| FuzzDelete FuzzFile
	| FuzzMove FuzzFile FuzzFile
	| FuzzDeleteDir FuzzDir
	| FuzzMoveDir FuzzDir FuzzDir
	| FuzzPause Delay
	deriving (Read, Show, Eq)

instance Arbitrary FuzzAction where
	arbitrary = frequency
		[ (50, FuzzAdd <$> arbitrary)
		, (50, FuzzDelete <$> arbitrary)
		, (10, FuzzMove <$> arbitrary <*> arbitrary)
		, (10, FuzzDeleteDir <$> arbitrary)
		, (10, FuzzMoveDir <$> arbitrary <*> arbitrary)
		, (10, FuzzPause <$> arbitrary)
		]

runFuzzAction :: FuzzAction -> Annex ()
runFuzzAction (FuzzAdd (FuzzFile f)) = liftIO $ do
	createDirectoryIfMissing True $ parentDir f
	n <- getStdRandom random :: IO Int
	writeFile f $ show n ++ "\n"
runFuzzAction (FuzzDelete (FuzzFile f)) = liftIO $ nukeFile f
runFuzzAction (FuzzMove (FuzzFile src) (FuzzFile dest)) = liftIO $
	rename src dest
runFuzzAction (FuzzDeleteDir (FuzzDir d)) = liftIO $
	removeDirectoryRecursive d
runFuzzAction (FuzzMoveDir (FuzzDir src) (FuzzDir dest)) = liftIO $
	rename src dest
runFuzzAction (FuzzPause d) = randomDelay d

genFuzzAction :: Annex FuzzAction
genFuzzAction = do
	tmpl <- liftIO $ Prelude.head <$> sample' (arbitrary :: Gen FuzzAction)
	-- Fix up template action to make sense in the current repo tree.
	case tmpl of
		FuzzAdd _ -> do
			f <- liftIO newFile
			maybe genFuzzAction (return . FuzzAdd) f
		FuzzDelete _ -> do
			f <- liftIO $ existingFile 0 ""
			maybe genFuzzAction (return . FuzzDelete) f
		FuzzMove _ _ -> do
			src <- liftIO $ existingFile 0 ""
			dest <- liftIO newFile
			case (src, dest) of
				(Just s, Just d) -> return $ FuzzMove s d
				_ -> genFuzzAction
		FuzzMoveDir _ _ -> do
			md <- liftIO existingDir
			case md of
				Nothing -> genFuzzAction
				Just d -> do
					newd <- liftIO $ newDir (parentDir $ toFilePath d)
					maybe genFuzzAction (return . FuzzMoveDir d) newd
		FuzzDeleteDir _ -> do
			d <- liftIO existingDir
			maybe genFuzzAction (return . FuzzDeleteDir) d
		FuzzPause _ -> return tmpl

existingFile :: Int -> FilePath -> IO (Maybe FuzzFile)
existingFile 0 _ = return Nothing
existingFile n top = do
	dir <- existingDirIncludingTop
	contents <- catchDefaultIO [] (getDirectoryContents dir)
	let files = filter isFuzzFile contents
	if null files
		then do
			let dirs = filter isFuzzDir contents
			if null dirs
				then return Nothing
				else do
					i <- getStdRandom $ randomR (0, length dirs - 1)
					existingFile (n - 1) (top </> dirs !! i)
		else do
			i <- getStdRandom $ randomR (0, length files - 1)
			return $ Just $ FuzzFile $ top </> dir </> files !! i

existingDirIncludingTop :: IO FilePath
existingDirIncludingTop = do
	dirs <- filter isFuzzDir <$> getDirectoryContents "."
	if null dirs
		then return "."
		else do
			n <- getStdRandom $ randomR (0, length dirs)
			return $ ("." : dirs) !! n

existingDir :: IO (Maybe FuzzDir)
existingDir = do
	d <- existingDirIncludingTop
	return $ if isFuzzDir d
		then Just $ FuzzDir d
		else Nothing

newFile :: IO (Maybe FuzzFile)
newFile = go (100 :: Int)
  where
	go 0 = return Nothing
	go n = do
		f <- genFuzzFile
		ifM (doesnotexist (toFilePath f))
			( return $ Just f
			, go (n - 1)
			)

newDir :: FilePath -> IO (Maybe FuzzDir)
newDir parent = go (100 :: Int)
  where
	go 0 = return Nothing
	go n = do
		(FuzzDir d) <- genFuzzDir
		ifM (doesnotexist (parent </> d))
			( return $ Just $ FuzzDir d
			, go (n - 1)
			)

doesnotexist :: FilePath -> IO Bool
doesnotexist f = isNothing <$> catchMaybeIO (getSymbolicLinkStatus f)