{-# LANGUAGE OverloadedStrings, BangPatterns #-}

{- Copyright 2016 Joey Hess <id@joeyh.name>
 -
 - Licensed under the GNU AGPL version 3 or higher.
 -}

module Main where

import Types
import Tunables
import qualified CmdLine
import UI
import Encryption
import Entropy
import Benchmark
import Tests
import Cost
import SecretKey
import Share
import Storage
import BackupRecord
import HTTP.Server
import qualified Gpg
import Data.Maybe
import Data.Time.Clock
import Data.Time.Calendar
import Data.Monoid
import Control.DeepSeq
import qualified Data.ByteString as B
import qualified Data.ByteString.UTF8 as BU8
import qualified Data.Set as S
import System.Posix.User (userGecos, getUserEntryForID, getEffectiveUserID)

main :: IO ()
main = do
	cmdline <- CmdLine.get
	ui <- selectUI (CmdLine.gui cmdline)
	let mkt = CmdLine.customizeShareParams cmdline
	(tunables, possibletunables) <- if CmdLine.testMode cmdline
		then do
			showInfo ui "Test mode"
				"Keysafe is running in test mode. This is not secure, and should not be used with real secret keys!"
			return (mkt testModeTunables, [mkt testModeTunables])
		else return (mkt defaultTunables, map (mkt . snd) knownTunings)
	storagelocations <- if CmdLine.localstorage cmdline
		then pure $ localStorageLocations (CmdLine.localstoragedirectory cmdline)
		else allStorageLocations (CmdLine.localstoragedirectory cmdline)
	dispatch cmdline ui storagelocations tunables possibletunables

dispatch :: CmdLine.CmdLine -> UI -> StorageLocations -> Tunables -> [Tunables] -> IO ()
dispatch cmdline ui storagelocations tunables possibletunables = do
	mode <- CmdLine.selectMode cmdline
	go mode (CmdLine.secretkeysource cmdline)
  where
	go CmdLine.Backup (Just secretkeysource) =
		backup cmdline storagelocations ui tunables secretkeysource
			=<< getSecretKey secretkeysource
	go CmdLine.Restore (Just secretkeydest) =
		restore cmdline storagelocations ui possibletunables secretkeydest
	go CmdLine.Backup Nothing =
		backup cmdline storagelocations ui tunables Gpg.anyKey
			=<< Gpg.getKeyToBackup ui
	go CmdLine.Restore Nothing =
		restore cmdline storagelocations ui possibletunables Gpg.anyKey
	go CmdLine.UploadQueued _ = do
		problems <- uploadQueued (CmdLine.localstoragedirectory cmdline)
		if null problems
			then return ()
			else showError ui ("Problem uploading queued data to servers:\n\n" ++ unlines problems ++ "\n\nYour secret keys have not yet been backed up.")
	go (CmdLine.Server) _ =
		runServer
			(CmdLine.localstoragedirectory cmdline)
			(CmdLine.serverConfig cmdline)
	go (CmdLine.Chaff hn) _ = storeChaff hn
		(CmdLine.serverPort (CmdLine.serverConfig cmdline))
	go CmdLine.Benchmark _ =
		benchmarkTunables tunables
	go CmdLine.Test _ =
		runTests

backup :: CmdLine.CmdLine -> StorageLocations -> UI -> Tunables -> SecretKeySource -> SecretKey -> IO ()
backup cmdline storagelocations ui tunables secretkeysource secretkey = do
	username <- userName
	Name theirname <- case CmdLine.name cmdline of
		Just n -> pure n
		Nothing -> fromMaybe (error "Aborting on no username") 
			<$> promptName ui "Enter your name"
				usernamedesc (Just username) validateName
	go theirname
  where
	go theirname = do
		cores <- fromMaybe 1 <$> getNumCores
		Name othername <- case CmdLine.name cmdline of
			Just n -> pure n
			Nothing -> fromMaybe (error "aborting on no othername")
				<$> promptName ui "Enter other name"
					othernamedesc Nothing validateName
		let name = Name (theirname <> " " <> othername)
		(kek, passwordentropy) <- promptpassword name
		let sis = shareIdents tunables name secretkeysource
		let cost = getCreationCost kek <> getCreationCost sis
		(r, queued, locs) <- withProgressIncremental ui "Encrypting and storing data"
			(encryptdesc cost cores) $ \addpercent -> do
				let esk = encrypt tunables kek secretkey
				shares <- genShares esk tunables
				_ <- esk `deepseq` addpercent 25
				_ <- sis `seq` addpercent 25
				let step = 50 `div` sum (map S.size shares)
				storeShares storagelocations sis shares (addpercent step)
		backuprecord <- mkBackupRecord (mapMaybe getServer locs) secretkeysource passwordentropy
		case r of
			StoreSuccess -> do
				storeBackupRecord backuprecord
				if queued
					then showInfo ui "Backup queued" "Some data was not sucessfully uploaded to servers, and has been queued for later upload. Run keysafe --uploadqueued at a later point to finish the backup."
					else showInfo ui "Backup success" "Your secret key was successfully encrypted and backed up."
			StoreFailure s -> showError ui ("There was a problem storing your encrypted secret key: " ++ s)
			StoreAlreadyExists -> do
				showError ui $ unlines
					[ "Another secret key is already being stored under the name you entered."
					, "Please try again with a different name."
					]
				go theirname
	promptpassword name = do
		password <- fromMaybe (error "Aborting on no password") 
			<$> promptPassword ui True "Enter password" passworddesc
		kek <- genKeyEncryptionKey tunables name password
		username <- userName
		let badwords = concatMap namewords [name, username]
		let passwordentropy = calcPasswordEntropy password badwords
		let crackcost = estimateAttackCost spotAWS $
			estimateBruteforceOf kek passwordentropy
		let mincost = Dollars 100000
		if crackcost < mincost
			then do
				showError ui $ "Weak password! It would cost only " ++ show crackcost ++ " to crack the password. Please think of a better one. More words would be good.."
				promptpassword name
			else do
				(thisyear, _, _) <- toGregorian . utctDay
					<$> getCurrentTime
				ok <- promptQuestion ui "Password strength estimate"
					(crackdesc crackcost thisyear)
					"Is your password strong enough?"
				if ok
					then return (kek, passwordentropy)
					else promptpassword name
	namewords (Name nb) = words (BU8.toString nb)
	keydesc = case secretkeysource of
		GpgKey _ -> "gpg secret key"
		KeyFile _ -> "secret key"
	usernamedesc = unlines
		[ "Keysafe is going to backup your " ++ keydesc ++ " securely."
		, ""
		, "You will be prompted for some information. To restore your " ++ keydesc
		, "at a later date, you will need to remember and enter the same information."
		, ""
		, "To get started, what is your name?"
		]
	othernamedesc = unlines
		[ "Now think of another name, which not many people know."
		, "This will be used to make it hard for anyone else to find"
		, "the backup of your " ++ keydesc ++ "."
		, ""
		, "Some suggestions:"
		, ""
		, otherNameSuggestions
		, ""
		, "Make sure to pick a name you will remember later,"
		, "when you restore your " ++ keydesc ++ "."
		]
	passworddesc = unlines
		[ "Pick a password that will be used to protect your secret key."
		, ""
		, "It's very important that this password be hard to guess."
		, ""
		, "And, it needs to be one that you will be able to remember years from now"
		, "in order to restore your secret key."
		]
	crackdesc crackcost thisyear = unlines $
		"Rough estimate of the cost to crack your password: " :
		costOverTimeTable crackcost thisyear
	encryptdesc cost cores = unlines
		[ "This will probably take around " ++ showCostMinutes cores cost
		, ""
		, "(It's a feature that this takes a while; it makes it hard"
		, "for anyone to find your data, or crack your password.)"
		, ""
		, "Please wait..."
		]

otherNameSuggestions :: String
otherNameSuggestions = unlines $ map ("  * " ++)
	[ "Your high-school sweetheart."
	, "Your first pet."
	, "Your favorite teacher."
	, "Your college roomate."
	, "A place you like to visit."
	]

restore :: CmdLine.CmdLine -> StorageLocations -> UI -> [Tunables] -> SecretKeySource -> IO ()
restore cmdline storagelocations ui possibletunables secretkeydest = do
	cores <- fromMaybe 1 <$> getNumCores
	username <- userName
	Name theirname <- case CmdLine.name cmdline of
		Just n -> pure n
		Nothing -> fromMaybe (error "Aborting on no username") 
			<$> promptName ui "Enter your name"
				namedesc (Just username) validateName
	Name othername <- case CmdLine.name cmdline of
		Just n -> pure n
		Nothing -> fromMaybe (error "aborting on no othername")
			<$> promptName ui "Enter other name"
				othernamedesc Nothing validateName
	let name = Name (theirname <> " " <> othername)
	password <- fromMaybe (error "Aborting on no password") 
		<$> promptPassword ui True "Enter password" passworddesc
	
	let mksis tunables = shareIdents tunables name secretkeydest
	r <- downloadInitialShares storagelocations ui mksis possibletunables
	case r of
		Nothing -> showError ui "No shares could be downloaded. Perhaps you entered the wrong name?"
		Just (tunables, shares, sis) -> do
			let candidatekeys = candidateKeyEncryptionKeys tunables name password
			let cost = getCreationCost candidatekeys 
				<> castCost (getDecryptionCost candidatekeys)
			case combineShares tunables [shares] of
				Left e -> showError ui e
				Right esk -> do
					final <- withProgress ui "Decrypting"
						(decryptdesc cost cores) $ \setpercent ->
							go tunables [shares] sis setpercent $
								tryDecrypt candidatekeys esk
					final
  where
	go tunables firstshares sis setpercent r = case r of
		DecryptFailed -> return $
			showError ui "Decryption failed! Probably you entered the wrong password."
		DecryptSuccess secretkey -> do
			_ <- setpercent 100
			writeSecretKey secretkeydest secretkey
			return $
				showInfo ui "Success" "Your secret key was successfully restored!"
		DecryptIncomplete kek -> do
			-- Download shares for another chunk.
			(nextshares, sis') <- retrieveShares storagelocations sis (return ())
			let shares = firstshares ++ [nextshares]
			case combineShares tunables shares of
				Left e -> return $ showError ui e
				Right esk -> 
					go tunables shares sis' setpercent $
						decrypt kek esk
	namedesc = unlines
		[ "When you backed up your secret key, you entered some information."
		, "To restore it, you'll need to remember what you entered back then."
		, ""
		, "To get started, what is your name?"
		]
	othernamedesc = unlines
		[ "What other name did you enter when you backed up your secret key?"
		, ""
		, "Back then, you were given some suggestions, like these:"
		, ""
		, otherNameSuggestions
		]
	passworddesc = unlines
		[ "Enter the password to unlock your secret key."
		]
	decryptdesc cost cores = unlines
		[ "This will probably take around " ++ showCostMinutes cores cost
		, ""
		, "(It's a feature that this takes so long; it prevents cracking your password.)"
		, ""
		, "Please wait..."
		]

-- | Try each possible tunable until the initial set of 
-- shares are found, and return the shares, and
-- ShareIdents to download subsequent sets.
downloadInitialShares
	:: StorageLocations
	-> UI
	-> (Tunables -> ShareIdents)
	-> [Tunables]
	-> IO (Maybe (Tunables, S.Set Share, ShareIdents))
downloadInitialShares storagelocations ui mksis possibletunables = do
	cores <- fromMaybe 1 <$> getNumCores
	withProgressIncremental ui "Downloading encrypted data" (message cores) $ \addpercent -> do
		go possibletunables addpercent
  where
	go [] _ = return Nothing
	go (tunables:othertunables) addpercent = do
		-- Just calculating the hash to generate the stream of idents
		-- probably takes most of the time.
		let !sis = mksis tunables
		addpercent 50
		let m = totalObjects (shareParams tunables)
		let step = 50 `div` m
		(shares, sis') <- retrieveShares storagelocations sis (addpercent step)
		if S.null shares
			then go othertunables addpercent
			else return $ Just (tunables, shares, sis')

	possiblesis = map mksis possibletunables
	message cores = unlines
		[ "This will probably take around "
			++ showCostMinutes cores (mconcat $ map getCreationCost possiblesis)
		, ""
		, "(It's a feature that this takes a while; it makes it hard"
		, "for anyone else to find your data.)"
		, ""
		, "Please wait..."
		]

validateName :: Name -> Maybe Problem
validateName (Name n)
	| B.length n < 2 = Just "The name should be at least 2 letters long."
	| otherwise = Nothing

userName :: IO Name
userName = do
	u <- getUserEntryForID =<< getEffectiveUserID
	return $ Name $ BU8.fromString $ takeWhile (/= ',') (userGecos u)