{-# LANGUAGE QuasiQuotes, TypeFamilies #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE PatternGuards #-}
{-# LANGUAGE Rank2Types #-}
-- | A Yesod plugin for Authentication via e-mail
--
-- This plugin works out of the box by only setting a few methods on the type class
-- that tell the plugin how to interoprate with your user data storage (your database).
-- However, almost everything is customizeable by setting more methods on the type class.
-- In addition, you can send all the form submissions via JSON and completely control the user's flow.
-- This is a standard registration e-mail flow
--
-- 1) A user registers a new e-mail address, and an e-mail is sent there
-- 2) The user clicks on the registration link in the e-mail
--    Note that at this point they are actually logged in (without a password)
--    That means that when they log out they will need to reset their password
-- 3) The user sets their password and is redirected to the site.
-- 4) The user can now
--    * logout and sign in
--    * reset their password
module Yesod.Auth.Email
    ( -- * Plugin
      authEmail
    , YesodAuthEmail (..)
    , EmailCreds (..)
    , saltPass
      -- * Routes
    , loginR
    , registerR
    , forgotPasswordR
    , setpassR
    , isValidPass
      -- * Types
    , Email
    , VerKey
    , VerUrl
    , SaltedPass
    , VerStatus
    , Identifier
     -- * Misc
    , loginLinkKey
    , setLoginLinkKey
     -- * Default handlers
    , defaultRegisterHandler
    , defaultForgotPasswordHandler
    , defaultSetPasswordHandler
    ) where

import Network.Mail.Mime (randomString)
import Yesod.Auth
import System.Random
import qualified Data.Text as TS
import qualified Data.Text as T
import qualified Data.Text.Encoding as TE
import qualified Crypto.Hash.MD5 as H
import Data.ByteString.Base16 as B16
import Data.Text.Encoding (encodeUtf8, decodeUtf8With)
import Data.Text.Encoding.Error (lenientDecode)
import Data.Text (Text)
import Yesod.Core
import qualified Yesod.PasswordStore as PS
import qualified Text.Email.Validate
import qualified Yesod.Auth.Message as Msg
import Control.Applicative ((<$>), (<*>))
import Control.Monad (void)
import Yesod.Form
import Data.Time (getCurrentTime, addUTCTime)
import Safe (readMay)

loginR, registerR, forgotPasswordR, setpassR :: AuthRoute
loginR = PluginR "email" ["login"]
registerR = PluginR "email" ["register"]
forgotPasswordR = PluginR "email" ["forgot-password"]
setpassR = PluginR "email" ["set-password"]

verify :: Text -> Text -> AuthRoute -- FIXME
verify eid verkey = PluginR "email" ["verify", eid, verkey]

type Email = Text
type VerKey = Text
type VerUrl = Text
type SaltedPass = Text
type VerStatus = Bool

-- | An Identifier generalizes an email address to allow users to log in with
-- some other form of credentials (e.g., username).
--
-- Note that any of these other identifiers must not be valid email addresses.
--
-- Since 1.2.0
type Identifier = Text

-- | Data stored in a database for each e-mail address.
data EmailCreds site = EmailCreds
    { emailCredsId :: AuthEmailId site
    , emailCredsAuthId :: Maybe (AuthId site)
    , emailCredsStatus :: VerStatus
    , emailCredsVerkey :: Maybe VerKey
    , emailCredsEmail :: Email
    }

class ( YesodAuth site
      , PathPiece (AuthEmailId site)
      , (RenderMessage site Msg.AuthMessage)
      )
  => YesodAuthEmail site where
    type AuthEmailId site

    -- | Add a new email address to the database, but indicate that the address
    -- has not yet been verified.
    --
    -- Since 1.1.0
    addUnverified :: Email -> VerKey -> HandlerT site IO (AuthEmailId site)

    -- | Send an email to the given address to verify ownership.
    --
    -- Since 1.1.0
    sendVerifyEmail :: Email -> VerKey -> VerUrl -> HandlerT site IO ()

    -- | Get the verification key for the given email ID.
    --
    -- Since 1.1.0
    getVerifyKey :: AuthEmailId site -> HandlerT site IO (Maybe VerKey)

    -- | Set the verification key for the given email ID.
    --
    -- Since 1.1.0
    setVerifyKey :: AuthEmailId site -> VerKey -> HandlerT site IO ()

    -- | Verify the email address on the given account.
    --
    -- Since 1.1.0
    verifyAccount :: AuthEmailId site -> HandlerT site IO (Maybe (AuthId site))

    -- | Get the salted password for the given account.
    --
    -- Since 1.1.0
    getPassword :: AuthId site -> HandlerT site IO (Maybe SaltedPass)

    -- | Set the salted password for the given account.
    --
    -- Since 1.1.0
    setPassword :: AuthId site -> SaltedPass -> HandlerT site IO ()

    -- | Get the credentials for the given @Identifier@, which may be either an
    -- email address or some other identification (e.g., username).
    --
    -- Since 1.2.0
    getEmailCreds :: Identifier -> HandlerT site IO (Maybe (EmailCreds site))

    -- | Get the email address for the given email ID.
    --
    -- Since 1.1.0
    getEmail :: AuthEmailId site -> HandlerT site IO (Maybe Email)

    -- | Generate a random alphanumeric string.
    --
    -- Since 1.1.0
    randomKey :: site -> IO Text
    randomKey _ = do
        stdgen <- newStdGen
        return $ TS.pack $ fst $ randomString 10 stdgen

    -- | Route to send user to after password has been set correctly.
    --
    -- Since 1.2.0
    afterPasswordRoute :: site -> Route site

    -- | Does the user need to provide the current password in order to set a
    -- new password?
    --
    -- Default: if the user logged in via an email link do not require a password.
    --
    -- Since 1.2.1
    needOldPassword :: AuthId site -> HandlerT site IO Bool
    needOldPassword aid' = do
        mkey <- lookupSession loginLinkKey
        case mkey >>= readMay . TS.unpack of
            Just (aidT, time) | Just aid <- fromPathPiece aidT, toPathPiece (aid `asTypeOf` aid') == toPathPiece aid' -> do
                now <- liftIO getCurrentTime
                return $ addUTCTime (60 * 30) time <= now
            _ -> return True

    -- | Check that the given plain-text password meets minimum security standards.
    --
    -- Default: password is at least three characters.
    checkPasswordSecurity :: AuthId site -> Text -> HandlerT site IO (Either Text ())
    checkPasswordSecurity _ x
        | TS.length x >= 3 = return $ Right ()
        | otherwise = return $ Left "Password must be at least three characters"

    -- | Response after sending a confirmation email.
    --
    -- Since 1.2.2
    confirmationEmailSentResponse :: Text -> HandlerT site IO TypedContent
    confirmationEmailSentResponse identifier = do
        mr <- getMessageRender
        selectRep $ do
            provideJsonMessage (mr msg)
            provideRep $ authLayout $ do
              setTitleI Msg.ConfirmationEmailSentTitle
              [whamlet|<p>_{msg}|]
      where
        msg = Msg.ConfirmationEmailSent identifier

    -- | Additional normalization of email addresses, besides standard canonicalization.
    --
    -- Default: Lower case the email address.
    --
    -- Since 1.2.3
    normalizeEmailAddress :: site -> Text -> Text
    normalizeEmailAddress _ = TS.toLower

    -- | Handler called to render the registration page.  The
    -- default works fine, but you may want to override it in
    -- order to have a different DOM.
    --
    -- Default: 'defaultRegisterHandler'.
    --
    -- Since: 1.2.6.
    registerHandler :: AuthHandler site Html
    registerHandler = defaultRegisterHandler

    -- | Handler called to render the \"forgot password\" page.
    -- The default works fine, but you may want to override it in
    -- order to have a different DOM.
    --
    -- Default: 'defaultForgotPasswordHandler'.
    --
    -- Since: 1.2.6.
    forgotPasswordHandler :: AuthHandler site Html
    forgotPasswordHandler = defaultForgotPasswordHandler

    -- | Handler called to render the \"set password\" page.  The
    -- default works fine, but you may want to override it in
    -- order to have a different DOM.
    --
    -- Default: 'defaultSetPasswordHandler'.
    --
    -- Since: 1.2.6.
    setPasswordHandler ::
         Bool
         -- ^ Whether the old password is needed.  If @True@, a
         -- field for the old password should be presented.
         -- Otherwise, just two fields for the new password are
         -- needed.
      -> AuthHandler site TypedContent
    setPasswordHandler = defaultSetPasswordHandler


authEmail :: YesodAuthEmail m => AuthPlugin m
authEmail =
    AuthPlugin "email" dispatch $ \tm ->
        [whamlet|
$newline never
<form method="post" action="@{tm loginR}">
    <table>
        <tr>
            <th>_{Msg.Email}
            <td>
                <input type="email" name="email" required>
        <tr>
            <th>_{Msg.Password}
            <td>
                <input type="password" name="password" required>
        <tr>
            <td colspan="2">
                <button type=submit .btn .btn-success>
                    _{Msg.LoginViaEmail}
                &nbsp;
                <a href="@{tm registerR}" .btn .btn-default>
                    _{Msg.RegisterLong}
|]
  where
    dispatch "GET" ["register"] = getRegisterR >>= sendResponse
    dispatch "POST" ["register"] = postRegisterR >>= sendResponse
    dispatch "GET" ["forgot-password"] = getForgotPasswordR >>= sendResponse
    dispatch "POST" ["forgot-password"] = postForgotPasswordR >>= sendResponse
    dispatch "GET" ["verify", eid, verkey] =
        case fromPathPiece eid of
            Nothing -> notFound
            Just eid' -> getVerifyR eid' verkey >>= sendResponse
    dispatch "POST" ["login"] = postLoginR >>= sendResponse
    dispatch "GET" ["set-password"] = getPasswordR >>= sendResponse
    dispatch "POST" ["set-password"] = postPasswordR >>= sendResponse
    dispatch _ _ = notFound

getRegisterR :: YesodAuthEmail master => HandlerT Auth (HandlerT master IO) Html
getRegisterR = registerHandler

-- | Default implementation of 'registerHandler'.
--
-- Since: 1.2.6
defaultRegisterHandler :: YesodAuthEmail master => AuthHandler master Html
defaultRegisterHandler = do
    email <- newIdent
    tp <- getRouteToParent
    lift $ authLayout $ do
        setTitleI Msg.RegisterLong
        [whamlet|
            <p>_{Msg.EnterEmail}
            <form method="post" action="@{tp registerR}">
                <div id="registerForm">
                    <label for=#{email}>_{Msg.Email}:
                    <input ##{email} type="email" name="email" width="150" autofocus>
                <button .btn>_{Msg.Register}
        |]

registerHelper :: YesodAuthEmail master
               => Bool -- ^ allow usernames?
               -> Route Auth
               -> HandlerT Auth (HandlerT master IO) TypedContent
registerHelper allowUsername dest = do
    y <- lift getYesod
    midentifier <- lookupPostParam "email"
    let eidentifier = case midentifier of
            Nothing -> Left Msg.NoIdentifierProvided
            Just x
                | Just x' <- Text.Email.Validate.canonicalizeEmail (encodeUtf8 x) ->
                    Right $ normalizeEmailAddress y $ decodeUtf8With lenientDecode x'
                | allowUsername -> Right $ TS.strip x
                | otherwise -> Left Msg.InvalidEmailAddress

    case eidentifier of
        Left route -> loginErrorMessageI dest route
        Right identifier -> do

            mecreds <- lift $ getEmailCreds identifier
            registerCreds <-
                case mecreds of
                    Just (EmailCreds lid _ _ (Just key) email) -> return $ Just (lid, key, email)
                    Just (EmailCreds lid _ _ Nothing email) -> do
                        key <- liftIO $ randomKey y
                        lift $ setVerifyKey lid key
                        return $ Just (lid, key, email)
                    Nothing
                        | allowUsername -> return Nothing
                        | otherwise -> do
                            key <- liftIO $ randomKey y
                            lid <- lift $ addUnverified identifier key
                            return $ Just (lid, key, identifier)

            case registerCreds of
                Nothing -> loginErrorMessageI dest (Msg.IdentifierNotFound identifier)
                Just (lid, verKey, email) -> do
                    render <- getUrlRender
                    let verUrl = render $ verify (toPathPiece lid) verKey
                    lift $ sendVerifyEmail email verKey verUrl
                    lift $ confirmationEmailSentResponse identifier

postRegisterR :: YesodAuthEmail master => HandlerT Auth (HandlerT master IO) TypedContent
postRegisterR = registerHelper False registerR

getForgotPasswordR :: YesodAuthEmail master => HandlerT Auth (HandlerT master IO) Html
getForgotPasswordR = forgotPasswordHandler

-- | Default implementation of 'forgotPasswordHandler'.
--
-- Since: 1.2.6
defaultForgotPasswordHandler :: YesodAuthEmail master => AuthHandler master Html
defaultForgotPasswordHandler = do
    tp <- getRouteToParent
    email <- newIdent
    lift $ authLayout $ do
        setTitleI Msg.PasswordResetTitle
        [whamlet|
            <p>_{Msg.PasswordResetPrompt}
            <form method="post" action="@{tp forgotPasswordR}">
                <div id="registerForm">
                    <label for=#{email}>_{Msg.ProvideIdentifier}
                    <input ##{email} type=text name="email" width="150" autofocus>
                <button .btn>_{Msg.SendPasswordResetEmail}
        |]

postForgotPasswordR :: YesodAuthEmail master => HandlerT Auth (HandlerT master IO) TypedContent
postForgotPasswordR = registerHelper True forgotPasswordR

getVerifyR :: YesodAuthEmail site
           => AuthEmailId site
           -> Text
           -> HandlerT Auth (HandlerT site IO) TypedContent
getVerifyR lid key = do
    realKey <- lift $ getVerifyKey lid
    memail <- lift $ getEmail lid
    mr <- lift getMessageRender
    case (realKey == Just key, memail) of
        (True, Just email) -> do
            muid <- lift $ verifyAccount lid
            case muid of
                Nothing -> invalidKey mr
                Just uid -> do
                    lift $ setCreds False $ Creds "email-verify" email [("verifiedEmail", email)] -- FIXME uid?
                    lift $ setLoginLinkKey uid
                    let msgAv = Msg.AddressVerified
                    selectRep $ do
                      provideRep $ do
                        lift $ setMessageI msgAv
                        fmap asHtml $ redirect setpassR
                      provideJsonMessage $ mr msgAv
        _ -> invalidKey mr
  where
    msgIk = Msg.InvalidKey
    invalidKey mr = messageJson401 (mr msgIk) $ lift $ authLayout $ do
        setTitleI msgIk
        [whamlet|
$newline never
<p>_{msgIk}
|]


postLoginR :: YesodAuthEmail master => HandlerT Auth (HandlerT master IO) TypedContent
postLoginR = do
    (identifier, pass) <- lift $ runInputPost $ (,)
        <$> ireq textField "email"
        <*> ireq textField "password"
    mecreds <- lift $ getEmailCreds identifier
    maid <-
        case ( mecreds >>= emailCredsAuthId
             , emailCredsEmail <$> mecreds
             , emailCredsStatus <$> mecreds
             ) of
            (Just aid, Just email, Just True) -> do
                mrealpass <- lift $ getPassword aid
                case mrealpass of
                    Nothing -> return Nothing
                    Just realpass -> return $
                        if isValidPass pass realpass
                            then Just email
                            else Nothing
            _ -> return Nothing
    let isEmail = Text.Email.Validate.isValid $ encodeUtf8 identifier
    case maid of
        Just email ->
            lift $ setCredsRedirect $ Creds
                (if isEmail then "email" else "username")
                email
                [("verifiedEmail", email)]
        Nothing ->
            loginErrorMessageI LoginR $
                if isEmail
                    then Msg.InvalidEmailPass
                    else Msg.InvalidUsernamePass

getPasswordR :: YesodAuthEmail master => HandlerT Auth (HandlerT master IO) TypedContent
getPasswordR = do
    maid <- lift maybeAuthId
    case maid of
        Nothing -> loginErrorMessageI LoginR Msg.BadSetPass
        Just _ -> do
            needOld <- maybe (return True) (lift . needOldPassword) maid
            setPasswordHandler needOld

-- | Default implementation of 'setPasswordHandler'.
--
-- Since: 1.2.6
defaultSetPasswordHandler :: YesodAuthEmail master => Bool -> AuthHandler master TypedContent
defaultSetPasswordHandler needOld = do
    tp <- getRouteToParent
    pass0 <- newIdent
    pass1 <- newIdent
    pass2 <- newIdent
    mr <- lift getMessageRender
    selectRep $ do
      provideJsonMessage $ mr Msg.SetPass
      provideRep $ lift $ authLayout $ do
          setTitleI Msg.SetPassTitle
          [whamlet|
$newline never
<h3>_{Msg.SetPass}
<form method="post" action="@{tp setpassR}">
    <table>
        $if needOld
            <tr>
                <th>
                    <label for=#{pass0}>Current Password
                <td>
                    <input ##{pass0} type="password" name="current" autofocus>
        <tr>
            <th>
                <label for=#{pass1}>_{Msg.NewPass}
            <td>
                <input ##{pass1} type="password" name="new" :not needOld:autofocus>
        <tr>
            <th>
                <label for=#{pass2}>_{Msg.ConfirmPass}
            <td>
                <input ##{pass2} type="password" name="confirm">
        <tr>
            <td colspan="2">
                <input type="submit" value=_{Msg.SetPassTitle}>
|]

postPasswordR :: YesodAuthEmail master => HandlerT Auth (HandlerT master IO) TypedContent
postPasswordR = do
    maid <- lift maybeAuthId
    case maid of
        Nothing -> loginErrorMessageI LoginR Msg.BadSetPass
        Just aid -> do
            tm <- getRouteToParent

            needOld <- lift $ needOldPassword aid
            if not needOld then confirmPassword aid tm else do
                current <- lift $ runInputPost $ ireq textField "current"
                mrealpass <- lift $ getPassword aid
                case mrealpass of
                    Nothing ->
                        lift $ loginErrorMessage (tm setpassR) "You do not currently have a password set on your account"
                    Just realpass
                        | isValidPass current realpass -> confirmPassword aid tm
                        | otherwise ->
                            lift $ loginErrorMessage (tm setpassR) "Invalid current password, please try again"

  where
    msgOk = Msg.PassUpdated
    confirmPassword aid tm = do
        (new, confirm) <- lift $ runInputPost $ (,)
            <$> ireq textField "new"
            <*> ireq textField "confirm"

        if new /= confirm
          then loginErrorMessageI setpassR Msg.PassMismatch
          else do
              isSecure <- lift $ checkPasswordSecurity aid new
              case isSecure of
                  Left e -> lift $ loginErrorMessage (tm setpassR) e
                  Right () -> do
                      salted <- liftIO $ saltPass new
                      y <- lift $ do
                          setPassword aid salted
                          deleteSession loginLinkKey
                          setMessageI msgOk
                          getYesod

                      mr <- lift getMessageRender
                      selectRep $ do
                        provideRep $
                          fmap asHtml $ lift $ redirect $ afterPasswordRoute y
                        provideJsonMessage (mr msgOk)

saltLength :: Int
saltLength = 5

-- | Salt a password with a randomly generated salt.
saltPass :: Text -> IO Text
saltPass = fmap (decodeUtf8With lenientDecode)
         . flip PS.makePassword 14
         . encodeUtf8

saltPass' :: String -> String -> String
saltPass' salt pass =
    salt ++ T.unpack (TE.decodeUtf8 $ B16.encode $ H.hash $ TE.encodeUtf8 $ T.pack $ salt ++ pass)

isValidPass :: Text -- ^ cleartext password
            -> SaltedPass -- ^ salted password
            -> Bool
isValidPass ct salted =
    PS.verifyPassword (encodeUtf8 ct) (encodeUtf8 salted) || isValidPass' ct salted

isValidPass' :: Text -- ^ cleartext password
            -> SaltedPass -- ^ salted password
            -> Bool
isValidPass' clear' salted' =
    let salt = take saltLength salted
     in salted == saltPass' salt clear
  where
    clear = TS.unpack clear'
    salted = TS.unpack salted'

-- | Session variable set when user logged in via a login link. See
-- 'needOldPassword'.
--
-- Since 1.2.1
loginLinkKey :: Text
loginLinkKey = "_AUTH_EMAIL_LOGIN_LINK"

-- | Set 'loginLinkKey' to the current time.
--
-- Since 1.2.1
setLoginLinkKey :: (YesodAuthEmail site, MonadHandler m, HandlerSite m ~ site) => AuthId site -> m ()
setLoginLinkKey aid = do
    now <- liftIO getCurrentTime
    setSession loginLinkKey $ TS.pack $ show (toPathPiece aid, now)