    {- Leave a message with lambdabot, the faithful secretary

    > 17:11 < davidhouse> @tell dmhouse foo
    > 17:11 < hsbot> Consider it noted
    > 17:11 < davidhouse> @tell dmhouse bar
    > 17:11 < hsbot> Consider it noted
    > 17:11 < dmhouse> hello!
    > 17:11 < hsbot> dmhouse: You have 2 new messages. '/msg hsbot @messages' to read them.
    > 17:11 < dmhouse> Notice how I'm speaking again, and hsbot isn't buzzing me more than that one time.
    > 17:12 < dmhouse> It'll buzz me after a day's worth of not checking my messages.
    > 17:12 < dmhouse> If I want to check them in the intermittent period, I can either send a /msg, or:
    > 17:12 < dmhouse> @messages?
    > 17:12 < hsbot> You have 2 messages
    > 17:12 < dmhouse> Let's check them, shall we?
    >
    > [In a /msg to hsbot]
    > 17:12 <hsbot> davidhouse said less than a minute ago: foo
    > 17:12 <hsbot> davidhouse said less than a minute ago: bar
    >
    > [Back in the channel
    > 17:12 < dmhouse> You needn't use a /msg, however. If you're not going to annoy the channel by printing 20 of
    >                  your messages, feel free to just type '@messages' in the channel.
    > 17:12 < davidhouse> @tell dmhouse foobar
    > 17:12 < hsbot> Consider it noted
    > 17:12 < davidhouse> @ask dmhouse barfoo
    > 17:12 < hsbot> Consider it noted
    > 17:12 < davidhouse> You can see there @ask. It's just a synonym for @tell, but it prints "foo asked X ago M",
    >                     which is more natural. E.g. '@ask dons whether he's applied my latest patch yet?'
    > 17:13 < dmhouse> For the admins, a useful little debugging tool is @print-notices.
    > 17:13 < hsbot> dmhouse: You have 2 new messages. '/msg hsbot @messages' to read them.
    > 17:14 < dmhouse> Notice that hsbot pinged me there, even though it's less than a day since I last checked my
    >                  messages, because there have been some new ones posted.
    > 17:14 < dmhouse> @print-notices
    > 17:14 < hsbot> {"dmhouse":=(Just Thu Jun  8 17:13:46 BST 2006,[Note {noteSender = "davidhouse", noteContents =
    >                "foobar", noteTime = Thu Jun  8 17:12:50 BST 2006, noteType = Tell},Note {noteSender =
                     "davidhouse", noteContents = "barfoo", noteTime = Thu Jun  8 17:12:55 BST 2006, noteType = Ask}])}
    > 17:15 < dmhouse> There you can see the two notes. The internal state is a map from recipient nicks to a pair of
    >                  (when we last buzzed them about having messages, a list of the notes they've got stacked up).
    > 17:16 < dmhouse> Finally, if you don't want to bother checking your messages, then the following command will
    >                  likely be useful.
    > 17:16 < dmhouse> @clear-messages
    > 17:16 < hsbot> Messages cleared.
    > 17:16 < dmhouse> That's all, folks!
    > 17:17 < dmhouse> Any comments, queries or complaints to dmhouse@gmail.com. The source should be fairly readable, so
    >                  hack away!
    -}

    module Lambdabot.Plugin.Social.Tell (tellPlugin) where

    import Lambdabot.Compat.AltTime
    import Lambdabot.Compat.FreenodeNick
    import Lambdabot.Plugin
    import Lambdabot.Util

    import Control.Monad
    import qualified Data.Map as M
    import Data.Maybe (fromMaybe)
    import Text.Printf (printf)

    -- | Was it @tell or @ask that was the original command?
    data NoteType    = Tell | Ask deriving (Show, Eq, Read)
    -- | The Note datatype. Fields self-explanatory.
    data Note        = Note { noteSender   :: FreenodeNick,
                              noteContents :: String,
                              noteTime     :: ClockTime,
                              noteType     :: NoteType }
                       deriving (Eq, Show, Read)
    -- | The state. A map of (times we last told this nick they've got messages, the
    --   messages themselves, the auto-reply)
    type NoticeEntry = (Maybe ClockTime, [Note], Maybe String)
    type NoticeBoard = M.Map FreenodeNick NoticeEntry

    type Tell = ModuleT NoticeBoard LB

    tellPlugin :: Module NoticeBoard
    tellPlugin = newModule
        { moduleCmds = return
            [ (command "tell")
                { help = say "tell <nick> <message>. When <nick> shows activity, tell them <message>."
                , process = doTell Tell . words
                }
            , (command "ask")
                { help = say "ask <nick> <message>. When <nick> shows activity, ask them <message>."
                , process = doTell Ask . words
                }
            , (command "messages")
                { help = say "messages. Check your messages, responding in private."
                , process = const (doMessages False)
                }
            , (command "messages-loud")
                { help = say "messages. Check your messages, responding in public."
                , process = const (doMessages True)
                }
            , (command "messages?")
                { help = say "messages?. Tells you whether you have any messages"
                , process = const $ do
                    sender <- getSender
                    ms <- getMessages sender
                    case ms of
                        Just _      -> doRemind sender say
                        Nothing     -> say "Sorry, no messages today."
                }
            , (command "clear-messages")
                { help = say "clear-messages. Clears your messages."
                , process = const $ do
                    sender <- getSender
                    clearMessages sender
                    say "Messages cleared."
                }
            , (command "auto-reply")
                { help = say "auto-reply. Lets lambdabot auto-reply if someone sends you a message"
                , process = doAutoReply
                }
            , (command "auto-reply?")
                { help = say "auto-reply?. Tells you your auto-reply status"
                , process = const $ do
                    sender <- getSender
                    a <- getAutoReply sender
                    case a of
                        Just s      -> say $ "Your auto-reply is \"" ++ s ++ "\"."
                        Nothing     -> say "You do not have an auto-reply message set."
                }
            , (command "clear-auto-reply")
                { help = say "clear-auto-reply. Clears your auto-reply message."
                , process = const $ do
                    sender <- getSender
                    clearAutoReply sender
                    say "Auto-reply message cleared."
                }
            , (command "print-notices")
                { privileged = True
                , help = say "print-notices. Print the current map of notes."
                , process = const ((say . show) =<< readMS)
                }
            , (command "purge-notices")
                { privileged = True
                , help = say $
                    "purge-notices [<nick> [<nick> [<nick> ...]]]]. "
                    ++ "Clear all notes for specified nicks, or all notices if you don't "
                    ++ "specify a nick."
                , process = \args -> do
                    users <- mapM readNick (words args)
                    if null users
                        then writeMS M.empty
                        else mapM_ clearMessages users
                    say "Messages purged."
                }
            ]
        , moduleDefState  = return M.empty
        , moduleSerialize = Just mapSerial
        -- Hook onto contextual. Grab nicks of incoming messages, and tell them
        -- if they have any messages, if it's less than a day since we last did so.
        , contextual = const $ do
            sender <- getSender
            remp <- needToRemind sender
            if remp
                then doRemind sender (lb . ircPrivmsg sender)
                else return ()
        }

    -- | Take a note and the current time, then display it
    showNote :: ClockTime -> Note -> Cmd Tell String
    showNote time note = do
        sender <- showNick (getFreenodeNick (noteSender note))
        let diff    = time `diffClockTimes` noteTime note
            ago     = case timeDiffPretty diff of
                        [] -> "less than a minute"
                        pr -> pr
            action  = case noteType note of Tell -> "said"; Ask -> "asked"
        return $ printf "%s %s %s ago: %s" sender action ago (noteContents note)

    -- | Is it less than a day since we last reminded this nick they've got messages?
    needToRemind :: Nick -> Cmd Tell Bool
    needToRemind n = do
      st  <- readMS
      now <- io getClockTime
      return $ case M.lookup (FreenodeNick n) st of
                 Just (Just lastTime, _, _) ->
                   let diff = now `diffClockTimes` lastTime
                   in diff > TimeDiff 86400
                 Just (Nothing,       _, _) -> True
                 Nothing                    -> True

    -- | Add a note to the NoticeBoard
    writeDown :: Nick -> Nick -> String -> NoteType -> Cmd Tell ()
    writeDown to from what ntype = do
      time <- io getClockTime
      let note = Note { noteSender   = FreenodeNick from,
                        noteContents = what,
                        noteTime     = time,
                        noteType     = ntype }
      modEntry to $ \(_, ns, a) -> (Nothing, ns ++ [note], a)

    -- | Return a user's notes, or Nothing if they don't have any
    getMessages :: Nick -> Cmd Tell (Maybe [Note])
    getMessages sender = do
      st  <- readMS
      return $ case M.lookup (FreenodeNick sender) st of
                 Nothing ->         Nothing
                 Just (_, [], _) -> Nothing
                 Just (_, ns, _) -> Just ns

    -- | Set a user's messages.
    setMessages :: Nick -> [Note] -> Cmd Tell ()
    setMessages sender msgs = modEntry sender $ \(t, _, a) -> (t, msgs, a)

    -- | Clear a user's messages.
    clearMessages :: Nick -> Cmd Tell ()
    clearMessages sender = modEntry sender $ \(_, _, a) -> (Nothing, [], a)

    -- | Sets a user's auto-reply message
    setAutoReply :: Nick -> String -> Cmd Tell ()
    setAutoReply sender msg = modEntry sender $ \(t, ns, _) -> (t, ns, Just msg)

    -- | Gets a user's auto-reply message
    getAutoReply :: Nick -> Cmd Tell (Maybe String)
    getAutoReply sender = fmap (join . fmap (\(_,_,a) -> a) . M.lookup (FreenodeNick sender)) readMS

    -- | Clears the auto-reply message
    clearAutoReply :: Nick -> Cmd Tell ()
    clearAutoReply sender = modEntry sender $ \(t, ns, _) -> (t, ns, Nothing)

    -- | Modifies an entry, taking care of missing entries and cleaning up empty entries.
    -- (We consider an entry empty even if it still has a timestamp.)
    modEntry :: Nick -> (NoticeEntry -> NoticeEntry) -> Cmd Tell ()
    modEntry sender f = modifyMS $ M.alter (cleanup . f . fromMaybe empty) (FreenodeNick sender)
      where empty = (Nothing, [], Nothing)
            cleanup (_, [], Nothing) = Nothing
            cleanup e = Just e

    -- * Handlers
    --

    -- | Give a user their messages
    doMessages :: Bool -> Cmd Tell ()
    doMessages loud = do
        sender <- getSender
        msgs <- getMessages sender

        let tellNote = if loud
                then say
                else lb . ircPrivmsg sender

        let loop [] = clearMessages sender
            loop (msg : msgs) = do
                time <- io getClockTime
                -- Note that 'showNote' may block and thus run into a timeout.
                -- Hence we update the list of pending messages after each message.
                showNote time msg >>= tellNote
                setMessages sender msgs
                loop msgs

        case msgs of
            Nothing -> say "You don't have any messages"
            Just msgs -> loop msgs

    verb :: NoteType -> String
    verb Ask = "ask"
    verb Tell= "tell"

    -- | Execute a @tell or @ask command.
    doTell :: NoteType -> [String] -> Cmd Tell ()
    doTell ntype []         = say ("Who should I " ++ verb ntype ++ "?")
    doTell ntype (who':args) = do
        let who     = dropFromEnd (== ':') who'
        recipient   <- readNick who
        sender      <- getSender
        me          <- getLambdabotName
        let rest = unwords args
            (record, res)
                | sender    == recipient   = (False, "You can " ++ verb ntype ++ " yourself!")
                | recipient == me          = (False, "Nice try ;)")
                | null args                = (False, "What should I " ++ verb ntype ++ " " ++ who ++ "?")
                | otherwise                = (True,  "Consider it noted.")
        when record $ do
            autoReply <- getAutoReply recipient
            case autoReply of
                Nothing -> return ()
                Just s -> say $ who ++ " lets you know: " ++ s
            writeDown recipient sender rest ntype
        say res

    -- | Execute a @auto-reply
    doAutoReply :: String -> Cmd Tell ()
    doAutoReply "" = say "No auto-reply message given. Did you mean @clear-auto-reply?"
    doAutoReply msg = do
        sender      <- getSender
        setAutoReply sender msg
        say "Auto-Reply messages noted. You can check the status with auto-reply? and clear it with clear-auto-reply."

    -- | Remind a user that they have messages.
    doRemind :: Nick -> (String -> Cmd Tell ()) -> Cmd Tell ()
    doRemind sender remind = do
        ms  <- getMessages sender
        now <- io getClockTime
        modEntry sender $ \(_,ns,a) -> (Just now, ns, a)
        case ms of
            Just msgs -> do
                me <- showNick =<< getLambdabotName
                let n = length msgs
                    (messages, pronoun)
                        | n > 1     = ("messages", "them")
                        | otherwise = ("message", "it")
                remind $ printf "You have %d new %s. '/msg %s @messages' to read %s."
                            n messages me pronoun
            Nothing -> return ()