{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE DeriveDataTypeable #-}
{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE FunctionalDependencies #-}

-- | Van Laarhoven lenses for XMPP types. The lenses are designed to work with
-- the lens library.
module Network.Xmpp.Lens
       ( Lens
         -- * Accessors
         -- | Reimplementation of the basic lens functions so you don't have to
         -- bring in all of lens library in to use the lenses
       , view
       , modify
       , set
         -- * Lenses
       , HasStanzaAttrs(..)
       , HasStanzaID(..)
       , sid'
       , HasStanzaPayload(..)
       , HasStanzaError(..)
       )
       where

import           Control.Applicative((<$>), Const(..))
import           Data.Functor.Identity(Identity(..))
import qualified Data.Text as Text
import           Data.Text(Text)
import           Data.XML.Types(Element)
import           Network.Xmpp.Types

-- | Van-Laarhoven lenses.
type Lens a b = Functor f => (b -> f b) -> a -> f a

class HasStanzaAttrs s where
    -- | From-attribute of the stanza
    from :: Lens s (Maybe Jid)
    -- | To-attribute of the stanza
    to   :: Lens s (Maybe Jid)
    -- | Langtag of the stanza
    lang :: Lens s (Maybe LangTag)


instance HasStanzaAttrs Message where
    from inj m@(Message{messageFrom=f}) = (\f' -> m{messageFrom = f'}) <$> inj f
    to inj m@(Message{messageTo=t}) = (\t' -> m{messageTo = t'}) <$> inj t
    lang inj m@(Message{messageLangTag=t}) =
        (\t' -> m{messageLangTag = t'}) <$> inj t


instance HasStanzaAttrs MessageError where
    from inj m@(MessageError{messageErrorFrom=f}) =
        (\f' -> m{messageErrorFrom = f'}) <$> inj f
    to inj m@(MessageError{messageErrorTo=t}) =
        (\t' -> m{messageErrorTo = t'}) <$> inj t
    lang inj m@(MessageError{messageErrorLangTag=t}) =
        (\t' -> m{messageErrorLangTag = t'}) <$> inj t

instance HasStanzaAttrs Presence where
    from inj m@(Presence{presenceFrom=f}) = (\f' -> m{presenceFrom = f'}) <$> inj f
    to inj m@(Presence{presenceTo=t}) = (\t' -> m{presenceTo = t'}) <$> inj t
    lang inj m@(Presence{presenceLangTag=t}) =
        (\t' -> m{presenceLangTag = t'}) <$> inj t

instance HasStanzaAttrs PresenceError where
    from inj m@(PresenceError{presenceErrorFrom=f}) =
        (\f' -> m{presenceErrorFrom = f'}) <$> inj f
    to inj m@(PresenceError{presenceErrorTo=t}) =
        (\t' -> m{presenceErrorTo = t'}) <$> inj t
    lang inj m@(PresenceError{presenceErrorLangTag=t}) =
        (\t' -> m{presenceErrorLangTag = t'}) <$> inj t

instance HasStanzaAttrs IQRequest where
    from inj m@(IQRequest{iqRequestFrom=f}) =
        (\f' -> m{iqRequestFrom = f'}) <$> inj f
    to inj m@(IQRequest{iqRequestTo=t}) =
        (\t' -> m{iqRequestTo = t'}) <$> inj t
    lang inj m@(IQRequest{iqRequestLangTag=t}) =
        (\t' -> m{iqRequestLangTag = t'}) <$> inj t

instance HasStanzaAttrs IQResult where
    from inj m@(IQResult{iqResultFrom=f}) =
        (\f' -> m{iqResultFrom = f'}) <$> inj f
    to inj m@(IQResult{iqResultTo=t}) =
        (\t' -> m{iqResultTo = t'}) <$> inj t
    lang inj m@(IQResult{iqResultLangTag=t}) =
        (\t' -> m{iqResultLangTag = t'}) <$> inj t

instance HasStanzaAttrs IQError where
    from inj m@(IQError{iqErrorFrom=f}) =
        (\f' -> m{iqErrorFrom = f'}) <$> inj f
    to inj m@(IQError{iqErrorTo=t}) =
        (\t' -> m{iqErrorTo = t'}) <$> inj t
    lang inj m@(IQError{iqErrorLangTag=t}) =
        (\t' -> m{iqErrorLangTag = t'}) <$> inj t

lift :: (forall s. HasStanzaAttrs s => Lens s a) -> Lens Stanza a
lift f inj (IQRequestS     s) = IQRequestS     <$> f inj s
lift f inj (IQResultS      s) = IQResultS      <$> f inj s
lift f inj (IQErrorS       s) = IQErrorS       <$> f inj s
lift f inj (MessageS       s) = MessageS       <$> f inj s
lift f inj (MessageErrorS  s) = MessageErrorS  <$> f inj s
lift f inj (PresenceS      s) = PresenceS      <$> f inj s
lift f inj (PresenceErrorS s) = PresenceErrorS <$> f inj s

instance HasStanzaAttrs Stanza where
    from = lift from
    to   = lift to
    lang = lift lang

class HasStanzaID s i | s -> i where
    sid :: Lens s i

instance HasStanzaID IQRequest Text where
    sid inj m@(IQRequest {iqRequestID = i}) = (\i' -> m{iqRequestID = i'}) <$>
                                                  inj i

instance HasStanzaID IQResult Text where
    sid inj m@(IQResult {iqResultID = i}) = (\i' -> m{iqResultID = i'}) <$>
                                                  inj i

instance HasStanzaID IQError Text where
    sid inj m@(IQError {iqErrorID = i}) = (\i' -> m{iqErrorID = i'}) <$>
                                                  inj i
instance HasStanzaID Message (Maybe Text) where
    sid inj m@(Message {messageID = i}) = (\i' -> m{messageID = i'}) <$>
                                                  inj i

instance HasStanzaID MessageError (Maybe Text) where
    sid inj m@(MessageError {messageErrorID = i}) =
        (\i' -> m{messageErrorID = i'}) <$> inj i

instance HasStanzaID Presence (Maybe Text) where
    sid inj m@(Presence {presenceID = i}) = (\i' -> m{presenceID = i'}) <$>
                                                  inj i

instance HasStanzaID PresenceError (Maybe Text) where
    sid inj m@(PresenceError {presenceErrorID = i}) =
        (\i' -> m{presenceErrorID = i'}) <$> inj i

-- | Access to the ID of a stanza. Setting the stanza ID of any non-IQ* stanza
-- to the empty string will instead set it to Nothing
sid' :: Lens Stanza Text
sid' inj (IQRequestS     s) = IQRequestS     <$> sid inj s
sid' inj (IQResultS      s) = IQResultS      <$> sid inj s
sid' inj (IQErrorS       s) = IQErrorS       <$> sid inj s
sid' inj (MessageS       s) = MessageS       <$> (sid . maybeNonempty) inj s
sid' inj (MessageErrorS  s) = MessageErrorS  <$> (sid . maybeNonempty) inj s
sid' inj (PresenceS      s) = PresenceS      <$> (sid . maybeNonempty) inj s
sid' inj (PresenceErrorS s) = PresenceErrorS <$> (sid . maybeNonempty) inj s

maybeNonempty :: Lens (Maybe Text) Text
maybeNonempty inj Nothing  = (\x -> if Text.null x then Nothing else Just x)
                               <$> inj Text.empty
maybeNonempty inj (Just x) = (\y -> if Text.null y then Nothing else Just y)
                               <$> inj x

class HasStanzaError s where
    -- | Error element of the stanza
    stanzaError :: Lens s StanzaError

instance HasStanzaError IQError where
    stanzaError inj m@IQError{iqErrorStanzaError = i} =
        (\i' -> m{iqErrorStanzaError = i'}) <$> inj i

instance HasStanzaError MessageError where
    stanzaError inj m@MessageError{messageErrorStanzaError = i} =
        (\i' -> m{messageErrorStanzaError = i'}) <$> inj i

instance HasStanzaError PresenceError where
    stanzaError inj m@PresenceError{presenceErrorStanzaError = i} =
        (\i' -> m{presenceErrorStanzaError = i'}) <$> inj i

class HasStanzaPayload s p | s -> p where
    -- | Payload element(s) of the stanza
    payload :: Lens s p

instance HasStanzaPayload IQRequest Element where
    payload inj m@IQRequest{iqRequestPayload = i} =
        (\i' -> m{iqRequestPayload = i'}) <$> inj i

instance HasStanzaPayload IQResult (Maybe Element) where
    payload inj m@IQResult{iqResultPayload = i} =
        (\i' -> m{iqResultPayload = i'}) <$> inj i

instance HasStanzaPayload IQError (Maybe Element) where
    payload inj m@IQError{iqErrorPayload = i} =
        (\i' -> m{iqErrorPayload = i'}) <$> inj i

instance HasStanzaPayload Message [Element] where
    payload inj m@Message{messagePayload = i} =
        (\i' -> m{messagePayload = i'}) <$> inj i

instance HasStanzaPayload MessageError [Element] where
    payload inj m@MessageError{messageErrorPayload = i} =
        (\i' -> m{messageErrorPayload = i'}) <$> inj i

instance HasStanzaPayload Presence [Element] where
    payload inj m@Presence{presencePayload = i} =
        (\i' -> m{presencePayload = i'}) <$> inj i

instance HasStanzaPayload PresenceError [Element] where
    payload inj m@PresenceError{presenceErrorPayload = i} =
        (\i' -> m{presenceErrorPayload = i'}) <$> inj i


-- | Read the value the lens is pointing to
view :: Lens a b -> a -> b
view l x = getConst $ l Const x

-- | Modify the value the lens is pointing to
modify :: Lens a b -> (b -> b) -> a -> a
modify l f x = runIdentity $ l (fmap f . Identity) x

-- | Replace the value the lens is pointing to
set :: Lens a b -> b -> a -> a
set l b x = modify l (const b) x