import Browser exposing (application, UrlRequest(..))
import Browser.Navigation as Nav
import Browser.Dom exposing (Viewport, setViewportOf)
import Scylla.Sync exposing (..)
import Scylla.Login exposing (..)
import Scylla.Model exposing (..)
import Scylla.Http exposing (..)
import Scylla.Views exposing (viewFull)
import Scylla.Route exposing (Route(..))
import Scylla.UserData exposing (..)
import Scylla.Notification exposing (..)
import Url exposing (Url)
import Url.Parser exposing (parse)
import Url.Builder
import Html exposing (div, text)
import Http
import Dict
import Task

type alias Flags =
    { token : Maybe String
    }

init : Flags -> Url -> Nav.Key -> (Model, Cmd Msg)
init flags url key =
    let
        model =
            { key = key
            , route = Maybe.withDefault Unknown <| parse Scylla.Route.route url
            , token = flags.token
            , loginUsername = ""
            , loginPassword = ""
            , apiUrl = "https://matrix.org"
            , sync =
                { nextBatch = ""
                , rooms = Nothing
                , presence = Nothing
                , accountData = Nothing
                }
            , errors = []
            , roomText = Dict.empty
            , transactionId = 0
            , userData = Dict.empty
            }
        cmd = case flags.token of
            Just _ -> Cmd.none
            Nothing -> Nav.pushUrl key <| Url.Builder.absolute [ "login" ] []
    in
        (model, cmd)

view : Model -> Browser.Document Msg
view m =
    { title = "Scylla"
    , body = viewFull m
    }

update : Msg -> Model -> (Model, Cmd Msg)
update msg model = case msg of
    ChangeApiUrl u -> ({ model | apiUrl = u }, Cmd.none)
    ChangeLoginUsername u -> ({ model | loginUsername = u }, Cmd.none)
    ChangeLoginPassword p -> ({ model | loginPassword = p }, Cmd.none)
    AttemptLogin -> (model, Scylla.Http.login model.apiUrl model.loginUsername model.loginPassword) -- TODO 
    TryUrl urlRequest -> updateTryUrl model urlRequest
    OpenRoom s -> (model, Nav.pushUrl model.key <| roomUrl s)
    ChangeRoute r -> updateChangeRoute model r
    ViewportAfterMessage v -> updateViewportAfterMessage model v
    ViewportChangeComplete _ -> (model, Cmd.none)
    ReceiveLoginResponse r -> updateLoginResponse model r
    ReceiveFirstSyncResponse r -> updateSyncResponse model r False
    ReceiveSyncResponse r -> updateSyncResponse model r True
    ReceiveUserData s r -> updateUserData model s r
    ChangeRoomText r t -> ({ model | roomText = Dict.insert r t model.roomText}, Cmd.none)
    SendRoomText r -> updateSendRoomText model r
    SendRoomTextResponse r -> (model, Cmd.none)
    ReceiveCompletedReadMarker r -> (model, Cmd.none)

updateChangeRoute : Model -> Route -> (Model, Cmd Msg)
updateChangeRoute m r =
    let
        joinedRoom = case r of
            Room rid -> Maybe.andThen (Dict.get rid) <| Maybe.andThen .join <| m.sync.rooms
            _ -> Nothing
        lastMessage = Maybe.andThen (findLastEvent (((==) "m.room.message") << .type_)) <| Maybe.andThen .events <| Maybe.andThen .timeline joinedRoom
        readMarkerCmd = case (r, lastMessage) of
            (Room rid, Just re) -> setReadMarkers m.apiUrl (Maybe.withDefault "" m.token) rid re.eventId <| Just re.eventId
            _ -> Cmd.none
    in
        ({ m | route = r }, readMarkerCmd)

updateViewportAfterMessage : Model -> Result Browser.Dom.Error Viewport -> (Model, Cmd Msg)
updateViewportAfterMessage m vr = 
    let
        cmd vp = if vp.scene.height - (vp.viewport.y + vp.viewport.height ) < 100
            then Task.attempt ViewportChangeComplete <| setViewportOf "events-wrapper" vp.viewport.x vp.scene.height
            else Cmd.none
    in
        (m, Result.withDefault Cmd.none <| Result.map cmd vr)

updateUserData : Model -> String -> Result Http.Error UserData -> (Model, Cmd Msg)
updateUserData m s r = case r of
    Ok ud -> ({ m | userData = Dict.insert s ud m.userData }, Cmd.none)
    Err e -> (m, userData m.apiUrl (Maybe.withDefault "" m.token) s)

updateSendRoomText : Model -> String -> (Model, Cmd Msg)
updateSendRoomText m r =
    let
        token = Maybe.withDefault "" m.token
        message = Maybe.andThen (\s -> if s == "" then Nothing else Just s)
            <| Dict.get r m.roomText
        command = Maybe.withDefault Cmd.none
            <| Maybe.map (sendTextMessage m.apiUrl token m.transactionId r) message
    in
        ({ m | roomText = Dict.insert r "" m.roomText, transactionId = m.transactionId + 1 }, command)

updateTryUrl : Model -> Browser.UrlRequest -> (Model, Cmd Msg)
updateTryUrl m ur = case ur of
    Internal u -> (m, Nav.pushUrl m.key (Url.toString u))
    _ -> (m, Cmd.none)

updateLoginResponse : Model -> Result Http.Error LoginResponse -> (Model, Cmd Msg)
updateLoginResponse model r = case r of
    Ok lr -> ( { model | token = Just lr.accessToken, loginUsername = lr.userId } , Cmd.batch
        [ firstSync model.apiUrl lr.accessToken
        , Nav.pushUrl model.key <| Url.Builder.absolute [] []
        ] )
    Err e  -> (model, Cmd.none)

updateSyncResponse : Model -> Result Http.Error SyncResponse -> Bool -> (Model, Cmd Msg)
updateSyncResponse model r notify =
    let
        token = Maybe.withDefault "" model.token
        nextBatch = Result.withDefault model.sync.nextBatch
            <| Result.map .nextBatch r
        syncCmd = sync nextBatch model.apiUrl token
        newUsers sr = List.filter (\s -> not <| Dict.member s model.userData) <| roomsUsers sr
        newUserCmd sr = Cmd.batch
            <| List.map (userData model.apiUrl
            <| Maybe.withDefault "" model.token)
            <| newUsers sr
        notification sr = findFirstBy
            (\(s, e) -> e.originServerTs)
            (\(s, e) -> e.sender /= model.loginUsername)
            <| notificationEvents sr
        notificationCmd sr = if notify
            then Maybe.withDefault Cmd.none
                    <| Maybe.map (\(s, e) -> sendNotificationPort
                    { name = displayName model e.sender
                    , text = notificationText e
                    , room = s
                    }) <| notification sr
            else Cmd.none
        room = currentRoomId model
        roomMessages sr = case room of
            Just rid -> List.filter (((==) "m.room.message") << .type_)
                <| Maybe.withDefault []
                <| Maybe.andThen .events
                <| Maybe.andThen .timeline
                <| Maybe.andThen (Dict.get rid)
                <| Maybe.andThen .join
                <| sr.rooms
            Nothing -> []
        setScrollCmd sr = if List.isEmpty 
            <| roomMessages sr
                then Cmd.none
                else Task.attempt ViewportAfterMessage (Browser.Dom.getViewportOf "events-wrapper")
        setReadReceiptCmd sr = case (room, List.head <| List.reverse <| roomMessages sr) of
            (Just rid, Just re) -> setReadMarkers model.apiUrl token rid re.eventId <| Just re.eventId
            _ -> Cmd.none
    in
        case r of
            Ok sr -> ({ model | sync = mergeSyncResponse model.sync sr }, Cmd.batch
                [ syncCmd
                , newUserCmd sr
                , notificationCmd sr
                , setScrollCmd sr
                , setReadReceiptCmd sr
                ])
            _ -> (model, syncCmd)

subscriptions : Model -> Sub Msg
subscriptions m = onNotificationClickPort OpenRoom

onUrlRequest : Browser.UrlRequest -> Msg
onUrlRequest = TryUrl

onUrlChange : Url -> Msg
onUrlChange = ChangeRoute << Maybe.withDefault Unknown << parse Scylla.Route.route

main = application
    { init = init
    , view = view
    , update = update
    , subscriptions = subscriptions
    , onUrlRequest = onUrlRequest
    , onUrlChange = onUrlChange
    }