package clientapi

import (
	"encoding/json"
	"errors"
	"net/http"
	"strings"

	"github.com/dariuszjaniak/warp/server/internal/delayedevents"
	"github.com/dariuszjaniak/warp/server/internal/httputil"
	"github.com/dariuszjaniak/warp/server/internal/matrix/id"
	"github.com/dariuszjaniak/warp/server/internal/roomserver"
	"github.com/dariuszjaniak/warp/server/internal/storage"
	"github.com/dariuszjaniak/warp/server/internal/userapi"
)

// roomError maps a roomserver error onto the Matrix error the spec answers
// it with.
//
// The roomserver's refusals carry their reason in the message — which rule
// said no, which membership was missing — and the message is passed through
// to the client. That is deliberate: "M_FORBIDDEN" on its own sends a user
// to their operator and the operator to the logs, and nothing in these
// messages is anything the caller could not work out by reading the room's
// state, which they are entitled to do.
func roomError(err error) error {
	var matrixErr *httputil.MatrixError
	switch {
	case err == nil:
		return nil
	case errors.As(err, &matrixErr):
		return err

	case errors.Is(err, roomserver.ErrNoSuchRoom):
		return httputil.NotFound("Unknown room")
	case errors.Is(err, roomserver.ErrNoSuchEvent):
		return httputil.NotFound("Unknown event")
	case errors.Is(err, roomserver.ErrNoSuchAlias):
		return httputil.NotFound("Unknown room alias")
	case errors.Is(err, roomserver.ErrAliasExists):
		return httputil.NewError(http.StatusConflict, httputil.ErrCodeRoomInUse,
			"That room alias is already taken")

	case errors.Is(err, roomserver.ErrUnknownRoomVersion),
		errors.Is(err, roomserver.ErrUnsupportedRoomVersion):
		return httputil.NewError(http.StatusBadRequest, httputil.ErrCodeUnsupportedVer, "%s", err.Error())

	case errors.Is(err, roomserver.ErrFederationDisabled):
		return httputil.Forbidden("%s", err.Error())
	case errors.Is(err, roomserver.ErrIncompatibleRoomVersion):
		return httputil.NewError(http.StatusBadRequest, "M_INCOMPATIBLE_ROOM_VERSION", "%s", err.Error())
	case errors.Is(err, roomserver.ErrNotInRoom):
		return httputil.Forbidden("%s", err.Error())
	case errors.Is(err, roomserver.ErrRemote), errors.Is(err, roomserver.ErrBadEvent):
		// Another server failed us; the client can do nothing about it but
		// try again, or try another server.
		return httputil.NewError(http.StatusBadGateway, httputil.ErrCodeUnknown, "%s", err.Error())
	case errors.Is(err, roomserver.ErrRejected), errors.Is(err, roomserver.ErrForbidden):
		return httputil.Forbidden("%s", err.Error())
	case errors.Is(err, roomserver.ErrInvalidContent):
		return httputil.BadJSON("%s", err.Error())

	default:
		return err
	}
}

// createRoomRequest is the POST /createRoom body.
type createRoomRequest struct {
	RoomVersion               string                       `json:"room_version"`
	Preset                    string                       `json:"preset"`
	Visibility                string                       `json:"visibility"`
	RoomAliasName             string                       `json:"room_alias_name"`
	Name                      string                       `json:"name"`
	Topic                     string                       `json:"topic"`
	Invite                    []string                     `json:"invite"`
	CreationContent           json.RawMessage              `json:"creation_content"`
	InitialState              []roomserver.StateEvent      `json:"initial_state"`
	PowerLevelContentOverride json.RawMessage              `json:"power_level_content_override"`
	IsDirect                  bool                         `json:"is_direct"`
	Invite3PID                []map[string]json.RawMessage `json:"invite_3pid"`
}

type createRoomResponse struct {
	RoomID    string `json:"room_id"`
	RoomAlias string `json:"room_alias,omitempty"`
}

// handleCreateRoom implements POST /_matrix/client/v3/createRoom.
func (c *ClientAPI) handleCreateRoom(w http.ResponseWriter, r *http.Request, auth userapi.Authenticated) error {
	var req createRoomRequest
	if _, err := httputil.DecodeOptionalJSON(w, r, &req); err != nil {
		return err
	}

	// Third-party invites go through an identity server, which Warp does
	// not talk to (PLAN.md phase 9). Saying so is better than creating the
	// room and quietly dropping the invites.
	if len(req.Invite3PID) > 0 {
		return httputil.Unknown(http.StatusBadRequest,
			"Third-party invites are not supported by this server")
	}

	if req.RoomAliasName != "" {
		if err := c.checkExclusiveAlias("#"+req.RoomAliasName+":"+c.serverName, auth); err != nil {
			return err
		}
	}

	resp, err := c.rooms.CreateRoom(r.Context(), roomserver.CreateRoomRequest{
		Creator:                   auth.UserID,
		Version:                   req.RoomVersion,
		Preset:                    req.Preset,
		Visibility:                req.Visibility,
		RoomAliasName:             req.RoomAliasName,
		Name:                      req.Name,
		Topic:                     req.Topic,
		Invite:                    req.Invite,
		CreationContent:           req.CreationContent,
		InitialState:              req.InitialState,
		PowerLevelContentOverride: req.PowerLevelContentOverride,
		IsDirect:                  req.IsDirect,
	})
	if err != nil {
		return roomError(err)
	}

	httputil.WriteJSON(w, http.StatusOK, createRoomResponse{
		RoomID:    resp.RoomID,
		RoomAlias: resp.Alias,
	})
	return nil
}

// eventIDResponse is what every endpoint that sends an event returns.
type eventIDResponse struct {
	EventID string `json:"event_id"`
}

// sendEventRequest is the body of a send or state PUT: any JSON object.
type sendEventRequest = json.RawMessage

// handleSendEvent implements
// PUT /_matrix/client/v3/rooms/{roomID}/send/{eventType}/{txnID}.
func (c *ClientAPI) handleSendEvent(w http.ResponseWriter, r *http.Request, auth userapi.Authenticated) error {
	roomID, err := pathRoomID(r)
	if err != nil {
		return err
	}
	eventType := r.PathValue("eventType")
	if eventType == "" {
		return httputil.MissingParam("An event type is required")
	}
	txnID := r.PathValue("txnID")
	if txnID == "" {
		return httputil.MissingParam("A transaction ID is required")
	}

	delay, delayed, err := c.delayRequested(r)
	if err != nil {
		return err
	}
	var content sendEventRequest
	if err := httputil.DecodeJSON(w, r, &content); err != nil {
		return err
	}
	if delayed {
		return c.scheduleDelayed(w, r, delayedevents.ScheduleRequest{
			UserID: auth.UserID, DeviceID: auth.DeviceID, RoomID: roomID,
			Type: eventType, Content: content, Delay: delay,
		})
	}

	eventID, err := c.rooms.SendEvent(r.Context(), roomserver.SendEventRequest{
		RoomID:      roomID,
		Sender:      auth.UserID,
		Type:        eventType,
		Content:     content,
		Transaction: transactionRef(auth, txnID),
	})
	if err != nil {
		return roomError(err)
	}
	httputil.WriteJSON(w, http.StatusOK, eventIDResponse{EventID: eventID})
	return nil
}

// handlePutState implements
// PUT /_matrix/client/v3/rooms/{roomID}/state/{eventType}[/{stateKey}].
//
// State events carry no transaction ID: the spec gives none, because a
// state event is idempotent in a way a message is not — sending the same
// state twice leaves the room in the state you asked for either way.
func (c *ClientAPI) handlePutState(w http.ResponseWriter, r *http.Request, auth userapi.Authenticated) error {
	roomID, err := pathRoomID(r)
	if err != nil {
		return err
	}
	eventType := r.PathValue("eventType")
	if eventType == "" {
		return httputil.MissingParam("An event type is required")
	}
	stateKey := r.PathValue("stateKey")

	delay, delayed, err := c.delayRequested(r)
	if err != nil {
		return err
	}
	var content sendEventRequest
	if err := httputil.DecodeJSON(w, r, &content); err != nil {
		return err
	}
	if delayed {
		return c.scheduleDelayed(w, r, delayedevents.ScheduleRequest{
			UserID: auth.UserID, DeviceID: auth.DeviceID, RoomID: roomID,
			Type: eventType, StateKey: &stateKey, Content: content, Delay: delay,
		})
	}

	eventID, err := c.rooms.SendEvent(r.Context(), roomserver.SendEventRequest{
		RoomID:   roomID,
		Sender:   auth.UserID,
		Type:     eventType,
		StateKey: &stateKey,
		Content:  content,
	})
	if err != nil {
		return roomError(err)
	}
	httputil.WriteJSON(w, http.StatusOK, eventIDResponse{EventID: eventID})
	return nil
}

// redactRequest is the PUT /rooms/{roomID}/redact/{eventID}/{txnID} body.
type redactRequest struct {
	Reason string `json:"reason"`
}

// handleRedact implements
// PUT /_matrix/client/v3/rooms/{roomID}/redact/{eventID}/{txnID}.
func (c *ClientAPI) handleRedact(w http.ResponseWriter, r *http.Request, auth userapi.Authenticated) error {
	roomID, err := pathRoomID(r)
	if err != nil {
		return err
	}
	eventID := r.PathValue("eventID")
	if err := id.ValidateEventID(eventID); err != nil {
		return httputil.InvalidParam("%s is not a valid event ID", eventID)
	}
	txnID := r.PathValue("txnID")
	if txnID == "" {
		return httputil.MissingParam("A transaction ID is required")
	}

	var req redactRequest
	if _, err := httputil.DecodeOptionalJSON(w, r, &req); err != nil {
		return err
	}

	redactionID, err := c.rooms.Redact(r.Context(), roomserver.RedactRequest{
		RoomID:      roomID,
		Sender:      auth.UserID,
		EventID:     eventID,
		Reason:      req.Reason,
		Transaction: transactionRef(auth, txnID),
	})
	if err != nil {
		return roomError(err)
	}
	httputil.WriteJSON(w, http.StatusOK, eventIDResponse{EventID: redactionID})
	return nil
}

// handleGetEvent implements
// GET /_matrix/client/v3/rooms/{roomID}/event/{eventID}.
func (c *ClientAPI) handleGetEvent(w http.ResponseWriter, r *http.Request, auth userapi.Authenticated) error {
	roomID, err := pathRoomID(r)
	if err != nil {
		return err
	}
	eventID := r.PathValue("eventID")
	if err := id.ValidateEventID(eventID); err != nil {
		return httputil.InvalidParam("%s is not a valid event ID", eventID)
	}

	clientEvent, err := c.rooms.Event(r.Context(), roomID, auth.UserID, eventID)
	if err != nil {
		return roomError(err)
	}
	httputil.WriteJSON(w, http.StatusOK, clientEvent)
	return nil
}

// handleGetState implements GET /_matrix/client/v3/rooms/{roomID}/state,
// which returns the room's whole current state as an array.
func (c *ClientAPI) handleGetState(w http.ResponseWriter, r *http.Request, auth userapi.Authenticated) error {
	roomID, err := pathRoomID(r)
	if err != nil {
		return err
	}
	state, err := c.rooms.RoomState(r.Context(), roomID, auth.UserID)
	if err != nil {
		return roomError(err)
	}
	httputil.WriteJSON(w, http.StatusOK, state)
	return nil
}

// handleGetStateEvent implements
// GET /_matrix/client/v3/rooms/{roomID}/state/{eventType}[/{stateKey}].
//
// It returns the event's content rather than the event: an inconsistency in
// the Client-Server API that predates most of it, and one every client
// relies on. The ?format=event query parameter asks for the whole event
// instead, which is how a client that wants the sender gets it.
func (c *ClientAPI) handleGetStateEvent(w http.ResponseWriter, r *http.Request, auth userapi.Authenticated) error {
	roomID, err := pathRoomID(r)
	if err != nil {
		return err
	}
	eventType := r.PathValue("eventType")
	if eventType == "" {
		return httputil.MissingParam("An event type is required")
	}
	stateKey := r.PathValue("stateKey")

	if r.URL.Query().Get("format") == "event" {
		state, err := c.rooms.StateEvent(r.Context(), roomID, auth.UserID, eventType, stateKey)
		if err != nil {
			return roomError(err)
		}
		httputil.WriteJSON(w, http.StatusOK, state)
		return nil
	}

	content, err := c.rooms.StateEventContent(r.Context(), roomID, auth.UserID, eventType, stateKey)
	if err != nil {
		return roomError(err)
	}
	httputil.WriteRawJSON(w, http.StatusOK, content)
	return nil
}

// membersResponse is the GET /rooms/{roomID}/members body.
type membersResponse struct {
	Chunk []roomserver.ClientEvent `json:"chunk"`
}

// handleGetMembers implements GET /_matrix/client/v3/rooms/{roomID}/members.
//
// The ?at= parameter is a sync token, and names the point in the event
// stream to report the membership as of. A client rendering an older part
// of a room's timeline needs it: the names and avatars to show against
// those messages are the ones their senders had then, not now.
func (c *ClientAPI) handleGetMembers(w http.ResponseWriter, r *http.Request, auth userapi.Authenticated) error {
	roomID, err := pathRoomID(r)
	if err != nil {
		return err
	}
	query := r.URL.Query()

	membership, notMembership := query.Get("membership"), query.Get("not_membership")
	for _, value := range []string{membership, notMembership} {
		if err := roomserver.ValidateMembershipFilter(value); err != nil {
			return roomError(err)
		}
	}

	// ?at= only has a meaning once there is a stream, so it is read here
	// rather than in the roomserver: the token format is the syncapi's.
	at, err := ParseSyncPosition(query.Get("at"))
	if err != nil {
		return err
	}

	members, err := c.rooms.Members(r.Context(), roomserver.MembersRequest{
		RoomID:        roomID,
		User:          auth.UserID,
		Membership:    membership,
		NotMembership: notMembership,
		At:            at,
	})
	if err != nil {
		return roomError(err)
	}
	httputil.WriteJSON(w, http.StatusOK, membersResponse{Chunk: members})
	return nil
}

// joinedMembersResponse is the GET /rooms/{roomID}/joined_members body.
type joinedMembersResponse struct {
	Joined map[string]roomserver.RoomMember `json:"joined"`
}

// handleGetJoinedMembers implements
// GET /_matrix/client/v3/rooms/{roomID}/joined_members.
func (c *ClientAPI) handleGetJoinedMembers(w http.ResponseWriter, r *http.Request, auth userapi.Authenticated) error {
	roomID, err := pathRoomID(r)
	if err != nil {
		return err
	}
	joined, err := c.rooms.JoinedMembers(r.Context(), roomID, auth.UserID)
	if err != nil {
		return roomError(err)
	}
	httputil.WriteJSON(w, http.StatusOK, joinedMembersResponse{Joined: joined})
	return nil
}

// joinedRoomsResponse is the GET /joined_rooms body.
type joinedRoomsResponse struct {
	JoinedRooms []string `json:"joined_rooms"`
}

// handleGetJoinedRooms implements GET /_matrix/client/v3/joined_rooms.
func (c *ClientAPI) handleGetJoinedRooms(w http.ResponseWriter, r *http.Request, auth userapi.Authenticated) error {
	rooms, err := c.rooms.JoinedRooms(r.Context(), auth.UserID)
	if err != nil {
		return roomError(err)
	}
	httputil.WriteJSON(w, http.StatusOK, joinedRoomsResponse{JoinedRooms: rooms})
	return nil
}

// pathRoomID reads and validates the {roomID} path value.
func pathRoomID(r *http.Request) (string, error) {
	roomID := r.PathValue("roomID")
	if err := id.ValidateRoomID(roomID); err != nil {
		return "", httputil.InvalidParam("%s is not a valid room ID", roomID)
	}
	return roomID, nil
}

// transactionRef builds the idempotency key for a send.
//
// It is keyed on the device rather than the user: the spec scopes a
// transaction ID to the access token, and two of a user's clients each
// counting from "m1" must not collide.
func transactionRef(auth userapi.Authenticated, txnID string) *storage.TransactionRef {
	return &storage.TransactionRef{
		Localpart: auth.Localpart,
		DeviceID:  auth.DeviceID,
		TxnID:     txnID,
	}
}

// aliasFromPath reads the {roomAlias} path value, which arrives percent-
// encoded because it contains a '#' and a ':'.
func aliasFromPath(r *http.Request) (string, error) {
	alias := r.PathValue("roomAlias")
	if alias == "" {
		return "", httputil.MissingParam("A room alias is required")
	}
	if !strings.HasPrefix(alias, "#") {
		return "", httputil.InvalidParam("%s is not a valid room alias", alias)
	}
	return alias, nil
}