package clientapi

import (
	"net/http"
	"strings"

	"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/userapi"
)

// joinRequest is the body of both join endpoints.
type joinRequest struct {
	Reason string `json:"reason"`

	// ThirdPartySigned is the proof an identity server issued for a
	// third-party invite. Warp does not talk to one, so it is refused
	// rather than ignored.
	ThirdPartySigned map[string]any `json:"third_party_signed"`
}

type joinResponse struct {
	RoomID string `json:"room_id"`
}

// handleJoinRoomByID implements POST /_matrix/client/v3/rooms/{roomID}/join.
func (c *ClientAPI) handleJoinRoomByID(w http.ResponseWriter, r *http.Request, auth userapi.Authenticated) error {
	roomID, err := pathRoomID(r)
	if err != nil {
		return err
	}
	return c.join(w, r, auth, roomID)
}

// handleJoinRoom implements POST /_matrix/client/v3/join/{roomIDOrAlias},
// the endpoint a client uses when all it has is an alias.
func (c *ClientAPI) handleJoinRoom(w http.ResponseWriter, r *http.Request, auth userapi.Authenticated) error {
	target := r.PathValue("roomIDOrAlias")
	switch {
	case strings.HasPrefix(target, "!"):
		if err := id.ValidateRoomID(target); err != nil {
			return httputil.InvalidParam("%s is not a valid room ID", target)
		}
		return c.join(w, r, auth, target)

	case strings.HasPrefix(target, "#"):
		resolved, err := c.resolveAlias(r.Context(), target)
		if err != nil {
			return roomError(err)
		}
		return c.join(w, r, auth, resolved.RoomID)

	default:
		return httputil.InvalidParam("%s is neither a room ID nor a room alias", target)
	}
}

// join is the body of both join endpoints.
func (c *ClientAPI) join(w http.ResponseWriter, r *http.Request, auth userapi.Authenticated, roomID string) error {
	var req joinRequest
	if _, err := httputil.DecodeOptionalJSON(w, r, &req); err != nil {
		return err
	}
	if len(req.ThirdPartySigned) > 0 {
		return httputil.Unknown(http.StatusBadRequest,
			"Third-party invites are not supported by this server")
	}

	joined, err := c.rooms.JoinRoom(r.Context(), roomserver.JoinRequest{
		RoomID:      roomID,
		User:        auth.UserID,
		Reason:      req.Reason,
		ServerNames: r.URL.Query()["server_name"],
	})
	if err != nil {
		return roomError(err)
	}
	httputil.WriteJSON(w, http.StatusOK, joinResponse{RoomID: joined})
	return nil
}

// reasonRequest is the body of /leave: a note, at most.
type reasonRequest struct {
	Reason string `json:"reason"`
}

// handleLeaveRoom implements POST /_matrix/client/v3/rooms/{roomID}/leave.
//
// The same endpoint rejects an invite, which is why it works on a room the
// caller has never been joined to.
func (c *ClientAPI) handleLeaveRoom(w http.ResponseWriter, r *http.Request, auth userapi.Authenticated) error {
	roomID, err := pathRoomID(r)
	if err != nil {
		return err
	}
	var req reasonRequest
	if _, err := httputil.DecodeOptionalJSON(w, r, &req); err != nil {
		return err
	}
	if err := c.rooms.LeaveRoom(r.Context(), roomID, auth.UserID, req.Reason); err != nil {
		return roomError(err)
	}
	httputil.WriteJSON(w, http.StatusOK, struct{}{})
	return nil
}

// targetRequest is the body of invite, kick, ban and unban.
type targetRequest struct {
	UserID string `json:"user_id"`
	Reason string `json:"reason"`

	// The identity-server fields of /invite. Their presence is what
	// distinguishes a third-party invite from an ordinary one.
	IDServer    string `json:"id_server"`
	Medium      string `json:"medium"`
	Address     string `json:"address"`
	IDAccessTok string `json:"id_access_token"`
}

// handleInvite implements POST /_matrix/client/v3/rooms/{roomID}/invite.
func (c *ClientAPI) handleInvite(w http.ResponseWriter, r *http.Request, auth userapi.Authenticated) error {
	roomID, req, err := c.targetRequest(w, r)
	if err != nil {
		return err
	}
	if req.Address != "" || req.Medium != "" || req.IDServer != "" {
		return httputil.Unknown(http.StatusBadRequest,
			"Third-party invites are not supported by this server")
	}

	// A user of this server that does not exist may be one an
	// application service creates on demand: a bridge's puppet for
	// somebody on the other network is invited before it is registered.
	if localpart, err := c.users.ParseLocalUserID(req.UserID); err == nil {
		if _, err := c.ensureAppServiceUser(r.Context(), localpart); err != nil {
			return err
		}
	}

	if err := c.rooms.InviteUser(r.Context(), roomserver.InviteRequest{
		RoomID: roomID,
		Sender: auth.UserID,
		Target: req.UserID,
		Reason: req.Reason,
	}); err != nil {
		return roomError(err)
	}
	httputil.WriteJSON(w, http.StatusOK, struct{}{})
	return nil
}

// handleKick implements POST /_matrix/client/v3/rooms/{roomID}/kick.
func (c *ClientAPI) handleKick(w http.ResponseWriter, r *http.Request, auth userapi.Authenticated) error {
	roomID, req, err := c.targetRequest(w, r)
	if err != nil {
		return err
	}
	if req.UserID == "" {
		return httputil.MissingParam("A user ID is required")
	}
	if err := c.rooms.KickUser(r.Context(), roomID, auth.UserID, req.UserID, req.Reason); err != nil {
		return roomError(err)
	}
	httputil.WriteJSON(w, http.StatusOK, struct{}{})
	return nil
}

// handleBan implements POST /_matrix/client/v3/rooms/{roomID}/ban.
func (c *ClientAPI) handleBan(w http.ResponseWriter, r *http.Request, auth userapi.Authenticated) error {
	roomID, req, err := c.targetRequest(w, r)
	if err != nil {
		return err
	}
	if req.UserID == "" {
		return httputil.MissingParam("A user ID is required")
	}
	if err := c.rooms.BanUser(r.Context(), roomID, auth.UserID, req.UserID, req.Reason); err != nil {
		return roomError(err)
	}
	httputil.WriteJSON(w, http.StatusOK, struct{}{})
	return nil
}

// handleUnban implements POST /_matrix/client/v3/rooms/{roomID}/unban.
func (c *ClientAPI) handleUnban(w http.ResponseWriter, r *http.Request, auth userapi.Authenticated) error {
	roomID, req, err := c.targetRequest(w, r)
	if err != nil {
		return err
	}
	if req.UserID == "" {
		return httputil.MissingParam("A user ID is required")
	}
	if err := c.rooms.UnbanUser(r.Context(), roomID, auth.UserID, req.UserID, req.Reason); err != nil {
		return roomError(err)
	}
	httputil.WriteJSON(w, http.StatusOK, struct{}{})
	return nil
}

// targetRequest decodes the body the four moderation endpoints share.
func (c *ClientAPI) targetRequest(w http.ResponseWriter, r *http.Request) (string, targetRequest, error) {
	roomID, err := pathRoomID(r)
	if err != nil {
		return "", targetRequest{}, err
	}
	var req targetRequest
	if err := httputil.DecodeJSON(w, r, &req); err != nil {
		return "", targetRequest{}, err
	}
	// A third-party invite has no user_id, which is why the check for one
	// is left to the handler.
	return roomID, req, nil
}