package adminapi

import (
	"errors"
	"net/http"

	"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"
)

// adminRoom is one row of the room list. Like the user list it is a flat
// shape, because the panel shows it as a table.
type adminRoom struct {
	RoomID         string `json:"room_id"`
	RoomVersion    string `json:"room_version"`
	Creator        string `json:"creator"`
	Name           string `json:"name,omitempty"`
	Topic          string `json:"topic,omitempty"`
	CanonicalAlias string `json:"canonical_alias,omitempty"`
	AvatarURL      string `json:"avatar_url,omitempty"`
	RoomType       string `json:"room_type,omitempty"`

	JoinRule          string `json:"join_rule,omitempty"`
	HistoryVisibility string `json:"history_visibility,omitempty"`
	GuestAccess       string `json:"guest_access,omitempty"`

	Published     bool  `json:"published"`
	JoinedMembers int   `json:"joined_members"`
	CreatedAtMS   int64 `json:"created_at_ms"`
}

type roomsResponse struct {
	Rooms []adminRoom `json:"rooms"`

	// Total is the number of rooms matching the query, not the number
	// returned, so the panel can page.
	Total int `json:"total"`

	Limit  int `json:"limit"`
	Offset int `json:"offset"`
}

// defaultRoomPageLimit is what a request without ?limit= gets.
const defaultRoomPageLimit = 50

// handleGetRooms implements GET /_warp/admin/v1/rooms.
func (a *AdminAPI) handleGetRooms(w http.ResponseWriter, r *http.Request, _ userapi.Authenticated) error {
	if err := a.requireRooms(); err != nil {
		return err
	}
	query := r.URL.Query()

	limit, err := intParam(query.Get("limit"), defaultRoomPageLimit)
	if err != nil {
		return httputil.InvalidParam("limit must be a number")
	}
	offset, err := intParam(query.Get("offset"), 0)
	if err != nil {
		return httputil.InvalidParam("offset must be a number")
	}
	if limit < 0 || offset < 0 {
		return httputil.InvalidParam("limit and offset must not be negative")
	}

	summaries, total, err := a.rooms.ListRooms(r.Context(), storage.RoomFilter{
		Search: query.Get("search"),
		Limit:  limit,
		Offset: offset,
	})
	if err != nil {
		return err
	}

	resp := roomsResponse{
		Rooms:  make([]adminRoom, 0, len(summaries)),
		Total:  total,
		Limit:  limit,
		Offset: offset,
	}
	for _, summary := range summaries {
		resp.Rooms = append(resp.Rooms, adminRoomOf(summary))
	}
	httputil.WriteJSON(w, http.StatusOK, resp)
	return nil
}

// roomDetailResponse is GET /_warp/admin/v1/rooms/{roomID}: the list row
// plus what only a count can answer.
type roomDetailResponse struct {
	adminRoom

	Members        int `json:"members"`
	InvitedMembers int `json:"invited_members"`

	Aliases []string `json:"aliases"`

	// ForwardExtremities is where the room's DAG currently ends. There is
	// normally exactly one; more than one means the room has forked, which
	// is worth an operator seeing.
	ForwardExtremities []string `json:"forward_extremities"`
}

// handleGetRoom implements GET /_warp/admin/v1/rooms/{roomID}.
func (a *AdminAPI) handleGetRoom(w http.ResponseWriter, r *http.Request, _ userapi.Authenticated) error {
	roomID, err := a.pathRoomID(r)
	if err != nil {
		return err
	}

	details, err := a.rooms.RoomDetails(r.Context(), roomID)
	if err != nil {
		return roomError(err)
	}
	httputil.WriteJSON(w, http.StatusOK, roomDetailResponse{
		adminRoom:          adminRoomOf(details.RoomSummary),
		Members:            details.Members,
		InvitedMembers:     details.InvitedMembers,
		Aliases:            details.Aliases,
		ForwardExtremities: details.ForwardExtremities,
	})
	return nil
}

// handleDeleteRoom implements DELETE /_warp/admin/v1/rooms/{roomID}: the
// purge.
//
// It is a DELETE on the room rather than a POST to an action, because that
// is what it is, and because the method makes a panel's confirm dialog
// mandatory in a way a POST does not. There is no undo: the room's events
// are deleted, and the members are not told, because the only way to tell
// them would have been to add an event to the room that no longer exists.
func (a *AdminAPI) handleDeleteRoom(w http.ResponseWriter, r *http.Request, auth userapi.Authenticated) error {
	roomID, err := a.pathRoomID(r)
	if err != nil {
		return err
	}

	if err := a.rooms.PurgeRoom(r.Context(), roomID); err != nil {
		return roomError(err)
	}
	a.audit(r.Context(), auth, auditRoomPurge, roomID, nil)
	httputil.WriteJSON(w, http.StatusOK, struct{}{})
	return nil
}

// forceLeaveRequest is the POST /rooms/{roomID}/force_leave body.
type forceLeaveRequest struct {
	UserID string `json:"user_id"`
}

// handleForceLeave implements POST /_warp/admin/v1/rooms/{roomID}/force_leave.
//
// It makes a user leave a room without asking the room's rules whether they
// may. A user stuck in a room — one whose power levels are broken, or whose
// last moderator has gone — is what this exists for, and in such a room the
// rules are exactly what is in the way. It is still an ordinary membership
// event, signed and added to the room, so the other members see what
// happened.
func (a *AdminAPI) handleForceLeave(w http.ResponseWriter, r *http.Request, auth userapi.Authenticated) error {
	roomID, err := a.pathRoomID(r)
	if err != nil {
		return err
	}
	var req forceLeaveRequest
	if err := httputil.DecodeJSON(w, r, &req); err != nil {
		return err
	}
	if req.UserID == "" {
		return httputil.MissingParam("A user ID is required")
	}

	if err := a.rooms.ForceLeave(r.Context(), roomID, req.UserID); err != nil {
		return roomError(err)
	}
	a.audit(r.Context(), auth, auditRoomForceLeave, roomID, map[string]any{"user_id": req.UserID})
	httputil.WriteJSON(w, http.StatusOK, struct{}{})
	return nil
}

// adminRoomOf projects a stored room onto the list row.
func adminRoomOf(summary storage.RoomSummary) adminRoom {
	return adminRoom{
		RoomID:            summary.ID,
		RoomVersion:       summary.Version,
		Creator:           summary.Creator,
		Name:              summary.Name,
		Topic:             summary.Topic,
		CanonicalAlias:    summary.CanonicalAlias,
		AvatarURL:         summary.AvatarURL,
		RoomType:          summary.RoomType,
		JoinRule:          summary.JoinRule,
		HistoryVisibility: summary.HistoryVisibility,
		GuestAccess:       summary.GuestAccess,
		Published:         summary.Published,
		JoinedMembers:     summary.JoinedMembers,
		CreatedAtMS:       summary.CreatedAtMS,
	}
}

// pathRoomID reads the {roomID} path value and insists there is a
// roomserver to ask about it.
func (a *AdminAPI) pathRoomID(r *http.Request) (string, error) {
	if err := a.requireRooms(); err != nil {
		return "", err
	}
	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
}

// requireRooms refuses a room endpoint on a server that started without a
// signing key, and so without a roomserver.
func (a *AdminAPI) requireRooms() error {
	if a.rooms == nil {
		return httputil.Unknown(http.StatusServiceUnavailable,
			"This server has no signing key, so it has no rooms")
	}
	return nil
}

// roomError maps a roomserver error onto a Matrix error. The admin API has
// a shorter list than the Client-Server one, because an admin endpoint
// never hits the authorisation rules.
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.ErrForbidden), errors.Is(err, roomserver.ErrRejected):
		return httputil.Forbidden("%s", err.Error())
	case errors.Is(err, roomserver.ErrInvalidContent):
		return httputil.BadJSON("%s", err.Error())
	default:
		return err
	}
}