package clientapi

import (
	"net/http"
	"strconv"
	"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"
)

// hierarchyResponse is what GET /hierarchy returns.
type hierarchyResponse struct {
	Rooms     []hierarchyRoom `json:"rooms"`
	NextBatch string          `json:"next_batch,omitempty"`
}

// hierarchyRoom is a room as /hierarchy shows it to a client:
// children_state is required there, an empty list for a room with no
// children. SpaceRoom leaves an empty one out, as the federation response
// wants for the children it lists; this field, being shallower, takes the
// JSON name over the embedded one.
type hierarchyRoom struct {
	roomserver.SpaceRoom
	ChildrenState []roomserver.SpaceChildEvent `json:"children_state"`
}

// hierarchyTokenPrefix marks a /hierarchy token: how far into the walk
// the next page starts.
const hierarchyTokenPrefix = "h"

// handleHierarchy implements GET /_matrix/client/v1/rooms/{roomID}/hierarchy.
func (c *ClientAPI) handleHierarchy(w http.ResponseWriter, r *http.Request, auth userapi.Authenticated) error {
	roomID, err := pathRoomID(r)
	if err != nil {
		return err
	}
	query := r.URL.Query()

	limit, err := intParam(query.Get("limit"))
	if err != nil {
		return err
	}
	suggestedOnly, err := boolParam(query.Get("suggested_only"))
	if err != nil {
		return err
	}
	maxDepth := -1
	if raw := query.Get("max_depth"); raw != "" {
		if maxDepth, err = strconv.Atoi(raw); err != nil || maxDepth < 0 {
			return httputil.InvalidParam("max_depth must be a non-negative integer")
		}
	}
	from := 0
	if raw := query.Get("from"); raw != "" {
		body, ok := strings.CutPrefix(raw, hierarchyTokenPrefix)
		if from, err = strconv.Atoi(body); !ok || err != nil || from < 0 {
			return httputil.InvalidParam("%q is not a hierarchy token", raw)
		}
	}

	page, err := c.rooms.Hierarchy(r.Context(), roomserver.HierarchyRequest{
		RoomID:        roomID,
		User:          auth.UserID,
		SuggestedOnly: suggestedOnly,
		MaxDepth:      maxDepth,
		From:          from,
		Limit:         limit,
	})
	if err != nil {
		return roomError(err)
	}
	resp := hierarchyResponse{Rooms: make([]hierarchyRoom, 0, len(page.Rooms))}
	for _, room := range page.Rooms {
		children := room.ChildrenState
		if children == nil {
			children = []roomserver.SpaceChildEvent{}
		}
		resp.Rooms = append(resp.Rooms, hierarchyRoom{SpaceRoom: room, ChildrenState: children})
	}
	if page.Next != 0 {
		resp.NextBatch = hierarchyTokenPrefix + strconv.Itoa(page.Next)
	}
	httputil.WriteJSON(w, http.StatusOK, resp)
	return nil
}

// handleRoomSummary implements
// GET /_matrix/client/v1/room_summary/{roomIDOrAlias}.
func (c *ClientAPI) handleRoomSummary(w http.ResponseWriter, r *http.Request, auth userapi.Authenticated) error {
	target := r.PathValue("roomIDOrAlias")
	via := r.URL.Query()["via"]

	roomID := target
	switch {
	case strings.HasPrefix(target, "#"):
		resolved, err := c.resolveAlias(r.Context(), target)
		if err != nil {
			return roomError(err)
		}
		roomID = resolved.RoomID
		via = append(via, resolved.Servers...)
	case id.ValidateRoomID(target) != nil:
		return httputil.InvalidParam("%s is not a room ID or alias", target)
	}

	resp, err := c.rooms.RoomSummary(r.Context(), roomserver.RoomSummaryRequest{
		RoomID: roomID,
		User:   auth.UserID,
		Via:    via,
	})
	if err != nil {
		return roomError(err)
	}
	httputil.WriteJSON(w, http.StatusOK, resp)
	return nil
}