package keyserver

import (
	"context"
	"encoding/json"
	"slices"

	"github.com/dariuszjaniak/warp/server/internal/federation"
	"github.com/dariuszjaniak/warp/server/internal/matrix/id"
	"github.com/dariuszjaniak/warp/server/internal/storage"
)

// The writing side of device list tracking: telling everyone who shares a
// room with a user that the user's keys changed.
//
// Locally that is a wake-up. The change is already in the device list
// stream, moved in the same transaction as the keys themselves, and every
// sync works out from the stream whose changes concern it; all a sync
// blocked in a long poll needs is to be told to look. Remotely it is an
// EDU to every server with a user in one of those rooms, which is how a
// server that has the user's keys cached knows to drop them.

// sharers is who shares a room with a user, the user included.
func (k *API) sharers(ctx context.Context, userID string) []string {
	out := []string{userID}
	if k.rooms == nil {
		return out
	}
	users, err := k.rooms.UsersSharingRooms(ctx, userID)
	if err != nil {
		// A missed wake-up costs a client one sync timeout, and a missed
		// EDU costs a remote server one stale key until the next change;
		// neither is worth failing the upload that caused it.
		k.log.Warn("could not read who shares a room with a user", "user_id", userID, "error", err)
		return out
	}
	for _, u := range users {
		if !slices.Contains(out, u) {
			out = append(out, u)
		}
	}
	return out
}

// changed reacts to a move of a user's device list: it wakes the local
// syncs it concerns and returns the other servers that have to hear of
// it.
func (k *API) changed(ctx context.Context, userID string) []string {
	users := k.sharers(ctx, userID)

	var (
		local   []string
		servers []string
	)
	for _, u := range users {
		server, err := id.ServerNameOf(u)
		switch {
		case err != nil:
			continue
		case server == k.serverName:
			local = append(local, u)
		case !slices.Contains(servers, server):
			servers = append(servers, server)
		}
	}
	if k.notifier != nil {
		k.notifier.NotifyUsers(local)
	}
	slices.Sort(servers)
	return servers
}

// federating reports whether there is a running queue to send EDUs to.
func (k *API) federating() bool {
	return k.outbound != nil && k.outbound.Running()
}

// announceDevices tells everyone about moves of a local user's devices:
// keys uploaded, changed or deleted. keys holds the current keys of the
// devices that still have them; a device missing from it is announced as
// deleted.
func (k *API) announceDevices(ctx context.Context, userID string, updates []storage.DeviceListUpdate, keys map[string]json.RawMessage) {
	if len(updates) == 0 {
		return
	}
	servers := k.changed(ctx, userID)
	if len(servers) == 0 || !k.federating() {
		return
	}
	for _, u := range updates {
		content := federation.DeviceListUpdateContent{
			UserID:   userID,
			DeviceID: u.DeviceID,
			StreamID: u.StreamPos,
		}
		if u.PrevPos > 0 {
			content.PrevID = []int64{u.PrevPos}
		}
		if raw, ok := keys[u.DeviceID]; ok {
			content.Keys = raw
		} else {
			content.Deleted = true
		}
		encoded, err := json.Marshal(content)
		if err != nil {
			continue
		}
		k.outbound.QueueEDU(ctx, servers, federation.EDU{Type: federation.EDUDeviceListUp, Content: encoded})
	}
}

// announceSigningKeys tells everyone a local user's cross-signing keys
// changed: the master key, or a signature on it, or the self-signing key.
// The user-signing key is not announced — nobody but its owner ever sees
// it.
func (k *API) announceSigningKeys(ctx context.Context, userID string) {
	servers := k.changed(ctx, userID)
	if len(servers) == 0 || !k.federating() {
		return
	}
	master, selfSigning, _, err := k.crossSigningKeys(ctx, userID, "")
	if err != nil {
		k.log.Warn("could not read cross-signing keys to announce them", "user_id", userID, "error", err)
		return
	}
	encoded, err := json.Marshal(federation.SigningKeyUpdateContent{
		UserID: userID, MasterKey: master, SelfSigningKey: selfSigning,
	})
	if err != nil {
		return
	}
	k.outbound.QueueEDU(ctx, servers, federation.EDU{Type: federation.EDUSigningKeys, Content: encoded})
}