package agentsvc

import (
	"context"
	"slices"
	"time"

	llmgwv1 "gitea.mynodes.xyz/ilker/llmgw/api/gen/llmgw/v1"
)

// SetControlPlanes gives the service where the list of control planes comes
// from. Every agent is told it when it registers, and again when it changes.
func (s *Service) SetControlPlanes(list func(context.Context) ([]string, error)) {
	s.mu.Lock()
	s.controlPlanes = list
	s.mu.Unlock()
}

// controlPlanesMsg is the list as an agent is sent it, or nil when there is
// none to send: a cluster with no list recorded keeps what its agents were
// configured with.
func (s *Service) controlPlanesMsg(ctx context.Context) *llmgwv1.ControlMessage {
	s.mu.RLock()
	list := s.controlPlanes
	s.mu.RUnlock()
	if list == nil {
		return nil
	}
	servers, err := list(ctx)
	if err != nil || len(servers) == 0 {
		return nil
	}
	return &llmgwv1.ControlMessage{Msg: &llmgwv1.ControlMessage_ControlPlanes{
		ControlPlanes: &llmgwv1.ControlPlanes{Servers: servers}}}
}

// WatchControlPlanes tells every connected agent the list when it changes,
// checking every so often. A control plane added by `llmgw server add` reaches
// the nodes within that time, without their being touched.
func (s *Service) WatchControlPlanes(ctx context.Context, every time.Duration) {
	var last []string
	t := time.NewTicker(every)
	defer t.Stop()
	for {
		if msg := s.controlPlanesMsg(ctx); msg != nil {
			now := msg.GetControlPlanes().GetServers()
			if !slices.Equal(now, last) {
				for _, node := range s.ConnectedNodes() {
					if err := s.send(node, msg); err != nil {
						s.log.Warn("could not tell a node the control planes", "node", node, "err", err)
					}
				}
				if last != nil {
					s.log.Info("told the nodes the control planes changed", "servers", now)
				}
				last = now
			}
		}
		select {
		case <-ctx.Done():
			return
		case <-t.C:
		}
	}
}