waku-org/go-waku

package rendezvous

import (
    "context"
    "math/rand"
    "sort"
    "time"

    "github.com/multiformats/go-multiaddr"
    "github.com/waku-org/go-waku/waku/v2/utils"
)

type RendezvousPointIterator struct {
    rendezvousPoints []*RendezvousPoint
}

// NewRendezvousPointIterator creates an iterator with a backoff mechanism to use random rendezvous points taking into account successful/unsuccesful connection attempts
func NewRendezvousPointIterator(rendezvousPoints []multiaddr.Multiaddr) *RendezvousPointIterator {
    var rendevousPoints []*RendezvousPoint
    for _, rp := range rendezvousPoints {
        peerID, err := utils.GetPeerID(rp)
        if err == nil {
            rendevousPoints = append(rendevousPoints, NewRendezvousPoint(peerID))
        }
    }

    return &RendezvousPointIterator{
        rendezvousPoints: rendevousPoints,
    }
}

// RendezvousPoints returns the list of rendezvous points registered in this iterator
func (r *RendezvousPointIterator) RendezvousPoints() []*RendezvousPoint {
    return r.rendezvousPoints
}

// Next will return a channel that will be triggered as soon as the next rendevous point is available to be used (depending on backoff time)
func (r *RendezvousPointIterator) Next(ctx context.Context) <-chan *RendezvousPoint {
    var dialableRP []*RendezvousPoint
    now := time.Now()
    for _, rp := range r.rendezvousPoints {
        if now.After(rp.NextTry()) {
            dialableRP = append(dialableRP, rp)
        }
    }

    result := make(chan *RendezvousPoint, 1)

    if len(dialableRP) > 0 {
        result <- r.rendezvousPoints[rand.Intn(len(r.rendezvousPoints))] // nolint: gosec
    } else {
        if len(r.rendezvousPoints) > 0 {
            sort.Slice(r.rendezvousPoints, func(i, j int) bool {
                return r.rendezvousPoints[i].nextTry.Before(r.rendezvousPoints[j].nextTry)
            })

            tryIn := r.rendezvousPoints[0].NextTry().Sub(now)
            timer := time.NewTimer(tryIn)
            defer timer.Stop()

            select {
            case <-ctx.Done():
                break
            case <-timer.C:
                result <- r.rendezvousPoints[0]
            }
        }
    }

    close(result)
    return result
}