// getNextBootstrapAddress returns the next available bootstrap
// address by consulting the first non-exhausted resolver from the
// slice supplied to the constructor or set using setBootstrap().
// The lock is assumed held.
func (g *Gossip) getNextBootstrapAddress() net.Addr {
	if len(g.resolvers) == 0 {
		log.Fatalf("no resolvers specified for gossip network")
	}

	// Run through resolvers round robin starting at last resolved index.
	for i := 0; i < len(g.resolvers); i++ {
		g.resolverIdx = (g.resolverIdx + 1) % len(g.resolvers)
		if g.resolverIdx == len(g.resolvers)-1 {
			g.triedAll = true
		}
		resolver := g.resolvers[g.resolverIdx]
		addr, err := resolver.GetAddress()
		if err != nil {
			log.Errorf("invalid bootstrap address: %+v, %v", resolver, err)
			continue
		} else if addr.String() == g.is.NodeAddr.String() {
			// Skip our own node address.
			continue
		}
		_, addrActive := g.bootstrapping[addr.String()]
		if !resolver.IsExhausted() || !addrActive {
			g.bootstrapping[addr.String()] = struct{}{}
			return addr
		}
	}

	return nil
}

// getNextBootstrapAddress returns the next available bootstrap
// address by consulting the first non-exhausted resolver from the
// slice supplied to the constructor or set using setBootstrap().
// The lock is assumed held.
func (g *Gossip) getNextBootstrapAddress() net.Addr {
	needBSCleanup := false
	defer func() {
		g.needBSCleanup = needBSCleanup
	}()

	// Run through resolvers round robin starting at last resolved index.
	for i := 0; i < len(g.resolvers); i++ {
		g.resolverIdx++
		g.resolverIdx %= len(g.resolvers)
		g.resolversTried[g.resolverIdx] = struct{}{}
		resolver := g.resolvers[g.resolverIdx]
		if addr, err := resolver.GetAddress(); err != nil {
			// Resolver has an invalid address. Set needBSCleanup to purge invalid
			// bootstrap addresses once gossip cluster is joined successfully.
			needBSCleanup = true
			if !g.needBSCleanup {
				log.Warningf(context.TODO(), "invalid bootstrap address: %+v, %v", resolver, err)
			}
			continue
		} else {
			addrStr := addr.String()
			if _, addrActive := g.bootstrapping[addrStr]; !addrActive {
				g.bootstrapping[addrStr] = struct{}{}
				return addr
			}
		}
	}

	return nil
}

// getNextBootstrapAddress returns the next available bootstrap
// address by consulting the first non-exhausted resolver from the
// slice supplied to the constructor or set using setBootstrap().
// The lock is assumed held.
func (g *Gossip) getNextBootstrapAddress() net.Addr {
	// Run through resolvers round robin starting at last resolved index.
	for i := 0; i < len(g.resolvers); i++ {
		g.resolverIdx++
		g.resolverIdx %= len(g.resolvers)
		g.resolversTried[g.resolverIdx] = struct{}{}
		resolver := g.resolvers[g.resolverIdx]
		if addr, err := resolver.GetAddress(); err != nil {
			log.Errorf("invalid bootstrap address: %+v, %v", resolver, err)
			continue
		} else {
			addrStr := addr.String()
			if _, addrActive := g.bootstrapping[addrStr]; !addrActive {
				g.bootstrapping[addrStr] = struct{}{}
				return addr
			}
		}
	}

	return nil
}