discover.go

// Copyright 2020 The Swarm Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package p2p

import (
	"context"
	"errors"
	"fmt"
	"math/rand"

	ma "github.com/multiformats/go-multiaddr"
	madns "github.com/multiformats/go-multiaddr-dns"
)

func Discover(ctx context.Context, addr ma.Multiaddr, f func(ma.Multiaddr) (bool, error)) (bool, error) {
	if comp, _ := ma.SplitFirst(addr); comp.Protocol().Name != "dnsaddr" {
		return f(addr)
	}

	dnsResolver := madns.DefaultResolver
	addrs, err := dnsResolver.Resolve(ctx, addr)
	if err != nil {
		return false, fmt.Errorf("dns resolve address %s: %w", addr, err)
	}
	if len(addrs) == 0 {
		return false, errors.New("non-resolvable API endpoint")
	}

	rand.Shuffle(len(addrs), func(i, j int) {
		addrs[i], addrs[j] = addrs[j], addrs[i]
	})
	for _, addr := range addrs {
		stopped, err := Discover(ctx, addr, f)
		if err != nil {
			return false, fmt.Errorf("discover %s: %w", addr, err)
		}

		if stopped {
			return true, nil
		}
	}

	return false, nil
}