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// Copyright (C) 2019-2023 Algorand, Inc.
// This file is part of go-algorand
//
// go-algorand is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as
// published by the Free Software Foundation, either version 3 of the
// License, or (at your option) any later version.
//
// go-algorand is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with go-algorand. If not, see <https://www.gnu.org/licenses/>.
package dnsaddr
import (
madns "github.com/multiformats/go-multiaddr-dns"
log "github.com/algorand/go-algorand/logging"
"github.com/algorand/go-algorand/tools/network"
)
// MultiaddrDNSResolveController returns a madns.Resolver, cycling through underlying net.Resolvers
type MultiaddrDNSResolveController struct {
resolver *madns.Resolver
nextResolvers []func() *madns.Resolver
controller network.ResolveController
}
// NewMultiaddrDNSResolveController constructs a MultiaddrDNSResolveController
func NewMultiaddrDNSResolveController(secure bool, fallbackDNSResolverAddress string) *MultiaddrDNSResolveController {
controller := network.NewResolveController(secure, fallbackDNSResolverAddress, log.Base())
nextResolvers := []func() *madns.Resolver{controller.SystemDnsaddrResolver}
if fallbackDNSResolverAddress != "" {
nextResolvers = append(nextResolvers, controller.FallbackDnsaddrResolver)
}
return &MultiaddrDNSResolveController{
resolver: nil,
nextResolvers: append(nextResolvers, controller.DefaultDnsaddrResolver),
controller: controller,
}
}
// NextResolver applies the nextResolvers functions in order and returns the most recent result
func (c *MultiaddrDNSResolveController) NextResolver() *madns.Resolver {
if len(c.nextResolvers) == 0 {
c.resolver = nil
} else {
c.resolver = c.nextResolvers[0]()
c.nextResolvers = c.nextResolvers[1:]
}
return c.resolver
}
// Resolver returns the current resolver, invokes NextResolver if the resolver is nil
func (c *MultiaddrDNSResolveController) Resolver() *madns.Resolver {
if c.resolver == nil {
c.resolver = c.NextResolver()
}
return c.resolver
}
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