package connmgr

import (
	"fmt"
	"github.com/p9c/p9/pkg/chaincfg"
	mrand "math/rand"
	"net"
	"strconv"
	"time"
	
	"github.com/p9c/p9/pkg/wire"
)

const (
	// These constants are used by the DNS seed code to pick a random last seen time.
	secondsIn3Days int32 = 24 * 60 * 60 * 3
	secondsIn4Days int32 = 24 * 60 * 60 * 4
)

// OnSeed is the signature of the callback function which is invoked when DNS seeding is succesful
type OnSeed func(addrs []*wire.NetAddress)

// LookupFunc is the signature of the DNS lookup function.
type LookupFunc func(string) ([]net.IP, error)

// SeedFromDNS uses DNS seeding to populate the address manager with peers.
func SeedFromDNS(
	chainParams *chaincfg.Params, reqServices wire.ServiceFlag,
	lookupFn LookupFunc, seedFn OnSeed,
) {
	for _, dnsseed := range chainParams.DNSSeeds {
		var host string
		if !dnsseed.HasFiltering || reqServices == wire.SFNodeNetwork {
			host = dnsseed.Host
		} else {
			host = fmt.Sprintf("x%x.%s", uint64(reqServices), dnsseed.Host)
		}
		go func(host string) {
			randSource := mrand.New(mrand.NewSource(time.Now().UnixNano()))
			seedpeers, e := lookupFn(host)
			if e != nil {
				E.F("DNS routeable failed on seed %s: %v", host, e)
				return
			}
			numPeers := len(seedpeers)
			D.F("%d addresses found from DNS seed %s", numPeers, host)
			if numPeers == 0 {
				return
			}
			addresses := make([]*wire.NetAddress, len(seedpeers))
			// if this errors then we have *real* problems
			intPort, _ := strconv.Atoi(chainParams.DefaultPort)
			for i, peer := range seedpeers {
				addresses[i] = wire.NewNetAddressTimestamp(
					// bitcoind seeds with addresses from a time randomly
					// selected between 3 and 7 days ago.
					time.Now().Add(
						-1*time.Second*time.Duration(
							secondsIn3Days+
								randSource.Int31n(secondsIn4Days),
						),
					),
					0, peer, uint16(intPort),
				)
			}
			seedFn(addresses)
		}(host)
	}
}