refactor-for-testability (#3)

Co-authored-by: jdl <jdl@desktop>
Co-authored-by: jdl <jdl@crumpington.com>
Reviewed-on: #3

peer/pubaddrs.go

@@ -0,0 +1,86 @@
+package peer
+
+import (
+	"net/netip"
+	"sort"
+	"sync"
+	"time"
+)
+
+type pubAddrStore struct {
+	lock      sync.Mutex
+	localPub  bool
+	localAddr netip.AddrPort
+	lastSeen  map[netip.AddrPort]time.Time
+	addrList  []netip.AddrPort
+}
+
+func newPubAddrStore(localAddr netip.AddrPort) *pubAddrStore {
+	return &pubAddrStore{
+		localPub:  localAddr.IsValid(),
+		localAddr: localAddr,
+		lastSeen:  map[netip.AddrPort]time.Time{},
+		addrList:  make([]netip.AddrPort, 0, 32),
+	}
+}
+
+func (store *pubAddrStore) Store(addr netip.AddrPort) {
+	if store.localPub {
+		return
+	}
+
+	if !addr.IsValid() {
+		return
+	}
+
+	if addr.Addr().IsPrivate() {
+		return
+	}
+
+	store.lock.Lock()
+	defer store.lock.Unlock()
+
+	if _, exists := store.lastSeen[addr]; !exists {
+		store.addrList = append(store.addrList, addr)
+	}
+	store.lastSeen[addr] = time.Now()
+	store.sort()
+}
+
+func (store *pubAddrStore) Get() (addrs [8]netip.AddrPort) {
+	store.lock.Lock()
+	defer store.lock.Unlock()
+
+	store.clean()
+
+	if store.localPub {
+		addrs[0] = store.localAddr
+		return
+	}
+
+	copy(addrs[:], store.addrList)
+	return
+}
+
+func (store *pubAddrStore) clean() {
+	if store.localPub {
+		return
+	}
+
+	for ip, lastSeen := range store.lastSeen {
+		if time.Since(lastSeen) > timeoutInterval {
+			delete(store.lastSeen, ip)
+		}
+	}
+	store.addrList = store.addrList[:0]
+	for ip := range store.lastSeen {
+		store.addrList = append(store.addrList, ip)
+	}
+	store.sort()
+}
+
+func (store *pubAddrStore) sort() {
+	sort.Slice(store.addrList, func(i, j int) bool {
+		return store.lastSeen[store.addrList[j]].Before(store.lastSeen[store.addrList[i]])
+	})
+}