refactor-for-testability (#3)

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

peer/mock-network_test.go

@@ -0,0 +1,80 @@
+package peer
+
+import (
+	"bytes"
+	"net"
+	"net/netip"
+	"sync"
+)
+
+type TestPacket struct {
+	Addr netip.AddrPort
+	Data []byte
+}
+
+type TestNetwork struct {
+	lock    sync.Mutex
+	packets map[netip.AddrPort]chan TestPacket
+}
+
+func NewTestNetwork() *TestNetwork {
+	return &TestNetwork{packets: map[netip.AddrPort]chan TestPacket{}}
+}
+
+func (n *TestNetwork) NewUDPConn(localAddr netip.AddrPort) *TestUDPConn {
+	n.lock.Lock()
+	defer n.lock.Unlock()
+	if _, ok := n.packets[localAddr]; !ok {
+		n.packets[localAddr] = make(chan TestPacket, 1024)
+	}
+	return &TestUDPConn{
+		addr:    localAddr,
+		n:       n,
+		packets: n.packets[localAddr],
+	}
+}
+
+func (n *TestNetwork) write(b []byte, from, to netip.AddrPort) {
+	n.lock.Lock()
+	defer n.lock.Unlock()
+	if _, ok := n.packets[to]; !ok {
+		n.packets[to] = make(chan TestPacket, 1024)
+	}
+	n.packets[to] <- TestPacket{
+		Addr: from,
+		Data: bytes.Clone(b),
+	}
+}
+
+type TestUDPConn struct {
+	addr    netip.AddrPort
+	n       *TestNetwork
+	packets chan TestPacket
+}
+
+func (c *TestUDPConn) WriteToUDPAddrPort(b []byte, addr netip.AddrPort) (int, error) {
+	c.n.write(b, c.addr, addr)
+	return len(b), nil
+}
+
+func (c *TestUDPConn) WriteToUDP(b []byte, addr *net.UDPAddr) (int, error) {
+	return c.WriteToUDPAddrPort(b, addr.AddrPort())
+}
+
+func (c *TestUDPConn) ReadFromUDPAddrPort(b []byte) (n int, addr netip.AddrPort, err error) {
+	pkt := <-c.packets
+	b = b[:len(pkt.Data)]
+	copy(b, pkt.Data)
+	return len(b), pkt.Addr, nil
+}
+
+func (c *TestUDPConn) Packets() (out []TestPacket) {
+	for {
+		select {
+		case pkt := <-c.packets:
+			out = append(out, pkt)
+		default:
+			return
+		}
+	}
+}