feat: Working lease manager

lease.go

@@ -0,0 +1,67 @@
+package main
+
+import (
+	"errors"
+	"fmt"
+	"time"
+
+	"go.uber.org/zap"
+)
+
+type ILeaseManager interface {
+	Request(xid TxId, clientAddr HwAddr) (*Lease, error)
+	Release(l Lease) error
+	Lookup(xid TxId) error
+}
+
+type LeaseManager struct {
+	leases map[TxId]Lease
+	count  byte
+}
+
+func NewLeaseManager() *LeaseManager {
+	m := &LeaseManager{
+		leases: make(map[TxId]Lease),
+	}
+	return m
+}
+
+func (m *LeaseManager) Request(xid TxId, clientAddr HwAddr) (*Lease, error) {
+	zap.S().Debugf("LeaseManager.Request(%v, %v)", xid, clientAddr)
+
+	if m.count > 254 {
+		return nil, errors.New("lease address pool exhausted")
+	}
+
+	assigned := [4]byte{10, 0, 0, m.count + 2}
+	lease := Lease{
+		TransactionId: xid,
+		TTL:           time.Now().Add(1 * time.Hour),
+		State:         Requested,
+		ClientAddr:    clientAddr,
+		Address:       assigned,
+	}
+	m.leases[xid] = lease
+
+	m.count += 1
+
+	zap.S().Debug("lease=", lease)
+	return &lease, nil
+}
+
+func (m LeaseManager) Release(l Lease) error {
+	_, found := m.leases[l.TransactionId]
+	if !found {
+		return fmt.Errorf("invalid lease %v", l)
+	}
+	delete(m.leases, l.TransactionId)
+	return nil
+}
+
+func (m LeaseManager) Lookup(xid TxId) (*Lease, error) {
+	lease, found := m.leases[xid]
+	if found {
+		return &lease, nil
+	}
+	return nil, fmt.Errorf("no lease found for xid %v", xid)
+}