micro/router/route.go

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package router
import (
"fmt"
"strings"
"github.com/olekukonko/tablewriter"
)
var (
// DefaultLocalMetric is default route cost for local network
DefaultLocalMetric = 1
// DefaultNetworkMetric is default route cost for micro network
DefaultNetworkMetric = 10
)
// AddPolicy defines routing table addition policy
type AddPolicy int
const (
// OverrideIfExists overrides route if it already exists
OverrideIfExists AddPolicy = iota
// IgnoreIfExists does not modify existing route
IgnoreIfExists
)
// String returns human reprensentation of policy
func (p AddPolicy) String() string {
switch p {
case OverrideIfExists:
return "OVERRIDE"
case IgnoreIfExists:
return "IGNORE"
default:
return "UNKNOWN"
}
}
// RouteOption is used to set routing table entry options
type RouteOption func(*RouteOptions)
// RouteOptions are route options
type RouteOptions struct {
// DestAddr is destination address
DestAddr string
// Gateway is the next route hop
Gateway Router
// Network defines micro network
Network string
// Metric is route cost metric
Metric int
// Policy defines route addition policy
Policy AddPolicy
}
// DestAddr sets destination address
func DestAddr(a string) RouteOption {
return func(o *RouteOptions) {
o.DestAddr = a
}
}
// Gateway sets the route gateway
func Gateway(r Router) RouteOption {
return func(o *RouteOptions) {
o.Gateway = r
}
}
// Network sets micro network
func Network(n string) RouteOption {
return func(o *RouteOptions) {
o.Network = n
}
}
// Metric sets route metric
func Metric(m int) RouteOption {
return func(o *RouteOptions) {
o.Metric = m
}
}
// RoutePolicy sets add route policy
func RoutePolicy(p AddPolicy) RouteOption {
return func(o *RouteOptions) {
o.Policy = p
}
}
// Route is routing table route
type Route interface {
// Options returns route options
Options() RouteOptions
}
type route struct {
opts RouteOptions
}
// NewRoute returns new routing table route
func NewRoute(opts ...RouteOption) Route {
eopts := RouteOptions{}
for _, o := range opts {
o(&eopts)
}
return &route{
opts: eopts,
}
}
// Options returns route options
func (r *route) Options() RouteOptions {
return r.opts
}
// String allows to print the route
func (r *route) String() string {
// this will help us build routing table string
sb := &strings.Builder{}
// create nice table printing structure
table := tablewriter.NewWriter(sb)
table.SetHeader([]string{"Destination", "Gateway", "Network", "Metric"})
strRoute := []string{
r.opts.DestAddr,
r.opts.Gateway.Address(),
r.opts.Network,
fmt.Sprintf("%d", r.opts.Metric),
}
table.Append(strRoute)
// render table into sb
table.Render()
return sb.String()
}