wireguard: Config.WriteTo()

Signed-off-by: Alejandro Mery <amery@jpi.io>

pkg/wireguard/config.go

@@ -1,17 +1,35 @@
 package wireguard
 
 import (
+	"bytes"
 	"errors"
 	"fmt"
 	"io"
 	"net/netip"
 	"strconv"
 	"strings"
+	"text/template"
 
 	"darvaza.org/core"
 	"gopkg.in/gcfg.v1"
 )
 
+var configTemplate = template.Must(template.New("config").Funcs(template.FuncMap{
+	"StringsJoin": strings.Join,
+}).Parse(`[Interface]
+Address = {{.Interface.Address}}
+PrivateKey = {{.Interface.PrivateKey}}
+ListenPort = {{.Interface.ListenPort}}
+{{range .Peer}}
+
+[Peer]
+# {{.Endpoint.Name}}
+PublicKey = {{.PublicKey}}
+Endpoint = {{.Endpoint}}
+AllowedIPs = {{ StringsJoin .AllowedIPs ", "}}
+{{end}}
+`))
+
 // Config represents a wgN.conf file
 type Config struct {
 	Interface InterfaceConfig
@@ -19,13 +37,24 @@ type Config struct {
 }
 
 // GetAddress is a shortcut to the interface's address
-func (f *Config) GetAddress() netip.Addr {
-	return f.Interface.Address
+func (wg *Config) GetAddress() netip.Addr {
+	return wg.Interface.Address
 }
 
 // Peers tells how many peers are described
-func (f *Config) Peers() int {
-	return len(f.Peer)
+func (wg *Config) Peers() int {
+	return len(wg.Peer)
+}
+
+// WriteTo writes a Wireguard [Config] onto the provided [io.Writer]
+func (wg *Config) WriteTo(w io.Writer) (int64, error) {
+	var buf bytes.Buffer
+
+	if err := configTemplate.Execute(&buf, wg); err != nil {
+		return 0, err
+	}
+
+	return buf.WriteTo(w)
 }
 
 // InterfaceConfig represents the [Interface] section