refactor-for-testability (#3)

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

peer/files.go

@@ -0,0 +1,90 @@
+package peer
+
+import (
+	"encoding/json"
+	"log"
+	"os"
+	"path/filepath"
+	"vppn/m"
+)
+
+type localConfig struct {
+	m.PeerConfig
+	PubKey      []byte
+	PrivKey     []byte
+	PubSignKey  []byte
+	PrivSignKey []byte
+}
+
+func configDir(netName string) string {
+	d, err := os.UserHomeDir()
+	if err != nil {
+		log.Fatalf("Failed to get user home directory: %v", err)
+	}
+	return filepath.Join(d, ".vppn", netName)
+}
+
+func peerConfigPath(netName string) string {
+	return filepath.Join(configDir(netName), "peer-config.json")
+}
+
+func peerStatePath(netName string) string {
+	return filepath.Join(configDir(netName), "peer-state.json")
+}
+
+func storeJson(x any, outPath string) error {
+	outDir := filepath.Dir(outPath)
+	_ = os.MkdirAll(outDir, 0700)
+
+	tmpPath := outPath + ".tmp"
+	buf, err := json.Marshal(x)
+	if err != nil {
+		return err
+	}
+
+	f, err := os.Create(tmpPath)
+	if err != nil {
+		return err
+	}
+
+	if _, err := f.Write(buf); err != nil {
+		f.Close()
+		return err
+	}
+
+	if err := f.Sync(); err != nil {
+		f.Close()
+		return err
+	}
+
+	if err := f.Close(); err != nil {
+		return err
+	}
+
+	return os.Rename(tmpPath, outPath)
+}
+
+func storePeerConfig(netName string, pc localConfig) error {
+	return storeJson(pc, peerConfigPath(netName))
+}
+
+func storeNetworkState(netName string, ps m.NetworkState) error {
+	return storeJson(ps, peerStatePath(netName))
+}
+
+func loadJson(dataPath string, ptr any) error {
+	data, err := os.ReadFile(dataPath)
+	if err != nil {
+		return err
+	}
+
+	return json.Unmarshal(data, ptr)
+}
+
+func loadPeerConfig(netName string) (pc localConfig, err error) {
+	return pc, loadJson(peerConfigPath(netName), &pc)
+}
+
+func loadNetworkState(netName string) (ps m.NetworkState, err error) {
+	return ps, loadJson(peerStatePath(netName), &ps)
+}