feat(proxystate): add state file package for persistent proxy

internal/proxystate/state.go

@@ -0,0 +1,56 @@
+package proxystate
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"path/filepath"
+	"syscall"
+)
+
+const stateFileName = "proxy-state.json"
+
+type State struct {
+	PID        int    `json:"pid"`
+	Addr       string `json:"addr"`
+	CACertPath string `json:"ca_cert_path"`
+}
+
+func StatePath(configDir string) string {
+	return filepath.Join(configDir, stateFileName)
+}
+
+func Write(path string, s State) error {
+	data, err := json.Marshal(s)
+	if err != nil {
+		return fmt.Errorf("marshal proxy state: %w", err)
+	}
+	return os.WriteFile(path, data, 0o600)
+}
+
+func Read(path string) (State, error) {
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return State{}, fmt.Errorf("read proxy state: %w", err)
+	}
+	var s State
+	if err := json.Unmarshal(data, &s); err != nil {
+		return State{}, fmt.Errorf("unmarshal proxy state: %w", err)
+	}
+	return s, nil
+}
+
+func Remove(path string) error {
+	return os.Remove(path)
+}
+
+func (s State) IsRunning() bool {
+	if s.PID <= 0 {
+		return false
+	}
+	proc, err := os.FindProcess(s.PID)
+	if err != nil {
+		return false
+	}
+	return proc.Signal(syscall.Signal(0)) == nil
+}

internal/proxystate/state_test.go

@@ -0,0 +1,56 @@
+package proxystate_test
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/safedep/pmg/internal/proxystate"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestWriteAndRead(t *testing.T) {
+	dir := t.TempDir()
+	path := proxystate.StatePath(dir)
+
+	s := proxystate.State{PID: 12345, Addr: "127.0.0.1:9999", CACertPath: "/tmp/ca.pem"}
+	require.NoError(t, proxystate.Write(path, s))
+
+	got, err := proxystate.Read(path)
+	require.NoError(t, err)
+	assert.Equal(t, s.PID, got.PID)
+	assert.Equal(t, s.Addr, got.Addr)
+	assert.Equal(t, s.CACertPath, got.CACertPath)
+}
+
+func TestReadMissingFile(t *testing.T) {
+	_, err := proxystate.Read(filepath.Join(t.TempDir(), "nonexistent.json"))
+	assert.Error(t, err)
+}
+
+func TestRemove(t *testing.T) {
+	dir := t.TempDir()
+	path := proxystate.StatePath(dir)
+
+	require.NoError(t, proxystate.Write(path, proxystate.State{PID: 1, Addr: "127.0.0.1:1"}))
+	require.NoError(t, proxystate.Remove(path))
+
+	_, err := os.Stat(path)
+	assert.True(t, os.IsNotExist(err))
+}
+
+func TestIsRunningCurrentProcess(t *testing.T) {
+	s := proxystate.State{PID: os.Getpid(), Addr: "127.0.0.1:1"}
+	assert.True(t, s.IsRunning())
+}
+
+func TestIsRunningDeadPID(t *testing.T) {
+	s := proxystate.State{PID: 999999999}
+	assert.False(t, s.IsRunning())
+}
+
+func TestStatePath(t *testing.T) {
+	path := proxystate.StatePath("/some/config/dir")
+	assert.Equal(t, "/some/config/dir/proxy-state.json", path)
+}