init monlet repo with stage 0-2 (docs, contract, agent MVP)

agent/internal/ids/ids.go

@@ -0,0 +1,40 @@
+package ids
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"github.com/google/uuid"
+
+	"github.com/monlet/agent/internal/config"
+)
+
+// LoadOrCreateAgentID returns configured ID if non-empty, otherwise loads
+// state_dir/agent_id, generating and persisting it on first run.
+func LoadOrCreateAgentID(stateDir, configured string) (string, error) {
+	if configured != "" {
+		return configured, nil
+	}
+	if err := os.MkdirAll(stateDir, 0o755); err != nil {
+		return "", fmt.Errorf("create state dir: %w", err)
+	}
+	path := filepath.Join(stateDir, "agent_id")
+	b, err := os.ReadFile(path)
+	if err == nil {
+		id := strings.TrimSpace(string(b))
+		if err := config.ValidateID("agent_id", id); err != nil {
+			return "", fmt.Errorf("persisted agent_id invalid: %w", err)
+		}
+		return id, nil
+	}
+	if !os.IsNotExist(err) {
+		return "", err
+	}
+	id := uuid.NewString()
+	if err := os.WriteFile(path, []byte(id+"\n"), 0o600); err != nil {
+		return "", err
+	}
+	return id, nil
+}