platform: modularize api/gui, add docs-tests-web foundation, and refresh root config

selective-vpn-api/app/transportcfg/history_helpers.go

@@ -0,0 +1,86 @@
+package transportcfg
+
+import (
+	"encoding/base64"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+func WriteFileAtomic(path string, data []byte, perm os.FileMode) error {
+	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
+		return err
+	}
+	tmp := path + ".tmp"
+	if err := os.WriteFile(tmp, data, perm); err != nil {
+		return err
+	}
+	return os.Rename(tmp, path)
+}
+
+func ReadJSONFiles(rootDir string) ([][]byte, error) {
+	entries, err := os.ReadDir(rootDir)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return [][]byte{}, nil
+		}
+		return nil, err
+	}
+	out := make([][]byte, 0, len(entries))
+	for _, ent := range entries {
+		if ent.IsDir() {
+			continue
+		}
+		name := strings.ToLower(strings.TrimSpace(ent.Name()))
+		if !strings.HasSuffix(name, ".json") {
+			continue
+		}
+		path := filepath.Join(rootDir, ent.Name())
+		data, err := os.ReadFile(path)
+		if err != nil {
+			continue
+		}
+		out = append(out, data)
+	}
+	return out, nil
+}
+
+func SelectRecordCandidate[T any](
+	records []T,
+	historyID string,
+	recordID func(T) string,
+	eligible func(T) bool,
+) (T, bool) {
+	id := strings.TrimSpace(historyID)
+	if id != "" {
+		for _, rec := range records {
+			if strings.TrimSpace(recordID(rec)) == id {
+				return rec, eligible(rec)
+			}
+		}
+		var zero T
+		return zero, false
+	}
+	for _, rec := range records {
+		if eligible(rec) {
+			return rec, true
+		}
+	}
+	var zero T
+	return zero, false
+}
+
+func DecodeBase64Optional(raw string, exists bool) ([]byte, bool, error) {
+	if !exists {
+		return nil, false, nil
+	}
+	s := strings.TrimSpace(raw)
+	if s == "" {
+		return nil, true, nil
+	}
+	data, err := base64.StdEncoding.DecodeString(s)
+	if err != nil {
+		return nil, false, err
+	}
+	return data, true, nil
+}