settings: Save future changes in a dedicated file

settings/diff.go

@@ -0,0 +1,117 @@
+package settings
+
+import (
+	"encoding/json"
+	"fmt"
+	"log"
+	"os"
+	"path"
+	"reflect"
+	"strconv"
+	"strings"
+	"time"
+)
+
+// DiffSettings returns only the fields that differs between the two objects.
+func DiffSettings(old, new *Settings) (ret map[string]interface{}) {
+	ret = map[string]interface{}{}
+	for _, field := range reflect.VisibleFields(reflect.TypeOf(*old)) {
+		if !reflect.DeepEqual(reflect.ValueOf(*old).FieldByName(field.Name).Interface(), reflect.ValueOf(*new).FieldByName(field.Name).Interface()) {
+			name := field.Name
+
+			if tag, ok := field.Tag.Lookup("json"); ok {
+				name = strings.Split(tag, ",")[0]
+			}
+
+			ret[name] = reflect.ValueOf(*new).FieldByName(field.Name).Interface()
+		}
+	}
+
+	return
+}
+
+type NextSettingsFile struct {
+	Id     int64                  `json:"id"`
+	Date   time.Time              `json:"date"`
+	Values map[string]interface{} `json:"values"`
+}
+
+func ReadNextSettingsFile(filename string, ts int64) (*NextSettingsFile, error) {
+	fd, err := os.Open(filename)
+	if err != nil {
+		return nil, fmt.Errorf("unable to open(%s): %w", filename, err)
+	} else {
+		defer fd.Close()
+
+		var s map[string]interface{}
+
+		jdec := json.NewDecoder(fd)
+
+		if err := jdec.Decode(&s); err != nil {
+			return nil, fmt.Errorf("an error occurs during JSON decoding of %s: %w", filename, err)
+		}
+
+		return &NextSettingsFile{
+			Id:     ts,
+			Date:   time.Unix(ts, 0),
+			Values: s,
+		}, nil
+	}
+}
+
+func ListNextSettingsFiles() ([]*NextSettingsFile, error) {
+	files, err := os.ReadDir(SettingsDir)
+	if err != nil {
+		return nil, err
+	}
+
+	var ret []*NextSettingsFile
+	for _, file := range files {
+		ts, err := strconv.ParseInt(file.Name()[:10], 10, 64)
+		if err == nil {
+			nsf, err := ReadNextSettingsFile(path.Join(SettingsDir, file.Name()), ts)
+			if err != nil {
+				return nil, err
+			}
+
+			ret = append(ret, nsf)
+		}
+	}
+
+	return ret, nil
+}
+
+func MergeNextSettingsUntil(until *time.Time) (map[string]interface{}, error) {
+	nsfs, err := ListNextSettingsFiles()
+	if err != nil {
+		return nil, err
+	}
+
+	ret := map[string]interface{}{}
+	for _, nsf := range nsfs {
+		if until == nil || time.Unix(nsf.Id, 0).Before(*until) {
+			for k, v := range nsf.Values {
+				ret[k] = v
+			}
+		}
+	}
+
+	return ret, nil
+}
+
+func MergeSettings(current Settings, new map[string]interface{}) *Settings {
+	for _, field := range reflect.VisibleFields(reflect.TypeOf(current)) {
+		name := field.Name
+
+		if tag, ok := field.Tag.Lookup("json"); ok {
+			name = strings.Split(tag, ",")[0]
+		}
+
+		if v, ok := new[name]; ok {
+			log.Println(name, field.Name, v)
+			reflect.ValueOf(&current).Elem().FieldByName(field.Name).Set(reflect.ValueOf(v))
+		}
+	}
+
+	return &current
+}

settings/settings.go

@@ -103,7 +103,7 @@ func ReadSettings(path string) (*Settings, error) {
 }
 
 // SaveSettings saves settings at the given location.
-func SaveSettings(path string, s *Settings) error {
+func SaveSettings(path string, s interface{}) error {
 	if fd, err := os.Create(path); err != nil {
 		return err
 	} else {