fix:#65 added new UID generation for ical File

backend/service/functions/string.go

@@ -1,6 +1,10 @@
 package functions
 
-import "strings"
+import (
+	"crypto/sha256"
+	"encoding/hex"
+	"strings"
+)
 
 // check if string is empty or contains only whitespaces
 func OnlyWhitespace(word string) bool {
@@ -25,3 +29,10 @@ func ReplaceEmptyString(word string, replacement string) string {
 	}
 	return word
 }
+
+func HashString(s string) string {
+	hash := sha256.New()
+	hash.Write([]byte(s))
+	hashInBytes := hash.Sum(nil)
+	return hex.EncodeToString(hashInBytes)
+}

backend/service/functions/string_test.go

@@ -31,3 +31,24 @@ func TestOnlyWhitespace(t *testing.T) {
 		})
 	}
 }
+
+func TestHashString(t *testing.T) {
+	type args struct {
+		s string
+	}
+	tests := []struct {
+		name string
+		args args
+		want string
+	}{
+		{"empty string", args{""}, "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"},
+		{"non-empty string", args{"abc"}, "ba7816bf8f01cfea414140de5dae2223b00361a396177a9cb410ff61f20015ad"},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := HashString(tt.args.s); got != tt.want {
+				t.Errorf("HashString() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}

backend/service/ical/icalFileGeneration.go

@@ -4,7 +4,6 @@ import (
 	"htwkalender/model"
 	"htwkalender/service/functions"
 	"htwkalender/service/names"
-	"strconv"
 	"time"
 
 	"github.com/jordic/goics"
@@ -32,16 +31,18 @@ func (icalModel IcalModel) EmitICal() goics.Componenter {
 	//add v time zone
 	icalModel.vtimezone(c)
 
-	var timeStamp = time.Now().Local().In(europeTime).Format("20060102T150405")
+	for _, event := range icalModel.Events {
-
-	for i, event := range icalModel.Events {
 		mapEntry, mappingFound := icalModel.Mapping[event.UUID]
 
 		s := goics.NewComponent()
 		s.SetType("VEVENT")
 
 		s.AddProperty(goics.FormatDateTime("DTSTAMP", time.Now().Local().In(europeTime)))
-		s.AddProperty("UID", strconv.FormatInt(int64(i), 16)+"-"+timeStamp+"@htwkalender.de")
+
+		// create a unique id for the event by hashing the event start, end, course and name
+		var eventHash = functions.HashString(event.Start.String() + event.End.String() + event.Course + event.Name)
+
+		s.AddProperty("UID", eventHash+"@htwkalender.de")
 		s.AddProperty(goics.FormatDateTime("DTEND", event.End.Time().Local().In(europeTime)))
 		s.AddProperty(goics.FormatDateTime("DTSTART", event.Start.Time().Local().In(europeTime)))