add api for getting total income/expense amounts by month

pkg/utils/datetimes.go

@@ -5,6 +5,8 @@ import "time"
 const (
 	longDateTimeFormat              = "2006-01-02 15:04:05"
 	longDateTimeWithoutSecondFormat = "2006-01-02 15:04"
+	shortDateTimeFormat             = "2006-1-2 15:4:5"
+	yearMonthDateTimeFormat         = "2006-01"
 )
 
 // FormatUnixTimeToLongDateTimeInServerTimezone returns a textual representation of the unix time formatted by long date time format
@@ -23,6 +25,17 @@ func FormatUnixTimeToLongDateTimeWithoutSecond(unixTime int64, timezone *time.Lo
 	return t.Format(longDateTimeWithoutSecondFormat)
 }
 
+// FormatUnixTimeToYearMonth returns year and month of specified unix time
+func FormatUnixTimeToYearMonth(unixTime int64, timezone *time.Location) string {
+	t := ParseFromUnixTime(unixTime)
+
+	if timezone != nil {
+		t = t.In(timezone)
+	}
+
+	return t.Format(yearMonthDateTimeFormat)
+}
+
 // ParseFromUnixTime parses a unix time and returns a golang time struct
 func ParseFromUnixTime(unixTime int64) time.Time {
 	return time.Unix(unixTime, 0)
@@ -34,6 +47,12 @@ func ParseFromLongDateTime(t string, utcOffset int16) (time.Time, error) {
 	return time.ParseInLocation(longDateTimeFormat, t, timezone)
 }
 
+// ParseFromShortDateTime parses a formatted string in short date time format
+func ParseFromShortDateTime(t string, utcOffset int16) (time.Time, error) {
+	timezone := time.FixedZone("Timezone", int(utcOffset)*60)
+	return time.ParseInLocation(shortDateTimeFormat, t, timezone)
+}
+
 // GetMinTransactionTimeFromUnixTime returns the minimum transaction time from unix time
 func GetMinTransactionTimeFromUnixTime(unixTime int64) int64 {
 	return unixTime * 1000