search: handle date ranges in search/filter query

Handle date ranges in the filter and search commands for searching and
filtering based on the Date: header. Implement a flag (-d) that accepts
a date range <start[..end]> where the start date is included in the
range but the end date is not, i.e. [start,end).

The start or end date can be omitted: "start", "start..", "..end", or
"start..end" are all valid inputs.

An example filter query would look like this: :filter -d 2022-11-09..

The dates should be in the YYYY-MM-DD format.

Signed-off-by: Koni Marti <koni.marti@gmail.com>
Acked-by: Robin Jarry <robin@jarry.cc>

1 files changed, 63 insertions, 0 deletions

diff --git a/worker/lib/daterange.go b/worker/lib/daterange.go
new file mode 100644
index 00000000..c996392c
--- /dev/null
+++ b/worker/lib/daterange.go
@@ -0,0 +1,63 @@
+package lib
+
+import (
+	"fmt"
+	"strings"
+	"time"
+)
+
+const dateFmt = "2006-01-02"
+
+// ParseDateRange parses a date range into a start and end date. Dates are
+// expected to be in the YYYY-MM-DD format.
+//
+// Start and end dates are connected by the range operator ".." where end date
+// is not included in the date range.
+//
+// ParseDateRange can also parse open-ended ranges, i.e. start.. or ..end are
+// allowed.
+func ParseDateRange(s string) (start, end time.Time, err error) {
+	s = strings.ReplaceAll(s, " ", "")
+	i := strings.Index(s, "..")
+	switch {
+	case i < 0:
+		// single date
+		start, err = time.Parse(dateFmt, s)
+		if err != nil {
+			err = fmt.Errorf("failed to parse date: %w", err)
+			return
+		}
+		end = start.AddDate(0, 0, 1)
+
+	case i == 0:
+		// end date only
+		if len(s) < 2 {
+			err = fmt.Errorf("no date found")
+			return
+		}
+		end, err = time.Parse(dateFmt, s[2:])
+		if err != nil {
+			err = fmt.Errorf("failed to parse date: %w", err)
+			return
+		}
+
+	case i > 0:
+		// start date first
+		start, err = time.Parse(dateFmt, s[:i])
+		if err != nil {
+			err = fmt.Errorf("failed to parse date: %w", err)
+			return
+		}
+		if len(s[i:]) <= 2 {
+			return
+		}
+		// and end dates if available
+		end, err = time.Parse(dateFmt, s[(i+2):])
+		if err != nil {
+			err = fmt.Errorf("failed to parse date: %w", err)
+			return
+		}
+	}
+
+	return
+}