1 files changed, 21 insertions, 0 deletions
diff --git a/internal/liturgy/citation.go b/internal/liturgy/citation.go
new file mode 100644
index 0000000..2c545c2
--- /dev/null
+++ b/internal/liturgy/citation.go
@@ -0,0 +1,21 @@
+package liturgy
+
+import (
+	"fmt"
+	"regexp"
+	"strings"
+)
+
+// citationRe captures a scripture reference in a trailing "(...)" of a section
+// heading, e.g. "Ewangelia (J 20, 1. 11-18)" -> "J 20, 1. 11-18".
+var citationRe = regexp.MustCompile(`\((.+)\)\s*$`)
+
+// ExtractCitation returns the scripture reference carried in a section
+// heading's trailing parentheses, or an error when the heading has none.
+func ExtractCitation(heading string) (string, error) {
+	m := citationRe.FindStringSubmatch(heading)
+	if m == nil {
+		return "", fmt.Errorf("no reference found in heading: %q", heading)
+	}
+	return strings.TrimSpace(m[1]), nil
+}