feat: add main gronx api

gronx.go

@@ -0,0 +1,75 @@
+package gronx
+
+import (
+	"errors"
+	"regexp"
+	"strings"
+	"time"
+)
+
+var literals = strings.NewReplacer(
+	"SUN", "0", "MON", "1", "TUE", "2", "WED", "3", "THU", "4", "FRI", "5", "SAT", "6",
+	"JAN", "1", "FEB", "2", "MAR", "3", "APR", "4", "MAY", "5", "JUN", "6", "JUL", "7",
+	"AUG", "8", "SEP", "9", "OCT", "10", "NOV", "11", "DEC", "12",
+)
+
+var expressions = map[string]string{
+	"@yearly":    "0 0 1 1 *",
+	"@annually":  "0 0 1 1 *",
+	"@monthly":   "0 0 1 * *",
+	"@weekly":    "0 0 * * 0",
+	"@daily":     "0 0 * * *",
+	"@hourly":    "0 * * * *",
+	"@always":    "* * * * *",
+	"@5minutes":  "*/5 * * * *",
+	"@10minutes": "*/10 * * * *",
+	"@15minutes": "*/15 * * * *",
+	"@30minutes": "0,30 * * * *",
+}
+
+var spaceRe = regexp.MustCompile(`\s+`)
+
+func normalize(expr string) []string {
+	expr = strings.Trim(expr, " \t")
+	if e, ok := expressions[strings.ToLower(expr)]; ok {
+		expr = e
+	}
+
+	expr = spaceRe.ReplaceAllString(expr, " ")
+	expr = literals.Replace(strings.ToUpper(expr))
+
+	return strings.Split(strings.ReplaceAll(expr, "  ", " "), " ")
+}
+
+type Gronx struct {
+	C Checker
+}
+
+func New() Gronx {
+	return Gronx{&SegmentChecker{}}
+}
+
+func (g *Gronx) IsDue(expr string, ref ...time.Time) (bool, error) {
+	segs := normalize(expr)
+	if len(segs) < 5 || len(segs) > 6 {
+		return false, errors.New("expr should contain 5 to 6 segments separated by space")
+	}
+
+	if len(ref) > 0 {
+		g.C.SetRef(ref[0])
+	} else {
+		g.C.SetRef(time.Now())
+	}
+
+	for pos, seg := range segs {
+		if seg == "*" || seg == "?" {
+			continue
+		}
+
+		if due, err := g.C.CheckDue(seg, pos); !due {
+			return due, err
+		}
+	}
+
+	return true, nil
+}