types: add simple duration type for parsing [0-9]+[wd]

pkg/types/duration.go

@@ -0,0 +1,47 @@
+package types
+
+import (
+	"regexp"
+	"strconv"
+	"time"
+
+	"github.com/pkg/errors"
+)
+
+var simpleDurationRegExp = regexp.MustCompile("^(\\d+)[hdw]$")
+
+var ErrNotSimpleDuration = errors.New("the given input is not simple duration format")
+
+type SimpleDuration struct {
+	Num      int64
+	Unit     string
+	Duration Duration
+}
+
+func ParseSimpleDuration(s string) (*SimpleDuration, error) {
+	if !simpleDurationRegExp.MatchString(s) {
+		return nil, errors.Wrapf(ErrNotSimpleDuration, "input %q is not a simple duration", s)
+	}
+
+	matches := simpleDurationRegExp.FindStringSubmatch(s)
+	numStr := matches[1]
+	unit := matches[2]
+	num, err := strconv.ParseInt(numStr, 10, 64)
+	if err != nil {
+		return nil, err
+	}
+
+	switch unit {
+	case "d":
+		d := Duration(time.Duration(num) * 24 * time.Hour)
+		return &SimpleDuration{num, unit, d}, nil
+	case "w":
+		d := Duration(time.Duration(num) * 7 * 24 * time.Hour)
+		return &SimpleDuration{num, unit, d}, nil
+	case "h":
+		d := Duration(time.Duration(num) * time.Hour)
+		return &SimpleDuration{num, unit, d}, nil
+	}
+
+	return nil, errors.Wrapf(ErrNotSimpleDuration, "input %q is not a simple duration", s)
+}

pkg/types/market.go

@@ -26,6 +26,12 @@ func (d *Duration) UnmarshalJSON(data []byte) error {
 
 	switch t := o.(type) {
 	case string:
+		sd, err := ParseSimpleDuration(t)
+		if err == nil {
+			*d = sd.Duration
+			return nil
+		}
+
 		dd, err := time.ParseDuration(t)
 		if err != nil {
 			return err