Add support for TestRail timespan type

Support TestRail's string-based timestamp types:
- Allow converting values such as "1w 2d" to and from native time.Duration values
- Add a unit test for marshaling and unmarshaling

timespan.go

@@ -0,0 +1,88 @@
+package testrail
+
+import (
+	"encoding/json"
+	"fmt"
+	"strconv"
+	"strings"
+	"time"
+)
+
+// Timespan field type.
+// e.g. "1m" or "2m 30s" -- similar to time.Duration
+//
+// For a description, see:
+// http://docs.gurock.com/testrail-api2/reference-results
+
+type timespan struct {
+	time.Duration
+}
+
+// Unmarshal TestRail timespan into a time.Duration.
+// Transform TestRail-specific formats into something time.ParseDuration understands:
+//   "4h 5m 6s" => "4h5m6s"
+//   "1d" => "8h"
+//   "1w" => "40h"
+//   "1d 2h" => "8h2h"
+//   "1w 2d 3h" => "40h16h3h"
+func (tsp *timespan) UnmarshalJSON(data []byte) error {
+	const (
+		// These are hardcoded in TestRail.
+		// https://discuss.gurock.com/t/estimate-fields/900
+		daysPerWeek = 5
+		hoursPerDay = 8
+	)
+	var (
+		err  error
+		span string
+	)
+
+	if err = json.Unmarshal(data, &span); err != nil {
+		return err
+	}
+
+	if span == "" {
+		return nil
+	}
+
+	var parts []string
+	for _, p := range strings.Fields(span) {
+		if len(p) < 2 {
+			return fmt.Errorf("%q: sequence is too short", p)
+		}
+		amount, err := strconv.Atoi(p[:len(p)-1])
+		if err != nil {
+			return fmt.Errorf("%q: cannot convert to int: %v", amount, err)
+		}
+		unit := p[len(p)-1]
+		switch unit {
+		case 'd':
+			unit = 'h'
+			amount *= hoursPerDay
+		case 'w':
+			unit = 'h'
+			amount *= daysPerWeek * hoursPerDay
+		}
+		parts = append(parts, fmt.Sprintf("%v%c", amount, unit))
+	}
+
+	tsp.Duration, err = time.ParseDuration(strings.Join(parts, ""))
+	if err != nil {
+		return fmt.Errorf("%q: %v", span, err)
+	}
+	return nil
+}
+
+func (tsp timespan) MarshalJSON() ([]byte, error) {
+	d := tsp.Duration
+
+	if d == 0 {
+		return []byte(`null`), nil
+	}
+
+	h, d := d/time.Hour, d%time.Hour
+	m, d := d/time.Minute, d%time.Minute
+	s := d / time.Second
+
+	return []byte(fmt.Sprintf(`"%dh %dm %ds"`, h, m, s)), nil
+}

timespan_test.go

@@ -0,0 +1,75 @@
+package testrail
+
+import (
+	"encoding/json"
+	"fmt"
+	"testing"
+	"time"
+)
+
+func TestTimespanUnmarshal(t *testing.T) {
+	var testData = []struct{ json, stringDuration string }{
+		{`null`, "0s"},
+		{`"15s"`, "15s"},
+		{`"12m"`, "12m"},
+		{`"11h"`, "11h"},
+		{`"4h 5m 6s"`, "4h5m6s"},
+		{`"1d"`, "8h"},
+		{`"1w"`, "40h"},
+		{`"1d 2h"`, "8h2h"},
+		{`"1w 2d 3h"`, "40h16h3h"},
+	}
+
+	for _, data := range testData {
+		var results []Result
+		js := []byte(fmt.Sprintf(`[{"elapsed":%v}]`, data.json))
+		if err := json.Unmarshal(js, &results); err != nil {
+			t.Fatal(err)
+		}
+
+		r := results[0]
+		expected, err := time.ParseDuration(data.stringDuration)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		if r.Elapsed.Duration != expected {
+			t.Fatalf("Wrong duration: %v", r.Elapsed.Duration)
+		}
+	}
+}
+
+func TestTimespanMarshal(t *testing.T) {
+	var testData = []struct{ json, stringDuration string }{
+		{`null`, "0s"},
+		{`"0h 0m 15s"`, "15s"},
+		{`"0h 12m 0s"`, "12m"},
+		{`"11h 0m 0s"`, "11h"},
+		{`"4h 5m 6s"`, "4h5m6s"},
+		{`"8h 0m 0s"`, "8h"},
+		{`"40h 0m 0s"`, "40h"},
+		{`"10h 0m 0s"`, "8h2h"},
+		{`"59h 0m 0s"`, "40h16h3h"},
+	}
+
+	for _, td := range testData {
+		duration, err := time.ParseDuration(td.stringDuration)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		result := Result{
+			Elapsed: timespan{
+				Duration: duration,
+			},
+		}
+		data, err := json.Marshal(result.Elapsed)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		if string(data) != td.json {
+			t.Fatalf("Wrong data: %v", string(data))
+		}
+	}
+}