Add support for human friendly duration formatting

duration.go

@@ -0,0 +1,62 @@
+package humanize
+
+import (
+	"strconv"
+	"strings"
+	"time"
+)
+
+type format struct {
+	key  string
+	unit time.Duration
+	name string
+}
+
+// Duration produces a formated duration as a string
+// it supports the following format flags:
+// %y - year
+// %m - month
+// %w - week
+// %H - hour
+// %M - minute
+// %S - second
+func Duration(format string, d time.Duration) string {
+	if format == "" {
+		format = "%y %m %w %d %H %M %S"
+	}
+	if d < 0 {
+		format = "-" + format
+		d *= -1
+	}
+	process := func(f string, unit time.Duration, name string) {
+		if strings.Contains(format, f) {
+			segment := int(d / unit)
+			format = strings.Replace(format, f, pluralize(segment, name), -1)
+			d %= unit
+		}
+	}
+
+	process("%y", 365*Day, "year")
+	process("%m", Month, "month")
+	process("%w", Week, "week")
+	process("%d", Day, "day")
+	process("%H", time.Hour, "hour")
+	process("%M", time.Minute, "minute")
+	process("%S", time.Second, "second")
+
+	// cleanup spaces
+	format = strings.Trim(format, " ")
+	return strings.Replace(format, "  ", " ", -1)
+}
+
+func pluralize(i int, s string) string {
+	if i == 0 {
+		return ""
+	}
+	s = strconv.Itoa(i) + " " + s
+
+	if i > 1 {
+		s += "s"
+	}
+	return s
+}

duration_test.go

@@ -0,0 +1,62 @@
+package humanize
+
+import (
+	"testing"
+	"time"
+)
+
+func TestDuration(t *testing.T) {
+	type test struct {
+		format   string
+		d        time.Duration
+		expected string
+	}
+	cases := map[string]test{
+		"default": {
+			format:   "%y %m %w %d %H %M %S",
+			d:        400*Day + 12*time.Hour + 17*time.Second,
+			expected: "1 year 1 month 5 days 12 hours 17 seconds",
+		},
+		"negative": {
+			format:   "%y %m %w %d %H %M %S",
+			d:        -(400*Day + 12*time.Hour + 17*time.Second),
+			expected: "-1 year 1 month 5 days 12 hours 17 seconds",
+		},
+		"years": {
+			format:   "%y",
+			d:        800 * Day,
+			expected: "2 years",
+		},
+		"zero": {
+			format:   "%y",
+			d:        0,
+			expected: "",
+		},
+		"neg years": {
+			format:   "%y",
+			d:        -800 * Day,
+			expected: "-2 years",
+		},
+		"year + week": {
+			format:   "%y %w",
+			d:        364 * Day,
+			expected: "52 weeks",
+		},
+		"month + hours": {
+			format:   "%w %H",
+			d:        15 * Day,
+			expected: "2 weeks 24 hours",
+		},
+		"seconds only": {
+			format:   "%S",
+			d:        Day,
+			expected: "86400 seconds",
+		},
+	}
+	for name, v := range cases {
+		result := Duration(v.format, v.d)
+		if result != v.expected {
+			t.Errorf("FAIL:%s\n\tExpected:%s\n\tActual:%s", name, v.expected, result)
+		}
+	}
+}