From 6cee9c0be88c5330ec14c8b9f2fc7af779b3019b Mon Sep 17 00:00:00 2001
From: gbaptista <guilhermebaptistasilva@gmail.com>
Date: Mon, 4 Mar 2019 07:43:59 -0300
Subject: [PATCH] support for the "04/27/2019" date format

---
 rules/en/en.go             |  1 +
 rules/en/slash_mdy.go      | 93 ++++++++++++++++++++++++++++++++++++++
 rules/en/slash_mdy_test.go | 44 ++++++++++++++++++
 3 files changed, 138 insertions(+)
 create mode 100644 rules/en/slash_mdy.go
 create mode 100644 rules/en/slash_mdy_test.go

diff --git a/rules/en/en.go b/rules/en/en.go
index 0b9bd9d..cd428b6 100644
--- a/rules/en/en.go
+++ b/rules/en/en.go
@@ -3,6 +3,7 @@ package en
 import "github.com/olebedev/when/rules"
 
 var All = []rules.Rule{
+	SlashMDY(rules.Override),
 	Weekday(rules.Override),
 	CasualDate(rules.Override),
 	CasualTime(rules.Override),
diff --git a/rules/en/slash_mdy.go b/rules/en/slash_mdy.go
new file mode 100644
index 0000000..1c5a42d
--- /dev/null
+++ b/rules/en/slash_mdy.go
@@ -0,0 +1,93 @@
+package en
+
+import (
+	"regexp"
+	"strconv"
+	"time"
+
+	"github.com/olebedev/when/rules"
+)
+
+/*
+
+- MM/DD/YYYY
+- 3/11/2015
+- 3/11/2015
+- 3/11
+
+also with "\", gift for windows' users
+*/
+
+var MONTHS_DAYS = []int{
+	0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31,
+}
+
+func getDays(year, month int) int {
+	// naive leap year check
+	if (year-2000)%4 == 0 && month == 2 {
+		return 29
+	}
+	return MONTHS_DAYS[month]
+}
+
+func SlashMDY(s rules.Strategy) rules.Rule {
+
+	return &rules.F{
+		RegExp: regexp.MustCompile("(?i)(?:\\W|^)" +
+			"([0-3]{0,1}[0-9]{1})" +
+			"[\\/\\\\]" +
+			"([0-3]{0,1}[0-9]{1})" +
+			"(?:[\\/\\\\]" +
+			"((?:1|2)[0-9]{3})\\s*)?" +
+			"(?:\\W|$)"),
+		Applier: func(m *rules.Match, c *rules.Context, o *rules.Options, ref time.Time) (bool, error) {
+			if (c.Day != nil || c.Month != nil || c.Year != nil) && s != rules.Override {
+				return false, nil
+			}
+
+			month, _ := strconv.Atoi(m.Captures[0])
+			day, _ := strconv.Atoi(m.Captures[1])
+			year := -1
+			if m.Captures[2] != "" {
+				year, _ = strconv.Atoi(m.Captures[2])
+			}
+
+			if day == 0 {
+				return false, nil
+			}
+		WithYear:
+			if year != -1 {
+				if getDays(year, month) >= day {
+					c.Year = &year
+					c.Month = &month
+					c.Day = &day
+				} else {
+					return false, nil
+				}
+				return true, nil
+			}
+
+			if int(ref.Month()) > month {
+				year = ref.Year() + 1
+				goto WithYear
+			}
+
+			if int(ref.Month()) == month {
+				if getDays(ref.Year(), month) >= day {
+					if day > ref.Day() {
+						year = ref.Year()
+					} else if day < ref.Day() {
+						year = ref.Year() + 1
+					} else {
+						return false, nil
+					}
+					goto WithYear
+				} else {
+					return false, nil
+				}
+			}
+
+			return true, nil
+		},
+	}
+}
diff --git a/rules/en/slash_mdy_test.go b/rules/en/slash_mdy_test.go
new file mode 100644
index 0000000..3d8e8d5
--- /dev/null
+++ b/rules/en/slash_mdy_test.go
@@ -0,0 +1,44 @@
+package en_test
+
+import (
+	"testing"
+	"time"
+
+	"github.com/olebedev/when"
+	"github.com/olebedev/when/rules"
+	"github.com/olebedev/when/rules/en"
+)
+
+// July 15 days offset from the begining of the year
+const OFFSET = 197
+
+func TestSlashMDY(t *testing.T) {
+	fixt := []Fixture{
+		{"The Deadline is 10/10/2016", 16, "10/10/2016", (284 - OFFSET) * 24 * time.Hour},
+		{"The Deadline is 2/1/2016", 16, "2/1/2016", (32 - OFFSET) * 24 * time.Hour},
+		{"The Deadline is 2/29/2016", 16, "2/29/2016", (60 - OFFSET) * 24 * time.Hour},
+
+		// next year
+		{"The Deadline is 2/28", 16, "2/28", (59 + 366 - OFFSET) * 24 * time.Hour},
+		{"The Deadline is 02/28/2017", 16, "02/28/2017", (59 + 366 - OFFSET) * 24 * time.Hour},
+
+		// right after w/o a year
+		{"The Deadline is 07/28", 16, "07/28", (210 - OFFSET) * 24 * time.Hour},
+
+		// before w/o a year
+		{"The Deadline is 06/30", 16, "06/30", (181 + 366 - OFFSET) * 24 * time.Hour},
+
+		// prev day will be added to the future
+		{"The Deadline is 07/14", 16, "07/14", (195 + 366 - OFFSET) * 24 * time.Hour},
+	}
+
+	w := when.New(nil)
+	w.Add(en.SlashMDY(rules.Override))
+
+	null = time.Date(2016, time.July, 15, 0, 0, 0, 0, time.UTC)
+
+	ApplyFixtures(t, "en.SlashMDY", w, fixt)
+
+	null = time.Date(2016, time.January, 6, 0, 0, 0, 0, time.UTC)
+
+}