recur

item/recur.go

@@ -0,0 +1,65 @@
+package item
+
+import "time"
+
+type RecurPeriod string
+
+const (
+	PeriodDay   RecurPeriod = "day"
+	PeriodMonth RecurPeriod = "month"
+)
+
+type Recur struct {
+	Start  time.Time
+	Period RecurPeriod
+	Count  int
+}
+
+func (r *Recur) On(date time.Time) bool {
+	switch r.Period {
+	case PeriodDay:
+		return r.onDays(date)
+	case PeriodMonth:
+		return r.onMonths(date)
+	default:
+		return false
+	}
+}
+
+func (r *Recur) onDays(date time.Time) bool {
+	if r.Start.After(date) {
+		return false
+	}
+
+	testDate := r.Start
+	for {
+		if testDate.Equal(date) {
+			return true
+		}
+		if testDate.After(date) {
+			return false
+		}
+
+		dur := time.Duration(r.Count) * 24 * time.Hour
+		testDate = testDate.Add(dur)
+	}
+}
+
+func (r *Recur) onMonths(date time.Time) bool {
+	if r.Start.After(date) {
+		return false
+	}
+
+	tDate := r.Start
+	for {
+		if tDate.Equal(date) {
+			return true
+		}
+		if tDate.After(date) {
+			return false
+		}
+
+		y, m, d := tDate.Date()
+		tDate = time.Date(y, m+time.Month(r.Count), d, 0, 0, 0, 0, time.UTC)
+	}
+}

item/recur_test.go

@@ -0,0 +1,105 @@
+package item_test
+
+import (
+	"testing"
+	"time"
+
+	"go-mod.ewintr.nl/planner/item"
+)
+
+func TestRecur(t *testing.T) {
+	t.Parallel()
+
+	t.Run("days", func(t *testing.T) {
+		r := item.Recur{
+			Start:  time.Date(2024, 12, 1, 0, 0, 0, 0, time.UTC),
+			Period: item.PeriodDay,
+			Count:  5,
+		}
+		day := 24 * time.Hour
+
+		for _, tc := range []struct {
+			name string
+			date time.Time
+			exp  bool
+		}{
+			{
+				name: "before",
+				date: time.Date(202, 1, 1, 0, 0, 0, 0, time.UTC),
+			},
+			{
+				name: "start",
+				date: r.Start,
+				exp:  true,
+			},
+			{
+				name: "after true",
+				date: r.Start.Add(15 * day),
+				exp:  true,
+			},
+			{
+				name: "after false",
+				date: r.Start.Add(16 * day),
+			},
+		} {
+			t.Run(tc.name, func(t *testing.T) {
+				if act := r.On(tc.date); tc.exp != act {
+					t.Errorf("exp %v, got %v", tc.exp, act)
+				}
+			})
+		}
+	})
+
+	t.Run("months", func(t *testing.T) {
+		r := item.Recur{
+			Start:  time.Date(2021, 2, 3, 0, 0, 0, 0, time.UTC),
+			Period: item.PeriodMonth,
+			Count:  3,
+		}
+
+		for _, tc := range []struct {
+			name string
+			date time.Time
+			exp  bool
+		}{
+			{
+				name: "before start",
+				date: time.Date(2021, 1, 27, 0, 0, 0, 0, time.UTC),
+			},
+			{
+				name: "on start",
+				date: time.Date(2021, 2, 3, 0, 0, 0, 0, time.UTC),
+				exp:  true,
+			},
+			{
+				name: "8 weeks after",
+				date: time.Date(2021, 3, 31, 0, 0, 0, 0, time.UTC),
+			},
+			{
+				name: "one month",
+				date: time.Date(2021, 3, 3, 0, 0, 0, 0, time.UTC),
+			},
+			{
+				name: "3 months",
+				date: time.Date(2021, 5, 3, 0, 0, 0, 0, time.UTC),
+				exp:  true,
+			},
+			{
+				name: "4 months",
+				date: time.Date(2021, 6, 3, 0, 0, 0, 0, time.UTC),
+			},
+			{
+				name: "6 months",
+				date: time.Date(2021, 8, 3, 0, 0, 0, 0, time.UTC),
+				exp:  true,
+			},
+		} {
+			t.Run(tc.name, func(t *testing.T) {
+				if act := r.On(tc.date); tc.exp != act {
+					t.Errorf("exp %v, got %v", tc.exp, act)
+				}
+			})
+		}
+	})
+
+}