time_vendor.go

// Copyright 2023 Hardfin, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package date

import (
	"time"
)

// daysBefore is vendored in from the standard library:
// https://github.com/golang/go/blob/go1.22.1/src/time/time.go#L1060-L1077
var daysBefore = [...]int32{
	0,
	31,
	31 + 28,
	31 + 28 + 31,
	31 + 28 + 31 + 30,
	31 + 28 + 31 + 30 + 31,
	31 + 28 + 31 + 30 + 31 + 30,
	31 + 28 + 31 + 30 + 31 + 30 + 31,
	31 + 28 + 31 + 30 + 31 + 30 + 31 + 31,
	31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30,
	31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30 + 31,
	31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30 + 31 + 30,
	31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30 + 31 + 30 + 31,
}

// daysIn is vendored in from the standard library:
// https://github.com/golang/go/blob/go1.22.1/src/time/time.go#L1079-L1084
func daysIn(m time.Month, year int) int {
	if m == time.February && isLeap(year) {
		return 29
	}
	return int(daysBefore[m] - daysBefore[m-1])
}

// isLeap is vendored in from the standard library:
// https://github.com/golang/go/blob/go1.22.1/src/time/time.go#L1448-L1450
func isLeap(year int) bool {
	return year%4 == 0 && (year%100 != 0 || year%400 == 0)
}