// Copyright (c) 2015-2022 MinIO, Inc.
//
// This file is part of MinIO Object Storage stack
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

// Package amztime implements AWS specific time parsing and deviations
package amztime

import (
	"errors"
	"net/http"
	"time"
)

// Supported amz date formats.
var amzDateFormats = []string{
	// Do not change this order, x-amz-date format is usually in
	// iso8601Format rest are meant for relaxed handling of other
	// odd SDKs that might be out there.
	"20060102T150405Z",
	time.RFC1123,
	time.RFC1123Z,
	// Add new AMZ date formats here.
}

// ErrMalformedDate always returned for dates that cannot be parsed.
var ErrMalformedDate = errors.New("malformed date")

// Parse parses date string via supported amz date formats.
func Parse(amzDateStr string) (time.Time, error) {
	for _, dateFormat := range amzDateFormats {
		amzDate, err := time.Parse(dateFormat, amzDateStr)
		if err == nil {
			return amzDate, nil
		}
	}
	return time.Time{}, ErrMalformedDate
}

var httpTimeFormats = []string{
	// Do not chagne this order, http time format dates
	// are usually in http.TimeFormat however there are
	// situations where for example aws-sdk-java doesn't
	// send the correct format.
	http.TimeFormat,
	"Mon, 2 Jan 2006 15:04:05 GMT",
}

// ParseHeader parses http.TimeFormat with an acceptable
// extension for http.TimeFormat - return time might be zero
// if the timeStr is invalid.
func ParseHeader(timeStr string) (time.Time, error) {
	for _, dateFormat := range httpTimeFormats {
		t, err := time.Parse(dateFormat, timeStr)
		if err == nil {
			return t, nil
		}
	}
	return time.Time{}, ErrMalformedDate
}
