/*
Copyright 2020 The Kubernetes Authors.

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

    http://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.
*/

/*
Copyright 2020 The Kubernetes Authors.

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

    http://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.
*/

/*
Copyright 2020 The Kubernetes Authors.

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

    http://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.
*/

// Copyright (C) 2013-2018 by Maxim Bublis <b@codemonkey.ru>
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

// Package uuid provides implementations of the Universally Unique Identifier (UUID), as specified in RFC-4122 and DCE 1.1.
//
// RFC-4122[1] provides the specification for versions 1, 3, 4, and 5.
//
// DCE 1.1[2] provides the specification for version 2.
//
// [1] https://tools.ietf.org/html/rfc4122
// [2] http://pubs.opengroup.org/onlinepubs/9696989899/chap5.htm#tagcjh_08_02_01_01
package uuid

import (
	"encoding/binary"
	"encoding/hex"
	"fmt"
	"time"
)

// Size of a UUID in bytes.
const Size = 16

// UUID is an array type to represent the value of a UUID, as defined in RFC-4122.
type UUID [Size]byte

// UUID versions.
const (
	_  byte = iota
	V1      // Version 1 (date-time and MAC address)
	V2      // Version 2 (date-time and MAC address, DCE security version)
	V3      // Version 3 (namespace name-based)
	V4      // Version 4 (random)
	V5      // Version 5 (namespace name-based)
)

// UUID layout variants.
const (
	VariantNCS byte = iota
	VariantRFC4122
	VariantMicrosoft
	VariantFuture
)

// UUID DCE domains.
const (
	DomainPerson = iota
	DomainGroup
	DomainOrg
)

// Timestamp is the count of 100-nanosecond intervals since 00:00:00.00,
// 15 October 1582 within a V1 UUID. This type has no meaning for V2-V5
// UUIDs since they don't have an embedded timestamp.
type Timestamp uint64

const _100nsPerSecond = 10000000

// Time returns the UTC time.Time representation of a Timestamp
func (t Timestamp) Time() (time.Time, error) {
	secs := uint64(t) / _100nsPerSecond
	nsecs := 100 * (uint64(t) % _100nsPerSecond)
	return time.Unix(int64(secs)-(epochStart/_100nsPerSecond), int64(nsecs)), nil
}

// TimestampFromV1 returns the Timestamp embedded within a V1 UUID.
// Returns an error if the UUID is any version other than 1.
func TimestampFromV1(u UUID) (Timestamp, error) {
	if u.Version() != 1 {
		err := fmt.Errorf("uuid: %s is version %d, not version 1", u, u.Version())
		return 0, err
	}
	low := binary.BigEndian.Uint32(u[0:4])
	mid := binary.BigEndian.Uint16(u[4:6])
	hi := binary.BigEndian.Uint16(u[6:8]) & 0xfff
	return Timestamp(uint64(low) + (uint64(mid) << 32) + (uint64(hi) << 48)), nil
}

// String parse helpers.
var (
	urnPrefix  = []byte("urn:uuid:")
	byteGroups = []int{8, 4, 4, 4, 12}
)

// Nil is the nil UUID, as specified in RFC-4122, that has all 128 bits set to
// zero.
var Nil = UUID{}

// Predefined namespace UUIDs.
var (
	NamespaceDNS  = Must(FromString("6ba7b810-9dad-11d1-80b4-00c04fd430c8"))
	NamespaceURL  = Must(FromString("6ba7b811-9dad-11d1-80b4-00c04fd430c8"))
	NamespaceOID  = Must(FromString("6ba7b812-9dad-11d1-80b4-00c04fd430c8"))
	NamespaceX500 = Must(FromString("6ba7b814-9dad-11d1-80b4-00c04fd430c8"))
)

// Version returns the algorithm version used to generate the UUID.
func (u UUID) Version() byte {
	return u[6] >> 4
}

// Variant returns the UUID layout variant.
func (u UUID) Variant() byte {
	switch {
	case (u[8] >> 7) == 0x00:
		return VariantNCS
	case (u[8] >> 6) == 0x02:
		return VariantRFC4122
	case (u[8] >> 5) == 0x06:
		return VariantMicrosoft
	case (u[8] >> 5) == 0x07:
		fallthrough
	default:
		return VariantFuture
	}
}

// Bytes returns a byte slice representation of the UUID.
func (u UUID) Bytes() []byte {
	return u[:]
}

// String returns a canonical RFC-4122 string representation of the UUID:
// xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx.
func (u UUID) String() string {
	buf := make([]byte, 36)

	hex.Encode(buf[0:8], u[0:4])
	buf[8] = '-'
	hex.Encode(buf[9:13], u[4:6])
	buf[13] = '-'
	hex.Encode(buf[14:18], u[6:8])
	buf[18] = '-'
	hex.Encode(buf[19:23], u[8:10])
	buf[23] = '-'
	hex.Encode(buf[24:], u[10:])

	return string(buf)
}

// SetVersion sets the version bits.
func (u *UUID) SetVersion(v byte) {
	u[6] = (u[6] & 0x0f) | (v << 4)
}

// SetVariant sets the variant bits.
func (u *UUID) SetVariant(v byte) {
	switch v {
	case VariantNCS:
		u[8] = (u[8]&(0xff>>1) | (0x00 << 7))
	case VariantRFC4122:
		u[8] = (u[8]&(0xff>>2) | (0x02 << 6))
	case VariantMicrosoft:
		u[8] = (u[8]&(0xff>>3) | (0x06 << 5))
	case VariantFuture:
		fallthrough
	default:
		u[8] = (u[8]&(0xff>>3) | (0x07 << 5))
	}
}

// Must is a helper that wraps a call to a function returning (UUID, error)
// and panics if the error is non-nil. It is intended for use in variable
// initializations such as
//  var packageUUID = uuid.Must(uuid.FromString("123e4567-e89b-12d3-a456-426655440000"))
func Must(u UUID, err error) UUID {
	if err != nil {
		panic(err)
	}
	return u
}
