# This file is a part of Julia. License is MIT: https://julialang.org/license

module UUIDs

using Random

export UUID, uuid1, uuid4, uuid_version

import Base: UUID

"""

uuid_version(u::UUID) -> Int

Inspects the given UUID and returns its version

(see [RFC 4122](https://www.ietf.org/rfc/rfc4122)).

# Examples

```jldoctest

julia> uuid_version(uuid4())

4

```

"""

uuid_version(u::UUID) = Int((u.value >> 76) & 0xf)

"""

uuid1([rng::AbstractRNG=GLOBAL_RNG]) -> UUID

Generates a version 1 (time-based) universally unique identifier (UUID), as specified

by RFC 4122. Note that the Node ID is randomly generated (does not identify the host)

according to section 4.5 of the RFC.

# Examples

```jldoctest; filter = r"[a-z0-9]{8}-([a-z0-9]{4}-){3}[a-z0-9]{12}"

julia> rng = MersenneTwister(1234);

julia> uuid1(rng)

UUID("cfc395e8-590f-11e8-1f13-43a2532b2fa8")

```

"""

function uuid1(rng::AbstractRNG=Random.GLOBAL_RNG)

u = rand(rng, UInt128)

# mask off clock sequence and node

u &= 0x00000000000000003fffffffffffffff

# set the unicast/multicast bit and version

u |= 0x00000000000010000000010000000000

# 0x01b21dd213814000 is the number of 100 nanosecond intervals

# between the UUID epoch and Unix epoch

timestamp = round(UInt64, time() * 1e7) + 0x01b21dd213814000

ts_low = timestamp & typemax(UInt32)

ts_mid = (timestamp >> 32) & typemax(UInt16)

ts_hi = (timestamp >> 48) & 0x0fff

u |= UInt128(ts_low) << 96

u |= UInt128(ts_mid) << 80

u |= UInt128(ts_hi) << 64

UUID(u)

end

"""

uuid4([rng::AbstractRNG=GLOBAL_RNG]) -> UUID

Generates a version 4 (random or pseudo-random) universally unique identifier (UUID),

as specified by RFC 4122.

# Examples

```jldoctest

julia> rng = MersenneTwister(1234);

julia> uuid4(rng)

UUID("196f2941-2d58-45ba-9f13-43a2532b2fa8")

```

"""

function uuid4(rng::AbstractRNG=Random.GLOBAL_RNG)

u = rand(rng, UInt128)

u &= 0xffffffffffff0fff3fffffffffffffff

u |= 0x00000000000040008000000000000000

UUID(u)

end

end