#!/usr/bin/env nomsu -V3.8.7.6
#
    A simple UUID function based on RFC 4122: http://www.ietf.org/rfc/rfc4122.txt

use "core/metaprogramming.nom"
use "core/math.nom"
use "core/collections.nom"
use "core/control_flow.nom"

%NaN_surrogate = {}
%nil_surrogate = {}
%obj_by_id = {}
set %obj_by_id's metatable to {__mode:"v"}
%id_by_obj = {}
set %id_by_obj 's metatable to {..}
    __mode:"k"
    __index: (..)
        [%self, %key] ->:
            if (%key == (nil)):
                return %self.%nil_surrogate
            if (%key != %key):
                return %self.%NaN_surrogate
            --- %retry ---
            %id = (uuid)
            if (%obj_by_id.%id != (nil)): go to %retry
            %self.%key = %id
            %obj_by_id.%id = %key
            return %id

action [uuid]:
    # Set all the other bits to randomly (or pseudo-randomly) chosen values.
    %bytes = [..]
        # time-low, time-mid, time-high-and-version
        randint (2 ^ (4 * 8)), randint (2 ^ (2 * 8)), randint (2 ^ (2 * 8 - 4))
        # clock-seq-and-reserved, clock-seq-low
        randint (2 ^ (1 * 8 - 2)), randint (2 ^ (1 * 8)), randint (2 ^ (3 * 8))
        # node
        randint (2 ^ (3 * 8))
    
    # Set the four most significant bits (bits 12 through 15) of the
    # time_hi_and_version field to the 4-bit version number from
    # Section 4.1.3.
    %bytes.3 += 0x4000
    
    # Set the two most significant bits (bits 6 and 7) of the
    # clock_seq_hi_and_reserved to zero and one, respectively.
    %bytes.4 += 0xC0
    return (=lua "('%08x-%04x-%04x-%02x%02x-%6x%6x'):format(unpack(\%bytes))")

# For strict identity checking, use (%x's id) == (%y's id)
test:
    assume (([] == []) and ((id of []) != (id of [])))
    seed random with 0
    %x = []
    assume ((id of %x) == (id of %x))
    seed random with 0
    assume ((id of %x) != (id of []))
    seed random
action [id of %, %'s id, %' id] %id_by_obj.%