rand: add rand.ulid() (#5979)

* removed debug println

* added newline to the end of the file

* time: add .unix_time_milli() method; rand,time: add tests

* rand: add more ulid tests; move tests to a separate file random_identifiers_test.v

* run vfmt over vlib/rand/random_identifiers_test.v

* speed up time.unix_time_milli

* simplify and speedup time.unix_time/0 and time.new_time/1

* update comment about rand.ulid()

* fix terminating 0 off by 1 issue in rand.ulid()

* optimize time.new_time()

* restore the master version of vlib/time/parse.v

* make test_unix_time more robust

Co-authored-by: Delyan Angelov <delian66@gmail.com>

vlib/rand/random_identifiers_test.v

@@ -0,0 +1,78 @@
+import time
+import rand
+
+// uuid_v4:
+fn test_rand_uuid_v4() {
+	uuid1 := rand.uuid_v4()
+	uuid2 := rand.uuid_v4()
+	uuid3 := rand.uuid_v4()
+	assert uuid1 != uuid2
+	assert uuid1 != uuid3
+	assert uuid2 != uuid3
+	assert uuid1.len == 36
+	assert uuid2.len == 36
+	assert uuid3.len == 36
+	assert uuid1[14] == `4`
+	assert uuid2[14] == `4`
+	assert uuid3[14] == `4`
+}
+
+// ulids:
+fn test_ulids_are_unique() {
+	ulid1 := rand.ulid()
+	ulid2 := rand.ulid()
+	ulid3 := rand.ulid()
+	assert ulid1.len == 26
+	assert ulid2.len == 26
+	assert ulid3.len == 26
+	assert ulid1 != ulid2
+	assert ulid1 != ulid3
+	assert ulid2 != ulid3
+}
+
+fn test_ulids_max_start_character_is_ok() {
+	ulid1 := rand.ulid()
+	// the largest valid ULID encoded in Base32 is 7ZZZZZZZZZZZZZZZZZZZZZZZZZ
+	assert (int(ulid1[0]) - 48) <= 7
+}
+
+fn test_ulids_generated_in_the_same_millisecond_have_the_same_prefix() {
+	mut t1 := time.utc()
+	mut t2 := time.utc()
+	mut ulid1 := ''
+	mut ulid2 := ''
+	mut ulid3 := ''
+	for {
+		t1 = time.utc()
+		ulid1 = rand.ulid()
+		ulid2 = rand.ulid()
+		ulid3 = rand.ulid()
+		t2 = time.utc()
+		if t1.unix_time_milli() == t2.unix_time_milli() {
+			break
+		}
+	}
+	ulid1_prefix := ulid1[0..10]
+	ulid2_prefix := ulid2[0..10]
+	ulid3_prefix := ulid3[0..10]
+	assert ulid1_prefix == ulid2_prefix
+	assert ulid1_prefix == ulid3_prefix
+}
+
+fn test_ulids_should_be_lexicographically_ordered_when_not_in_same_millisecond() {
+	ulid1 := rand.ulid()
+	time.sleep_ms(1)
+	ulid2 := rand.ulid()
+	time.sleep_ms(1)
+	ulid3 := rand.ulid()
+	mut all := [ulid3, ulid2, ulid1]
+	// eprintln('all before: $all')
+	all.sort()
+	// eprintln('all  after: $all')
+	s1 := all[0]
+	s2 := all[1]
+	s3 := all[2]
+	assert s1 == ulid1
+	assert s2 == ulid2
+	assert s3 == ulid3
+}