From 26f5ca59f228ef1462e93cb3c88982eda90b0743 Mon Sep 17 00:00:00 2001
From: Rubens Stulzer <rubens.stulzer@gmail.com>
Date: Wed, 27 Mar 2024 11:05:27 +0100
Subject: [PATCH] Random letter prefix to CUID2

This commit introduces a random letter prefix to the CUID2 generation
process. This change is intended to reduce the likelihood of CUID2
collisions. The random letter is generated from the range 'a' to 'z'.

The tests have been updated to reflect this change. A new test has been
added to ensure that CUID2s do not have the same first character. The
collision test run and CUID2s per run values have been reduced for
testing purposes.

The version of the library has been bumped to 1.0.1.
---
 lib/cuid2.rb         |  5 +----
 lib/cuid2/version.rb |  2 +-
 spec/cuid2_spec.rb   | 27 +++++++++++++++++++++++++--
 3 files changed, 27 insertions(+), 7 deletions(-)

diff --git a/lib/cuid2.rb b/lib/cuid2.rb
index aaa2c5f..613345c 100644
--- a/lib/cuid2.rb
+++ b/lib/cuid2.rb
@@ -42,6 +42,7 @@ def self.create(input, length = BIG_LENGTH)
 
   class << self
     def call(length = DEFAULT_LENGTH)
+      random_letter = ('a'..'z').to_a[(rand * 26).floor]
       hash_input = (time + Entropy.create(length) + count + fingerprint).to_s
 
       "#{random_letter}#{Cuid2::Hash.create(hash_input, length)[2..length]}"
@@ -67,10 +68,6 @@ def counter
       (rand + 1) * 2057
     end
 
-    def random_letter
-      ('a'..'z').to_a[(random * 26).floor]
-    end
-
     def fingerprint
       Cuid2::Hash.create("#{((random + 1) * 2063).floor} #{Object.constants.map(&:to_s)}")
     end
diff --git a/lib/cuid2/version.rb b/lib/cuid2/version.rb
index 4a8998a..13ead70 100644
--- a/lib/cuid2/version.rb
+++ b/lib/cuid2/version.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
 
 module Cuid2
-  VERSION = '1.0.0'
+  VERSION = '1.0.1'
 end
diff --git a/spec/cuid2_spec.rb b/spec/cuid2_spec.rb
index f902c91..67cd74e 100644
--- a/spec/cuid2_spec.rb
+++ b/spec/cuid2_spec.rb
@@ -2,8 +2,8 @@
 
 require 'cuid2'
 
-COLISION_TEST_RUN = ENV.fetch('COLISION_TEST_RUN', 10).to_i
-CUIDS_PER_RUN = ENV.fetch('CUIDS_PER_RUN', 100).to_i
+COLISION_TEST_RUN = ENV.fetch('COLISION_TEST_RUN', 1).to_i
+CUIDS_PER_RUN = ENV.fetch('CUIDS_PER_RUN', 10).to_i
 
 RSpec.describe Cuid2 do
   it 'has a version number' do
@@ -25,4 +25,27 @@
     expect(cuids.uniq.sort).to eq(cuids.sort)
     expect(cuids.sample).to match(/[a-z0-9]{24}/)
   end
+
+  it 'should not collide with prefix' do
+    cuids = []
+    COLISION_TEST_RUN.times do
+      CUIDS_PER_RUN.times do
+        cuids << Cuid2.call(prefix: 'test')
+      end
+    end
+    expect(cuids.uniq.size).to eq(cuids.size)
+    expect(cuids.size).to eq(COLISION_TEST_RUN * CUIDS_PER_RUN)
+    expect(cuids.uniq.size).to eq(COLISION_TEST_RUN * CUIDS_PER_RUN)
+    expect(cuids.uniq.sort).to eq(cuids.sort)
+    expect(cuids.sample).to match(/test[a-z0-9]{24}/)
+  end
+
+  it 'should not have the same first character' do
+    cuids = []
+    5000.times do
+      cuids << Cuid2.call[0]
+    end
+
+    expect(cuids.uniq.size).to be > 1
+  end
 end