From 23f163d43e396880123ff966cf88423124b29db2 Mon Sep 17 00:00:00 2001
From: Markus Doits <markus.doits@stellenticket.de>
Date: Fri, 15 Oct 2021 17:35:29 +0200
Subject: [PATCH] Make installing dalli and redis gem optional

---
 Gemfile                     |  3 +++
 README.md                   | 18 ++++++++++++++----
 lib/suo.rb                  | 17 ++++++++++++-----
 lib/suo/client/memcached.rb |  6 +++++-
 lib/suo/client/redis.rb     |  4 ++++
 suo.gemspec                 |  2 --
 6 files changed, 38 insertions(+), 12 deletions(-)

diff --git a/Gemfile b/Gemfile
index b4e2a20..2aef6ca 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,3 +1,6 @@
 source "https://rubygems.org"
 
 gemspec
+
+gem 'redis'
+gem 'dalli'
diff --git a/README.md b/README.md
index 39a86b0..598584e 100644
--- a/README.md
+++ b/README.md
@@ -6,11 +6,21 @@ Suo provides a very performant distributed lock solution using Compare-And-Set (
 
 ## Installation
 
-Add this line to your application’s Gemfile:
+1. Install the gem
 
-```ruby
-gem 'suo'
-```
+   ```ruby
+   gem 'suo'
+   ```
+
+2. Install at least one caching library gem
+
+   ```ruby
+   # to use Suo::Client::Memcached
+   gem 'dalli'
+
+   # to use Suo::Client::Redis
+   gem 'redis'
+   ```
 
 ## Usage
 
diff --git a/lib/suo.rb b/lib/suo.rb
index 77130ac..e06fae0 100644
--- a/lib/suo.rb
+++ b/lib/suo.rb
@@ -1,10 +1,16 @@
 require "securerandom"
 require "monitor"
 
-require "dalli"
-require "dalli/cas/client"
+begin
+  require "dalli"
+  require "dalli/cas/client"
+rescue LoadError
+end
 
-require "redis"
+begin
+  require "redis"
+rescue LoadError
+end
 
 require "msgpack"
 
@@ -12,5 +18,6 @@
 
 require "suo/errors"
 require "suo/client/base"
-require "suo/client/memcached"
-require "suo/client/redis"
+
+require "suo/client/memcached" if defined?(Dalli)
+require "suo/client/redis" if defined?(Redis)
diff --git a/lib/suo/client/memcached.rb b/lib/suo/client/memcached.rb
index dbc74b8..23a73af 100644
--- a/lib/suo/client/memcached.rb
+++ b/lib/suo/client/memcached.rb
@@ -2,7 +2,11 @@ module Suo
   module Client
     class Memcached < Base
       def initialize(key, options = {})
-        options[:client] ||= Dalli::Client.new(options[:connection] || ENV["MEMCACHE_SERVERS"] || "127.0.0.1:11211")
+        if !options[:client] && !defined?(::Dalli)
+          raise "Dalli class found. Please make sure you have 'dalli' as a dependency in your gemfile (`gem 'dalli'`)."
+        end
+
+        options[:client] ||= ::Dalli::Client.new(options[:connection] || ENV["MEMCACHE_SERVERS"] || "127.0.0.1:11211")
         super
       end
 
diff --git a/lib/suo/client/redis.rb b/lib/suo/client/redis.rb
index 2a106c7..e8f7127 100644
--- a/lib/suo/client/redis.rb
+++ b/lib/suo/client/redis.rb
@@ -4,6 +4,10 @@ class Redis < Base
       OK_STR = "OK".freeze
 
       def initialize(key, options = {})
+        if !options[:client] && !defined?(::Redis)
+          raise "Redis class not found. Please make sure you have 'redis' as a dependency in your gemfile (`gem 'redis'`)."
+        end
+
         options[:client] ||= ::Redis.new(options[:connection] || {})
         super
       end
diff --git a/suo.gemspec b/suo.gemspec
index cada028..fe42dea 100644
--- a/suo.gemspec
+++ b/suo.gemspec
@@ -21,8 +21,6 @@ Gem::Specification.new do |spec|
 
   spec.required_ruby_version = ">= 2.5"
 
-  spec.add_dependency "dalli"
-  spec.add_dependency "redis"
   spec.add_dependency "msgpack"
 
   spec.add_development_dependency "bundler"