implement flipper via singleton + updated readme docs

README.md

@@ -22,7 +22,35 @@ dependencies:
 require "flipper"
 ```
 
-TODO: Write usage instructions here
+```
+Flipper.adapter = Kiwi::MemoryStore.new
+Flipper.adapter = Kiwi::RedisStore.new(Redis.new)
+```
+
+You are free to use anyone of the supported adapeters/stores from [crystal-kiwi](https://github.com/greyblake/crystal-kiwi)
+
+```crystal
+Flipper.enable(:feature_name)
+
+if Flipper.enabled?(:feature_name)
+  puts "Feature launched, Let's roll!"
+else
+  puts "Feature not released yet."
+end
+
+Flipper.disable(:search)
+
+if Flipper.disabled?(:search)
+  puts "Search is not available yet!"
+end
+```
+
+## Roadmap
+
+- [x] Simple Logic Gate
+- [ ] Groups
+- [ ] Individual Users/Actors
+- [ ] Percentage of Actors
 
 ## Contributing
 

spec/flipper_spec.cr

@@ -1,6 +1,12 @@
 require "./spec_helper"
 
 describe Flipper do
+  it "attempting to use flipper without adapter raise error" do
+    expect_raises(Flipper::AdapterNotSet) do
+      Flipper.enable(:search)
+    end
+  end
+
   it "works as expected with MemoryStore" do
     works_as_expected_with(Kiwi::MemoryStore.new)
   end

spec/spec_helper.cr

@@ -11,49 +11,57 @@ require "kiwi/memcached_store"
 
 macro works_as_expected_with(store)
   adapter = {{store}}
+  Flipper.adapter = adapter
 
   describe Flipper do
-    context "#enable" do
+
+    context ".adapter" do
+
+      it "can be read back" do
+        Flipper.adapter.should_not be_nil
+      end
+
+      it "should be Kiwi::Store" do
+        Flipper.adapter.should be_a(Kiwi::Store)
+      end
+
+    end
+
+    context ".enable" do
       it "should enable a feature" do
-        flipper = Flipper.new(adapter)
-        flipper.enable(:search).should be_true
+        Flipper.enable(:search).should be_true
       end
     end
 
-    context "#disable" do
+    context ".disable" do
       it "should disable a feature" do
-        flipper = Flipper.new(adapter)
-        flipper.disable(:search).should be_true
+        Flipper.disable(:search).should be_true
       end
     end
 
-    context "#enabled?" do
+    context ".enabled?" do
       it "should check if a feature is enabled?" do
-        flipper = Flipper.new(adapter)
-        flipper.enable(:search)
-        flipper.enabled?(:search).should be_true
-        flipper.disabled?(:search).should be_false
+        Flipper.enable(:search)
+        Flipper.enabled?(:search).should be_true
+        Flipper.disabled?(:search).should be_false
       end
 
       it "should return false for a non-existent feature" do
-        flipper = Flipper.new(adapter)
-        flipper.enabled?(:non_existent_feature).should be_false
-        flipper.disabled?(:non_existent_feature).should be_true
+        Flipper.enabled?(:non_existent_feature).should be_false
+        Flipper.disabled?(:non_existent_feature).should be_true
       end
     end
 
-    context "#disabled?" do
+    context ".disabled?" do
       it "should check if a feature is disabled?" do
-        flipper = Flipper.new(adapter)
-        flipper.disable(:search)
-        flipper.enabled?(:search).should be_false
-        flipper.disabled?(:search).should be_true
+        Flipper.disable(:search)
+        Flipper.enabled?(:search).should be_false
+        Flipper.disabled?(:search).should be_true
       end
 
       it "should return true for a non-existent feature" do
-        flipper = Flipper.new(adapter)
-        flipper.enabled?(:non_existent_feature).should be_false
-        flipper.disabled?(:non_existent_feature).should be_true
+        Flipper.enabled?(:non_existent_feature).should be_false
+        Flipper.disabled?(:non_existent_feature).should be_true
       end
     end
   end

src/flipper.cr

@@ -1,27 +1,42 @@
 require "./flipper/*"
 
 class Flipper
-  def initialize(@adapter : Kiwi::Store)
+  class AdapterNotSet < Exception
   end
 
-  def enable(feature)
-    @adapter.set(feature.to_s, "true") == "true"
+  def self.adapter=(adapter : Kiwi::Store)
+    @@adapter = adapter
   end
 
-  def disable(feature)
-    @adapter.set(feature.to_s, "false") == "false"
+  def self.adapter
+    raise Flipper::AdapterNotSet.new unless @@adapter
+    @@adapter
   end
 
-  def enabled?(feature)
-    stored_value = @adapter.get(feature.to_s)
-    if stored_value.nil? || stored_value == "false"
-      false
-    elsif stored_value == "true"
-      true
+  def self.enable(feature)
+    adapter.try do |adapter|
+      adapter.set(feature.to_s, "true") == "true"
     end
   end
 
-  def disabled?(feature)
+  def self.disable(feature)
+    adapter.try do |adapter|
+      adapter.set(feature.to_s, "false") == "false"
+    end
+  end
+
+  def self.enabled?(feature)
+    adapter.try do |adapter|
+      stored_value = adapter.get(feature.to_s)
+      if stored_value.nil? || stored_value == "false"
+        false
+      elsif stored_value == "true"
+        true
+      end
+    end
+  end
+
+  def self.disabled?(feature)
     !enabled?(feature)
   end
 end