Add email and domain whitelist options

README.md

@@ -34,6 +34,24 @@ Optionally prefix the subject line:
       subject_prefix: '[STAGING]'
     )
 
+Optionally white-list emails:
+
+    Mail.register_interceptor RecipientInterceptor.new(
+      ENV['EMAIL_RECIPIENTS'],
+      email_whitelist: ['[email protected]']
+    )
+
+Optionally white-list domains:
+
+    Mail.register_interceptor RecipientInterceptor.new(
+      ENV['EMAIL_RECIPIENTS'],
+      domain_whitelist: ['example.com']
+    )
+
+Note: If one or more of the original recipients match the email white-list or domain white-list,
+the email's to field will not be overridden. However, non-white-listed emails will be removed from
+the email's to field.
+
 Credits
 -------
 

lib/recipient_interceptor.rb

@@ -1,15 +1,18 @@
 require 'mail'
 
 class RecipientInterceptor
+
   def initialize(recipients, options = {})
     @recipients = normalize_to_array(recipients)
+    @email_whitelist = options[:email_whitelist] || []
+    @domain_whitelist = options[:domain_whitelist] || []
     @subject_prefix = options[:subject_prefix]
   end
 
   def delivering_email(message)
     add_custom_headers message
     add_subject_prefix message
-    message.to = @recipients
+    message.to = sanitize_recipients(message)
     message.cc = []
     message.bcc = []
   end
@@ -41,4 +44,25 @@ def add_custom_headers(message)
       end
     end
   end
+
+  def sanitize_recipients(message)
+    recipients = message.to
+    sanitized_recipients = recipients.select { |email| whitelisted?(email) }
+    sanitized_recipients.any? ? sanitized_recipients : @recipients
+  end
+
+  def whitelisted?(email)
+    whitelisted_email?(email) || whitelisted_domain?(email)
+  end
+
+  def whitelisted_email?(email)
+    @email_whitelist.include?(email)
+  end
+
+  def whitelisted_domain?(email)
+    @domain_whitelist.any? do |domain|
+      email =~ /@#{domain}$/
+    end
+  end
+
 end

spec/recipient_interceptor_spec.rb

@@ -40,6 +40,98 @@
     expect(response.to).to eq [recipient_string]
   end
 
+  context 'given an email white-list' do
+    context 'for emails with one recipient' do
+      it 'does not override the to field for a white-listed email' do
+        Mail.register_interceptor RecipientInterceptor.new(
+          '[email protected]',
+          email_whitelist: ['[email protected]']
+        )
+
+        response = deliver_mail to: '[email protected]'
+        expect(response.to).to eq ['[email protected]']
+      end
+
+      it 'overrides the to field for a non-white-listed email' do
+        Mail.register_interceptor RecipientInterceptor.new(
+          '[email protected]',
+          email_whitelist: ['[email protected]']
+        )
+
+        response = deliver_mail to: '[email protected]'
+        expect(response.to).to eq ['[email protected]']
+      end
+    end
+
+    context 'for emails with multiple recipients' do
+      it 'strips non-white-listed emails, leaving white-listed ones' do
+        Mail.register_interceptor RecipientInterceptor.new(
+          '[email protected]',
+          email_whitelist: ['[email protected]']
+        )
+
+        response = deliver_mail to: ['[email protected]', '[email protected]']
+        expect(response.to).to eq ['[email protected]']
+      end
+
+      it 'replaces all recipients when none is white-listed' do
+        Mail.register_interceptor RecipientInterceptor.new(
+          '[email protected]',
+          email_whitelist: ['[email protected]']
+        )
+
+        response = deliver_mail to: ['[email protected]', '[email protected]']
+        expect(response.to).to eq ['[email protected]']
+      end
+    end
+  end
+
+  context 'given an domain white-list' do
+    context 'for emails with one recipient' do
+      it 'does not override the to field for a white-listed email' do
+        Mail.register_interceptor RecipientInterceptor.new(
+          '[email protected]',
+          domain_whitelist: ['whitelisted.com']
+        )
+
+        response = deliver_mail to: '[email protected]'
+        expect(response.to).to eq ['[email protected]']
+      end
+
+      it 'overrides the to field for a non-white-listed email' do
+        Mail.register_interceptor RecipientInterceptor.new(
+          '[email protected]',
+          domain_whitelist: ['whitelisted.com']
+        )
+
+        response = deliver_mail to: '[email protected]'
+        expect(response.to).to eq ['[email protected]']
+      end
+    end
+
+    context 'for emails with multiple recipients' do
+      it 'strips non-white-listed emails, leaving white-listed ones' do
+        Mail.register_interceptor RecipientInterceptor.new(
+          '[email protected]',
+          domain_whitelist: ['whitelisted.com']
+        )
+
+        response = deliver_mail to: ['[email protected]', '[email protected]', '[email protected]']
+        expect(response.to).to eq ['[email protected]', '[email protected]']
+      end
+
+      it 'replaces all recipients when none is white-listed' do
+        Mail.register_interceptor RecipientInterceptor.new(
+          '[email protected]',
+          domain_whitelist: ['whitelisted.com']
+        )
+
+        response = deliver_mail to: ['[email protected]', '[email protected]']
+        expect(response.to).to eq ['[email protected]']
+      end
+    end
+  end
+
   it 'does not prefix subject by default' do
     Mail.register_interceptor RecipientInterceptor.new(recipient_string)
 
@@ -67,17 +159,17 @@ def recipient_array
     ['[email protected]', '[email protected]']
   end
 
-  def deliver_mail
+  def deliver_mail(options = {})
     Mail.defaults do
       delivery_method :test
     end
 
     Mail.deliver do
-      from '[email protected]'
-      to '[email protected]'
-      cc '[email protected]'
-      bcc '[email protected]'
-      subject 'some subject'
+      from options.fetch(:from, '[email protected]')
+      to options.fetch(:to, '[email protected]')
+      cc options.fetch(:cc, '[email protected]')
+      bcc options.fetch(:bcc, '[email protected]')
+      subject options.fetch(:subject, 'some subject')
     end
   end