Fixed #to_json with prefix address

see. flori/json#503

lib/ipaddr-ext.rb

@@ -1,4 +1,9 @@
 require "ipaddr"
+require 'json'
+
+require "ipaddr-ext/version"
 require "ipaddr-ext/extensions"
+require "ipaddr-ext/json"
 
 IPAddr.send(:include, IPAddrExt::Extensions)
+IPAddr.send(:include, IPAddrExt::JSON)

lib/ipaddr-ext/extensions.rb

@@ -1,7 +1,5 @@
 # frozen_string_literal: true
 
-require_relative "version"
-
 module IPAddrExt
   module Extensions
     # Returns the broadcast address

lib/ipaddr-ext/json.rb

@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+
+module IPAddrExt
+  module JSON
+    def to_json
+      if ipv4? && prefix == 32
+        format("\"%s\"", to_s)
+      elsif ipv6? && prefix == 128
+        format("\"%s\"", to_s)
+      else
+        format("\"%s/%s\"", to_s, prefix)
+      end
+    end
+  end
+end

spec/ipaddr-ext/json_spec.rb

@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+RSpec.describe IPAddrExt::JSON do
+  context "#to_json" do
+    it "ipv4" do
+      expect(IPAddr.new("192.168.1.1").to_json).to eq "\"192.168.1.1\""
+      expect(IPAddr.new("192.168.1.2/32").to_json).to eq "\"192.168.1.2\""
+      expect(IPAddr.new("192.168.1.0/24").to_json).to eq "\"192.168.1.0/24\""
+    end
+
+    it "ipv6" do
+      expect(IPAddr.new("3ffe:505:2::1").to_json).to eq "\"3ffe:505:2::1\""
+      expect(IPAddr.new("3ffe:505:2::2/128").to_json).to eq "\"3ffe:505:2::2\""
+      expect(IPAddr.new("3ffe:505:2::/64").to_json).to eq "\"3ffe:505:2::/64\""
+    end
+  end
+end