add support for will_paginate; remove Kaminari dependency

There's no reason why Kaminari runtime dependency needs to be declared,
as api-pagination will operate on any object that responds to:
 - current_page
 - total_pages
 - first_page?
 - last_page?

This monkey-patches WillPaginate::CollectionMethods to make it quack
like Kaminari::PageScopeMethods, so that the plugin supports both
libraries.

A dummy paginated class is provided for the purpose of tests.

Author: mislav

api-pagination.gemspec

@@ -17,7 +17,6 @@ Gem::Specification.new do |s|
   s.require_paths = ['lib']
 
   s.add_dependency 'rails', '>= 3.0.0'
-  s.add_dependency 'kaminari', '>= 0.13.0'
 
   s.add_development_dependency 'bundler', '~> 1.3'
   s.add_development_dependency 'rspec-rails'

lib/api-pagination.rb

@@ -1,5 +1,4 @@
 require 'api-pagination/version'
-require 'kaminari'
 
 module ApiPagination
   protected
@@ -29,3 +28,10 @@ def paginate(scope)
 
 ActionController::Base.send(:include, ApiPagination) if defined?(ActionController::Base)
 ActionController::API.send(:include, ApiPagination)  if defined?(ActionController::API)
+
+if defined?(WillPaginate::CollectionMethods)
+  WillPaginate::CollectionMethods.module_eval do
+    def first_page?() !previous_page end
+    def last_page?() !next_page end
+  end
+end

spec/dummy/app/controllers/numbers_controller.rb

@@ -1,8 +1,20 @@
 class NumbersController < ApplicationController
   after_filter only: [:index] { paginate(:numbers) }
 
+  # quacks like Kaminari
+  PaginatedSet = Struct.new(:current_page, :total_count) do
+    def limit_value() 25 end
+
+    def total_pages
+      total_count.zero? ? 1 : (total_count.to_f / limit_value).ceil
+    end
+
+    def first_page?() current_page == 1 end
+    def last_page?() current_page == total_pages end
+  end
+
   def index
-    @numbers = Kaminari.paginate_array((1..params[:count].to_i).to_a).page(params[:page])
+    @numbers = PaginatedSet.new(params.fetch(:page, 1).to_i, params.fetch(:count).to_i)
     render json: @numbers
   end
 end

spec/dummy/config/application.rb

@@ -7,7 +7,6 @@
 # require "sprockets/railtie"
 
 Bundler.require(*Rails.groups)
-require 'kaminari'
 require 'api-pagination'
 
 module Dummy