Searchkick extra (#75)

* added Searchkick extra

docs/extras/searchkick.md

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+---
+title: Searchkick
+---
+# Searchkick Extra
+
+This extra adds a specialized pagination for `Searchkick::Results` objects without the need to override the `pagy_get_items` in your controller.
+
+The `Searchkick::Results` object has already done pagination calculations, we just need to tell Pagy how to read page and total values. It is expected that you let Searchkick handle the `page` and `per_page` variables instead of providing those values as options to Pagy.
+
+## Synopsys
+
+See [extras](../extras.md) for general usage info.
+
+In a controller:
+
+```ruby
+@pagy_s, @models = pagy_searchkick(
+  Model.search("*",
+    {
+      where: {
+        ...
+      },
+      fields: [...],
+      select: [...],
+      load: true,
+      page: params[:page],
+      per_page: 25
+    }
+  )
+  ,
+  ...
+ )
+
+# independently paginate some other collections as usual
+@pagy_b, @records = pagy(some_scope, ...)
+```
+
+## Files
+
+This extra is composed of 1 file:
+
+- [searchkick.rb](https://github.com/ddnexus/pagy/blob/master/lib/pagy/extras/searchkick.rb)
+
+## Methods
+
+This extra adds the `pagy_searchkick` method to the `Pagy::Backend` to be used in place (or in parallel) of the `pagy` method when you have to paginate a `Searchkick::Results` object. It also adds a `pagy_searchkick_get_variables` sub-method, used for easy customization of variables by overriding.
+
+**Notice**: there is no `pagy_searchkick_get_items` method to override, since the items are fetched directly by Searchkick.
+
+### pagy_searchkick(Model.search(...), vars=nil)
+
+This method is the same as the generic `pagy` method, but specialized for Searchkick. (see the [pagy doc](../api/backend.md#pagycollection-varsnil))
+
+### pagy_searchkick_get_vars(array)
+
+This sub-method is the same as the `pagy_get_vars` sub-method, but it is called only by the `pagy_searchkick` method. (see the [pagy_get_vars doc](../api/backend.md#pagy_get_varscollection-vars)).

lib/pagy/extras/searchkick.rb

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+# See the Pagy documentation: https://ddnexus.github.io/pagy/extras/searchkick
+
+class Pagy
+  # Add specialized backend methods to paginate Searchkick::Results
+  module Backend ; private
+    # Return Pagy object and items
+    def pagy_searchkick(results, vars={})
+      pagy = Pagy.new(pagy_searchkick_get_vars(results, vars))
+      return pagy, results
+    end
+
+    def pagy_searchkick_get_vars(results, vars)
+      # Return the merged variables to initialize the Pagy object
+      { count: results.total_count,
+        page:  results.options[:page],
+        items: results.options[:per_page] }.merge!(vars)
+    end
+  end
+end

test/pagy/extras/searchkick_test.rb

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+require_relative '../../test_helper'
+require 'pagy/extras/searchkick'
+
+SingleCov.covered!
+
+describe Pagy::Backend do
+
+  let(:backend) { TestController.new }
+
+  class Searchkick
+    class Results
+      def initialize(params); @params = params; end
+      def total_count; 1000; end
+      def options
+        {
+          page: @params[:page] || 1,
+          per_page: 25
+        }
+      end
+    end
+  end
+
+  describe "#pagy_searchkick" do
+
+    before do
+      @collection = Searchkick::Results.new(backend.params)
+    end
+
+    it 'paginates with defaults' do
+      pagy, _items = backend.send(:pagy_searchkick, @collection)
+      pagy.must_be_instance_of Pagy
+      pagy.count.must_equal 1000
+      pagy.items.must_equal 25
+      pagy.page.must_equal backend.params[:page]
+    end
+
+    it 'paginates with vars' do
+      pagy, _items = backend.send(:pagy_searchkick, @collection, link_extra: 'X')
+      pagy.must_be_instance_of Pagy
+      pagy.count.must_equal 1000
+      pagy.items.must_equal 25
+      pagy.vars[:link_extra].must_equal 'X'
+    end
+
+  end
+
+  describe "#pagy_searchkick_get_vars" do
+
+    before do
+      @collection = Searchkick::Results.new(backend.params)
+    end
+
+    it 'gets defaults' do
+      vars   = {}
+      merged = backend.send :pagy_searchkick_get_vars, @collection, vars
+      merged.keys.must_include :count
+      merged.keys.must_include :page
+      merged[:count].must_equal 1000
+      merged[:items].must_equal 25
+      merged[:page].must_equal 3
+    end
+
+    it 'gets vars' do
+      vars   = {link_extra: 'X'}
+      merged = backend.send :pagy_searchkick_get_vars, @collection, vars
+      merged.keys.must_include :count
+      merged.keys.must_include :page
+      merged.keys.must_include :link_extra
+      merged[:count].must_equal 1000
+      merged[:items].must_equal 25
+      merged[:link_extra].must_equal 'X'
+    end
+
+  end
+
+end