Extract an overridable PageFinder class

README.md

@@ -121,6 +121,36 @@ Then modify it to subclass from High Voltage, adding whatever you need:
         end
     end
 
+Custom finding
+--------------
+
+You can further control the algorithm used to find pages by overriding
+the `page_finder_factory` method:
+
+    class PagesController < HighVoltage::PagesController
+      private
+
+      def page_finder_factory
+        Rot13PageFinder
+      end
+    end
+
+The easiest thing is to subclass `HighVoltage::PageFinder`, which
+provides you with `page_id`:
+
+    class Rot13PageFinder < HighVoltage::PageFinder
+      def find
+        paths = super.split('/')
+        directory = paths[0..-2]
+        filename = paths[-1].tr('a-z','n-za-m')
+
+        File.join(*directory, filename)
+      end
+    end
+
+Use this to create a custom file mapping, clean filenames for your file
+system, A/B test, and so on.
+
 Testing
 -------
 

app/controllers/high_voltage/pages_controller.rb

@@ -1,11 +1,11 @@
-class HighVoltage::PagesController < ApplicationController
-  VALID_CHARACTERS = "a-zA-Z0-9~!@$%^&*()#`_+-=<>\"{}|[];',?".freeze
+require 'high_voltage/page_finder'
 
+class HighVoltage::PagesController < ApplicationController
   unloadable
   layout Proc.new { |_| HighVoltage.layout }
 
   rescue_from ActionView::MissingTemplate do |exception|
-    if exception.message =~ %r{Missing template #{content_path}}
+    if exception.message =~ %r{Missing template #{page_finder.content_path}}
       raise ActionController::RoutingError, "No such page: #{params[:id]}"
     else
       raise exception
@@ -16,22 +16,17 @@ def show
     render :template => current_page
   end
 
-  protected
+  private
 
-    def current_page
-      "#{content_path}#{clean_path}"
-    end
-
-    def clean_path
-      path = Pathname.new("/#{clean_id}")
-      path.cleanpath.to_s[1..-1]
-    end
+  def current_page
+    page_finder.find
+  end
 
-    def content_path
-      HighVoltage.content_path
-    end
+  def page_finder
+    page_finder_factory.new(params[:id])
+  end
 
-    def clean_id
-      params[:id].tr("^#{VALID_CHARACTERS}", '')
-    end
+  def page_finder_factory
+    HighVoltage::PageFinder
+  end
 end

lib/high_voltage/page_finder.rb

@@ -0,0 +1,37 @@
+module HighVoltage
+  # A command for finding pages by id. This encapsulates the concepts of
+  # mapping page names to file names.
+  class PageFinder
+    VALID_CHARACTERS = "a-zA-Z0-9~!@$%^&*()#`_+-=<>\"{}|[];',?".freeze
+
+    def initialize(page_id)
+      @page_id = page_id
+    end
+
+    # Produce a template path to the page, in a format understood by
+    # `render :template => find`
+    def find
+      "#{content_path}#{clean_path}"
+    end
+
+    def content_path
+      HighVoltage.content_path
+    end
+
+    protected
+
+    # The raw page id passed in by the user
+    attr_reader :page_id
+
+    private
+
+    def clean_path
+      path = Pathname.new("/#{clean_id}")
+      path.cleanpath.to_s[1..-1]
+    end
+
+    def clean_id
+      @page_id.tr("^#{VALID_CHARACTERS}", '')
+    end
+  end
+end

spec/controllers/alternative_finder_controller_spec.rb

@@ -0,0 +1,13 @@
+require 'spec_helper'
+
+describe AlternativeFinderController do
+
+  render_views
+
+  it 'renders the file from the alternative directory' do
+    get :show, :id => 'ebg13'
+
+    response.should be_success
+    response.should render_template('rot13')
+  end
+end

spec/controllers/subclassed_pages_controller_spec.rb

@@ -18,15 +18,6 @@
     end
   end
 
-  describe "on GET to /subclassed_pages/also_dir/nested" do
-    before { get :show, :id => 'also_dir/also_nested' }
-
-    it "should respond with success and render template" do
-      response.should be_success
-      response.should render_template('other_pages/also_dir/also_nested')
-    end
-  end
-
   it "should raise a routing error for an invalid page" do
     lambda { get :show, :id => "invalid" }.should raise_error(ActionController::RoutingError)
   end

spec/dummy/app/controllers/alternative_finder_controller.rb

@@ -0,0 +1,14 @@
+class AlternativeFinderController < HighVoltage::PagesController
+  private
+
+  def page_finder_factory
+    Rot13PageFinder
+  end
+
+  class Rot13PageFinder < HighVoltage::PageFinder
+    def find
+      paths = super.split('/')
+      "#{paths[0..-2].join('/')}/#{paths[-1].tr('a-z','n-za-m')}"
+    end
+  end
+end

spec/dummy/app/controllers/subclassed_pages_controller.rb

@@ -1,7 +1,3 @@
 class SubclassedPagesController < HighVoltage::PagesController
   layout 'alternate'
-
-  def content_path
-    'other_pages/'
-  end
 end

spec/dummy/app/views/pages/also_dir/also_nested.html.erb

@@ -0,0 +1 @@
+hello <%= 'world' %> from a nested dir

spec/dummy/app/views/pages/also_exists.html.erb

@@ -0,0 +1 @@
+hello <%= 'world' %>

spec/dummy/app/views/pages/also_exists_but_references_nonexistent_partial.html.erb

@@ -0,0 +1,2 @@
+hello <%= 'world' %>
+<%= render 'nonexistent' %>

spec/dummy/app/views/pages/rot13.html.erb

@@ -0,0 +1 @@
+alternative

spec/dummy/config/routes.rb

@@ -1,3 +1,4 @@
 Dummy::Application.routes.draw do
   match "/subclassed_pages/*id" => 'subclassed_pages#show', :format => false
+  match "/alternative_finder/*id" => 'alternative_finder#show', :format => false
 end

spec/high_voltage/page_finder_spec.rb

@@ -0,0 +1,53 @@
+require 'spec_helper'
+require 'high_voltage/page_finder'
+
+describe HighVoltage::PageFinder do
+  it 'produces the name of an existing template' do
+    find('existing').should == 'pages/existing'
+  end
+
+  it 'produces the name of a nested template' do
+    find('dir/nested').should == 'pages/dir/nested'
+  end
+
+  it 'uses a custom content path' do
+    with_content_path('other_pages/') do
+      find('also_exists').should == 'other_pages/also_exists'
+    end
+  end
+
+  it 'exposes the content path' do
+    with_content_path('another_thing/') do
+      page_finder.content_path.should == 'another_thing/'
+    end
+  end
+
+  it 'provides the page_id' do
+    subclass = Class.new(HighVoltage::PageFinder) do
+      def page_name
+        "the page is #{page_id}"
+      end
+    end
+
+    subclass.new('sweet page').page_name.should == 'the page is sweet page'
+  end
+
+  private
+
+  def find(page_id)
+    page_finder(page_id).find
+  end
+
+  def page_finder(page_id = 'whatever')
+    HighVoltage::PageFinder.new(page_id)
+  end
+
+  def with_content_path(path)
+    original_content_path = HighVoltage.content_path
+    HighVoltage.content_path = path
+
+    yield
+
+    HighVoltage.content_path = original_content_path
+  end
+end