module Rostra
  module Base
    module ApplicationHelper

      # Snippet used to share a question on Twitter.
      #
      def twitter_sharing_link
        raw %{
          <a href="https://twitter.com/share" class="twitter-share-button" data-count="none">Tweet</a>
          <script type="text/javascript" src="//platform.twitter.com/widgets.js"></script>
        }
      end

      # Snippet used to share a question on Facebook.
      #
      def facebook_sharing_link(question)
        raw %{
          <div class="fb-like" data-href="#{question_url(question)}" data-send="true" data-layout="button_count" data-width="450" data-show-faces="true" data-font="arial"></div>
        }
      end

      # Javascript snippet required by facebook to support share links.
      #
      def include_facebook_sharing_link_javascript
        raw %{
          <div id="fb-root"></div>
          <script>(function(d, s, id) {
            var js, fjs = d.getElementsByTagName(s)[0];
            if (d.getElementById(id)) return;
            js = d.createElement(s); js.id = id;
            js.src = "//connect.facebook.net/en_US/all.js#xfbml=1";
            fjs.parentNode.insertBefore(js, fjs);
          }(document, 'script', 'facebook-jssdk'));</script>
        }
      end

      # Method used to render to user names (e.g. where it says: "John Does says:"). You can,
      # for example, use this method to turn "John Doe" into a link to his profile page.
      #
      def link_to_profile(user)
        link_to user.rostra_user_name, main_app.user_url(user)
      end

      # Used to add meta description tags to rostra pages
      #
      def include_meta_description
        description = case "#{controller_name}##{action_name}"
        when "questions#show" then @question.title
        when "questions#index" then "Recently asked questions"
        end
        tag(:meta, { :name => "description", :content => description })
      end

      # Used to add meta keyword tags to rostra pages
      #
      def include_meta_keywords
        keywords = case "#{controller_name}##{action_name}"
        when "questions#show" then @question.tag_list.join(', ')
        when "questions#index" then "add, some, default, keywords"
        end
        tag(:meta, { :name => "keywords", :content => keywords })
      end

      # Used to populate both the +title+ and +h1+ elements for each page.
      #
      def page_title_helper
        case "#{controller_name}##{action_name}"
        when "questions#show" then @question.title
        when "questions#index" then
          if params[:tag_search].present?
            "Recent Questions for tag #{params[:tag_search]}"
          else
            "Recent Questions"
          end
        when "questions#new" then "Post a new question"
        when "questions#edit" then "Editing question"
        when "answers#edit" then "Editing answer"
        else "Recent Questions"
        end
      end

      # Creates a list of tags linking to the index showing only questions with that tag
      #
      def tag_list(question)
        tags = question.tags.map { |tag| link_to tag, questions_path(:tag_search => "#{tag}")}.join(', ')
        content_tag :div, "Tags: #{tags}".html_safe, class: 'tags'
      end

      # Finds the url to the user's avatar following this logic:
      #
      #   1. Calls +avatar+ on the user object
      #   2. Uses the users email address to look for a gravatar
      #   3. Renders +app/assets/images/rostra/anonymous_avatar.png+
      #
      def rostra_user_avatar(user)
        if user.respond_to?(:avatar)
          url = user.avatar
        else
          default_url = "#{main_app.root_url}assets/rostra/anonymous_avatar.png"
          gravatar_id = Digest::MD5.hexdigest(user.rostra_user_email.downcase)
          url = "http://gravatar.com/avatar/#{gravatar_id}.png?s=48&d=#{CGI.escape(default_url)}"
        end
        image_tag(url, class: 'avatar')
      end

      # Method to build links for ajax-y voting arrows.
      #
      def link_to_vote(direction, resource)
        if can_participate_in_rostra? && ( (direction == :up && rostra_user.voted_for?(resource)) || (direction == :down && rostra_user.voted_against?(resource)) )
          selected = 'selected'
        else
          selected = ''
        end
        entity_arrow = direction == :up ? '&#x25B2;' : '&#x25BC;'
        link_to entity_arrow.html_safe, vote_path(resource, direction), method: :put, remote: true, title: "vote #{direction}", class: "vote #{direction} #{selected}"
      end

      # Returns a rostra object's base class name. For example, +@question+ is an instance of
      # Rostra::Question and so:
      #
      #   class_name(@question)  # => 'question'
      #
      def class_name(resource)
        resource.class.name.split('::').last.downcase
      end

      # Checks for the current page using rails 3 route-style syntax:
      #
      #   current_rostra_page?('questions#new')
      #
      def current_rostra_page?(controller_and_action)
        controller_and_action == "#{controller_name}##{action_name}"
      end

      private

      def vote_path(resource, direction)
        return '#' if !can_participate_in_rostra? || can?(:manage, resource)

        if resource.is_a?(Rostra::Question)
          vote_question_path(resource, vote_direction: direction)
        else
          vote_question_answer_path(resource.question, resource, vote_direction: direction)
        end
      end

    end
  end
end