module Dugway
  module Tags
    class Paginate < ::Liquid::Block
      Syntax = /(\w+)\s+from\s+(#{ Liquid::QuotedFragment })\s*(by\s*(#{ Liquid::QuotedFragment }))?/

      def initialize(tag_name, markup, tokens)
        if markup =~ Syntax
          @variable_name = $1
          @collection_name = $2
          @per_page = $3.present? ? $4 : nil

          @attributes = { 'inner_window' => 3, 'outer_window' => 1 }

          markup.scan(Liquid::TagAttributes) { |key, value|
            @attributes[key] = value
          }

          @limit = @attributes['limit']
        else
          raise SyntaxError.new("Syntax Error in tag 'paginate' - Valid syntax: paginate [variable] from [collection] by [number]")
        end

        super
      end

      def render(context)
        @context = context
        @limit = context[@limit].present? ? context[@limit] : (@limit.present? ? @limit.to_i : nil)
        @per_page = context[@per_page].present? ? context[@per_page] : (@per_page.present? ? @per_page.to_i : nil)
        @order = context[@attributes['order']].present? ? context[@attributes['order']] : @attributes['order']

        context.stack do
          context['internal'] = {
            'per_page' => @per_page,
            'order' => @order,
            'page' => @context.registers[:params][:page] && @context.registers[:params][:page].to_i,
            'limit' => @limit
          }

          collection = context[@collection_name]
          context[@variable_name] = collection
          current_page = collection.current_page

          pagination = {
            'page_size' => collection.per_page,
            'current_page' => current_page,
            'current_offset' => collection.offset
          }

          context['paginate'] = pagination

          collection_size = collection.total_entries

          raise ArgumentError.new("Cannot paginate array '#{ @collection_name }'. Not found.")  if collection_size.nil?

          page_count = collection.total_pages

          pagination['items'] = collection_size
          pagination['pages'] = page_count

          pagination['previous'] = collection.previous_page.blank? ? no_link('&laquo; Previous') : link('&laquo; Previous', collection.previous_page)

          pagination['next'] = collection.next_page.blank? ? no_link('Next &raquo;') : link('Next &raquo;', collection.next_page)

          pagination['parts'] = []

          if page_count > 1
            inner_window = @attributes['inner_window'].to_i
            outer_window = @attributes['outer_window'].to_i

            min = current_page - inner_window
            max = current_page + inner_window

            # Adjust lower or upper limit if other is out of bounds
            if max > page_count
              min -= max - page_count
            elsif min < 1
              max += 1 - min
            end

            current = min..max
            beginning = 1..(1 + outer_window)
            tail = (page_count - outer_window)..page_count
            visible = [current, beginning, tail].map(&:to_a).flatten
            visible &= (1..page_count).to_a

            hellip_break = false

            1.upto(page_count) { |page|
              if page == current_page
                pagination['parts'] << no_link(page)
              elsif visible.include?(page)
                pagination['parts'] << link(page, page)
              elsif page == beginning.last + 1 || page == tail.first - 1
                next  if hellip_break

                pagination['parts'] << no_link('&hellip;')
                hellip_break = true
                next
              end

              hellip_break = false
            }
          end

          render_all @nodelist, context
        end
      end

      private

      def no_link(title)
        { 'title' => title.to_s, 'is_link' => false }
      end

      def link(title, page)
        { 'title' => title.to_s, 'url' => current_url + "?page=#{ page }#{ search }", 'is_link' => true }
      end

      def search
        @context.registers[:params]['search'].present? ? "&search=#{ @context.registers[:params]['search'] }" : nil
      end

      def current_url
        @context.registers[:path]
      end
    end
  end
end