# See Pagy::Frontend API documentation: https://ddnexus.github.io/pagy/api/frontend
# frozen_string_literal: true

require 'pagy/url_helpers'
require 'pagy/i18n'

class Pagy
  # Used for search and replace, hardcoded also in the pagy.js file
  PAGE_PLACEHOLDER  = '__pagy_page__'
  LABEL_PLACEHOLDER = '__pagy_label__'

  # Frontend modules are specially optimized for performance.
  # The resulting code may not look very elegant, but produces the best benchmarks
  module Frontend
    include UrlHelpers

    # Generic pagination: it returns the html with the series of links to the pages
    def pagy_nav(pagy, pagy_id: nil, link_extra: '', **vars)
      p_id   = %( id="#{pagy_id}") if pagy_id
      link   = pagy_link_proc(pagy, link_extra: link_extra)
      p_prev = pagy.prev
      p_next = pagy.next

      html = +%(<nav#{p_id} class="pagy-nav pagination" aria-label="pager">)
      html << if p_prev
                %(<span class="page prev">#{link.call p_prev, pagy_t('pagy.nav.prev'), 'aria-label="previous"'}</span> )
              else
                %(<span class="page prev disabled">#{pagy_t('pagy.nav.prev')}</span> )
              end
      pagy.series(**vars).each do |item| # series example: [1, :gap, 7, 8, "9", 10, 11, :gap, 36]
        html << case item
                when Integer then %(<span class="page">#{link.call item}</span> )
                when String  then %(<span class="page active">#{pagy.label_for(item)}</span> )
                when :gap    then %(<span class="page gap">#{pagy_t('pagy.nav.gap')}</span> )
                else raise InternalError, "expected item types in series to be Integer, String or :gap; got #{item.inspect}"
                end
      end
      html << if p_next
                %(<span class="page next">#{link.call p_next, pagy_t('pagy.nav.next'), 'aria-label="next"'}</span>)
              else
                %(<span class="page next disabled">#{pagy_t('pagy.nav.next')}</span>)
              end
      html << %(</nav>)
    end

    # Return examples: "Displaying items 41-60 of 324 in total" or "Displaying Products 41-60 of 324 in total"
    def pagy_info(pagy, pagy_id: nil, item_name: nil, i18n_key: nil)
      p_id    = %( id="#{pagy_id}") if pagy_id
      p_count = pagy.count
      key     = if    p_count.zero?   then 'pagy.info.no_items'
                elsif pagy.pages == 1 then 'pagy.info.single_page'
                else                       'pagy.info.multiple_pages' # rubocop:disable Lint/ElseLayout
                end

      %(<span#{p_id} class="pagy-info">#{
          pagy_t key, item_name: item_name || pagy_t(i18n_key || pagy.vars[:i18n_key], count: p_count),
                      count: p_count, from: pagy.from, to: pagy.to
        }</span>)
    end

    # Return a performance optimized proc to generate the HTML links
    # Benchmarked on a 20 link nav: it is ~22x faster and uses ~18x less memory than rails' link_to
    def pagy_link_proc(pagy, link_extra: '')
      p_prev      = pagy.prev
      p_next      = pagy.next
      left, right = %(<a href="#{pagy_url_for pagy, PAGE_PLACEHOLDER}" #{
                        pagy.vars[:link_extra]} #{link_extra}).split(PAGE_PLACEHOLDER, 2)
      lambda do |page, text = pagy.label_for(page), extra_attrs = ''|
        %(#{left}#{page}#{right}#{ case page
                                   when p_prev then ' rel="prev"'
                                   when p_next then ' rel="next"'
                                   else             ''
                                   end } #{extra_attrs}>#{text}</a>)
      end
    end

    # Similar to I18n.t: just ~18x faster using ~10x less memory
    # (@pagy_locale explicitly initialized in order to avoid warning)
    def pagy_t(key, **opts)
      Pagy::I18n.t(@pagy_locale ||= nil, key, **opts)
    end
  end
end