# frozen_string_literal: true

require 'addressable'
require 'parallel'

module Html2rss
  class AutoSource
    module Scraper
      ##
      # Scrapes articles by looking for common markup tags (article, section, li)
      # containing an <a href> tag.
      #
      # See:
      # 1. https://developer.mozilla.org/en-US/docs/Web/HTML/Element/article
      class SemanticHtml
        include Enumerable

        ##
        # Map of parent element names to CSS selectors for finding <a href> tags.
        ANCHOR_TAG_SELECTORS = {
          'section' => ['section :not(section) a[href]'],
          'tr' => ['table tr :not(tr) a[href]'],
          'article' => [
            'article :not(article) a[href]',
            'article a[href]'
          ],
          'li' => [
            'ul > li :not(li) a[href]',
            'ol > li :not(li) a[href]'
          ]
        }.freeze

        # Check if the parsed_body contains articles
        # @param parsed_body [Nokogiri::HTML::Document] The parsed HTML document
        # @return [Boolean] True if articles are found, otherwise false.
        def self.articles?(parsed_body)
          return false unless parsed_body

          ANCHOR_TAG_SELECTORS.each_value do |selectors|
            return true if selectors.any? { |selector| parsed_body.at_css(selector) }
          end
          false
        end

        # Finds the closest ancestor tag matching the specified tag name
        # @param current_tag [Nokogiri::XML::Node] The current tag to start searching from
        # @param tag_name [String] The tag name to search for
        # @param stop_tag [String] The tag name to stop searching at
        # @return [Nokogiri::XML::Node] The found ancestor tag or the current tag if matched
        def self.find_tag_in_ancestors(current_tag, tag_name, stop_tag: 'html')
          return current_tag if current_tag.name == tag_name

          stop_tags = Set[tag_name, stop_tag]

          while current_tag.respond_to?(:parent) && !stop_tags.member?(current_tag.name)
            current_tag = current_tag.parent
          end

          current_tag
        end

        # Finds the closest matching selector upwards in the DOM tree
        # @param current_tag [Nokogiri::XML::Node] The current tag to start searching from
        # @param selector [String] The CSS selector to search for
        # @return [Nokogiri::XML::Node, nil] The closest matching tag or nil if not found
        def self.find_closest_selector(current_tag, selector: 'a[href]:not([href=""])')
          current_tag.at_css(selector) || find_closest_selector_upwards(current_tag, selector:)
        end

        # Helper method to find a matching selector upwards
        # @param current_tag [Nokogiri::XML::Node] The current tag to start searching from
        # @param selector [String] The CSS selector to search for
        # @return [Nokogiri::XML::Node, nil] The closest matching tag or nil if not found
        def self.find_closest_selector_upwards(current_tag, selector:)
          while current_tag
            found = current_tag.at_css(selector)
            return found if found

            return nil unless current_tag.respond_to?(:parent)

            current_tag = current_tag.parent
          end
        end

        # Returns an array of [tag_name, selector] pairs
        # @return [Array<[String, String]>] Array of tag name and selector pairs
        def self.anchor_tag_selector_pairs
          ANCHOR_TAG_SELECTORS.flat_map do |tag_name, selectors|
            selectors.map { |selector| [tag_name, selector] }
          end
        end

        def initialize(parsed_body, url:)
          @parsed_body = parsed_body
          @url = url
        end

        attr_reader :parsed_body

        ##
        # @yieldparam [Hash] The scraped article hash
        # @return [Enumerator] Enumerator for the scraped articles
        def each
          return enum_for(:each) unless block_given?

          SemanticHtml.anchor_tag_selector_pairs.each do |tag_name, selector|
            parsed_body.css(selector).each do |selected_tag|
              article_tag = SemanticHtml.find_tag_in_ancestors(selected_tag, tag_name)
              article_hash = Extractor.new(article_tag, url: @url).call

              yield article_hash if article_hash
            end
          end
        end
      end
    end
  end
end