# frozen_string_literal: true

require_relative '../../lib/gitlab/utils/markdown'

module HamlLint
  class Linter
    # This class is responsible for detection of help_page_path helpers
    # with incorrect links or anchors
    class DocumentationLinks < Linter
      include ::HamlLint::LinterRegistry
      include ::Gitlab::Utils::Markdown

      DOCS_DIRECTORY = File.join(File.expand_path('../..', __dir__), 'doc')

      HELP_PATH_LINK_PATTERN = <<~PATTERN
      `(send nil? {:help_page_url :help_page_path} $...)
      PATTERN

      MARKDOWN_HEADER = %r{\A\#{1,6}\s+(?<header>.+)\Z}.freeze

      def visit_script(node)
        check(node)
      end

      def visit_silent_script(node)
        check(node)
      end

      def visit_tag(node)
        check(node)
      end

      private

      def check(node)
        match = extract_link_and_anchor(node)

        return if match.empty?

        path_to_file = detect_path_to_file(match[:link])

        unless File.file?(path_to_file)
          record_lint(node, "help_page_path points to the unknown location: #{path_to_file}")
          return
        end

        unless correct_anchor?(path_to_file, match[:anchor])
          record_lint(node, "anchor (#{match[:anchor]}) is missing in: #{path_to_file}")
        end
      end

      def extract_link_and_anchor(node)
        ast_tree = fetch_ast_tree(node)

        return {} unless ast_tree

        link_match, attributes_match = ::RuboCop::NodePattern.new(HELP_PATH_LINK_PATTERN).match(ast_tree)

        { link: fetch_link(link_match), anchor: fetch_anchor(attributes_match) }.compact
      end

      def fetch_ast_tree(node)
        # Sometimes links are provided via data attributes in html tag
        return node.parsed_attributes.syntax_tree if node.type == :tag

        node.parsed_script.syntax_tree
      end

      def detect_path_to_file(link)
        path = File.join(DOCS_DIRECTORY, link)
        path += '.md' unless path.end_with?('.md')
        path
      end

      def fetch_link(link_match)
        return unless link_match && link_match.str_type?

        link_match.value
      end

      def fetch_anchor(attributes_match)
        return unless attributes_match

        attributes_match.each_pair do |pkey, pvalue|
          break pvalue.value if pkey.value == :anchor
        end
      end

      def correct_anchor?(path_to_file, anchor)
        return true unless anchor

        File.open(path_to_file).any? do |line|
          result = line.match(MARKDOWN_HEADER)

          string_to_anchor(result[:header]) == anchor if result
        end
      end
    end
  end
end