#!/usr/bin/env ruby

require 'net/http'
require 'uri'
require 'nokogiri'
require 'set'

# Method to fetch and parse HTML from a URL
def fetch_html(url)
  response = Net::HTTP.get_response(URI(url))
  response.body if response.is_a?(Net::HTTPSuccess)
rescue StandardError => e
  puts "Error fetching #{url}: #{e.message}"
  nil
end

# Method to find and check links on a page
def check_links(url, domain)
  html = fetch_html(url)
  return unless html

  checked = Set.new
  broken = Set.new

  document = Nokogiri::HTML(html)
  links = document.css('a').map { |link| link['href'] }.compact

  internal_links = links.select do |link|
    link.start_with?('/') || link.start_with?('./') || URI(link).host == domain
  end
  puts "Internal links: #{internal_links}"

  internal_links.uniq.each do |link|
    full_url = link.start_with?('/') || link.start_with?('./') ? "#{url}#{link}" : link
    full_url.sub!('./', '/')
    next if checked.include?(full_url)

    broken << full_url unless check_link(full_url)
    checked << full_url
  end

  broken
end

# Method to check if a link is broken
def check_link(url)
  uri = URI(url)
  response = Net::HTTP.get_response(uri)

  if response.is_a?(Net::HTTPSuccess)
    puts "Working link: #{url}"
    true
  else
    puts "Broken link: #{url} (HTTP #{response.code})"
    false
  end
rescue StandardError => e
  puts "Error checking #{url}: #{e.message}"
  false
end

# Main program
if ARGV.length != 1
  puts 'Usage: ruby brokenlinkfinder.rb <URL>'
  exit
end

start_url = ARGV.first
domain = URI(start_url).host

check_links(start_url, domain).each do |broken|
  puts "Broken: #{broken}"
end