class LinkCheck

def check_schemes(link, line)
  case link.scheme
  when 'mailto'
    handle_mailto(link, line)
  when 'tel'
    handle_tel(link, line)
  when 'http'
    return unless @options[:enforce_https]
    add_issue("#{link.href} is not an HTTPS link", line: line)
  end
end

def external_link_check(link, line)
  if !link.exists?
    add_issue("trying to find hash of #{link.href}, but #{link.absolute_path} does not exist", line: line)
  else
    target_html = create_nokogiri link.absolute_path
    unless hash_check target_html, link.hash
      add_issue("linking to #{link.href}, but #{link.hash} does not exist", line: line)
    end
  end
end

def handle_hash(link, line)
  if link.internal?
    unless hash_check @html, link.hash
      add_issue("linking to internal hash ##{link.hash} that does not exist", line: line)
    end
  elsif link.external?
    external_link_check(link, line)
  end
end

def handle_mailto(link, line)
  if link.path.empty?
    add_issue("#{link.href} contains no email address", line: line)
  elsif !link.path.include?('@')
    add_issue("#{link.href} contains an invalid email address", line: line)
  end
end

def handle_tel(link, line)
  add_issue("#{link.href} contains no phone number", line: line) if link.path.empty?
end

def hash_check(html, href_hash)
  decoded_href_hash = URI.decode(href_hash)
  html.xpath("//*[case_insensitive_equals(@id, '#{href_hash}')]", \
             "//*[case_insensitive_equals(@name, '#{href_hash}')]", \
             "//*[case_insensitive_equals(@id, '#{decoded_href_hash}')]", \
             "//*[case_insensitive_equals(@name, '#{decoded_href_hash}')]", \
             XpathFunctions.new).length > 0
end

def missing_href?
  blank?(@link.href) && blank?(@link.name) && blank?(@link.id)
end

def placeholder?
  (!blank?(@link.id) || !blank?(@link.name)) && @link.href.nil?
end

def run
  @html.css('a, link').each do |node|
    @link = create_element(node)
    line = @node.line
    next if @link.ignore?
    next if placeholder?
    next if @link.allow_hash_href? && @link.href == '#'
    # is it even a valid URL?
    unless @link.valid?
      add_issue("#{@link.href} is an invalid URL", line: line)
      next
    end
    check_schemes(@link, line)
    # is there even an href?
    if missing_href?
      # HTML5 allows dropping the href: http://git.io/vBX0z
      next if @html.internal_subset.name == 'html' && @html.internal_subset.external_id.nil?
      add_issue('anchor has no href attribute', line: line)
      next
    end
    # intentionally here because we still want valid? & missing_href? to execute
    next if @link.non_http_remote?
    # does the file even exist?
    if @link.remote?
      add_to_external_urls(@link.href, line)
      next
    elsif !@link.internal? && !@link.exists?
      add_issue("internally linking to #{@link.href}, which does not exist", line: line)
    end
    # does the local directory have a trailing slash?
    if @link.unslashed_directory? @link.absolute_path
      add_issue("internally linking to a directory #{@link.absolute_path} without trailing slash", line: line)
      next
    end
    # verify the target hash
    handle_hash(@link, line) if @link.hash
  end
  external_urls
end