discourse/lib/retrieve_title.rb

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require_dependency 'final_destination'
module RetrieveTitle
class ReadEnough < StandardError; end
def self.crawl(url)
extract_title(fetch_beginning(url))
rescue Exception
# If there was a connection error, do nothing
end
def self.extract_title(html)
title = nil
if doc = Nokogiri::HTML(html)
title = doc.at('title')&.inner_text
# A horrible hack - YouTube uses `document.title` to populate the title
# for some reason. For any other site than YouTube this wouldn't be worth it.
if title == "YouTube" && html =~ /document\.title *= *"(.*)";/
title = Regexp.last_match[1].sub(/ - YouTube$/, '')
end
if !title && node = doc.at('meta[property="og:title"]')
title = node['content']
end
end
if title.present?
title.gsub!(/\n/, ' ')
title.gsub!(/ +/, ' ')
title.strip!
return title
end
nil
end
private
def self.max_chunk_size(uri)
# Amazon and YouTube leave the title until very late. Exceptions are bad
# but these are large sites.
return 80 if uri.host =~ /amazon\.(com|ca|co\.uk|es|fr|de|it|com\.au|com\.br|cn|in|co\.jp|com\.mx)$/
return 300 if uri.host =~ /youtube\.com$/ || uri.host =~ /youtu.be/
# default is 10k
10
end
# Fetch the beginning of a HTML document at a url
def self.fetch_beginning(url)
fd = FinalDestination.new(url)
uri = fd.resolve
return "" unless uri
result = ""
streamer = lambda do |chunk, _, _|
result << chunk
# Using exceptions for flow control is really bad, but there really seems to
# be no sane way to get a stream to stop reading in Excon (or Net::HTTP for
# that matter!)
raise ReadEnough.new if result.size > (max_chunk_size(uri) * 1024)
end
Excon.get(uri.to_s, response_block: streamer, read_timeout: 20, headers: fd.request_headers)
result
rescue Excon::Errors::SocketError => ex
return result if ex.socket_error.is_a?(ReadEnough)
raise
rescue ReadEnough
result
end
end