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@conroywhitney
Created February 20, 2021 17:18
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Ruby on Rails implementation of purging AMP cache (https://developers.google.com/amp/cache/update-cache)
# app/models/amp_purge.rb
#
# frozen_string_literal: true
#
# Ruby on Rails implementation of purging AMP cache
# https://developers.google.com/amp/cache/update-cache
#
# Replace "example" with your domain
#
# Run like:
# $ rails c
# > AmpPurge.new("/foo/bar.amp").purge
#
# Open the "Signed URL" in your browser
# You should see an OK response
require "base64"
require "openssl"
class AmpPurge
attr_accessor :article_path
def initialize(article_path)
@article_path = article_path
end
def purge
puts "Unsigned Path ----------------"
puts unsigned_path
puts "Valid Signature? -------------"
puts public_key.verify(digest, signature, unsigned_path)
puts "Signed URL -------------------"
puts signed_url
end
private
def base64_signature
Base64.urlsafe_encode64(signature)
end
def base_url
"https://www-example-com.cdn.ampproject.org"
end
def digest
OpenSSL::Digest::SHA256.new
end
def params
{
amp_action: "flush",
amp_ts: Time.now.utc.to_i
}
end
def private_key
OpenSSL::PKey::RSA.new(
File.read(Rails.root.join("amp-private-key.pem"))
)
end
def public_key
OpenSSL::PKey::RSA.new(
File.read(Rails.root.join("amp-public-key.pem"))
)
end
def signature
private_key.sign(digest, unsigned_path)
end
def signed_url
"#{base_url}#{unsigned_path}&amp_url_signature=#{base64_signature}"
end
def unsigned_path
"/update-cache/c/s/www.example.com#{article_path}?#{params.to_param}"
end
end
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