Cache the test app to S3 on Travis

.travis.yml

@@ -1,10 +1,11 @@
 language: ruby
 install:
-  - time ./script/bundle_cache download
-  - time bundle install --without development --path=~/.bundle
-  - time ./script/bundle_cache upload
-script:
+  - time ./script/travis_cache download_bundle
+  - time bundle install --without development --path=./bundle
+  - time ./script/travis_cache download_app
   - time bundle exec rake setup
+  - time ./script/travis_cache upload
+script:
   - time bundle exec rake test_with_coveralls
 rvm:
   - 1.9.3

script/travis_cache

@@ -0,0 +1,99 @@
+#!/usr/bin/env ruby
+
+require 'base64'
+require 'digest'
+require 'openssl'
+require 'shellwords'
+
+URL    = 'https://s3.amazonaws.com/ActiveAdmin'
+PREFIX = "ruby_#{RUBY_VERSION}-rails_#{ENV.fetch 'RAILS'}-"
+ID     = ENV.fetch 'AWS_S3_ID'
+SECRET = ENV.fetch 'AWS_S3_SECRET'
+
+def download_bundle
+  s3 :save, file: 'bundle.sha2', as: 'remote_bundle.sha2'
+  s3 :save, file: 'bundle.tgz',  as: 'remote_bundle.tgz', untar: true
+end
+
+# Don't use an existing archive if the Gemfile.lock changed
+def download_app
+  s3 :save, file: 'app.sha2', as: 'remote_app.sha2'
+  if !digest_changed?('Gemfile.lock', 'remote_bundle.sha2', 'bundle.sha2') &&
+     !digest_changed?('spec/support', 'remote_app.sha2',    'app.sha2')
+    s3 :save, file: 'app.tgz', as: 'remote_app.tgz', untar: 'spec'
+  end
+end
+
+def upload
+  [ ['Gemfile.lock', 'bundle', 'bundle'],
+    ['spec/support', 'app',    'spec/rails']
+  ].each do |to_check, name, to_save|
+    puts "=> Checking #{to_check} for changes"
+    if digest_changed? to_check, "remote_#{name}.sha2", "#{name}.sha2"
+      puts "  => Changes found"
+
+      puts "  => Creating an archive"
+      `tar -cjf #{to_save} #{name}.tgz`
+
+      puts "  => Uploading a new archive"
+      s3 :upload, file: "#{name}.tgz"
+      s3 :upload, file: "#{name}.sha2"
+    else
+      puts "  => There were no changes, doing nothing"
+    end
+  end
+end
+
+def digest_changed?(to_check, old_digest_file, new_digest_file)
+  if File.exists? new_digest_file
+    digest = File.read new_digest_file
+  else
+    # Supports a single file, as well as a folder
+    files   = Dir[to_check, "#{to_check}/**/*"].reject{ |f| File.directory? f }
+    content = files.map{ |f| File.read f }.join
+    digest  = Digest::SHA2.hexdigest content
+    File.write new_digest_file, digest
+  end
+
+  old_digest = File.read old_digest_file if File.exists? old_digest_file
+
+  digest != old_digest
+end
+
+def sign(secret, to_sign, digest = 'sha1')
+  Base64.strict_encode64 OpenSSL::HMAC.digest OpenSSL::Digest.new(digest), secret, to_sign
+end
+
+# s3 :list
+# s3 :upload, file: 'foo'
+# s3 :find,   file: 'foo'
+# s3 :save,   file: 'foo', as: 'bar'
+# s3 :save,   file: 'foo', untar: true
+# s3 :save,   file: 'foo', untar: 'another_directory'
+def s3(action, options = {})
+  verb      = {list: :get, upload: :put, find: :get, save: :get}.fetch action
+  file      = PREFIX + options.fetch(:file) unless action == :list
+  extra_arg = {
+    upload: ->{ %[-T "#{file}"] },
+    save:   ->{ %[-o "#{options[:as]}"] if options[:as] }
+              }[action].call
+  if options[:untar]
+    do_after = "&& tar -xf #{options[:as] || file}"
+    do_after << " -C #{options[:untar]}" if options[:untar].is_a? String
+  end
+
+  now       = Time.now.strftime "%a, %d %b %Y %H:%M:%S %z"
+  signature = sign SECRET, "#{verb.upcase}\n\n\n#{now}\n/ActiveAdmin/#{file}"
+  headers   = ["Authorization: AWS #{ID}:#{signature}", "Date: #{now}"].map do |h|
+    "-H #{Shellwords.escape h}"
+  end.join ' '
+
+  output = `curl -f #{headers} #{extra_arg} #{URL}/#{file} #{do_after}`
+  [$?.success?, output]
+end
+
+if %w[download_bundle download_app upload].include? ARGV[0]
+  send ARGV[0]
+else
+  raise "unexpected argument(s): #{ARGV}"
+end