api-rewrite.rb

require 'bundler/inline'

gemfile do
  source 'https://rubygems.org'
  gem 'ffast',
      git: 'https://github.com/jonatas/fast.git',
      require: 'fast'
end

[
  'client.read_all_streams_forward(count: 1)',
  'client.read_all_streams_forward(count: 1, start: :head)'
].each do |sample|
  ast = Fast.ast(sample)
  new_code = Fast.replace ast,
                          '(send (send nil client) $_ $... )',
                          ->(node, captures) {
                            method, args = captures
                            new_method_call = 'read'
                            new_method_call << '.backward' if method == :read_all_streams_backward
                            key_values = args.children.map { |e| Fast.capture(e, '(pair (sym $_) (_ $_)))') }
                            key_values.each do |key, value|
                              new_method_call << '.'
                              new_method_call << case key
                                                 when :count
                                                   'limit'
                                                 when :start
                                                   'from'
                                                 else
                                                   key.to_s
                                                 end
                              new_method_call << "(#{value.inspect})"
                            end

                            replace_range = node.location.selector
                            replace_range = replace_range.join(node.location.end) if node.location.end

                            replace(replace_range, new_method_call)
                          }
  puts "#{sample} => #{new_code}"
end