Converts params that appear in a Rails log to HTTP GET/POST params

convert_params.rb

require 'json'
require 'cgi'

def convert(data)
  params = JSON.parse(data.gsub('=>', ':'))
  [].tap do |out|
    walk_hash(params, out, [])
  end.join('&')
end

def walk_hash(hash, out, prefixes)
  hash.each_pair do |key, val|
    if val.is_a?(Hash)
      walk_hash(val, out, prefixes + [key])
    elsif val.is_a?(Array)
      val.each do |elem|
        out << "#{format_prefixes(prefixes + [key])}[]=#{CGI.escape(val.to_s)}"
      end
    else
      out << "#{format_prefixes(prefixes + [key])}=#{CGI.escape(val.to_s)}"
    end
  end
end

def format_prefixes(prefixes)
  if prefixes.empty?
    ''
  else
    "#{prefixes.first}#{prefixes[1..-1].map { |p| "[#{p}]" }.join}"
  end
end

params = '{"user"=>{"first_name"=>"[FILTERED]", "referral"=>["1234"], "timezone_offset_minutes"=>-120, "locale"=>"en", "date_of_birth"=>"2000-1-1", "unique_name_is_unspecified"=>"[FILTERED]", "assignment_id"=>"abc123", "password"=>"[FILTERED]", "send_email"=>true, "email_address"=>"[email protected]"}, "assignment_id"=>"def456c", "client_secret"=>"fakefakefake", "client_id"=>"blarg"}'
puts convert(params)

# prints:
# user[first_name]=%5BFILTERED%5D&user[referral][]=%5B%221234%22%5D&user[timezone_offset_minutes]=-120&user[locale]=en&user[date_of_birth]=2000-1-1&user[unique_name_is_unspecified]=%5BFILTERED%5D&user[assignment_id]=abc123&user[password]=%5BFILTERED%5D&user[send_email]=true&user[email_address]=foo%40bar.com&assignment_id=def456c&client_secret=fakefakefake&client_id=blarg