class Bundler::EnvironmentPreserver

def self.env_to_hash(env)
  to_hash = env.to_hash
  return to_hash unless Gem.win_platform?
  to_hash.each_with_object({}) {|(k,v), a| a[k.upcase] = v }
end

def self.from_env
  new(env_to_hash(ENV), BUNDLER_KEYS)
end

def backup
  env = @original.clone
  @keys.each do |key|
    value = env[key]
    if !value.nil? && !value.empty?
      env[@prefix + key] ||= value
    elsif value.nil?
      env[@prefix + key] ||= INTENTIONALLY_NIL
    end
  end
  env
end

def initialize(env, keys)
  @original = env
  @keys = keys
  @prefix = BUNDLER_PREFIX
end

def replace_with_backup
  unless Gem.win_platform?
    ENV.replace(backup)
    return
  end
  # Fallback logic for Windows below to workaround
  # https://bugs.ruby-lang.org/issues/16798. Can be dropped once all
  # supported rubies include the fix for that.
  ENV.clear
  backup.each {|k, v| ENV[k] = v }
end

def restore
  env = @original.clone
  @keys.each do |key|
    value_original = env[@prefix + key]
    next if value_original.nil? || value_original.empty?
    if value_original == INTENTIONALLY_NIL
      env.delete(key)
    else
      env[key] = value_original
    end
    env.delete(@prefix + key)
  end
  env
end