module MeowTest
  Failure = Class.new(StandardError)

  @tests = []

  class << self
    attr_reader :tests, :last_result

    def test(name, &block)
      @tests << [name, block]
    end

    def assert(value, message = "Expected value to be truthy")
      raise Failure, message unless value
    end

    def refute(value, message = "Expected value to be falsey")
      raise Failure, message if value
    end

    def assert_equal(expected, actual, message = nil)
      return if expected == actual

      detail = "Expected #{expected.inspect}, got #{actual.inspect}"
      raise Failure, [message, detail].compact.join(": ")
    end

    def assert_empty(value, message = nil)
      assert(value.empty?, message || "Expected #{value.inspect} to be empty")
    end

    def run!
      failures = []
      @tests.each do |name, test|
        test.call
        puts "PASS #{name}"
      rescue StandardError => error
        failures << [name, error]
        puts "FAIL #{name}: #{error.class}: #{error.message}"
      end

      @last_result = {
        :tests => @tests.length,
        :passed => @tests.length - failures.length,
        :failures => failures.length,
        :failure_details => failures.map { |name, error| "#{name}: #{error.class}: #{error.message}" }
      }
      puts "#{@last_result[:passed]}/#{@last_result[:tests]} tests passed"
      raise Failure, @last_result[:failure_details].join("\n") unless failures.empty?

      @last_result
    end
  end
end