class RSpec::Matchers::BuiltIn::ThrowSymbol

def actual_result
  return "but was not a block" unless Proc === @block
  "got #{caught}"
end

def caught
  throw_description(@caught_symbol || 'nothing', @caught_arg)
end

def description
  "throw #{expected}"
end

def does_not_match?(given_proc)
  !matches?(given_proc) && Proc === given_proc
end

def expected(symbol_desc='a Symbol')
  throw_description(@expected_symbol || symbol_desc, @expected_arg)
end

def expects_call_stack_jump?
  true
end

def failure_message
  "expected #{expected} to be thrown, #{actual_result}"
end

def failure_message_when_negated
  "expected #{expected('no Symbol')}#{' not' if @expected_symbol} to be thrown, #{actual_result}"
end

def initialize(expected_symbol=nil, expected_arg=nil)
  @expected_symbol = expected_symbol
  @expected_arg = expected_arg
  @caught_symbol = @caught_arg = nil
end

def matches?(given_proc)
  @block = given_proc
  return false unless Proc === given_proc
  begin
    if @expected_symbol.nil?
      given_proc.call
    else
      @caught_arg = catch :proc_did_not_throw_anything do
        catch @expected_symbol do
          given_proc.call
          throw :proc_did_not_throw_anything, :nothing_thrown
        end
      end
      if @caught_arg == :nothing_thrown
        @caught_arg = nil
      else
        @caught_symbol = @expected_symbol
      end
    end
    # Ruby 1.8 uses NameError with `symbol'
    # Ruby 1.9 uses ArgumentError with :symbol
  rescue NameError, ArgumentError => e
    unless (match_data = e.message.match(/uncaught throw (`|\:)([a-zA-Z0-9_]*)(')?/))
      other_exception = e
      raise
    end
    @caught_symbol = match_data.captures[1].to_sym
  rescue => other_exception
    raise
  ensure
    # rubocop:disable Lint/EnsureReturn
    unless other_exception
      if @expected_symbol.nil?
        return !!@caught_symbol
      else
        if @expected_arg.nil?
          return @caught_symbol == @expected_symbol
        else
          return (@caught_symbol == @expected_symbol) && values_match?(@expected_arg, @caught_arg)
        end
      end
    end
    # rubocop:enable Lint/EnsureReturn
  end
end

def supports_block_expectations?
  true
end

def supports_value_expectations?
  false
end

def throw_description(symbol, arg)
  symbol_description = symbol.is_a?(String) ? symbol : description_of(symbol)
  arg_description = if arg
                      " with #{description_of arg}"
                    elsif @expected_arg && @caught_symbol == @expected_symbol
                      " with no argument"
                    else
                      ""
                    end
  symbol_description + arg_description
end