module RSpec
  module Matchers
    module BuiltIn
      class ThrowSymbol
        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)
          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 e.message =~ /uncaught throw (`|\:)([a-zA-Z0-9_]*)(')?/
              other_exception = e
              raise
            end
            @caught_symbol = $2.to_sym
          rescue => other_exception
            raise
          ensure
            unless other_exception
              if @expected_symbol.nil?
                return !@caught_symbol.nil?
              else
                if @expected_arg.nil?
                  return @caught_symbol == @expected_symbol
                else
                  return (@caught_symbol == @expected_symbol) & (@caught_arg == @expected_arg)
                end
              end
            end
          end
        end

        def failure_message_for_should
          "expected #{expected} to be thrown, got #{caught}"
        end

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

        def description
          "throw #{expected}"
        end

        private

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

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

        def throw_description(symbol, arg)
          symbol_description = symbol.is_a?(String) ? symbol : symbol.inspect

          arg_description = if arg
                              " with #{arg.inspect}"
                            elsif @expected_arg && @caught_symbol == @expected_symbol
                              " with no argument"
                            else
                              ""
                            end

          symbol_description + arg_description
        end
      end
    end
  end
end