The die is cast!

Your task in this kata is to write a "dice roller" that interprets a subset of dice notation.

Description

In most role-playing games, die rolls required by the system are given in the form AdX. A and X are variables, separated by the letter d, which stands for die or dice.

• A is the number of dice to be rolled (usually omitted if 1).
• X is the number of faces of each die.

Here are some examples of input:

'd6' => // One 6-sided die
'2d4' => // Two 4-sided dice

Modifiers

As an addition to the above rules the input may also contain modifiers in the form +N or -N where N is an integer.

Here are some examples of input containing modifiers:

'd3+4' => // One 3-sided die plus 4 (will be in range 5 -> 7)
'd3+4-1' => // One 3-sided die plus 4 minus 1 (will be in range 4 -> 6)

Modifiers must be applied after all dice has been summed up.

Output

Your function must support two types of output depending on the second argument; verbose and summed.

Summed output

If the verbose flag isn't set your function should sum up all the dice and modifiers and return the result as an integer.

Verbose output

With the verbose flag your function should return an object/hash containing an array (dice) with all the dice rolls, and a integer (modifier) containing the sum of the modifiers which defaults to zero.

Example of verbose output:

roll('3d7 +3 -2', true) // => { dice: [ 6, 4, 5 ], modifier: 1 }

Invalid input

Here are some examples of invalid inputs:

'' // Empty
{} // Not a string
'abc' // Not dice notation
'2d6+3 abc' // Contains extra bytes
'abc 2d6+3' // Contains extra bytes
'2d6++4' // Invalid modifiers

Additional information

• Your solution should ignore all whitespace.
• roll should return false for invalid input.