currency input validation

gistfile1.rb

# Managing potentially messy input from a free-form text input that's supposed to represent currency.
#
# Acceptable:
# 1
# 12
# 123
# 1234
# 1234.56
# $1
# $12
# $123
# $1234
# $1234.56
# $1,234
# $1,234.56
# $1,234,567.89
# .12
# $.12
#
# Unacceptable:
# 12$
# $
# .1
# 12.3
# 12,34
# nine thousand dollars and one cent


def cents_from_messy_currency_string(str)

  currency_format = /
    \A
    \s*    # leading spaces are fine
    \$?    # optional dollar sign
    \s*    # spaces after the dollar sign are fine
    (
      (\.\d{2})    #  .23
    |
      \d+(\.\d{2})?    #  1234, 1234.56
    |
      \d{1,3}(,\d{3})+(\.\d{2})?    # 1,000 123,000,000, 1,000.24
    )
    \s*    # trailing spaces are fine
    \Z
  /x

  return nil unless str =~ currency_format
  sanitized = str.gsub /[^0-9.]/, ''
  sanitized['.'] ? sanitized.sub('.', '').to_i : sanitized.to_i*100

end