Challenge #12: Is it a valid copy?

At the North Pole, they still use paper photocopiers. The elves use them to copy the letters that children send to Santa so they can send them to all the gift departments.

However, they are very old and don’t work very well. Every time they make a copy, the quality of the copy slightly decreases, a phenomenon known as generational loss.

You need to detect if one letter is a copy of another. The letters are very long and you can’t read them, but you can compare them with an algorithm.

There’s a big probability that a character would degrade in each copy (it doesn't always happen!). And when it does, the rule it follows is:

• The characters from A to Z degrade from uppercase to lowercase (A-Z ⇒ a-z)
• Letters degrade in a series of characters in this order: a-z ⇒ # ⇒ + ⇒ : ⇒ . ⇒
• Once the letters have degraded into the symbols, they can continue to degrade.
• Note that the last one is a blank space, not an empty character.
• Characters that are not letters (like digits) do not degrade.

Knowing this and receiving the original letter and the copy, you must determine if the copy is a copy of the original.

checkIsValidCopy('Santa Claus is coming', 'sa#ta cl#us is comin#') // true
checkIsValidCopy('Santa Claus is coming', 'p#nt: cla#s #s c+min#') // false (for the initial p)
checkIsValidCopy('Santa Claus', 's#+:. c:. s') // true
checkIsValidCopy('Santa Claus', 's#+:.#c:. s') // false (there is a # where it should not be)

To understand how photocopies work and their degradation, look at this example:

original:  'Santa Claus'
1st copy:  'santa cla#s'
2nd copy:  'sa#t# cl#+s'
3rd copy:  'sa+## c#+:s'
4th copy:  's#++. c+:.s'
5th copy:  's#+:. c:. s'

Therefore s#+:. c+:++ is a valid copy of Santa Claus. And, as you can see, the degradation of the letters does not occur in a specific order, it is random.

Based on the CodeWars challenge Photocopy decay