Check if contains four digits year number in apple script - regex

Question

Now I am working on a file-rename-applescript-project. Here is an example: The.Fantasy.1997.DVDRip.XviD-ETRG.avi.
Now I want to check if the filename contains four digits year number. In this case, it's 1997. The year number MUST begin with 19 or 20 and MUST contain four digits.
If the result is true I will do something, if false I will do something else.
I try to use regex but can't find the solution. It's out of my range. Now I m looking for help here, Thanks a million.

Answer 1

If you want to avoid regex completely, do something like below, using text item delimiters:
(*
This first bit breaks the string up into a list of words by cutting the string
at the period delimiter.
*)
set tid to my text item delimiters
set my text item delimiters to "."
set bits_list to text items of file_name_string
set my text item delimiters to tid
(*
This repeat loop goes though the list of words and tests them (first) to see
if it can be converted to an integer, and (second) whether the number is between
1900 and 2100. If so, it chooses it as the year.
*)
repeat with this_item in bits_list
try
set possibleYear to this_item as integer
if possibleYear ≥ 1900 and possibleYear < 2100 then
-- do what you want with the year value here
exit repeat
end if
end try
end repeat
Of course, this will not work properly if there's a number in the name (e.g., "2001.A.Space.Odyssey.1968.avi") or if a file name has different delimiters (e.g., a space or a dash). But you'd run into those problems using regex as well, so...

Answer 2

Since you're only wishing to check whether or the filename contains a four-digit year within the range 1900-2099, you can do this very simply by defining a handler like so:
on hasYearInTitle(filmTitle as text)
repeat with yyyy from 1900 to 2099
if yyyy is in the filmTitle then return true
end repeat
return false
end hasYearInTitle
Then you can call this handler and pass it a film title, like so:
hasYearInTitle("The.Fantasy.1997.DVDRip.XviD-ETRG.avi") --> true
hasYearInTitle("The.Fantasy.197.DVDRip.XviD-ETRG.avi") --> false
hasYearInTitle("2001.A.Space.Odyssey.1968.avi") --> true
hasYearInTitle("2001.A.Space.Odyssey.avi") --> true (hm...)
As a side-note, films indexed by newznab servers follow a strict file-naming protocol that allow a media server (on your machine) to parse it easily and extract information quickly, pertaining to (as seen in your example file name): the film's title, the film's release date, the source material, the encoding quality, the encoding format (codec), the release group, and the containing file format.
Although some filenames contain more information, and some they should always appear in an set order. This makes them very simple to parse yourself should you need to, but if you're looking to create an organised media library, you would be best looking at using media server, of which there are excellent, freeware, long-standing software options available for macOS and pretty much any other operating system.

Answer 3

The regex .+\.(?:19:20)\d{2}\..+ should do it
The breakdown:
.+ 1 or more any characters
\. An actual dot
(?:19|20) The string "19" or "20" (non-capturing group)
\d{2} Exactly two digits
\. An actual dot
.+ 1 or more any characters