import Foundation
let pattern = #"(?<!ca.)(?<!vs.)(?<!\w\.\w.)(?<![A-Z][a-z]\.)(?<![A-Z][a-z][a-z]\.)(?<![A-Z][a-z][a-z][a-z]\.)((?<=[.!?])|(?<=[.!?][\'"]))[\s]{1,20}((?=[A-Z])|(?=[0-9])|(?=\"))"#
let regex = try! NSRegularExpression(pattern: pattern)
let testString = #""#
let stringRange = NSRange(location: 0, length: testString.utf16.count)
let substitutionString = #"\n\n"#
let result = regex.stringByReplacingMatches(in: testString, range: stringRange, withTemplate: substitutionString)
print(result)
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Swift 5.2, please visit: https://developer.apple.com/documentation/foundation/nsregularexpression