calculateCharsetSize function
Calculates character set size for password entropy.
Implementation
int calculateCharsetSize(String input) {
bool hasLower = RegExp(r'[a-z]').hasMatch(input);
bool hasUpper = RegExp(r'[A-Z]').hasMatch(input);
bool hasDigits = RegExp(r'[0-9]').hasMatch(input);
bool hasSpecial = RegExp(r'[^a-zA-Z0-9]').hasMatch(input);
int size = 0;
if (hasLower) size += 26;
if (hasUpper) size += 26;
if (hasDigits) size += 10;
if (hasSpecial) size += 32; // Common special chars
return size;
}