feat: Add function to calculate checksum and last word of a manually generated mnemonic

src/lib.rs

@@ -529,6 +529,28 @@ impl Mnemonic {
  let (arr, len) = self.to_entropy_array();
  arr[0..len].to_vec()
  }
+
+ /// Calculates the final word (based on the checksum) of a manually generated mnemonic.
+ /// There are multiple valid checksums, the first one (alphabetically) is picked.
+ #[cfg(feature = "std")]
+ pub fn finalize_mnemonic<'a, S: Into<Cow<'a, str>>>(s: S) -> Result<Mnemonic, Error> {
+ let mut words = s.into();
+ Mnemonic::normalize_utf8_cow(&mut words);
+ let language = Mnemonic::language_of(&words)?;
+
+ for word in language.word_list() {
+ let potential_mnemonic = format!("{} {}", words, word);
+ match Mnemonic::parse_in_normalized(language, &potential_mnemonic) {
+ Ok(mnemonic) => return Ok(mnemonic),
+ Err(e) => match e {
+ Error::InvalidChecksum => {}, // Keep searching.
+ _ => return Err(e)
+ }
+ }
+ }
+ Err(Error::InvalidChecksum)
+ }
+
 }
 
 impl fmt::Display for Mnemonic {
@@ -1023,4 +1045,30 @@ mod tests {
  assert_eq!(seed, &mnemonic.to_seed(passphrase)[..], "failed vector: {}", mnemonic_str);
  }
  }
+
+ #[test]
+ fn test_finalize_mnemonic() {
+ let vectors = [
+ (
+ "ozone drill grab fiber curtain grace pudding thank cruise elder eight",
+ "about"
+ ),
+ (
+ "light rule cinnamon wrap drastic word pride squirrel upgrade then income fatal apart sustain crack supply proud",
+ "access"
+ ),
+ (
+ "hamster diagram private dutch cause delay private meat slide toddler razor book happy fancy gospel tennis maple dilemma loan word shrug inflict delay",
+ "balance"
+ ),
+ (
+ "あいこくしん　あいこくしん　あいこくしん　あいこくしん　あいこくしん　あいこくしん　あいこくしん　あいこくしん　あいこくしん　あいこくしん　あいこくしん",
+ "あおぞら"
+ )
+ ];
+
+ for vector in &vectors {
+ assert_eq!(Mnemonic::parse(format!("{} {}", vector.0, vector.1)), Mnemonic::finalize_mnemonic(vector.0));
+ }
+ }
 }