Function validate 

pub fn validate(
    code: &str,
    alphabet: &Alphabet,
    expected_length: usize,
    damm_table: &DammTable,
) -> ValidationResult

Validate a promotional code and return detailed result.

This function checks:

1. Code length matches expected length
2. All characters are in the alphabet
3. Damm check digit is correct

Arguments

• code - The code to validate (including check digit)
• alphabet - The alphabet used for the code
• expected_length - Expected total length (code_length + 1 for check digit)
• damm_table - Damm table for check digit validation

Returns

ValidationResult with detailed information about any validation failure.

Example

use promocrypt_core::{validate, Alphabet, DammTable, ValidationResult};

let alphabet = Alphabet::default_alphabet();
let damm = DammTable::new(alphabet.len());

let result = validate("INVALIDCODE", &alphabet, 10, &damm);
// result will indicate specific failure reason