oauth2_utils 2.0.0

use crate::consts::{CV_DEFAULT_SIZE, CV_MAX_SIZE, CV_MIN_SIZE};
use crate::errors::CodeVerifierError;
use crate::urlsafe::{urlsafe_b64encode, urlsafe_token};
use sha2::{Digest, Sha256};

type CodeVerifierResult = Result<String, CodeVerifierError>;
/// Generates a random [code verifier](https://datatracker.ietf.org/doc/html/rfc7636#section-4.1)
/// string of a specified size.
///
/// ## Arguments:
///
/// `n`: The number of characters to generate.
/// <br>
/// ### PANICS !
/// if not between `43` & `128`. Defaults to `96` characters if no size is provided.
pub fn gen_code_verifier(n: Option<usize>) -> CodeVerifierResult {
    let size: usize = n.unwrap_or(CV_DEFAULT_SIZE);
    if size > CV_MAX_SIZE {
        return Err(CodeVerifierError::TooBig);
    }
    if size < CV_MIN_SIZE {
        return Err(CodeVerifierError::TooSmall);
    }
    Ok(urlsafe_token(size))
}

/// Generates a URL safe base64 encoded string from the code verifier.
///
/// ## Arguments:
///
/// `code_verifier`:  a random string that is generated by the client and used to create a code challenge.
pub fn gen_code_challenge(code_verifier: &str) -> String {
    urlsafe_b64encode(Sha256::digest(code_verifier))
}
#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_gen_code_verifier_default_size() {
        let code_verifier_result: CodeVerifierResult = gen_code_verifier(None);
        assert!(code_verifier_result.is_ok());
        let code_verifier = code_verifier_result.unwrap();
        assert_eq!(code_verifier.len(), CV_DEFAULT_SIZE);
    }

    #[test]
    fn test_gen_code_verifier_custom_size_within_range() {
        let custom_size: usize = 64;
        let code_verifier_result: CodeVerifierResult =
            gen_code_verifier(Some(custom_size));
        assert!(code_verifier_result.is_ok());
        let code_verifier = code_verifier_result.unwrap();
        assert_eq!(code_verifier.len(), custom_size);
    }

    #[test]
    fn test_gen_code_verifier_custom_size_too_small() {
        let custom_size: usize = CV_MIN_SIZE - 1;
        let code_verifier_result: CodeVerifierResult =
            gen_code_verifier(Some(custom_size));
        assert!(code_verifier_result.is_err()); // Ensure error occurred
        let err = code_verifier_result.err().unwrap();
        assert_eq!(err, CodeVerifierError::TooSmall);
    }

    #[test]
    fn test_gen_code_verifier_custom_size_too_large() {
        let custom_size: usize = CV_MAX_SIZE + 1;
        let code_verifier_result: CodeVerifierResult =
            gen_code_verifier(Some(custom_size));
        assert!(code_verifier_result.is_err());
        let err = code_verifier_result.err().unwrap();
        assert_eq!(err, CodeVerifierError::TooBig);
    }

    #[test]
    fn test_gen_code_challenge() {
        let code_verifier: &str = "foo_bar";
        let code_challenge: String = gen_code_challenge(code_verifier);

        let mut hasher = Sha256::new();
        hasher.update(code_verifier);
        let hash_result = hasher.finalize();
        let expected_challenge = urlsafe_b64encode(&hash_result);
        assert_eq!(code_challenge, expected_challenge);
    }
}