#[cfg(feature = "crypto")]
mod crypto {
    use openssl::{error::ErrorStack, md::Md, pkey::Id, pkey_ctx::PkeyCtx, version::version};

    /// Performs HKDF-SHA-256; copy of version from `./src/crypto.rs`.
    fn hkdf_sha_256<const N: usize>(salt: &[u8], ikm: &[u8]) -> Result<[u8; N], ErrorStack> {
        let mut output = [0; N];
        let mut ctx = PkeyCtx::new_id(Id::HKDF)?;
        ctx.derive_init()?;
        ctx.set_hkdf_md(Md::sha256())?;
        ctx.set_hkdf_salt(salt)?;
        ctx.set_hkdf_key(ikm)?;
        ctx.derive(Some(&mut output)).unwrap();
        Ok(output)
    }

    pub fn test_openssl() {
        // Having a working hkdf_sha_256 implementation is essential for some parts
        // of the library functioning. We should fail early if something goes wrong.
        //
        // Empty IKM fails (with malloc error) unless you have OpenSSL 3.0.0 to pull
        // in this patch: https://github.com/openssl/openssl/pull/12826
        //
        // caBLE uses empty IKM.
        let salt = [
            0x30, 0x7a, 0x70, 0x6e, 0x63, 0x38, 0x2e, 0x8e, 0x9d, 0x46, 0xcc, 0xdb, 0xc, 0xeb,
            0xed, 0x5c, 0x2b, 0x19, 0x28, 0xc5, 0xae, 0x2d, 0xee, 0x63, 0x52, 0xe1, 0x30, 0xac,
            0xe1, 0xf7, 0x4f, 0x44,
        ];
        let expected = [
            0x1f, 0xba, 0x3c, 0xce, 0x17, 0x62, 0x2c, 0x68, 0x26, 0x8d, 0x9f, 0x75, 0xb5, 0xa8,
            0xa3, 0x35, 0x1b, 0x51, 0x7f, 0x9, 0x6f, 0xb5, 0xe2, 0x94, 0x94, 0x1a, 0xf7, 0xe3,
            0xa6, 0xa8, 0xd6, 0xe1, 0xe3, 0x4f, 0x1a, 0xa3, 0x74, 0x72, 0x38, 0xc0, 0x4d, 0x3b,
            0xd2, 0x5e, 0x7, 0xef, 0x1b, 0x35, 0xfe, 0xf3, 0x59, 0x0, 0xd, 0x75, 0x56, 0x15, 0xcd,
            0x85, 0xbe, 0x27, 0xcf, 0xc8, 0x7, 0xd1,
        ];

        let r: Result<[u8; 64], _> = hkdf_sha_256(&salt, &[]);
        if !matches!(r, Ok(actual) if actual == expected) {
            println!(
                r#"
Your version of OpenSSL did not perform HKDF-SHA-256 with a zero-length
secret correctly, because of an OpenSSL bug. This issue will cause
webauthn-authenticator-rs to malfunction.

Please upgrade to OpenSSL v3.0.0 or later.
"#
            );
            match r {
                Ok(actual) => {
                    println!("Diagnostic: Result mismatched.");
                    println!("Expected: {expected:02x?}");
                    println!("Actual  : {actual:02x?}");
                }
                Err(e) => {
                    println!("Diagnostic: OpenSSL error: {e:?}");
                }
            }
            println!();
            println!("OpenSSL version string: {}", version());
            panic!("The installed version of OpenSSL is unusable.");
        }
    }
}

fn main() {
    #[cfg(feature = "crypto")]
    crypto::test_openssl();
}