use strum::{Display, EnumString};

/// The encryption method.
#[non_exhaustive]
#[allow(missing_docs)]
#[derive(Ord, PartialOrd, Debug, Clone, Copy, PartialEq, Eq, Hash, Display, EnumString)]
#[strum(serialize_all = "SCREAMING-KEBAB-CASE")]
pub enum EncryptionMethod {
    /// The [`MediaSegment`]s are completely encrypted using the Advanced
    /// Encryption Standard ([AES-128]) with a 128-bit key, Cipher Block
    /// Chaining (CBC), and [Public-Key Cryptography Standards #7 (PKCS7)]
    /// padding.
    ///
    /// CBC is restarted on each segment boundary, using either the
    /// Initialization Vector (IV) or the Media Sequence Number as the IV
    ///
    /// ```
    /// # let media_sequence_number = 5;
    /// # assert_eq!(
    /// format!("0x{:032x}", media_sequence_number)
    /// # , "0x00000000000000000000000000000005".to_string());
    /// ```
    ///
    /// [`MediaSegment`]: crate::MediaSegment
    /// [AES-128]: http://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.197.pdf
    /// [Public-Key Cryptography Standards #7 (PKCS7)]: https://tools.ietf.org/html/rfc5652
    #[strum(serialize = "AES-128")]
    Aes128,
    /// The [`MediaSegment`]s contain media samples, such as audio or video,
    /// that are encrypted using the Advanced Encryption Standard ([`AES-128`]).
    ///
    /// How these media streams are encrypted and encapsulated in a segment
    /// depends on the media encoding and the media format of the segment.
    ///
    /// `fMP4` [`MediaSegment`]s are encrypted using the `cbcs` scheme of
    /// [Common Encryption].
    /// Encryption of other [`MediaSegment`] formats containing [H.264], [AAC],
    /// [AC-3], and Enhanced [AC-3] media streams is described in the
    /// [HTTP Live Streaming (HLS) SampleEncryption specification].
    ///
    /// [`MediaSegment`]: crate::MediaSegment
    /// [`AES-128`]: http://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.197.pdf
    /// [Common Encryption]: https://tools.ietf.org/html/rfc8216#ref-COMMON_ENC
    /// [H.264]: https://tools.ietf.org/html/rfc8216#ref-H_264
    /// [AAC]: https://tools.ietf.org/html/rfc8216#ref-ISO_14496
    /// [AC-3]: https://tools.ietf.org/html/rfc8216#ref-AC_3
    /// [HTTP Live Streaming (HLS) SampleEncryption specification]:
    /// https://tools.ietf.org/html/rfc8216#ref-SampleEnc
    SampleAes,
}

#[cfg(test)]
mod tests {
    use super::*;
    use pretty_assertions::assert_eq;

    #[test]
    fn test_display() {
        assert_eq!(EncryptionMethod::Aes128.to_string(), "AES-128".to_string());
        assert_eq!(
            EncryptionMethod::SampleAes.to_string(),
            "SAMPLE-AES".to_string()
        );
    }

    #[test]
    fn test_parser() {
        assert_eq!(
            EncryptionMethod::Aes128,
            "AES-128".parse::<EncryptionMethod>().unwrap()
        );

        assert_eq!(
            EncryptionMethod::SampleAes,
            "SAMPLE-AES".parse::<EncryptionMethod>().unwrap()
        );

        assert!("unknown".parse::<EncryptionMethod>().is_err());
    }
}