pub mod cipher_aead_aes_gcm;
pub mod cipher_aes_cm_hmac_sha1;

use bytes::Bytes;

use crate::error::Result;

///NOTE: Auth tag and AEAD auth tag are placed at the different position in SRTCP
///
///In non-AEAD cipher, the authentication tag is placed *after* the ESRTCP word
///(Encrypted-flag and SRTCP index).
///
///> AES_128_CM_HMAC_SHA1_80
///> | RTCP Header | Encrypted payload |E| SRTCP Index | Auth tag |
///>                                   ^               |----------|
///>                                   |                ^
///>                                   |                authTagLen=10
///>                                   aeadAuthTagLen=0
///
///In AEAD cipher, the AEAD authentication tag is embedded in the ciphertext.
///It is *before* the ESRTCP word (Encrypted-flag and SRTCP index).
///
///> AEAD_AES_128_GCM
///> | RTCP Header | Encrypted payload | AEAD auth tag |E| SRTCP Index |
///>                                   |---------------|               ^
///>                                    ^                              authTagLen=0
///>                                    aeadAuthTagLen=16
///
///See https://tools.ietf.org/html/rfc7714 for the full specifications.

/// Cipher represents a implementation of one
/// of the SRTP Specific ciphers.
pub(crate) trait Cipher {
    /// Get authenticated tag length.
    fn auth_tag_len(&self) -> usize;

    /// Retrieved RTCP index.
    fn get_rtcp_index(&self, input: &[u8]) -> usize;

    /// Encrypt RTP payload.
    fn encrypt_rtp(
        &mut self,
        payload: &[u8],
        header: &rtp::header::Header,
        roc: u32,
    ) -> Result<Bytes>;

    /// Decrypt RTP payload.
    fn decrypt_rtp(
        &mut self,
        payload: &[u8],
        header: &rtp::header::Header,
        roc: u32,
    ) -> Result<Bytes>;

    /// Encrypt RTCP payload.
    fn encrypt_rtcp(&mut self, payload: &[u8], srtcp_index: usize, ssrc: u32) -> Result<Bytes>;

    /// Decrypt RTCP payload.
    fn decrypt_rtcp(&mut self, payload: &[u8], srtcp_index: usize, ssrc: u32) -> Result<Bytes>;
}