use clipbin_core::VideoCodec;

/// Official OBS hardware encoders for each codec, most preferred first.
///
/// Texture-based encoders come first because they take frames straight from
/// the GPU; their counterparts copy each frame through system memory. Software
/// encoders are deliberately absent: a codec without a working hardware
/// encoder is unavailable, never silently software-encoded.
pub fn hardware_candidates(codec: VideoCodec) -> &'static [&'static str] {
    #[cfg(windows)]
    return match codec {
        VideoCodec::H264 => &[
            "obs_nvenc_h264_tex",
            "h264_texture_amf",
            "obs_qsv11_v2",
            "obs_nvenc_h264_soft",
            "obs_qsv11_soft_v2",
            "h264_fallback_amf",
        ],
        VideoCodec::Hevc => &[
            "obs_nvenc_hevc_tex",
            "h265_texture_amf",
            "obs_qsv11_hevc",
            "obs_nvenc_hevc_soft",
            "obs_qsv11_hevc_soft",
            "h265_fallback_amf",
        ],
        VideoCodec::Av1 => &[
            "obs_nvenc_av1_tex",
            "av1_texture_amf",
            "obs_qsv11_av1",
            "obs_nvenc_av1_soft",
            "obs_qsv11_av1_soft",
            "av1_fallback_amf",
        ],
    };

    #[cfg(not(windows))]
    return match codec {
        VideoCodec::H264 => &[
            "obs_nvenc_h264_tex",
            "ffmpeg_vaapi_tex",
            "obs_nvenc_h264_soft",
            "ffmpeg_vaapi",
        ],
        VideoCodec::Hevc => &[
            "obs_nvenc_hevc_tex",
            "hevc_ffmpeg_vaapi_tex",
            "obs_nvenc_hevc_soft",
            "hevc_ffmpeg_vaapi",
        ],
        VideoCodec::Av1 => &[
            "obs_nvenc_av1_tex",
            "av1_ffmpeg_vaapi_tex",
            "obs_nvenc_av1_soft",
            "av1_ffmpeg_vaapi",
        ],
    };
}

/// Registered encoders for `codec`, in preference order.
///
/// Registration only means the plugin loaded. Whether the device can actually
/// encode is proven by starting an output; see `Recorder`.
pub fn registered_candidates<'a>(
    codec: VideoCodec,
    registered: &[impl AsRef<str>],
) -> Vec<&'a str> {
    hardware_candidates(codec)
        .iter()
        .copied()
        .filter(|id| registered.iter().any(|r| r.as_ref() == *id))
        .collect()
}

pub const ALL_CODECS: [VideoCodec; 3] = [VideoCodec::H264, VideoCodec::Hevc, VideoCodec::Av1];

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

    #[test]
    fn candidates_keep_preference_order_and_skip_unregistered() {
        let first = hardware_candidates(VideoCodec::Hevc)[0];
        let third = hardware_candidates(VideoCodec::Hevc)[2];
        let registered = [third, "obs_x264", first];
        assert_eq!(
            registered_candidates(VideoCodec::Hevc, &registered),
            [first, third]
        );
    }

    #[test]
    fn software_encoders_are_never_candidates() {
        for codec in ALL_CODECS {
            for id in hardware_candidates(codec) {
                assert!(
                    ![
                        "obs_x264",
                        "ffmpeg_svt_av1",
                        "ffmpeg_aom_av1",
                        "ffmpeg_openh264"
                    ]
                    .contains(id)
                );
            }
        }
    }
}