// client/src/input/camera.rs
#![forbid(unsafe_code)]

use anyhow::Result;
use anyhow::Context;
use gstreamer as gst;
use gstreamer_app as gst_app;
use gst::prelude::*;
use lesavka_common::lesavka::VideoPacket;

pub struct CameraCapture {
    pipeline: gst::Pipeline,
    sink:     gst_app::AppSink,
}

impl CameraCapture {
    pub fn new(device_fragment: Option<&str>) -> anyhow::Result<Self> {
        gst::init().ok();

        // Pick device
        let dev = device_fragment
            .and_then(Self::find_device)
            .unwrap_or_else(|| "/dev/video0".into());

        // let (enc, raw_caps) = Self::pick_encoder();
        // (NVIDIA → VA-API → software x264).
        let (enc, kf_prop, kf_val) = Self::choose_encoder();
        tracing::info!("📸 using encoder element: {enc}");
        let (src_caps, preenc) = match enc {
            "nvh264enc" => (
                "video/x-raw(memory:NVMM),format=NV12,width=1280,height=720",
                "nvvidconv !"
            ),
            "vaapih264enc" => (
                "video/x-raw,format=NV12,width=1280,height=720",
                "videoconvert !"
            ),
            _ => ("video/x-raw,width=1280,height=720", "videoconvert !"),
        };        

        // let desc = format!(
        //     "v4l2src device={dev} do-timestamp=true ! {raw_caps},width=1280,height=720 ! \
        //     videoconvert ! {enc} key-int-max=30 ! \
        //     h264parse config-interval=-1 ! \
        //     appsink name=asink emit-signals=true max-buffers=60 drop=true"
        // );
        // tracing::debug!(%desc, "📸 pipeline-desc");
        // Build a pipeline that works for any of the three encoders.
        //  * nvh264enc needs NVMM memory caps;
        //  * vaapih264enc wants system-memory caps;
        //  * x264enc needs the usual raw caps.
        let desc = format!(
            "v4l2src device={dev} do-timestamp=true ! {src_caps} ! \
             {preenc} {enc} {kf_prop}={kf_val} ! \
             h264parse config-interval=-1 ! video/x-h264,stream-format=byte-stream,alignment=au ! \
             queue max-size-buffers=30 leaky=downstream ! \
             appsink name=asink emit-signals=true max-buffers=60 drop=true"
        );
        tracing::info!(%enc, ?desc, "📸 using encoder element");

        let pipeline: gst::Pipeline = gst::parse::launch(&desc)
            .context("gst parse_launch(cam)")?
            .downcast::<gst::Pipeline>()
            .expect("not a pipeline");

        tracing::debug!("📸 pipeline built OK – setting PLAYING…");
        let sink: gst_app::AppSink = pipeline
            .by_name("asink")
            .expect("appsink element not found")
            .downcast::<gst_app::AppSink>()
            .expect("appsink down‑cast");

        pipeline.set_state(gst::State::Playing)?;
        tracing::info!("📸 webcam pipeline ▶️ device={dev}");

        Ok(Self { pipeline, sink })
    }

    pub fn pull(&self) -> Option<VideoPacket> {
        let sample = self.sink.pull_sample().ok()?;
        let buf    = sample.buffer()?;
        let map    = buf.map_readable().ok()?;
        let pts = buf.pts().unwrap_or(gst::ClockTime::ZERO).nseconds() / 1_000;
        Some(VideoPacket { id: 2, pts, data: map.as_slice().to_vec() })
    }

    /// Fuzzy‑match devices under `/dev/v4l/by-id`
    fn find_device(substr: &str) -> Option<String> {
        let dir = std::fs::read_dir("/dev/v4l/by-id").ok()?;
        for e in dir.flatten() {
            let p = e.path();
            if p.file_name()?.to_string_lossy().contains(substr) {
                if let Ok(target) = std::fs::read_link(&p) {
                    return Some(format!("/dev/{}", target.file_name()?.to_string_lossy()));
                }
            }
        }
        None
    }

    /// Cheap stub used when the web‑cam is disabled
    pub fn new_stub() -> Self {
        let pipeline = gst::Pipeline::new();
        let sink: gst_app::AppSink = gst::ElementFactory::make("appsink")
            .build()
            .expect("appsink")
            .downcast::<gst_app::AppSink>()
            .unwrap();
        Self { pipeline, sink }
    }

    #[allow(dead_code)]                       // helper kept for future heuristics
    fn pick_encoder() -> (&'static str, &'static str) {
        let encoders = &[
            ("nvh264enc",  "video/x-raw(memory:NVMM),format=NV12"),
            ("vaapih264enc","video/x-raw,format=NV12"),
            ("v4l2h264enc", "video/x-raw"),               // RPi, Jetson, etc.
            ("x264enc",     "video/x-raw"),               // software
        ];
        for (name, caps) in encoders {
            if gst::ElementFactory::find(name).is_some() {
                return (name, caps);
            }
        }
        // last resort – software
        ("x264enc", "video/x-raw")
    }

    fn choose_encoder() -> (&'static str, &'static str, &'static str) {
        match () {
            _ if gst::ElementFactory::find("nvh264enc").is_some() =>
                ("nvh264enc",  "gop-size",        "30"),
            _ if gst::ElementFactory::find("vaapih264enc").is_some() =>
                ("vaapih264enc","keyframe-period","30"),
            _ if gst::ElementFactory::find("v4l2h264enc").is_some() =>
                ("v4l2h264enc","idrcount",        "30"),
            _ => ("x264enc",  "key-int-max",     "30"),
        }
    }
}