use anyhow::Context;
use gstreamer as gst;
use gstreamer::prelude::*;
use gstreamer_app as gst_app;
use std::fs;
use lesavka_common::lesavka::VideoPacket;
use std::path::{Path, PathBuf};
use std::sync::{
    Arc,
    atomic::{AtomicBool, AtomicU64, Ordering},
};
use tracing::warn;

use crate::camera::{CameraCodec, CameraConfig};
use crate::video_support::{
    contains_idr, dev_mode_enabled, require_h264_decoder, require_hevc_decoder,
};

#[path = "webcam_sink/constructor.rs"]
mod constructor;
#[path = "webcam_sink/frame_handoff.rs"]
mod frame_handoff;
mod mjpeg_spool;

#[cfg(not(coverage))]
use gst::MessageView::{Error, StateChanged, Warning};

/// Push H.264 or MJPEG frames into the USB UVC gadget.
///
/// Inputs: a UVC device node and the negotiated camera configuration.
/// Outputs: a live `WebcamSink` that accepts `VideoPacket`s.
/// Why: the UVC sink owns the GStreamer pipeline details for gadget output so
/// the relay logic can focus on session lifecycle instead of media plumbing.
pub struct WebcamSink {
    appsrc: gst_app::AppSrc,
    pipe: gst::Pipeline,
    clock_aligned: AtomicBool,
    next_pts_us: AtomicU64,
    frame_step_us: u64,
    mjpeg_spool_path: Option<PathBuf>,
    direct_mjpeg_appsrc: Option<gst_app::AppSrc>,
    normalized_mjpeg_sink: Option<gst_app::AppSink>,
    hevc_mjpeg_appsrc: Option<gst_app::AppSrc>,
    decoded_mjpeg_sink: Option<gst_app::AppSink>,
    last_mjpeg_passthrough_bytes: AtomicU64,
    direct_mjpeg_max_bytes: usize,
    uvc_width: u16,
    uvc_height: u16,
    direct_mjpeg_profile_mismatch_seen: AtomicBool,
    last_decoded_mjpeg_bytes: AtomicU64,
    direct_mjpeg_normalize_bypassed: AtomicBool,
    normalized_mjpeg_miss_count: AtomicU64,
    normalized_mjpeg_memory_check_count: AtomicU64,
    decoded_mjpeg_miss_count: AtomicU64,
    decode_recovery_needs_irap: AtomicBool,
    #[cfg(not(coverage))]
    _bus_watch: Option<WebcamBusWatchHandle>,
}

fn uvc_sink_session_clock_align_enabled() -> bool {
    std::env::var("LESAVKA_UVC_SESSION_CLOCK_ALIGN")
        .ok()
        .map(|value| {
            let trimmed = value.trim();
            !(trimmed.eq_ignore_ascii_case("0")
                || trimmed.eq_ignore_ascii_case("false")
                || trimmed.eq_ignore_ascii_case("no")
                || trimmed.eq_ignore_ascii_case("off"))
        })
        .unwrap_or(true)
}

fn uvc_mjpeg_v4l2sink_io_mode() -> String {
    let value = std::env::var("LESAVKA_UVC_MJPEG_IO_MODE").unwrap_or_else(|_| "mmap".to_string());
    let trimmed = value.trim().to_ascii_lowercase();
    match trimmed.as_str() {
        "auto" | "rw" | "mmap" | "userptr" | "dmabuf" | "dmabuf-import" => trimmed,
        _ => {
            warn!(
                value,
                "invalid LESAVKA_UVC_MJPEG_IO_MODE; falling back to mmap"
            );
            "mmap".to_string()
        }
    }
}

fn positive_u64_env(name: &str, default: u64) -> u64 {
    std::env::var(name)
        .ok()
        .and_then(|value| value.trim().parse::<u64>().ok())
        .filter(|value| *value > 0)
        .unwrap_or(default)
}

fn uvc_appsrc_max_buffers() -> u64 {
    positive_u64_env("LESAVKA_UVC_APP_MAX_BUFFERS", 4)
}

fn uvc_appsrc_max_bytes() -> u64 {
    positive_u64_env("LESAVKA_UVC_APP_MAX_BYTES", 4 * 1024 * 1024)
}

fn uvc_appsrc_max_time_ns() -> u64 {
    positive_u64_env("LESAVKA_UVC_APP_MAX_TIME_NS", 200_000_000)
}

fn uvc_appsrc_leaky_type() -> String {
    std::env::var("LESAVKA_UVC_APP_LEAKY_TYPE")
        .ok()
        .map(|value| value.trim().to_ascii_lowercase())
        .filter(|value| matches!(value.as_str(), "downstream" | "upstream" | "none"))
        .unwrap_or_else(|| "downstream".to_string())
}

fn looks_like_mjpeg_frame(data: &[u8]) -> bool {
    data.len() >= 4 && data.starts_with(&[0xff, 0xd8, 0xff])
}

fn looks_like_annex_b_hevc(data: &[u8]) -> bool {
    data.starts_with(&[0, 0, 0, 1]) || data.starts_with(&[0, 0, 1])
}

fn uvc_hevc_freshness_queue_buffers() -> u32 {
    positive_u64_env("LESAVKA_UVC_HEVC_FRESHNESS_QUEUE_BUFFERS", 2)
        .clamp(1, 4) as u32
}

fn uvc_hevc_decode_miss_limit() -> u64 {
    positive_u64_env("LESAVKA_UVC_HEVC_DECODE_MISS_LIMIT", 15)
}

/// Bound the UVC ingress queue so decode/UVC stalls cannot turn into RSS growth.
///
/// Inputs: the UVC `appsrc`. Output: side-effect-only GStreamer properties.
/// Why: live webcam output should prefer dropping stale frames over buffering
/// seconds or minutes of encoded media when the physical sink falls behind.
fn configure_uvc_appsrc(appsrc: &gst_app::AppSrc) {
    appsrc.set_property("block", false);
    if appsrc.has_property("max-buffers", None) {
        appsrc.set_property("max-buffers", uvc_appsrc_max_buffers());
    }
    if appsrc.has_property("max-bytes", None) {
        appsrc.set_property("max-bytes", uvc_appsrc_max_bytes());
    }
    if appsrc.has_property("max-time", None) {
        appsrc.set_property("max-time", uvc_appsrc_max_time_ns());
    }
    if appsrc.has_property("leaky-type", None) {
        appsrc.set_property_from_str("leaky-type", &uvc_appsrc_leaky_type());
    }
}

/// Build a tiny leaky queue for the decoded HEVC handoff branch.
///
/// Inputs: a stable queue name. Output: configured GStreamer queue element.
/// Why: hidden raw/JPEG backlogs are memory leaks in a live webcam path; after
/// HEVC is decoded it is safe to drop stale raw frames and keep only the newest
/// candidate for MJPEG publication while absorbing normal decoder scheduling
/// jitter.
#[cfg(not(coverage))]
fn build_hevc_freshness_queue(name: &str) -> anyhow::Result<gst::Element> {
    let queue = gst::ElementFactory::make("queue")
        .name(name)
        .property("max-size-buffers", uvc_hevc_freshness_queue_buffers())
        .property("max-size-bytes", 0u32)
        .property("max-size-time", 0u64)
        .build()?;
    queue.set_property_from_str("leaky", "downstream");
    Ok(queue)
}

#[cfg(not(coverage))]
fn direct_mjpeg_normalize_pull_timeout() -> gst::ClockTime {
    gst::ClockTime::from_mseconds(u64::from(
        hevc_mjpeg_guard::direct_mjpeg_normalize_pull_timeout_ms(),
    ))
}

#[cfg(not(coverage))]
fn current_process_rss_kb() -> Option<u64> {
    let status = fs::read_to_string("/proc/self/status").ok()?;
    status.lines().find_map(|line| {
        let rest = line.strip_prefix("VmRSS:")?;
        rest.split_whitespace().next()?.parse::<u64>().ok()
    })
}

/// Drain normalized direct-MJPEG output down to the freshest sample.
///
/// Inputs: the direct-MJPEG normalization appsink. Output: newest available
/// sample, if any. Why: decode/re-encode should sanitize browser-facing MJPEG
/// without letting stale frames accumulate behind the live webcam feed.
#[cfg(not(coverage))]
fn freshest_direct_mjpeg_sample(sink: &gst_app::AppSink) -> Option<gst::Sample> {
    let mut newest = sink.try_pull_sample(direct_mjpeg_normalize_pull_timeout());
    while let Some(sample) = sink.try_pull_sample(gst::ClockTime::ZERO) {
        newest = Some(sample);
    }
    newest
}

#[cfg(not(coverage))]
fn build_direct_mjpeg_normalize_branch(
    pipeline: &gst::Pipeline,
    width: i32,
    height: i32,
    _fps: i32,
) -> anyhow::Result<(gst_app::AppSrc, gst_app::AppSink)> {
    let src = gst::ElementFactory::make("appsrc")
        .name("direct_mjpeg_normalize_src")
        .build()?
        .downcast::<gst_app::AppSrc>()
        .expect("direct MJPEG normalize appsrc");
    src.set_is_live(true);
    src.set_format(gst::Format::Time);
    src.set_property("do-timestamp", true);
    configure_uvc_appsrc(&src);
    let caps_in = gst::Caps::builder("image/jpeg").build();
    src.set_caps(Some(&caps_in));

    let caps_mjpeg = gst::Caps::builder("image/jpeg")
        .field("parsed", true)
        .field("width", width)
        .field("height", height)
        .field("pixel-aspect-ratio", gst::Fraction::new(1, 1))
        .field("colorimetry", "2:4:7:1")
        .build();
    let decoder = gst::ElementFactory::make("jpegdec").build()?;
    let decoded_queue = build_hevc_freshness_queue("direct_mjpeg_normalize_decoded_queue")?;
    let convert = gst::ElementFactory::make("videoconvert").build()?;
    let scale = gst::ElementFactory::make("videoscale").build()?;
    let raw_caps = gst::Caps::builder("video/x-raw")
        .field("width", width)
        .field("height", height)
        .build();
    let raw_capsfilter = gst::ElementFactory::make("capsfilter")
        .property("caps", &raw_caps)
        .build()?;
    let encoder = gst::ElementFactory::make("jpegenc")
        .property(
            "quality",
            hevc_mjpeg_guard::direct_mjpeg_jpeg_quality() as i32,
        )
        .build()?;
    let encoded_caps = gst::ElementFactory::make("capsfilter")
        .property("caps", &caps_mjpeg)
        .build()?;
    let encoded_queue = build_hevc_freshness_queue("direct_mjpeg_normalize_encoded_queue")?;
    let sink = gst::ElementFactory::make("appsink")
        .name("direct_mjpeg_normalize_sink")
        .property("sync", false)
        .property("enable-last-sample", false)
        .property("emit-signals", false)
        .property("max-buffers", 1u32)
        .property("drop", true)
        .build()?
        .downcast::<gst_app::AppSink>()
        .expect("direct MJPEG normalize appsink");

    pipeline.add_many([
        src.upcast_ref(),
        &decoder,
        &decoded_queue,
        &convert,
        &scale,
        &raw_capsfilter,
        &encoder,
        &encoded_caps,
        &encoded_queue,
        sink.upcast_ref(),
    ])?;
    gst::Element::link_many([
        src.upcast_ref(),
        &decoder,
        &decoded_queue,
        &convert,
        &scale,
        &raw_capsfilter,
        &encoder,
        &encoded_caps,
        &encoded_queue,
        sink.upcast_ref(),
    ])?;
    Ok((src, sink))
}

#[cfg(not(coverage))]
fn add_hevc_mjpeg_spool_branch(
    pipeline: &gst::Pipeline,
    width: i32,
    height: i32,
    fps: i32,
) -> anyhow::Result<(gst_app::AppSrc, gst_app::AppSink)> {
    let src = gst::ElementFactory::make("appsrc")
        .name("dynamic_hevc_mjpeg_src")
        .build()?
        .downcast::<gst_app::AppSrc>()
        .expect("dynamic HEVC appsrc");
    src.set_is_live(true);
    src.set_format(gst::Format::Time);
    src.set_property("do-timestamp", false);
    configure_uvc_appsrc(&src);
    let caps_hevc = gst::Caps::builder("video/x-h265")
        .field("stream-format", "byte-stream")
        .field("alignment", "au")
        .build();
    src.set_caps(Some(&caps_hevc));

    let caps_mjpeg = gst::Caps::builder("image/jpeg")
        .field("parsed", true)
        .field("width", width)
        .field("height", height)
        .field("framerate", gst::Fraction::new(fps, 1))
        .field("pixel-aspect-ratio", gst::Fraction::new(1, 1))
        .field("colorimetry", "2:4:7:1")
        .build();
    let h265parse = gst::ElementFactory::make("h265parse")
        .property("disable-passthrough", true)
        .property("config-interval", -1i32)
        .build()?;
    let decoder_name = require_hevc_decoder()?;
    let decoder = gst::ElementFactory::make(decoder_name)
        .build()
        .with_context(|| format!("building dynamic HEVC decoder element {decoder_name}"))?;
    configure_hevc_decoder(&decoder);
    let decoded_queue = build_hevc_freshness_queue("dynamic_hevc_mjpeg_decoded_queue")?;
    let convert = gst::ElementFactory::make("videoconvert").build()?;
    let encoder = gst::ElementFactory::make("jpegenc")
        .property("quality", hevc_mjpeg_guard::hevc_jpeg_quality() as i32)
        .build()?;
    let caps = gst::ElementFactory::make("capsfilter")
        .property("caps", &caps_mjpeg)
        .build()?;
    let encoded_queue = build_hevc_freshness_queue("dynamic_hevc_mjpeg_encoded_queue")?;
    let sink = gst::ElementFactory::make("appsink")
        .name("dynamic_hevc_mjpeg_spool_sink")
        .property("sync", false)
        .property("enable-last-sample", false)
        .property("emit-signals", false)
        .property("max-buffers", 1u32)
        .property("drop", true)
        .build()?
        .downcast::<gst_app::AppSink>()
        .expect("dynamic HEVC appsink");

    pipeline.add_many([
        src.upcast_ref(),
        &h265parse,
        &decoder,
        &decoded_queue,
        &convert,
        &encoder,
        &caps,
        &encoded_queue,
        sink.upcast_ref(),
    ])?;
    gst::Element::link_many([
        src.upcast_ref(),
        &h265parse,
        &decoder,
        &decoded_queue,
        &convert,
        &encoder,
        &caps,
        &encoded_queue,
        sink.upcast_ref(),
    ])?;
    Ok((src, sink))
}

/// Configure conservative recovery knobs on hardware HEVC decoders.
///
/// Inputs: a decoder element selected by `require_hevc_decoder`. Output:
/// side-effect-only property updates when the element supports them. Why: the
/// Pi stateless decoder can otherwise hold onto corrupt or dependency-missing
/// pictures after live HEVC packet drops, starving the MJPEG UVC handoff.
#[cfg(not(coverage))]
fn configure_hevc_decoder(decoder: &gst::Element) {
    if decoder.has_property("discard-corrupted-frames", None) {
        decoder.set_property("discard-corrupted-frames", true);
    }
    if decoder.has_property("automatic-request-sync-points", None) {
        decoder.set_property("automatic-request-sync-points", true);
    }
}

#[cfg(not(coverage))]
struct WebcamBusWatchHandle {
    alive: Arc<AtomicBool>,
    join: Option<std::thread::JoinHandle<()>>,
}

#[cfg(not(coverage))]
impl WebcamBusWatchHandle {
    fn spawn(bus: gst::Bus, label: &'static str) -> Self {
        let alive = Arc::new(AtomicBool::new(true));
        let alive_flag = Arc::clone(&alive);
        let join = std::thread::spawn(move || {
            while alive_flag.load(Ordering::Relaxed) {
                let Some(msg) = bus.timed_pop(gst::ClockTime::from_mseconds(250)) else {
                    continue;
                };
                match msg.view() {
                    StateChanged(state)
                        if state.current() == gst::State::Playing
                            && msg.src().is_some_and(|src| src.is::<gst::Pipeline>()) =>
                    {
                        tracing::debug!(target: "lesavka_server::video", label, "📸 UVC webcam pipeline ▶️");
                    }
                    Error(err) => tracing::error!(
                        target: "lesavka_server::video",
                        label,
                        "📸💥 UVC webcam pipeline error from {:?}: {} ({})",
                        msg.src().map(gst::prelude::GstObjectExt::path_string),
                        err.error(),
                        err.debug().unwrap_or_default()
                    ),
                    Warning(warning) => tracing::warn!(
                        target: "lesavka_server::video",
                        label,
                        "📸⚠️  UVC webcam pipeline warning from {:?}: {} ({})",
                        msg.src().map(gst::prelude::GstObjectExt::path_string),
                        warning.error(),
                        warning.debug().unwrap_or_default()
                    ),
                    _ => {}
                }
            }
        });
        Self {
            alive,
            join: Some(join),
        }
    }
}

#[cfg(not(coverage))]
impl Drop for WebcamBusWatchHandle {
    fn drop(&mut self) {
        self.alive.store(false, Ordering::Relaxed);
        if let Some(join) = self.join.take() {
            let _ = join.join();
        }
    }
}

#[cfg(not(coverage))]
fn spawn_webcam_bus_logger(
    pipeline: &gst::Pipeline,
    label: &'static str,
) -> Option<WebcamBusWatchHandle> {
    pipeline
        .bus()
        .map(|bus| WebcamBusWatchHandle::spawn(bus, label))
}

impl Drop for WebcamSink {
    fn drop(&mut self) {
        let _ = self.pipe.set_state(gst::State::Null);
        #[cfg(not(coverage))]
        {
            let _ = self._bus_watch.take();
        }
    }
}