//! Generic telemetry emission helpers.

use std::sync::Arc;
use std::sync::OnceLock;

use swactor::actor::ActorAddress;
use swactor::process_observer::ProcessOutputObserver;
use swactor::runtime::Runtime;

use super::mux::Mux;
use super::wire::{TelemetryFrame, encode_delivery};
use crate::frame::{ChannelId, Frame, Lifetime, NodeId, StreamId};
use crate::record::Record;

/// Legacy sink for frames after mux drain has assigned positions.
pub trait FrameSink: Send {
    /// Ship one positioned frame for `stream`. Best-effort: a sink may drop.
    fn ship(&mut self, stream: &StreamId, frame: &Frame);
}

/// Static identity a node needs to build its mux.
pub struct EmitterConfig {
    pub node_hex: String,
    pub life: u64,
    pub mux_capacity: usize,
}

struct MuxProcObserver {
    mux: Arc<Mux>,
    channel_for: Arc<dyn Fn(&str, bool) -> ChannelId + Send + Sync>,
}

impl ProcessOutputObserver for MuxProcObserver {
    fn on_output(&self, label: &str, is_stderr: bool, data: &[u8]) {
        self.mux
            .submit((self.channel_for)(label, is_stderr), data.to_vec());
    }
}

/// Legacy per-node emitter retained while runtime callsites move to
/// [`crate::TelemetryEndpoint`]. New code should register channels on the
/// endpoint and submit through [`crate::TelemetryProducer`].
pub struct TelemetryEmitter {
    stream_id: StreamId,
    mux: Arc<Mux>,
    sink: Box<dyn FrameSink>,
}

impl TelemetryEmitter {
    pub fn new(cfg: EmitterConfig, sink: Box<dyn FrameSink>) -> Self {
        let stream_id = StreamId::new(NodeId::new(&cfg.node_hex), Lifetime(cfg.life));
        let mux = Arc::new(Mux::new(stream_id.clone(), cfg.mux_capacity));
        Self {
            stream_id,
            mux,
            sink,
        }
    }

    pub fn stream_id(&self) -> &StreamId {
        &self.stream_id
    }

    pub fn mux(&self) -> &Arc<Mux> {
        &self.mux
    }

    pub fn assigned(&self) -> u64 {
        self.mux.assigned()
    }

    pub fn dropped(&self) -> u64 {
        self.mux.dropped()
    }

    pub fn submit_record<R: Record>(&self, channel: ChannelId, record: &R) -> bool {
        self.mux.submit(channel, record.encode())
    }

    pub fn submit_text(&self, channel: ChannelId, text: impl AsRef<[u8]>) -> bool {
        self.mux.submit(channel, text.as_ref().to_vec())
    }

    pub fn submit_bytes(&self, channel: ChannelId, bytes: Vec<u8>) -> bool {
        self.mux.submit(channel, bytes)
    }

    pub fn submit_text_owned(&self, channel: ChannelId, text: String) -> bool {
        self.mux.submit(channel, text.into_bytes())
    }

    /// Build a legacy/custom process-output observer that writes chunks into this mux.
    pub fn process_observer_with<F>(&self, channel_for: F) -> Arc<dyn ProcessOutputObserver>
    where
        F: Fn(&str, bool) -> ChannelId + Send + Sync + 'static,
    {
        Arc::new(MuxProcObserver {
            mux: self.mux.clone(),
            channel_for: Arc::new(channel_for),
        })
    }

    pub fn tick(&mut self) {
        for frame in self.mux.drain() {
            self.sink.ship(&self.stream_id, &frame);
        }
    }

    pub fn event_sink(&self) -> TelemetryEventSink {
        TelemetryEventSink {
            mux: self.mux.clone(),
        }
    }
}

/// A thread-safe submit handle. Legacy; prefer [`crate::TelemetryProducer`].
#[derive(Clone)]
pub struct TelemetryEventSink {
    mux: Arc<Mux>,
}

impl TelemetryEventSink {
    pub fn submit_record<R: Record>(&self, channel: ChannelId, record: &R) -> bool {
        self.mux.submit(channel, record.encode())
    }

    pub fn submit_text(&self, channel: ChannelId, text: impl AsRef<[u8]>) -> bool {
        self.mux.submit(channel, text.as_ref().to_vec())
    }

    pub fn submit_bytes(&self, channel: ChannelId, bytes: Vec<u8>) -> bool {
        self.mux.submit(channel, bytes)
    }

    pub fn submit_text_owned(&self, channel: ChannelId, text: String) -> bool {
        self.mux.submit(channel, text.into_bytes())
    }
}

/// A sink that drops everything.
pub struct NoopSink;

impl FrameSink for NoopSink {
    fn ship(&mut self, _stream: &StreamId, _frame: &Frame) {}
}

/// Legacy swactor frame sink retained until MVP runtime cutover removes it.
pub struct ClusterFrameSink {
    rt: Runtime,
    sink: Arc<OnceLock<ActorAddress>>,
}

impl ClusterFrameSink {
    pub fn new(rt: Runtime, sink: Arc<OnceLock<ActorAddress>>) -> Self {
        Self { rt, sink }
    }
}

impl FrameSink for ClusterFrameSink {
    fn ship(&mut self, stream: &StreamId, frame: &Frame) {
        if let Some(addr) = self.sink.get() {
            let _ = self.rt.send_to(
                *addr,
                TelemetryFrame {
                    payload: encode_delivery(stream, frame),
                },
            );
        }
    }
}