//! End-to-end T2 (unidirectional stream) tests. Mirrors the T1 harness:
//! spin up substrate's listener with channels owned by the test, drive a
//! `SimulatorClient` against it, assert what arrives on the T2 receiver.
//!
//! Run with `cargo test -p simulator`.

use std::collections::HashMap;
use std::net::SocketAddr;
use std::path::PathBuf;
use std::time::Duration;

use anyhow::Result;
use simulator::client::SimulatorClient;
use substrate::config::QuicConfig;
use substrate::transport::server::{accept_loop, bind_endpoint};
use substrate::transport::{QuicMessage, SensorType, T1Sender, T2Sender, T3Sender};
use tokio::sync::mpsc;
use uuid::Uuid;

fn cert_path(name: &str) -> PathBuf {
    [env!("CARGO_MANIFEST_DIR"), "..", "certs", name].iter().collect()
}

fn loopback_config(cert: PathBuf, key: PathBuf) -> QuicConfig {
    QuicConfig {
        server_port: 0,
        server_interface: "127.0.0.1".to_string(),
        server_cert: cert.to_string_lossy().into_owned(),
        server_key: key.to_string_lossy().into_owned(),
        t1_capacity: 1024,
        t2_capacity: 512,
        t3_capacity: 256,
    }
}

#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
async fn t2_single_stream_preserves_order() -> Result<()> {
    simulator::install_crypto_provider();

    let cert = cert_path("server.crt");
    let key = cert_path("server.key");
    let cfg = loopback_config(cert.clone(), key);

    let endpoint = bind_endpoint(&cfg)?;
    let server_addr: SocketAddr = endpoint.local_addr()?;

    let (t1_tx, _t1_rx) = mpsc::channel(64);
    let (t2_tx, mut t2_rx) = mpsc::channel(64);
    let (t3_tx, _t3_rx) = mpsc::channel(64);

    let server_task = tokio::spawn(accept_loop(
        endpoint,
        T1Sender::new(t1_tx),
        T2Sender::new(t2_tx),
        T3Sender::new(t3_tx),
    ));

    let client = SimulatorClient::connect(server_addr, "localhost", &cert).await?;

    let device = Uuid::from_u128(0x0011_2233_4455_6677_8899_aabb_ccdd_eeff);
    const N: u32 = 10;
    let msgs: Vec<QuicMessage> = (0..N)
        .map(|i| QuicMessage {
            device_id: device,
            sensor_id: 1,
            raw_value: f64::from(i),
            timestamp_us: 1_700_000_000_000_000 + u64::from(i),
            sequence_number: i,
            sensor_type: SensorType::Pressure.as_u8(),
        })
        .collect();

    client.send_uni_stream(&msgs).await?;

    for expected in &msgs {
        let received = tokio::time::timeout(Duration::from_secs(2), t2_rx.recv())
            .await
            .expect("missed T2 message")
            .expect("T2 channel closed unexpectedly");
        assert_eq!(received, *expected);
    }

    client.close().await;
    server_task.abort();
    Ok(())
}

#[tokio::test(flavor = "multi_thread", worker_threads = 4)]
async fn t2_concurrent_streams_each_internally_ordered() -> Result<()> {
    simulator::install_crypto_provider();

    let cert = cert_path("server.crt");
    let key = cert_path("server.key");
    let cfg = loopback_config(cert.clone(), key);

    let endpoint = bind_endpoint(&cfg)?;
    let server_addr: SocketAddr = endpoint.local_addr()?;

    let (t1_tx, _t1_rx) = mpsc::channel(64);
    let (t2_tx, mut t2_rx) = mpsc::channel(256);
    let (t3_tx, _t3_rx) = mpsc::channel(64);

    let server_task = tokio::spawn(accept_loop(
        endpoint,
        T1Sender::new(t1_tx),
        T2Sender::new(t2_tx),
        T3Sender::new(t3_tx),
    ));

    let client = SimulatorClient::connect(server_addr, "localhost", &cert).await?;

    // 4 devices × 8 messages each on independent uni streams. Cross-stream
    // ordering may interleave; per-stream ordering must be strict.
    const DEVICES: usize = 4;
    const PER_DEVICE: u32 = 8;
    let device_ids: Vec<Uuid> = (0..DEVICES).map(|_| Uuid::new_v4()).collect();

    let mut handles = Vec::with_capacity(DEVICES);
    for &device in &device_ids {
        let conn = client.conn.clone();
        handles.push(tokio::spawn(async move {
            let msgs: Vec<QuicMessage> = (0..PER_DEVICE)
                .map(|i| QuicMessage {
                    device_id: device,
                    sensor_id: 0,
                    raw_value: f64::from(i),
                    timestamp_us: 1_700_000_000_000_000 + u64::from(i),
                    sequence_number: i,
                    sensor_type: SensorType::Generic.as_u8(),
                })
                .collect();
            // Use the connection directly so each task owns its own stream
            // — same wire pattern as `SimulatorClient::send_uni_stream`.
            let mut send = conn.open_uni().await.expect("open_uni");
            for m in &msgs {
                send.write_all(&m.to_bytes()).await.expect("write_all");
            }
            send.finish().expect("finish");
        }));
    }
    for h in handles {
        h.await?;
    }

    // Drain DEVICES × PER_DEVICE messages, group by device, assert per-device
    // sequence numbers are strictly increasing from 0.
    let total = DEVICES * PER_DEVICE as usize;
    let mut by_device: HashMap<Uuid, Vec<u32>> = HashMap::new();
    for _ in 0..total {
        let msg = tokio::time::timeout(Duration::from_secs(2), t2_rx.recv())
            .await
            .expect("missed T2 message")
            .expect("T2 channel closed unexpectedly");
        by_device.entry(msg.device_id).or_default().push(msg.sequence_number);
    }

    assert_eq!(by_device.len(), DEVICES, "expected one entry per device");
    for (dev, seqs) in &by_device {
        let expected: Vec<u32> = (0..PER_DEVICE).collect();
        assert_eq!(seqs, &expected, "out-of-order or missing sequence for {dev}");
    }

    client.close().await;
    server_task.abort();
    Ok(())
}