//! End-to-end T1 datagram test: spin up substrate's listener in-process with
//! channels the test owns, drive a `SimulatorClient` against it, and assert
//! the datagram lands in the T1 receiver decoded.
//!
//! Run with `cargo test -p simulator`.

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 {
        // Port 0 lets the OS pick a free ephemeral port — tests can run in
        // parallel without colliding on a fixed bind.
        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(),
    }
}

#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
async fn t1_datagram_decoded_into_ecs_channel() -> Result<()> {
    simulator::install_crypto_provider();

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

    // Bind the substrate's listener on an ephemeral port.
    let endpoint = bind_endpoint(&cfg)?;
    let server_addr: SocketAddr = endpoint.local_addr()?;

    // Channels the test owns — gives us direct visibility into what the T1
    // demux pushes into the ECS bridge.
    let (t1_tx, mut t1_rx) = mpsc::channel(64);
    let (t2_tx, _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),
    ));

    // Connect a client and send one datagram.
    let client = SimulatorClient::connect(server_addr, "localhost", &cert).await?;

    let sent = QuicMessage {
        device_id: Uuid::from_u128(0xdead_beef_cafe_f00d_1234_5678_90ab_cdef),
        sensor_id: 7,
        raw_value: 42.0,
        timestamp_us: 1_700_000_000_000_001,
        sequence_number: 1,
        sensor_type: SensorType::Temperature.as_u8(),
    };
    client.send_datagram(&sent)?;

    // Wait for the substrate's read_datagrams reader to push it into T1.
    let received = tokio::time::timeout(Duration::from_secs(2), t1_rx.recv())
        .await
        .expect("did not observe T1 datagram within 2s")
        .expect("T1 channel closed unexpectedly");

    assert_eq!(received, sent);

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

#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
async fn t1_burst_preserves_order_and_count() -> 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()?;

    // T1 capacity 64 ≥ burst size 32 so nothing is dropped under loopback.
    let (t1_tx, mut t1_rx) = mpsc::channel(64);
    let (t2_tx, _t2_rx) = mpsc::channel(8);
    let (t3_tx, _t3_rx) = mpsc::channel(8);

    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(0xa1a2_a3a4_b5b6_b7b8_c9ca_cbcc_cdce_cfd0);
    const BURST: u32 = 32;
    for seq in 0..BURST {
        let msg = QuicMessage {
            device_id: device,
            sensor_id: 0,
            raw_value: f64::from(seq),
            timestamp_us: 1_700_000_000_000_000 + u64::from(seq),
            sequence_number: seq,
            sensor_type: SensorType::Generic.as_u8(),
        };
        client.send_datagram(&msg)?;
    }

    // Drain BURST messages with a per-message timeout. Loopback shouldn't
    // reorder QUIC datagrams within a single connection.
    for expected_seq in 0..BURST {
        let msg = tokio::time::timeout(Duration::from_secs(2), t1_rx.recv())
            .await
            .unwrap_or_else(|_| panic!("missed datagram seq={expected_seq}"))
            .expect("T1 channel closed");
        assert_eq!(msg.sequence_number, expected_seq);
        assert_eq!(msg.device_id, device);
        assert_eq!(msg.raw_value, f64::from(expected_seq));
    }

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