//! Integration tests for `TcpSyncBackend` push and pull.
//!
//! Spins up a real TCP server (same direction-aware logic as the CLI), then
//! exercises `TcpSyncBackend::push` and `TcpSyncBackend::pull` end-to-end.

use std::net::{IpAddr, Ipv4Addr, SocketAddr};
use std::path::PathBuf;

use clawhdf5_onion::format::NO_PARENT;
use clawhdf5_onion::writer::OnionFile;
use clawsync_agent::backend::{SyncBackend, TcpSyncBackend};
use clawsync_onion::differ::diff_revisions;
use clawsync_onion::iblt::IbltSketch;
use clawsync_onion::manifest::{ClawSyncManifest, IbltManifest};
use clawsync_onion::merger::merge_packets;
use clawsync_onion::selector::SyncSelector;
use clawsync_transport::protocol::SyncMessage;
use clawsync_transport::tcp::TcpServer;
use tempfile::TempDir;

const H5_MAGIC: &[u8] = b"\x89HDF\r\n\x1a\n";

fn any_addr() -> SocketAddr {
    SocketAddr::new(IpAddr::V4(Ipv4Addr::LOCALHOST), 0)
}

/// Create a temp HDF5 stub with `n` committed onion revisions, flushed.
fn make_onion(n: u8) -> (TempDir, PathBuf, OnionFile) {
    let dir = TempDir::new().unwrap();
    let h5 = dir.path().join("data.h5");
    std::fs::write(&h5, H5_MAGIC).unwrap();
    let mut onion = OnionFile::create(&h5, 4096).unwrap();
    for i in 0..n {
        let mut s = onion.begin_session(None).unwrap();
        s.record_page(0, &vec![i; 4096]);
        onion.commit_session(s, Some(&format!("rev {i}"))).unwrap();
    }
    onion.flush().unwrap();
    (dir, h5, onion)
}

// ─────────────────────────────────────────────────────────────────────────────
// Direction-aware server helper (mirrors CLI handle_client)
// ─────────────────────────────────────────────────────────────────────────────

async fn run_server(server: TcpServer, mut dst: OnionFile) -> OnionFile {
    let (mut conn, _) = server.accept().await.unwrap();

    match conn.recv().await.unwrap() {
        // ── IBLT pre-flight (push direction) ─────────────────────────────
        SyncMessage::IbltRequest {
            sketch: client_iblt,
        } => {
            let server_revs: Vec<u64> = dst.list_revisions().iter().map(|s| s.revision).collect();

            // Decode diff: what client has that server lacks
            let diff = client_iblt.diff_against(&server_revs).unwrap();

            // Build server's sketch with the same embedded seed
            let client_sketch = IbltSketch::from_bytes(&client_iblt.sketch).unwrap();
            let seed = client_sketch.seed();
            let srv_sketch = IbltSketch::from_keys(&server_revs, seed);
            let server_iblt = IbltManifest {
                agent_id: "test-server".to_string(),
                file_blake3: [0u8; 32],
                revision_count: server_revs.len() as u64,
                head_revision: server_revs.last().copied().unwrap_or(0),
                head_blake3: [0u8; 32],
                last_write: 0.0,
                sketch_cells: srv_sketch.cell_count() as u32,
                sketch: srv_sketch.to_bytes(),
            };
            conn.send(&SyncMessage::IbltResponse {
                sketch: server_iblt,
                missing_from_remote: diff.only_in_b.clone(), // client has, server lacks
            })
            .await
            .unwrap();

            let mut packets = Vec::new();
            loop {
                match conn.recv().await.unwrap() {
                    SyncMessage::LayerPacket { packet } => {
                        let rev = packet.revision;
                        conn.send(&SyncMessage::Ack { revision: rev })
                            .await
                            .unwrap();
                        packets.push(packet);
                    }
                    SyncMessage::SyncComplete { .. } => break,
                    other => panic!("server: unexpected {other:?}"),
                }
            }
            if !packets.is_empty() {
                merge_packets(&mut dst, packets, true).unwrap();
            }
        }

        // ── Flat manifest (pull direction) ────────────────────────────────
        SyncMessage::ManifestRequest {
            revision_count: remote_rev_count,
            ..
        } => {
            let local_rev_count = dst.revision_count();
            let manifest = ClawSyncManifest::from_onion("server", &dst, H5_MAGIC);
            conn.send(&SyncMessage::ManifestResponse { manifest })
                .await
                .unwrap();

            if local_rev_count > remote_rev_count {
                let remote_head = if remote_rev_count == 0 {
                    NO_PARENT
                } else {
                    remote_rev_count - 1
                };
                let packets = diff_revisions(&dst, remote_head).unwrap();
                let total = packets.len() as u64;
                let mut bytes_sent = 0u64;
                for packet in packets {
                    bytes_sent += packet.page_data_size() as u64;
                    conn.send(&SyncMessage::LayerPacket { packet })
                        .await
                        .unwrap();
                    match conn.recv().await.unwrap() {
                        SyncMessage::Ack { .. } => {}
                        other => panic!("expected Ack, got {other:?}"),
                    }
                }
                conn.send(&SyncMessage::SyncComplete {
                    revisions_transferred: total,
                    bytes_transferred: bytes_sent,
                })
                .await
                .unwrap();
            } else {
                let mut packets = Vec::new();
                loop {
                    match conn.recv().await.unwrap() {
                        SyncMessage::LayerPacket { packet } => {
                            let rev = packet.revision;
                            conn.send(&SyncMessage::Ack { revision: rev })
                                .await
                                .unwrap();
                            packets.push(packet);
                        }
                        SyncMessage::SyncComplete { .. } => break,
                        other => panic!("server: unexpected {other:?}"),
                    }
                }
                if !packets.is_empty() {
                    merge_packets(&mut dst, packets, true).unwrap();
                }
            }
        }

        other => panic!("server: expected IbltRequest or ManifestRequest, got {other:?}"),
    }

    dst
}

// ─────────────────────────────────────────────────────────────────────────────
// Push tests
// ─────────────────────────────────────────────────────────────────────────────

/// `TcpSyncBackend::push` sends all revisions to an empty server.
#[tokio::test]
async fn backend_push_all_to_empty() {
    let (_src_dir, src_h5, src_onion) = make_onion(4);
    let (_dst_dir, _dst_h5, dst_onion) = make_onion(0);

    let server = TcpServer::bind(any_addr()).await.unwrap();
    let addr = server.local_addr;
    let server_task = tokio::spawn(run_server(server, dst_onion));

    let backend = TcpSyncBackend::new(addr, "test-agent");
    let stats = backend.push(&src_h5, &SyncSelector::All).await.unwrap();

    assert_eq!(stats.revisions_transferred, 4);

    let dst_final = server_task.await.unwrap();
    assert_eq!(dst_final.revision_count(), 4);
    let _ = src_onion;
}

/// `TcpSyncBackend::push` sends only the missing delta (N-K).
#[tokio::test]
async fn backend_push_partial_delta() {
    const K: u8 = 3;
    const N: u8 = 7;

    let (_src_dir, src_h5, src_onion) = make_onion(N);
    let (_dst_dir, _dst_h5, dst_onion) = make_onion(K);

    let server = TcpServer::bind(any_addr()).await.unwrap();
    let addr = server.local_addr;
    let server_task = tokio::spawn(run_server(server, dst_onion));

    let backend = TcpSyncBackend::new(addr, "agent");
    let stats = backend.push(&src_h5, &SyncSelector::All).await.unwrap();

    assert_eq!(stats.revisions_transferred, (N - K) as u64);

    let dst_final = server_task.await.unwrap();
    assert_eq!(dst_final.revision_count(), N as u64);
    let _ = src_onion;
}

/// `TcpSyncBackend::push` when already in sync transfers zero revisions.
#[tokio::test]
async fn backend_push_already_in_sync() {
    let (_src_dir, src_h5, src_onion) = make_onion(3);
    let (_dst_dir, _dst_h5, dst_onion) = make_onion(3);

    let server = TcpServer::bind(any_addr()).await.unwrap();
    let addr = server.local_addr;
    let server_task = tokio::spawn(run_server(server, dst_onion));

    let backend = TcpSyncBackend::new(addr, "agent");
    let stats = backend.push(&src_h5, &SyncSelector::All).await.unwrap();

    assert_eq!(stats.revisions_transferred, 0);
    let _ = (src_onion, server_task.await.unwrap());
}

// ─────────────────────────────────────────────────────────────────────────────
// Pull tests
// ─────────────────────────────────────────────────────────────────────────────

/// `TcpSyncBackend::pull` receives all revisions from a full server.
#[tokio::test]
async fn backend_pull_all_from_server() {
    let (_srv_dir, _srv_h5, srv_onion) = make_onion(5);
    let (cli_dir, cli_h5, cli_onion) = make_onion(0);

    let server = TcpServer::bind(any_addr()).await.unwrap();
    let addr = server.local_addr;
    let server_task = tokio::spawn(run_server(server, srv_onion));

    let backend = TcpSyncBackend::new(addr, "agent");
    let stats = backend.pull(&cli_h5).await.unwrap();

    assert_eq!(stats.revisions_transferred, 5);

    server_task.await.unwrap();
    // Re-open from disk to verify the sidecar was updated.
    let cli_after = OnionFile::open(&cli_h5).unwrap();
    assert_eq!(cli_after.revision_count(), 5);
    let _ = (cli_dir, cli_onion);
}

/// `TcpSyncBackend::pull` when already in sync returns zero transfers.
#[tokio::test]
async fn backend_pull_already_in_sync() {
    let (_srv_dir, _srv_h5, srv_onion) = make_onion(3);
    let (_cli_dir, cli_h5, cli_onion) = make_onion(3);

    let server = TcpServer::bind(any_addr()).await.unwrap();
    let addr = server.local_addr;
    let server_task = tokio::spawn(run_server(server, srv_onion));

    let backend = TcpSyncBackend::new(addr, "agent");
    let stats = backend.pull(&cli_h5).await.unwrap();

    assert_eq!(
        stats.revisions_transferred, 0,
        "nothing to pull when in sync"
    );
    let _ = (cli_onion, server_task.await.unwrap());
}

/// `TcpSyncBackend::pull` fetches only the missing delta.
#[tokio::test]
async fn backend_pull_partial_delta() {
    const K: u8 = 2;
    const N: u8 = 6;

    let (_srv_dir, _srv_h5, srv_onion) = make_onion(N);
    let (_cli_dir, cli_h5, cli_onion) = make_onion(K);

    let server = TcpServer::bind(any_addr()).await.unwrap();
    let addr = server.local_addr;
    let server_task = tokio::spawn(run_server(server, srv_onion));

    let backend = TcpSyncBackend::new(addr, "agent");
    let stats = backend.pull(&cli_h5).await.unwrap();

    assert_eq!(stats.revisions_transferred, (N - K) as u64);

    server_task.await.unwrap();
    let cli_after = OnionFile::open(&cli_h5).unwrap();
    assert_eq!(cli_after.revision_count(), N as u64);
    let _ = cli_onion;
}

// ─────────────────────────────────────────────────────────────────────────────
// local_manifest
// ─────────────────────────────────────────────────────────────────────────────

/// `local_manifest` reflects the correct revision count.
#[test]
fn backend_local_manifest_revision_count() {
    let (_dir, h5, _onion) = make_onion(4);
    let backend = TcpSyncBackend::new(any_addr(), "agent");
    let mf = backend.local_manifest(&h5).unwrap();
    assert_eq!(mf.revision_count, 4);
    assert_eq!(mf.agent_id, "agent");
}