use crate::auth::{find_key, verify_signature};
use crate::keys::parse_authorized_keys;
use crate::persist;
use crate::state::{AppState, AttachSink};
use axum::extract::ws::{Message, WebSocket};
use axum::extract::{State, WebSocketUpgrade};
use axum::response::IntoResponse;
use futures_util::{SinkExt, StreamExt};
use rand::RngCore;
use rsh_types::{
    AttachIOFrame, BackendOpMsg, BackendStubMsg, OpEvent, OpMsg, OpReq, OpResp, SessionRecord,
    SessionView,
};
use ssh_key::PublicKey;
use std::sync::Arc;
use tokio::sync::mpsc;

pub async fn handler(
    ws: WebSocketUpgrade,
    State(state): State<Arc<AppState>>,
) -> impl IntoResponse {
    ws.on_upgrade(move |socket| run(socket, state))
}

async fn run(mut socket: WebSocket, state: Arc<AppState>) {
    let pubkey = match auth_handshake(&mut socket, &state).await {
        Ok(k) => k,
        Err(reason) => {
            let _ = send(&mut socket, &BackendOpMsg::AuthFail { reason }).await;
            return;
        }
    };
    if send(&mut socket, &BackendOpMsg::AuthOk).await.is_err() {
        return;
    }
    tracing::info!(fingerprint = %pubkey.fingerprint(Default::default()), "operator authed");

    let (out_tx, mut out_rx) = mpsc::channel::<BackendOpMsg>(128);
    let (mut sink, mut stream) = socket.split();

    let writer = tokio::spawn(async move {
        while let Some(msg) = out_rx.recv().await {
            let text = match serde_json::to_string(&msg) {
                Ok(t) => t,
                Err(_) => break,
            };
            if sink.send(Message::Text(text)).await.is_err() {
                break;
            }
        }
        let _ = sink.close().await;
    });

    let mut attached: Option<(String, u64, u64)> = None;

    while let Some(Ok(msg)) = stream.next().await {
        let text = match msg {
            Message::Text(t) => t,
            Message::Binary(b) => match String::from_utf8(b) {
                Ok(s) => s,
                Err(_) => continue,
            },
            Message::Close(_) => break,
            _ => continue,
        };
        let op: OpMsg = match serde_json::from_str(&text) {
            Ok(v) => v,
            Err(e) => {
                tracing::warn!("bad op msg: {e}");
                continue;
            }
        };
        let (req_id, body) = match op {
            OpMsg::Req { id, body } => (id, body),
            _ => continue,
        };
        let resp = handle_req(&state, &out_tx, &mut attached, req_id, body).await;
        if let Some(r) = resp {
            if out_tx.send(BackendOpMsg::Resp { id: req_id, body: r }).await.is_err() {
                break;
            }
        }
    }

    if let Some((s, c, _)) = attached {
        if let Some(handle) = state.connections.get(&(s, c)) {
            let mut a = handle.attach.lock().await;
            *a = None;
        }
    }
    drop(out_tx);
    let _ = writer.await;
}

async fn auth_handshake(socket: &mut WebSocket, state: &Arc<AppState>) -> Result<PublicKey, String> {
    let init = recv_op(socket).await.ok_or_else(|| "no message".to_string())?;
    let offered_str = match init {
        OpMsg::AuthInit { pubkey_openssh } => pubkey_openssh,
        _ => return Err("expected AuthInit".into()),
    };
    let offered = PublicKey::from_openssh(&offered_str).map_err(|e| format!("bad pubkey: {e}"))?;
    let keys = state.authorized_keys.read().await;
    let matched = find_key(&keys, &offered).cloned();
    drop(keys);
    let matched = matched.ok_or_else(|| "key not authorized".to_string())?;

    let mut nonce = [0u8; 32];
    rand::thread_rng().fill_bytes(&mut nonce);
    send(socket, &BackendOpMsg::Challenge { nonce }).await.map_err(|e| e.to_string())?;
    let signed = recv_op(socket).await.ok_or_else(|| "no signature".to_string())?;
    let (sig_bytes, _alg) = match signed {
        OpMsg::AuthSign { signature, alg } => (signature, alg),
        _ => return Err("expected AuthSign".into()),
    };
    verify_signature(&matched, &nonce, &sig_bytes).map_err(|e| e.to_string())?;
    Ok(matched)
}

async fn handle_req(
    state: &Arc<AppState>,
    out_tx: &mpsc::Sender<BackendOpMsg>,
    attached: &mut Option<(String, u64, u64)>,
    req_id: u64,
    body: OpReq,
) -> Option<OpResp> {
    match body {
        OpReq::SessionList => Some(OpResp::Sessions(list_sessions(state).await)),
        OpReq::SessionCreate { name, password_hash } => {
            let mut s = state.sessions.write().await;
            if s.contains_key(&name) {
                return Some(OpResp::Err(format!("session '{name}' already exists")));
            }
            let rec = SessionRecord {
                id: name.clone(),
                password_hash,
                created_at: now_unix(),
            };
            s.insert(name.clone(), rec.clone());
            let snapshot: Vec<_> = s.values().cloned().collect();
            drop(s);
            if let Err(e) = persist::save_sessions(&state.cfg.sessions_path(), &snapshot).await {
                return Some(OpResp::Err(format!("persist: {e}")));
            }
            let view = SessionView {
                id: rec.id.clone(),
                has_password: rec.password_hash.is_some(),
                created_at: rec.created_at,
                connection_count: 0,
            };
            let _ = state.event_bus.send(OpEvent::NewSession(view));
            Some(OpResp::Ok)
        }
        OpReq::SessionDelete { name, disconnect } => {
            let mut s = state.sessions.write().await;
            if s.remove(&name).is_none() {
                return Some(OpResp::Err(format!("no such session '{name}'")));
            }
            let snapshot: Vec<_> = s.values().cloned().collect();
            drop(s);
            if let Err(e) = persist::save_sessions(&state.cfg.sessions_path(), &snapshot).await {
                return Some(OpResp::Err(format!("persist: {e}")));
            }
            if disconnect {
                disconnect_session(state, &name).await;
            }
            let _ = state.event_bus.send(OpEvent::SessionDeleted { session: name });
            Some(OpResp::Ok)
        }
        OpReq::SessionUpdate { name, set_password_hash, disconnect } => {
            let mut s = state.sessions.write().await;
            let Some(rec) = s.get_mut(&name) else {
                return Some(OpResp::Err(format!("no such session '{name}'")));
            };
            if let Some(pw) = set_password_hash {
                rec.password_hash = pw;
            }
            let snapshot: Vec<_> = s.values().cloned().collect();
            drop(s);
            if let Err(e) = persist::save_sessions(&state.cfg.sessions_path(), &snapshot).await {
                return Some(OpResp::Err(format!("persist: {e}")));
            }
            if disconnect {
                disconnect_session(state, &name).await;
            }
            Some(OpResp::Ok)
        }
        OpReq::ConnectionList { session } => {
            Some(OpResp::Connections(state.list_connections(session.as_deref())))
        }
        OpReq::Attach { session, connection_id, pty: _, cols, rows } => {
            let conn_id = match connection_id {
                Some(c) => c,
                None => {
                    let mut found = None;
                    for kv in state.connections.iter() {
                        if kv.key().0 == session {
                            if found.is_some() {
                                return Some(OpResp::Err("multiple connections; specify id".into()));
                            }
                            found = Some(kv.key().1);
                        }
                    }
                    match found {
                        Some(c) => c,
                        None => return Some(OpResp::Err("no connections".into())),
                    }
                }
            };
            let Some(handle) = state.connections.get(&(session.clone(), conn_id)).map(|h| h.clone()) else {
                return Some(OpResp::Err("connection not found".into()));
            };
            {
                let mut a = handle.attach.lock().await;
                *a = Some(AttachSink { req_id, sender: out_tx.clone() });
            }
            let _ = handle.to_stub.send(BackendStubMsg::Resize { cols, rows }).await;
            *attached = Some((session, conn_id, req_id));
            Some(OpResp::AttachReady { connection_id: conn_id })
        }
        OpReq::AttachIO(frame) => {
            let Some((session, conn_id, _)) = attached.clone() else {
                return Some(OpResp::Err("not attached".into()));
            };
            let Some(handle) = state.connections.get(&(session, conn_id)).map(|h| h.clone()) else {
                return Some(OpResp::Err("connection gone".into()));
            };
            match frame {
                AttachIOFrame::Stdin(b) => {
                    let _ = handle.to_stub.send(BackendStubMsg::Stdin(b)).await;
                }
                AttachIOFrame::Resize { cols, rows } => {
                    let _ = handle.to_stub.send(BackendStubMsg::Resize { cols, rows }).await;
                }
                AttachIOFrame::Kill => {
                    let _ = handle.to_stub.send(BackendStubMsg::Kill).await;
                }
                AttachIOFrame::Eof => {
                    let _ = handle.to_stub.send(BackendStubMsg::Stdin(Vec::new())).await;
                }
            }
            None
        }
        OpReq::Detach => {
            if let Some((s, c, _)) = attached.take() {
                if let Some(handle) = state.connections.get(&(s, c)) {
                    let mut a = handle.attach.lock().await;
                    *a = None;
                }
            }
            Some(OpResp::Ok)
        }
        OpReq::KeysList => {
            let text = persist::load_authorized_keys_text(&state.cfg.authorized_keys_path())
                .await
                .unwrap_or_default();
            let keys: Vec<String> = text
                .lines()
                .map(|l| l.trim().to_string())
                .filter(|l| !l.is_empty())
                .collect();
            Some(OpResp::Keys(keys))
        }
        OpReq::KeysAppend { keys } => {
            let path = state.cfg.authorized_keys_path();
            let mut text = persist::load_authorized_keys_text(&path).await.unwrap_or_default();
            for k in keys {
                let k = k.trim();
                if k.is_empty() {
                    continue;
                }
                if !text.lines().any(|l| l.trim() == k) {
                    if !text.is_empty() && !text.ends_with('\n') {
                        text.push('\n');
                    }
                    text.push_str(k);
                    text.push('\n');
                }
            }
            if let Err(e) = persist::save_authorized_keys_text(&path, &text).await {
                return Some(OpResp::Err(format!("persist: {e}")));
            }
            reload_authorized_keys(state, &text).await;
            Some(OpResp::Ok)
        }
        OpReq::KeysRemove { keys } => {
            let path = state.cfg.authorized_keys_path();
            let text = persist::load_authorized_keys_text(&path).await.unwrap_or_default();
            let targets: Vec<String> = keys.iter().map(|k| k.trim().to_string()).collect();
            let new: String = text
                .lines()
                .filter(|l| {
                    let lt = l.trim();
                    !targets.iter().any(|t| t == lt)
                })
                .collect::<Vec<_>>()
                .join("\n");
            let new = if new.is_empty() { new } else { format!("{}\n", new) };
            if let Err(e) = persist::save_authorized_keys_text(&path, &new).await {
                return Some(OpResp::Err(format!("persist: {e}")));
            }
            reload_authorized_keys(state, &new).await;
            Some(OpResp::Ok)
        }
        OpReq::KeysReplace { content } => {
            let path = state.cfg.authorized_keys_path();
            if let Err(e) = persist::save_authorized_keys_text(&path, &content).await {
                return Some(OpResp::Err(format!("persist: {e}")));
            }
            reload_authorized_keys(state, &content).await;
            Some(OpResp::Ok)
        }
        OpReq::Watch { session } => {
            let mut rx = state.event_bus.subscribe();
            let tx = out_tx.clone();
            tokio::spawn(async move {
                while let Ok(ev) = rx.recv().await {
                    let pass = match &ev {
                        OpEvent::NewConnection(v) => session.as_ref().map_or(true, |s| &v.session_id == s),
                        OpEvent::ConnectionClosed { session: s, .. } => session.as_ref().map_or(true, |x| x == s),
                        OpEvent::NewSession(v) => session.as_ref().map_or(true, |s| &v.id == s),
                        OpEvent::SessionDeleted { session: s } => session.as_ref().map_or(true, |x| x == s),
                    };
                    if !pass {
                        continue;
                    }
                    if tx.send(BackendOpMsg::Event(ev)).await.is_err() {
                        break;
                    }
                }
            });
            Some(OpResp::WatchStarted)
        }
    }
}

async fn list_sessions(state: &Arc<AppState>) -> Vec<SessionView> {
    let s = state.sessions.read().await;
    s.values()
        .map(|r| SessionView {
            id: r.id.clone(),
            has_password: r.password_hash.is_some(),
            created_at: r.created_at,
            connection_count: state.connection_count(&r.id),
        })
        .collect()
}

async fn disconnect_session(state: &Arc<AppState>, name: &str) {
    let mut to_kill = Vec::new();
    for kv in state.connections.iter() {
        if kv.key().0 == name {
            to_kill.push((kv.key().clone(), kv.value().clone()));
        }
    }
    for (_, handle) in &to_kill {
        let _ = handle.to_stub.send(BackendStubMsg::Kill).await;
    }
}

async fn reload_authorized_keys(state: &Arc<AppState>, text: &str) {
    let parsed = parse_authorized_keys(text);
    let mut k = state.authorized_keys.write().await;
    *k = parsed;
}

async fn send(socket: &mut WebSocket, msg: &BackendOpMsg) -> Result<(), axum::Error> {
    let t = serde_json::to_string(msg).map_err(|e| axum::Error::new(e))?;
    socket.send(Message::Text(t)).await
}

async fn recv_op(socket: &mut WebSocket) -> Option<OpMsg> {
    loop {
        match socket.recv().await? {
            Ok(Message::Text(t)) => return serde_json::from_str(&t).ok(),
            Ok(Message::Binary(b)) => return serde_json::from_slice(&b).ok(),
            Ok(Message::Ping(_)) | Ok(Message::Pong(_)) => continue,
            Ok(Message::Close(_)) => return None,
            Err(_) => return None,
        }
    }
}

fn now_unix() -> i64 {
    std::time::SystemTime::now()
        .duration_since(std::time::UNIX_EPOCH)
        .map(|d| d.as_secs() as i64)
        .unwrap_or(0)
}