use crate::api::messages::IncomingMessage;
use crate::api::peers;
use crate::sidecar::SidecarHandle;
use parking_lot::Mutex;
use std::collections::VecDeque;
use std::sync::Arc;
use std::time::Duration;
use tauri::{AppHandle, Emitter};
use tokio::task::JoinHandle;
use tracing::warn;

const PEERS_INTERVAL: Duration = Duration::from_secs(3);
const ROUTES_INTERVAL: Duration = Duration::from_secs(5);
const INBOX_INTERVAL: Duration = Duration::from_secs(2);
const INBOX_RETRY_BACKOFF: Duration = Duration::from_secs(2);
const INBOX_CAPACITY: usize = 200;

pub struct Poller {
    peers_handle: Mutex<Option<JoinHandle<()>>>,
    routes_handle: Mutex<Option<JoinHandle<()>>>,
    inbox_handle: Mutex<Option<JoinHandle<()>>>,
    inbox: Mutex<VecDeque<IncomingMessage>>,
}

impl Poller {
    pub fn new() -> Arc<Self> {
        Arc::new(Self {
            peers_handle: Mutex::new(None),
            routes_handle: Mutex::new(None),
            inbox_handle: Mutex::new(None),
            inbox: Mutex::new(VecDeque::with_capacity(INBOX_CAPACITY)),
        })
    }

    pub fn start(self: &Arc<Self>, app: AppHandle, sidecar: Arc<SidecarHandle>) {
        self.stop();
        *self.peers_handle.lock() = Some(spawn_peers_loop(app.clone(), Arc::clone(&sidecar)));
        *self.routes_handle.lock() = Some(spawn_routes_loop(app.clone(), Arc::clone(&sidecar)));
        *self.inbox_handle.lock() = Some(spawn_inbox_loop(
            app,
            Arc::clone(&sidecar),
            Arc::clone(self),
        ));
    }

    pub fn stop(&self) {
        for slot in [&self.peers_handle, &self.routes_handle, &self.inbox_handle] {
            if let Some(h) = slot.lock().take() {
                h.abort();
            }
        }
    }

    pub fn inbox_snapshot(&self) -> Vec<IncomingMessage> {
        self.inbox.lock().iter().cloned().collect()
    }

    pub fn clear_inbox(&self) {
        self.inbox.lock().clear();
    }

    fn push_inbox(&self, msg: IncomingMessage) {
        let mut buf = self.inbox.lock();
        if buf.len() >= INBOX_CAPACITY {
            buf.pop_front();
        }
        buf.push_back(msg);
    }
}

fn spawn_peers_loop(app: AppHandle, sidecar: Arc<SidecarHandle>) -> JoinHandle<()> {
    tokio::spawn(async move {
        let mut first = true;
        loop {
            if !first {
                tokio::time::sleep(PEERS_INTERVAL).await;
            }
            first = false;

            let Some(client) = sidecar.client() else {
                break;
            };
            match client.list_peers().await {
                Ok(list) => {
                    let stats = peers::aggregate(&list);
                    let _ = app.emit("peers://updated", &list);
                    let _ = app.emit("stats://updated", &stats);
                }
                Err(e) => warn!(error = %e, "poller: list_peers failed"),
            }
        }
    })
}

fn spawn_routes_loop(app: AppHandle, sidecar: Arc<SidecarHandle>) -> JoinHandle<()> {
    tokio::spawn(async move {
        let mut first = true;
        loop {
            if !first {
                tokio::time::sleep(ROUTES_INTERVAL).await;
            }
            first = false;

            let Some(client) = sidecar.client() else {
                break;
            };
            match client.routes_snapshot().await {
                Ok(snap) => {
                    let _ = app.emit("routes://updated", &snap);
                }
                Err(e) => warn!(error = %e, "poller: routes_snapshot failed"),
            }
        }
    })
}

fn spawn_inbox_loop(
    app: AppHandle,
    sidecar: Arc<SidecarHandle>,
    me: Arc<Poller>,
) -> JoinHandle<()> {
    tokio::spawn(async move {
        loop {
            tokio::time::sleep(INBOX_INTERVAL).await;
            let Some(client) = sidecar.client() else {
                break;
            };
            // Short-poll: timeout=0 returns immediately if no message.
            // We previously used a 30s long-poll, but mycelium 0.6.1's
            // HTTP server appears to serialise requests behind a single
            // worker — holding the connection for 30s starved every
            // other endpoint (peers, routes, admin) until our own
            // 10s reqwest timeout kicked in.
            match client.pop_message(false, 0, None).await {
                Ok(Some(msg)) => {
                    me.push_inbox(msg.clone());
                    let _ = app.emit("messages://incoming", &msg);
                }
                Ok(None) => {}
                Err(e) => {
                    warn!(error = %e, "inbox: pop_message failed");
                    tokio::time::sleep(INBOX_RETRY_BACKOFF).await;
                }
            }
        }
    })
}