/**
 * data-binder.js — apre una singola sottoscrizione SignalK delta locale
 * e smista i valori ai tile per path.
 *
 * Espone window.dataBinder con:
 *   subscribe(path, fn)      → unsubscribe()
 *   getLatest(path)          → ultimo valore visto (o null)
 *   onConnState(fn)          → notifica connesso/disconnesso
 */
(function () {
    const subs = new Map();              // path -> Set<fn>
    const latest = new Map();            // path -> { value, ts }
    const stateListeners = new Set();
    let ws = null;
    let reconnectTimer = null;

    function notify(path, value) {
        latest.set(path, { value, ts: Date.now() });
        const ss = subs.get(path);
        if (!ss) return;
        for (const fn of ss) { try { fn(value); } catch (e) { console.warn(e); } }
    }

    function notifyState(s) { for (const fn of stateListeners) { try { fn(s); } catch (_) {} } }

    function connect() {
        const url = `ws://${location.host}/signalk/v1/stream?subscribe=all`;
        try { ws = new WebSocket(url); }
        catch (err) { console.error('[BINDER] WS create:', err); scheduleReconnect(); return; }

        ws.onopen = () => { notifyState({ connected: true }); console.log('[BINDER] WS connected'); };
        ws.onerror = (e) => console.warn('[BINDER] WS error', e);
        ws.onclose = () => { notifyState({ connected: false }); scheduleReconnect(); };
        ws.onmessage = (ev) => {
            let msg;
            try { msg = JSON.parse(ev.data); } catch { return; }
            if (!msg.updates) return;
            for (const u of msg.updates) {
                if (!u.values) continue;
                for (const v of u.values) {
                    if (!v.path) continue;
                    notify(v.path, v.value);
                    // espandi position in lat/lon per chi si iscrive a quelli
                    if (v.path === 'navigation.position' && v.value && typeof v.value === 'object') {
                        if (v.value.latitude  != null) notify('navigation.position.latitude',  v.value.latitude);
                        if (v.value.longitude != null) notify('navigation.position.longitude', v.value.longitude);
                    }
                }
            }
        };
    }

    function scheduleReconnect() {
        if (reconnectTimer) return;
        reconnectTimer = setTimeout(() => { reconnectTimer = null; connect(); }, 3000);
    }

    function subscribe(path, fn) {
        if (!subs.has(path)) subs.set(path, new Set());
        subs.get(path).add(fn);
        const last = latest.get(path);
        if (last) { try { fn(last.value); } catch (_) {} }
        return () => subs.get(path)?.delete(fn);
    }

    function getLatest(path) { return latest.get(path)?.value ?? null; }
    function onConnState(fn) { stateListeners.add(fn); return () => stateListeners.delete(fn); }

    connect();

    window.dataBinder = { subscribe, getLatest, onConnState };
})();