/**
 * Hoover — websocket.js
 *
 * WebSocket connection manager with auto-reconnect. WS messages are routed
 * to model-based refresh and direct onMessage handlers.
 * Page-level subscribe/unsubscribe is replaced by the model layer.
 *
 * The JWT is read from the auth model (single source of truth). After 3
 * failed close attempts a token refresh is triggered through the auth
 * model; the reconnect decision branches on the model's token state —
 * never on the refresh promise. Terminal (no-token) transitions are
 * handled by the auth model's onSuccess (clears storage, redirects,
 * dispatches auth:logout).
 *
 * The refresh path is capped at 2 consecutive failing episodes (3 closed
 * connections each): if refresh + reconnect still cannot establish a
 * socket, the WS path itself is dead, and retrying would loop token
 * rotation forever. Reconnection is then abandoned until the page is
 * reloaded; the UI keeps working via the REST API.
 */

import { refreshByTopic } from './model.js';
import { refreshAuth, getAuthToken } from './auth_model.js';

let _wsConn = null;
let _wsReconnectMs = 0;
let _wsFailCount = 0;
// Consecutive refresh→reconnect episodes that still failed. Capped so a
// dead WS path cannot loop `refreshAuth()` forever (each 200 refresh rotates
// the user's token pair, so an unbounded loop storms the refresh endpoint).
let _wsRefreshStreak = 0;
let _wsGivingUp = false;
let _wsClosingHandled = false;

/** Direct onMessage handlers — { topics, handler, unsubscribed }[] */
const _directHandlers = [];

/**
 * Build the WebSocket URL from the current origin. nginx proxies /ws to
 * the daemon's WebSocket port.
 */
function _wsUrl() {
    const proto = location.protocol === 'https:' ? 'wss:' : 'ws:';
    return proto + '//' + location.host + '/ws';
}

/** Attempt a WebSocket connection.
 *  Passes the JWT as the WebSocket subprotocol name (Sec-WebSocket-Protocol)
 *  instead of a query parameter, keeping it out of logs and browser history.
 *  The token is sent as-is, WITHOUT a "Bearer " prefix: subprotocol names
 *  must be valid RFC 6455 tokens and a JWT (base64url + dots) is one, but
 *  the space in "Bearer <token>" is not a token character — the browser
 *  rejects the whole constructor with a SyntaxError.
 *  No token: no socket is created — the daemon 401s unauthenticated WS
 *  connections and connect() only runs while authenticated.
 */
function _wsConnect() {
    if (_wsConn && _wsConn.readyState <= 1) return;

    _wsClosingHandled = false;
    const token = getAuthToken();
    if (!token) return;

    _wsConn = new WebSocket(_wsUrl(), [token]);

    _wsConn.onopen = () => {
        _wsReconnectMs = 0;
        _wsFailCount = 0;
        _wsRefreshStreak = 0;
        _wsGivingUp = false;
        _wsClosingHandled = false;
    };

    _wsConn.onclose = async () => {
        if (_wsClosingHandled) return;
        _wsClosingHandled = true;
        if (!getAuthToken()) return;
        if (_wsGivingUp) return;
        _wsFailCount++;

        if (_wsFailCount >= 3) {
            const oldConn = _wsConn;
            _wsFailCount = 0;
            _wsRefreshStreak++;
            if (_wsRefreshStreak >= 2) {
                // Refresh + reconnect has failed twice in a row — the WS path
                // is dead (not just the token). Stop retrying: the page keeps
                // working API-only, and a fresh page load (or the next
                // successful socket) restarts the cycle.
                _wsGivingUp = true;
                console.error(
                    '[WS] giving up after repeated refresh+reconnect failures; ' +
                        'live updates paused until the page is reloaded',
                );
                return;
            }
            await refreshAuth();   // never rejects; failure path handled by model onSuccess
            if (getAuthToken()) {
                _wsReconnectMs = 0;
                _wsConn = null;
                if (oldConn) oldConn.close();
                setTimeout(_wsConnect, 100);
            }
            // No token after the refresh: onSuccess already cleared storage
            // and redirected to #/login; the no-token guard at the top of
            // onclose stops further reconnect attempts.
            return;
        }

        _wsReconnectMs = Math.min(_wsReconnectMs * 2 + 1000, 15000);
        setTimeout(_wsConnect, _wsReconnectMs);
    };

    _wsConn.onerror = () => {
        _wsConn.close();
    };

    _wsConn.onmessage = (ev) => {
        try {
            const msg = typeof ev.data === 'string' ? JSON.parse(ev.data) : ev.data;
            handleMessage(msg);
        } catch (err) {
            console.warn('[WS] Failed to parse message:', err);
        }
    };
}

/**
 * Route an incoming WS message to model refresh and direct handlers.
 *
 * Expected message shapes:
 *   { type: 'versions', updated: ['firewall', 'dnsmasq', …] }
 *   { type: 'tick',    subsystems: ['firewall', 'wireguard', …] }
 *   { type: 'notify',  topic: 'firewall' }
 *   { type: 'status',  topic: 'firewall', … }
 */
function handleMessage(msg) {
    const topics = [];

    if (msg.type === 'versions' || msg.type === 'refresh' || msg.type === 'tick') {
        topics.push(...(msg.updated || msg.subsystems || msg.topics || []));
    } else if (msg.type === 'notify') {
        topics.push(msg.topic);
    } else if (msg.type === 'status') {
        topics.push(msg.topic || '*');
    }

    // Refresh models for each topic
    for (const topic of topics) {
        refreshByTopic(topic);
    }

    // Notify direct onMessage handlers
    for (const h of _directHandlers) {
        if (h.unsubscribed) continue;
        if (topics.some(t => h.topics.includes(t) || h.topics.includes('*'))) {
            try { h.handler(msg); } catch (err) { console.warn('[WS] Handler error:', err); }
        }
    }
}

/**
 * Public subscribe API for direct one-off usage (e.g. from page code).
 * Handler receives the raw parsed message when a matching topic arrives.
 * @param {string|string[]} topics
 * @param {function} handler
 * @returns {function} unsubscribe
 */
export function onMessage(topics, handler) {
    const tArray = Array.isArray(topics) ? topics : [topics];
    const entry = { topics: tArray, handler, unsubscribed: false };
    _directHandlers.push(entry);
    return () => {
        entry.unsubscribed = true;
        const idx = _directHandlers.indexOf(entry);
        if (idx !== -1) _directHandlers.splice(idx, 1);
    };
}

/** Start the WebSocket connection. */
export function connect() {
    _wsConnect();
}

/** Close the WS socket (terminal auth transition). */
export function disconnect() {
    if (_wsConn) {
        _wsConn.close();
        _wsConn = null;
    }
}