/**
 * Hoover — websocket.js
 *
 * WebSocket connection manager with auto-reconnect, subscribe/unsubscribe
 * per component per topic, and version-track messages.
 *
 * The _wsSubs Map stores entries keyed by renderer function so that
 * auto-refresh messages from the backend can trigger page reloads.
 */

import { setSubscribeFn } from './component.js';

const _wsSubs = new Map();
let _wsConn = null;
let _wsReconnectMs = 0;

/**
 * Build the WebSocket URL.  Supports an override via `window.__WS_URL__`
 * (useful for proxy setups).  Falls back to port 9091 when the current
 * origin has no port (nginx fronting the WS on a different port).
 */
function _wsUrl() {
    if (window.__WS_URL__) return window.__WS_URL__;
    const proto = location.protocol === 'https:' ? 'wss:' : 'ws:';
    return proto + '//' + location.host + '/ws';
}

/** Attempt a WebSocket connection. */
function _wsConnect() {
    if (_wsConn && _wsConn.readyState <= 1) return;

    _wsConn = new WebSocket(_wsUrl());

    _wsConn.onopen = () => {
        _wsReconnectMs = 0;
    };

    _wsConn.onclose = () => {
        _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 (_) {}
    };
}

/**
 * Route an incoming WS message to subscribed components.
 *
 * Expected message shapes:
 *   { type: 'versions', updated: ['firewall', 'dnsmasq', …] }
 *   { type: 'notify',  topic: 'firewall' }
 *   { type: 'status',  topic: 'firewall', … }
 *
 * Components subscribed to wildcard ('*') match every topic.
 */
function handleMessage(msg) {
    const topics = [];

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

    for (const s of _wsSubs.values()) {
        if (s.unsubscribed) continue;
        if (s.topic === '*') {
            s.loadFn(s.state);
        } else if (topics.some(t => t === s.topic || t === '*')) {
            s.loadFn(s.state);
        }
    }
}

/**
 * Subscribe a component to WS topics.
 *
 * Called by component.js on mount.  Returns an unsubscribe function
 * called by component.js on unmount.
 *
 * @param {function} componentFn – The page renderer function (used as map key)
 * @param {string} topic         – Topic to listen for ('*' = all)
 * @param {function} loadFn      – Function to call when topic updates
 * @param {object} state         – Reactive state passed to loadFn
 * @returns {function} unsubscribe
 */
function subscribe(componentFn, topic, loadFn, state) {
    const entry = { componentFn, topic, loadFn, state, unsubscribed: false };
    _wsSubs.set(componentFn, entry);

    return () => {
        entry.unsubscribed = true;
        _wsSubs.delete(componentFn);
    };
}

/** Register the subscribe function with component.js and kick off connection. */
setSubscribeFn(subscribe);

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

/**
 * Public subscribe API for direct one-off usage (e.g. from page code).
 * @param {string|string[]} topics
 * @param {function} handler
 * @returns {function} unsubscribe
 */
export function onMessage(topics, handler) {
    const tArray = Array.isArray(topics) ? topics : [topics];
    const fns = [];
    for (const t of tArray) {
        const entry = {
            componentFn: handler, topic: t, loadFn: handler, state: {},
            unsubscribed: false
        };
        _wsSubs.set(handler + ':' + t, entry);
        fns.push(() => { entry.unsubscribed = true; _wsSubs.delete(handler + ':' + t); });
    }
    return () => fns.forEach(f => f());
}