/**
 * 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, isComponentStateMounted, getComponentEntry } from './component.js?v=6';

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 (_) {}
    };
}

/** Per-state debounce timer (shared across all subscriptions for that state). */
const _wsDebounceTimers = new Map();

/**
 * Fire the debounced load for a component state.
 *
 * Only one load fires per state regardless of how many subscriptions
 * matched.  Passes the mount entry so refactorLoad can toggle
 * loading / refreshing flags correctly.
 */
function debouncedLoad(state, entry) {
    if (!isComponentStateMounted(state)) return;
    // Abort any in-flight load for this component
    if (entry && entry.loadAbort) entry.loadAbort.abort();
    const ac = new AbortController();
    const firstSub = [..._wsSubs.values()]
        .find(s => !s.unsubscribed && s.state === state);
    if (firstSub) {
        firstSub.loadFn(state, ac, entry);
    }
}

/**
 * Debounce helper: coalesces all matching subscriptions for the same
 * component state into a single reload, keyed by state object.
 */
function scheduleReload(state) {
    if (_wsDebounceTimers.has(state)) {
        clearTimeout(_wsDebounceTimers.get(state));
    }
    _wsDebounceTimers.set(state, setTimeout(() => {
        _wsDebounceTimers.delete(state);
        const entry = getComponentEntry(state);
        debouncedLoad(state, entry);
    }, 300));
}

/**
 * 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.
 *
 * Uses per-component-state debouncing (300ms) to prevent a burst of WS
 * messages or multiple matching topics from triggering overlapping
 * loads.  All subscriptions that share the same state object are
 * coalesced into a single debounced reload.
 */
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 || '*');
    }

    // Track which states have already been scheduled to avoid
    // double-scheduling when multiple subscriptions of the same
    // component match the same message.
    const scheduled = new Set();

    for (const s of _wsSubs.values()) {
        if (s.unsubscribed || !isComponentStateMounted(s.state)) continue;

        const matched = s.topic === '*' || topics.some(t => t === s.topic || t === '*');
        if (!matched) continue;

        if (scheduled.has(s.state)) continue;
        scheduled.add(s.state);
        scheduleReload(s.state);
    }
}

/**
 * Subscribe a component to WS topics.
 *
 * Called by component.js on mount.  Returns an unsubscribe function
 * called by component.js on unmount.
 *
 * Key is `componentFn + ':' + topic` so a component can subscribe to
 * multiple topics without overwriting previous subscriptions.
 *
 * @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 key = componentFn + ':' + topic;
    const entry = { componentFn, topic, loadFn, state, unsubscribed: false };
    _wsSubs.set(key, entry);

    return () => {
        entry.unsubscribed = true;
        // Clear per-state debounce timer if this was the last active
        // subscription for that state
        const remaining = [..._wsSubs.values()]
            .some(s => !s.unsubscribed && s.state === entry.state);
        if (!remaining && _wsDebounceTimers.has(entry.state)) {
            clearTimeout(_wsDebounceTimers.get(entry.state));
            _wsDebounceTimers.delete(entry.state);
        }
        _wsSubs.delete(key);
    };
}

/** 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;
            if (_wsDebounceTimers.has(entry.state)) {
                clearTimeout(_wsDebounceTimers.get(entry.state));
                _wsDebounceTimers.delete(entry.state);
            }
            _wsSubs.delete(handler + ':' + t);
        });
    }
    return () => fns.forEach(f => f());
}