/**
 * @fileoverview Centralized reactive state store with pub/sub.
 *
 * Wraps a plain data object in a Proxy so that `BB.state.foo = bar` triggers
 * subscribers. The Proxy approach (vs. explicit getters/setters) keeps the API
 * concise: any property access reads directly from `data`, any assignment calls
 * `set()` which notifies listeners.
 */
(function() {
    'use strict';

    const subscribers = {};
    const data = {
        sources: [],
        items: [],
        currentSource: '',
        currentOrder: 'chronological',
        currentSearch: '',
        currentPage: 0,
        hasMore: false,
        selectedItemId: null,
        selectedPluginId: null,
        allTags: [],
        currentTag: '',
        queryFeeds: [],
        currentQueryFeed: null,
        sessionArticlesRead: 0,
        sessionArticlesStarred: 0,
    };

    /**
     * Subscribe to changes on a state key. Returns an unsubscribe function.
     * @param {string} key - State property name to watch.
     * @param {function(any, any): void} callback - Called with (newValue, oldValue).
     * @returns {function(): void} Unsubscribe function.
     */
    function subscribe(key, callback) {
        if (!subscribers[key]) subscribers[key] = [];
        subscribers[key].push(callback);
        return () => {
            subscribers[key] = subscribers[key].filter(cb => cb !== callback);
        };
    }

    /**
     * Update a state value and notify all subscribers for that key.
     * @param {string} key - State property name.
     * @param {any} value - New value.
     */
    function set(key, value) {
        const old = data[key];
        data[key] = value;
        if (subscribers[key]) {
            subscribers[key].forEach(cb => cb(value, old));
        }
    }

    /**
     * Read a state value.
     * @param {string} key - State property name.
     * @returns {any} Current value.
     */
    function get(key) {
        return data[key];
    }

    /**
     * Reset pagination to the first page, optionally clearing selection.
     * @param {boolean} [clearSelection=false] - Also clear selectedItemId.
     */
    function resetPagination(clearSelection) {
        set('currentPage', 0);
        if (clearSelection) set('selectedItemId', null);
    }

    // Proxy for direct access: BB.state.sources etc.
    BB.state = new Proxy(data, {
        get(target, prop) {
            if (prop === 'subscribe') return subscribe;
            if (prop === 'set') return set;
            if (prop === 'get') return get;
            if (prop === 'resetPagination') return resetPagination;
            return target[prop];
        },
        set(target, prop, value) {
            set(prop, value);
            return true;
        },
    });
})();