/**
 * Runtime Configuration Service
 * 
 * This service fetches and caches configuration from the /api/config endpoint,
 * allowing the application to use runtime environment variables instead of
 * build-time values.
 * 
 * Usage:
 *   import { getApiUrl, getBackofficeUrl, initConfig } from '@/lib/config';
 *   
 *   // Initialize once at app startup (optional, auto-initializes on first use)
 *   await initConfig();
 *   
 *   // Get URLs (returns cached values or defaults)
 *   const apiUrl = getApiUrl();
 */

export interface RuntimeConfig {
    apiUrl: string;
    backofficeUrl: string;
    seederApiUrl: string;
    scraperApiUrl: string;
}

// Default values (fallback to build-time env or hardcoded defaults)
const defaultConfig: RuntimeConfig = {
    apiUrl: process.env.NEXT_PUBLIC_API_URL || 'http://localhost:8521',
    backofficeUrl: process.env.NEXT_PUBLIC_BACKOFFICE_URL || 'http://localhost:3001',
    seederApiUrl: process.env.NEXT_PUBLIC_SEEDER_API_URL || 'http://localhost:3002',
    scraperApiUrl: process.env.NEXT_PUBLIC_SCRAPER_API_URL || 'http://localhost:3003',
};

let cachedConfig: RuntimeConfig | null = null;
let isInitialized = false;
let initPromise: Promise<RuntimeConfig> | null = null;

/**
 * Initialize the config from the server.
 * Safe to call multiple times - only fetches once.
 */
export async function initConfig(): Promise<RuntimeConfig> {
    // If already initialized, return cached config
    if (isInitialized && cachedConfig) {
        return cachedConfig;
    }

    // If already initializing, wait for that promise
    if (initPromise) {
        return initPromise;
    }

    // Start initialization
    initPromise = (async () => {
        try {
            // Only fetch if we're in the browser
            if (typeof window !== 'undefined') {
                const response = await fetch('/api/config');
                if (response.ok) {
                    cachedConfig = await response.json();
                    console.log('[Config] Loaded runtime config:', cachedConfig);
                } else {
                    console.warn('[Config] Failed to fetch config, using defaults');
                    cachedConfig = defaultConfig;
                }
            } else {
                // Server-side: use defaults
                cachedConfig = defaultConfig;
            }
        } catch (error) {
            console.warn('[Config] Error fetching config, using defaults:', error);
            cachedConfig = defaultConfig;
        }

        isInitialized = true;
        return cachedConfig!;
    })();

    return initPromise;
}

/**
 * Get the full config object.
 * Returns cached config if initialized, otherwise defaults.
 */
export function getConfig(): RuntimeConfig {
    // Trigger async init in background if not initialized
    if (!isInitialized && typeof window !== 'undefined') {
        initConfig();
    }
    return cachedConfig || defaultConfig;
}

/**
 * Get the API base URL.
 * @returns The API URL (e.g., "https://api.gohorsejobs.com")
 */
export function getApiUrl(): string {
    return getConfig().apiUrl;
}

/**
 * Get the full API URL with /api/v1 suffix.
 * @returns The full API URL (e.g., "https://api.gohorsejobs.com/api/v1")
 */
export function getApiV1Url(): string {
    return `${getConfig().apiUrl}/api/v1`;
}

/**
 * Get the Backoffice URL.
 */
export function getBackofficeUrl(): string {
    return getConfig().backofficeUrl;
}

/**
 * Get the Seeder API URL.
 */
export function getSeederApiUrl(): string {
    return getConfig().seederApiUrl;
}

/**
 * Get the Scraper API URL.
 */
export function getScraperApiUrl(): string {
    return getConfig().scraperApiUrl;
}