// NatsUtils.js (Stateless Utility - Minimal Imports Version)

// Import only the essentials needed for basic pub/sub/req/status
// We assume these are all exported by your "../esm/nats.js" bundle
import {
    connect,        // For establishing the connection
    JSONCodec,      // For encoding/decoding JSON payloads
    StringCodec,    // For decoding potential error payloads or raw strings
    // Subscription object type might be implicitly handled or imported if needed for type hinting
    // Methods like publish, subscribe, request, status, close are part of the 'nc' object returned by connect.
} from "../nats.ws-1.30.3/esm/nats.js"; // <--- Adjust this path as needed

class NatsUtils {

    /**
     * Get NATS Codecs.
     * @returns {{jsonCodec: object, stringCodec: object}}
     */
    static getCodecs() {
        // We need to instantiate them. The imports just bring in the classes/factories.
        try {
            return { jsonCodec: JSONCodec(), stringCodec: StringCodec() };
        } catch (e) {
            console.error("Failed to create NATS codecs. Ensure nats.ws is loaded correctly.", e);
            // Return dummy objects or null to avoid breaking caller immediately,
            // but subsequent operations will likely fail.
            return { jsonCodec: null, stringCodec: null };
        }
    }

    /**
     * Connect to NATS server.
     * @param {string} url - WebSocket URL
     * @param {object} [options] - NATS connection options
     * @returns {Promise<NatsConnection>} - The connection instance (nc)
     */
    static async Natsconnect(url, options = {}) {
        console.log(`Attempting NATS connection to ${url}...`);
        try {
            // 'connect' is imported directly
            const nc = await connect({ servers: url, ...options });
            console.log("NATS connected.");
            nc.publish("enter", JSONCodec().encode({ id:"gwx" })); // Example publish
            nc.publish("enter", JSONCodec().encode({ id:"gwx2" })); // Example publish
            console.log("Published 'enter' message.",nc);
            return nc;
        } catch (err) {
            console.error("NATS connection failed:", err);
            throw err; // Re-throw for the caller to handle
        }
    }

    /**
     * Disconnect from NATS.
     * @param {NatsConnection} nc - The connection instance
     * @returns {Promise<void>}
     */
    static async disconnect(nc) {
        if (nc && !nc.isClosed()) {
            console.log("Closing NATS connection...");
            try {
                await nc.close(); // Use the close method on the connection object
                console.log("NATS connection closed.");
            } catch (err) {
                console.error("Error closing NATS connection:", err);
            }
        }
    }

    /**
     * Check if connected.
     * @param {NatsConnection} nc - The connection instance
     * @returns {boolean}
     */
    static isConnected(nc) {
        // Use the isClosed method on the connection object
        return nc && !nc.isClosed();
    }

    /**
     * Publish a JSON message.
     * @param {NatsConnection} nc
     * @param {object} jsonCodec - Instance from getCodecs()
     * @param {string} subject
     * @param {object} data - JSON object
     * @returns {boolean} - Success indicator
     */
    static publish(nc, jsonCodec, subject, data) {
        if (!this.isConnected(nc)) return false;
        if (!jsonCodec) { console.error("JSON Codec required for publish"); return false; }
        try {
            // Use the publish method on the connection object
            nc.publish(subject, jsonCodec.encode(data));
            console.log(`Published to ${subject}:`, data);
            return true;
        } catch (err) {
            console.error(`Publish to ${subject} failed:`, err);
            return false;
        }
    }

    /**
     * Subscribe to a subject for JSON messages.
     * @param {NatsConnection} nc
     * @param {object} jsonCodec - Instance from getCodecs()
     * @param {string} subject
     * @param {function(object, string): void} callback - Receives (decodedData, messageSubject)
     * @returns {NatsSubscription | null} - The subscription object (for unsubscribing)
     */
    static subscribe(nc, jsonCodec, subject, callback) {
        if (!this.isConnected(nc)) return null;
        if (!jsonCodec) { console.error("JSON Codec required for subscribe"); return null; }
        try {
            // Use the subscribe method on the connection object
            const sub = nc.subscribe(subject, {
                callback: (err, msg) => {
                    if (err) { /* ... error handling ... */ return; }
                    try {
                        callback(jsonCodec.decode(msg.data), msg.subject);
                    } catch (decodeErr) { /* ... decode error handling ... */ }
                },
            });
            console.log(`Subscription created for ${subject}`);
            return sub;
        } catch (err) {
            console.error(`Subscribe to ${subject} failed:`, err);
            return null;
        }
    }

    /**
     * Unsubscribe.
     * @param {NatsSubscription} subscription - The object returned by subscribe
     */
    static unsubscribe(subscription) {
        if (subscription && typeof subscription.unsubscribe === 'function') {
            try {
                const subSubject = subscription.getSubject ? subscription.getSubject() : 'unknown'; // Get subject if method exists
                subscription.unsubscribe();
                console.log(`Unsubscribed from ${subSubject}`);
            } catch (err) {
                console.error(`Unsubscribe failed:`, err);
            }
        }
    }

    /**
     * Send a JSON request and wait for a JSON reply.
     * @param {NatsConnection} nc
     * @param {object} jsonCodec - Instance from getCodecs()
     * @param {string} subject
     * @param {object} data - JSON request object
     * @param {number} [timeoutMs=10000] - Timeout
     * @returns {Promise<object>} - Promise resolving with the JSON response object
     */
    static async request(nc, jsonCodec, subject, data, timeoutMs = 10000) {
        if (!this.isConnected(nc)) throw new Error("NATS not connected");
        if (!jsonCodec) throw new Error("JSON Codec required for request");
        try {
            // Use the request method on the connection object
            const responseMsg = await nc.request(subject, jsonCodec.encode(data), { timeout: timeoutMs });
            return jsonCodec.decode(responseMsg.data);
        } catch (err) {
            console.error(`Request to ${subject} failed:`, err.message);
            throw err;
        }
    }

    /**
     * Monitor connection status events.
     * @param {NatsConnection} nc
     * @param {function(string, any?): void} statusCallback - Receives (statusType, eventData)
     */
    static monitorStatus(nc, statusCallback) {
        if (!nc) return;
        (async () => {
            try {
                console.log("Starting NATS status monitoring...");
                statusCallback('monitoring_started');
                // Use the status async iterator on the connection object
                for await (const s of nc.status()) {
                    statusCallback(s.type, s.data);
                }
                console.log("NATS status monitoring finished (connection closed).");
                statusCallback('closed');
            } catch (err) {
                console.error("NATS status monitoring error:", err);
                statusCallback('monitoring_error', err);
            }
        })();
    }
}

// Make it globally available or export
window.NatsUtils = NatsUtils;
// export default NatsUtils;