import { connect, StringCodec } from "nats.ws";
import { writable } from "svelte/store";
import msghandlerCSR from './msghandler-csr.js';

export const connectionStatus = writable(null);

let config = null;

export function setConfig(cfg) {
  config = cfg;
}

connectionStatus.subscribe(status => {
  console.log('[NATS] Status updated:', status);
});

let nc = null;
let sc = StringCodec();
let subs = new Map();
let reconnectTimer = null;
let isDisconnecting = false;

export async function getNats(opts = {}) {
  const servers = opts.servers || (import.meta.env.VITE_NATS_URL) || (config?.nats_server_info?.url) || "wss://natsws.yiem.cc";
  console.log('[NATS] Connecting to:', servers);
  
  clearTimeout(reconnectTimer);
  reconnectTimer = null;
  isDisconnecting = false;
  
  try {
    connectionStatus.set({ state: "connecting", message: `connecting to ${servers}` });
    console.log('[NATS] Status: connecting');
    nc = await connect({ servers });
    console.log('[NATS] Connected successfully!');
    connectionStatus.set({ state: "connected", message: `connected to ${servers}` });
    isDisconnecting = false;

    // Track connection state changes for status dot
    // nats.ws emits status events for disconnect/reconnect
    const statusSub = nc.status();
    (async () => {
      for await (const status of statusSub) {
        console.log('[NATS] Status event:', status.type, status.data);
        if (status.type === 'disconnect') {
          connectionStatus.set({ state: 'disconnected', message: 'connection lost' });
        } else if (status.type === 'reconnect') {
          connectionStatus.set({ state: 'connected', message: 'reconnected' });
        } else if (status.type === 'connect') {
          connectionStatus.set({ state: 'connected', message: `connected to ${servers}` });
        }
      }
    })();

    // Also monitor permanent closure
    nc.closed().then((err) => {
      if (isDisconnecting) return;
      if (err) {
        console.log('[NATS] Connection permanently closed with error:', err);
        connectionStatus.set({ state: "error", message: String(err) });
      } else {
        console.log('[NATS] Connection permanently closed normally');
        connectionStatus.set({ state: "disconnected", message: "connection closed" });
      }
    });

    return nc;
  } catch (e) {
    console.error('[NATS] Connection failed:', e);
    connectionStatus.set({ state: "error", message: String(e) });
    // nats.ws will automatically attempt reconnect when we call getNats() again
    throw e;
  }
}

export async function subscribe(subject, onMessage) {
  console.log('[NATS] Subscribing to:', subject);
  if (!nc) await getNats();
  const sub = nc.subscribe(subject);
  subs.set(subject, sub);
  console.log('[NATS] Subscription created for:', subject);
  (async () => {
    for await (const m of sub) {
      let text = "";
      try {
        text = sc.decode(m.data);
        let parsed = {};
        try { parsed = JSON.parse(text); } catch (e) { parsed = { text }; }
        console.log('[NATS] Received message on', subject, ':', parsed);
        onMessage(parsed);
      } catch (e) {
        console.warn("nats message parse error", e);
      }
    }
  })();
  return {
    unsubscribe: async () => {
      console.log('[NATS] Unsubscribing from:', subject);
      try { sub.unsubscribe(); } catch (e) {}
      subs.delete(subject);
    }
  };
}

export async function publish(subject, payload = {}, opts = {}) {
  console.log('[NATS] Publishing to subject:', subject);
  console.log('[NATS] Payload type:', typeof payload);
  console.log('[NATS] Payload (as JSON):', typeof payload === 'string' ? payload : JSON.stringify(payload, null, 2));
  if (!nc) {
    console.log('[NATS] No connection, attempting to connect...');
    await getNats(opts);
  }
  const msg = typeof payload === "string" ? payload : JSON.stringify(payload);
  console.log('[NATS] Final message to publish (first 300 chars):', msg.substring(0, 300) + (msg.length > 300 ? '...' : ''));
  console.log('[NATS] Message length:', msg.length);
  console.log('[NATS] NATS connection exists:', !!nc);
  console.log('[NATS] About to publish...');
  nc.publish(subject, sc.encode(msg));
  console.log('[NATS] Message published successfully to:', subject);
}

export async function closeNats() {
  console.log('[NATS] Closing connection...');
  clearTimeout(reconnectTimer);
  reconnectTimer = null;
  isDisconnecting = true;
  connectionStatus.set({ state: "disconnected", message: "closing" });
  try {
    for (const s of subs.values()) {
      try { s.unsubscribe(); } catch (e) {}
    }
    subs.clear();
    if (nc) {
      await nc.close();
      nc = null;
    }
    console.log('[NATS] Connection closed');
    connectionStatus.set({ state: "disconnected", message: "closed" });
  } catch (e) {
    console.error('[NATS] Error closing connection:', e);
    connectionStatus.set({ state: "error", message: String(e) });
  }
}

export async function connectNATS(brokerUrl, cfg) {
  console.log('[NATS] Connecting with broker URL:', brokerUrl);
  
  let serverUrl = brokerUrl;
  
  if (!serverUrl && cfg) {
    serverUrl = cfg?.nats_server_info?.url || 'wss://natsws.yiem.cc';
  }
  
  console.log('[NATS] Using server URL:', serverUrl);
  setConfig(cfg);
  await getNats({ servers: serverUrl });
}

export async function request(subject, payload, opts = {}) {
  console.log('[NATS] Requesting from:', subject, 'payload:', payload);
  const { timeout, ...getNatsOpts } = opts;
  if (!nc) await getNats(getNatsOpts);
  
  const msg = typeof payload === "string" ? payload : JSON.stringify(payload);
  const requestOpts = timeout ? { timeout } : {};
  const response = await nc.request(subject, sc.encode(msg), requestOpts);
  const responseText = sc.decode(response.data);
  let responseJson;
  try {
    responseJson = JSON.parse(responseText);
  } catch (e) {
    responseJson = { text: responseText };
  }
  console.log('[NATS] Request response:', responseJson);
  return responseJson;
}

export async function reply(subject, handler, opts = {}) {
  console.log('[NATS] Setting up reply handler on:', subject);
  if (!nc) await getNats(opts);
  
  const sub = nc.subscribe(subject);
  subs.set(subject, sub);
  
  (async () => {
    for await (const m of sub) {
      let text = "";
      try {
        text = sc.decode(m.data);
        let parsed = {};
        try { parsed = JSON.parse(text); } catch (e) { parsed = { text }; }
        console.log('[NATS] Received request on', subject, ':', parsed);
        
        const response = handler(parsed, m);
        const responseMsg = typeof response === "string" ? response : JSON.stringify(response);
        nc.publish(m.subject, sc.encode(responseMsg));
        console.log('[NATS] Reply sent to:', m.subject);
      } catch (e) {
        console.warn("nats reply handler error", e);
      }
    }
  })();
  
  return {
    unsubscribe: async () => {
      console.log('[NATS] Unsubscribing from:', subject);
      try { sub.unsubscribe(); } catch (e) {}
      subs.delete(subject);
    }
  };
}

export async function sendMsghandlerRequest(subject, functioncall, args, config) {
  console.log('[NATS] Sending msghandler request:', functioncall);
  
  const payload = {
    functioncall: functioncall,
    args: args
  };
  
  const brokerUrl = config?.nats_server_info?.url || 'wss://natsws.yiem.cc';
  const fileserverUrl = config?.file_server_url || 'https://fileserver.yiem.cc';
  
  const [envelope, envelopeJsonStr] = await msghandlerCSR.smartpack(
    subject,
    [["db_request", payload, "dictionary"]],
    { broker_url: brokerUrl, fileserver_url: fileserverUrl }
  );
  
  console.log('[NATS] Request envelope created, sending...');
  const natsReply = await request(subject, envelopeJsonStr);

  console.log('[NATS] Response received, unpacking...');
  const unpackedEnvelope = await msghandlerCSR.smartunpack(natsReply);
  console.log('-----');
  console.log(unpackedEnvelope);
  console.log('===== 1');
  for (const [dataname, data, type] of unpackedEnvelope.payloads) {
    console.log('[NATS] Extracted payload:', dataname, type);
    if (type === "jsontable" || type === "dictionary") {
      console.log('[NATS] Request successful:', data);
      return data;
    }
    if (type === "text") {
      console.error('[NATS] Error response:', data);
      throw new Error(data);
    }
  }
  
  throw new Error('No valid response found');
}