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://nats.yiem.cc";
  console.log('[NATS] Connecting to:', servers);
  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;

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

    return nc;
  } catch (e) {
    console.error('[NATS] Connection failed:', e);
    connectionStatus.set({ state: "error", message: String(e) });
    attemptReconnect(servers);
    throw e;
  }
}

async function attemptReconnect(servers, retryCount = 0) {
  const maxDelay = 30000;
  const baseDelay = Math.min(1000 * Math.pow(2, retryCount), maxDelay);
  
  console.log(`[NATS] Reconnecting in ${baseDelay}ms (attempt ${retryCount + 1})...`);
  
  reconnectTimer = setTimeout(async () => {
    try {
      connectionStatus.set({ state: "connecting", message: `reconnecting to ${servers}` });
      nc = await connect({ servers });
      console.log('[NATS] Reconnected successfully!');
      connectionStatus.set({ state: "connected", message: `connected to ${servers}` });
      isDisconnecting = false;
      
      const subsCopy = Array.from(subs.entries());
      for (const [subject, onMessage] of subsCopy) {
        try {
          await subscribe(subject, onMessage);
        } catch (e) {
          console.warn(`[NATS] Failed to re-subscribe to ${subject}:`, e);
        }
      }
    } catch (e) {
      console.error('[NATS] Reconnection failed:', e);
      connectionStatus.set({ state: "error", message: String(e) });
      attemptReconnect(servers, retryCount + 1);
    }
  }, baseDelay);
}

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, 'payload:', payload);
  if (!nc) await getNats(opts);
  const msg = typeof payload === "string" ? payload : JSON.stringify(payload);
  nc.publish(subject, sc.encode(msg));
  console.log('[NATS] Message published successfully');
}

export async function closeNats() {
  console.log('[NATS] Closing connection...');
  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://nats.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);
  if (!nc) await getNats(opts);
  
  const msg = typeof payload === "string" ? payload : JSON.stringify(payload);
  const response = await nc.request(subject, sc.encode(msg));
  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://nats.yiem.cc';
  const fileserverUrl = config?.file_server_url || 'http://localhost:8080';
  
  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;
    }