import type { IJMAPClient } from '@/lib/jmap/client-interface';
import { TransportError } from '@/lib/jmap/client';
import { debug } from '@/lib/debug';

const STORAGE_KEY = 'vncmail:pending-ops';

export type OperationType =
  | 'sendEmail'
  | 'createEvent'
  | 'updateEvent'
  | 'deleteEvent'
  | 'createContact'
  | 'updateContact'
  | 'deleteContact'
  | 'createTask'
  | 'updateTask'
  | 'deleteTask';

export interface PendingOperation {
  id: string;
  type: OperationType;
  accountId: string;
  payload: unknown;
  createdAt: string;
  retryCount: number;
}

function loadOps(): PendingOperation[] {
  try {
    const raw = localStorage.getItem(STORAGE_KEY);
    if (!raw) return [];
    return JSON.parse(raw) as PendingOperation[];
  } catch {
    return [];
  }
}

function saveOps(ops: PendingOperation[]): void {
  try {
    localStorage.setItem(STORAGE_KEY, JSON.stringify(ops));
  } catch {
    debug.error('offline-write-queue', 'Failed to persist pending operations');
  }
}

export function enqueueOperation(
  op: Omit<PendingOperation, 'id' | 'createdAt' | 'retryCount'>,
): void {
  const ops = loadOps();
  ops.push({
    ...op,
    id: crypto.randomUUID(),
    createdAt: new Date().toISOString(),
    retryCount: 0,
  });
  saveOps(ops);
  notifyCountChanged(getPendingOperationsCount());
}

export function dequeueOperation(id: string): void {
  const ops = loadOps();
  saveOps(ops.filter((o) => o.id !== id));
  notifyCountChanged(getPendingOperationsCount());
}

export function getPendingOperations(accountId: string): PendingOperation[] {
  return loadOps().filter((o) => o.accountId === accountId);
}

export function getPendingOperationsCount(): number {
  return loadOps().length;
}

export function clearAllOperations(): void {
  saveOps([]);
  notifyCountChanged(0);
}

export async function processQueue(
  client: IJMAPClient,
  accountId: string,
): Promise<{ succeeded: number; failed: number }> {
  const ops = getPendingOperations(accountId);
  let succeeded = 0;
  let failed = 0;

  for (const op of ops) {
    try {
      await executeOperation(client, op);
      dequeueOperation(op.id);
      succeeded++;
    } catch {
      op.retryCount += 1;
      failed++;
      if (op.retryCount >= 5) {
        dequeueOperation(op.id);
        debug.warn('offline-write-queue', 'Dropping operation after max retries', {
          id: op.id,
          type: op.type,
        });
        failed++;
      }
    }
  }

  // Persist updated retry counts for failed operations
  const allOps = loadOps();
  for (const failedOp of ops.filter((o) => allOps.some((a) => a.id === o.id))) {
    const idx = allOps.findIndex((a) => a.id === failedOp.id);
    if (idx >= 0) allOps[idx] = failedOp;
  }
  saveOps(allOps);

  notifyCountChanged(getPendingOperationsCount());

  return { succeeded, failed };
}

async function executeOperation(
  client: IJMAPClient,
  op: PendingOperation,
): Promise<void> {
  switch (op.type) {
    case 'sendEmail': {
      const p = op.payload as {
        to: string[];
        subject: string;
        body: string;
        cc?: string[];
        bcc?: string[];
        identityId?: string;
        fromEmail?: string;
        draftId?: string;
        fromName?: string;
        htmlBody?: string;
        attachments?: Array<{
          blobId: string;
          name: string;
          type: string;
          size: number;
          disposition?: 'attachment' | 'inline';
          cid?: string;
        }>;
        inReplyTo?: string[];
        references?: string[];
        delayedUntil?: string;
        envelopeMailFrom?: string;
        options?: { requestReadReceipt?: boolean };
      };
      await client.sendEmail(
        p.to,
        p.subject,
        p.body,
        p.cc,
        p.bcc,
        p.identityId,
        p.fromEmail,
        p.draftId,
        p.fromName,
        p.htmlBody,
        p.attachments,
        p.inReplyTo,
        p.references,
        p.delayedUntil,
        p.envelopeMailFrom,
        p.options,
      );
      break;
    }
    case 'createEvent':
      await client.createCalendarEvent(op.payload as Record<string, unknown>);
      break;
    case 'updateEvent': {
      const up = op.payload as { id: string; updates: Record<string, unknown> };
      await client.updateCalendarEvent(up.id, up.updates);
      break;
    }
    case 'deleteEvent':
      await client.deleteCalendarEvent(op.payload as string);
      break;
    case 'createContact':
      await client.createContact(op.payload as Record<string, unknown>);
      break;
    case 'updateContact': {
      const uc = op.payload as { id: string; updates: Record<string, unknown> };
      await client.updateContact(uc.id, uc.updates);
      break;
    }
    case 'deleteContact': {
      const dc = op.payload as { id: string; targetAccountId?: string };
      await client.deleteContact(dc.id, dc.targetAccountId);
      break;
    }
    case 'createTask':
      await client.createCalendarTask(op.payload as Record<string, unknown>);
      break;
    case 'updateTask': {
      const ut = op.payload as { id: string; updates: Record<string, unknown> };
      await client.updateCalendarTask(ut.id, ut.updates);
      break;
    }
    case 'deleteTask': {
      const dt = op.payload as { id: string; targetAccountId?: string };
      await client.deleteCalendarTask(dt.id, dt.targetAccountId);
      break;
    }
    default:
      throw new Error(`Unknown operation type: ${op.type}`);
  }
}

const countListeners = new Set<(count: number) => void>();

export function onPendingCountChange(listener: (count: number) => void): () => void {
  countListeners.add(listener);
  return () => countListeners.delete(listener);
}

function notifyCountChanged(count: number): void {
  for (const listener of countListeners) {
    try {
      listener(count);
    } catch {
      /* noop */
    }
  }
}

export function isNetworkError(error: unknown): boolean {
  if (error instanceof TransportError) return true;
  if (error instanceof TypeError) return true;
  if (error instanceof Error) {
    const msg = error.message.toLowerCase();
    return (
      msg.includes('network') ||
      msg.includes('fetch') ||
      msg.includes('econnrefused') ||
      msg.includes('timeout') ||
      msg.includes('offline') ||
      msg.includes('abort')
    );
  }
  return false;
}

let cleanupHandler: (() => void) | null = null;

export function initOfflineQueueHandler(
  getClient: () => IJMAPClient | null,
  getAccountId: () => string | null,
): () => void {
  if (typeof window === 'undefined') return () => {};

  const handleOnline = () => {
    const client = getClient();
    const accountId = getAccountId();
    if (!client || !accountId) return;
    processQueue(client, accountId).catch((err) => {
      debug.error('offline-write-queue', 'Failed to process queue on reconnect', err);
    });
  };

  window.addEventListener('online', handleOnline);

  cleanupHandler = () => window.removeEventListener('online', handleOnline);

  return cleanupHandler;
}