import { createTRPCClient, httpBatchLink } from '@trpc/client';
import superjson from 'superjson';
import type { AppRouter } from '@repo/api';
import { db } from './db';
import { broadcast } from './broadcast';

let _client: ReturnType<typeof createTRPCClient<AppRouter>> | null = null;

function getClient() {
  if (!_client) {
    _client = createTRPCClient<AppRouter>({
      links: [httpBatchLink({ url: '/api/trpc', transformer: superjson })],
    });
  }
  return _client;
}

function httpStatus(err: unknown): number | null {
  if (typeof err === 'object' && err !== null && 'data' in err) {
    const d = (err as { data?: { httpStatus?: number } }).data;
    return d?.httpStatus ?? null;
  }
  return null;
}

function isNetworkErr(err: unknown): boolean {
  return err instanceof TypeError;
}

let _running = false;

export async function runSync(): Promise<void> {
  if (_running || !navigator.onLine) return;
  _running = true;
  try {
    const items = await db.pending.orderBy('queuedAt').toArray();
    if (!items.length) return;

    const client = getClient();

    for (const item of items) {
      try {
        let photoKey: string | undefined;

        if (item.photoBlob) {
          const { uploadUrl, photoKey: key } = await client.storage.signPhotoUpload.mutate({
            contentType: 'image/jpeg',
            byteSize: item.photoBlob.size,
          });
          const res = await fetch(uploadUrl, {
            method: 'PUT',
            body: item.photoBlob,
            headers: { 'Content-Type': 'image/jpeg' },
          });
          if (!res.ok) throw new Error(`Photo PUT ${res.status}`);
          photoKey = key;
        }

        await client.maintenanceRequest.create.mutate({
          workstationId: item.workstationId,
          description: item.description,
          photoKey,
          clientRequestId: item.clientRequestId,
        });

        await db.pending.delete(item.clientRequestId);
        broadcast({ type: 'synced', clientRequestId: item.clientRequestId });
      } catch (err) {
        if (isNetworkErr(err)) break; // no connectivity — stop this cycle

        const status = httpStatus(err);

        if (status === 409) {
          // Already exists (duplicate clientRequestId) — idempotent success
          await db.pending.delete(item.clientRequestId);
          broadcast({ type: 'synced', clientRequestId: item.clientRequestId });
          continue;
        }

        if (status !== null && status >= 400 && status < 500) {
          // 4xx other than 409 — permanent failure, move to dead-letter
          await db.deadLetters.put({
            clientRequestId: item.clientRequestId,
            error: err instanceof Error ? err.message : String(err),
            failedAt: Date.now(),
          });
          await db.pending.delete(item.clientRequestId);
          broadcast({ type: 'dead-letter', clientRequestId: item.clientRequestId });
          continue;
        }

        // 5xx / unknown — increment retries, leave in queue
        await db.pending.update(item.clientRequestId, {
          retries: (item.retries ?? 0) + 1,
          lastError: err instanceof Error ? err.message : String(err),
        });
      }
    }

    const remaining = await db.pending.count();
    broadcast({ type: 'queue-update', pendingCount: remaining });
  } finally {
    _running = false;
  }
}