iistwin/server/utils/webhook.ts

import { storage } from '../storage';

export interface SendWebhookOptions {
  retries?: number;
  taskId?: number;
  organizationId?: number;
  botId?: number;
  eventType?: string;
}

/**
 * Simple counting semaphore to cap concurrent outbound webhook requests.
 */
class Semaphore {
  private slots: number;
  private queue: Array<() => void> = [];

  constructor(slots: number) {
    this.slots = slots;
  }

  acquire(): Promise<void> {
    if (this.slots > 0) {
      this.slots--;
      return Promise.resolve();
    }
    return new Promise(resolve => this.queue.push(resolve));
  }

  release(): void {
    if (this.queue.length > 0) {
      const next = this.queue.shift()!;
      next();
    } else {
      this.slots++;
    }
  }
}

// Max 5 concurrent outbound webhook requests across the whole process
const webhookSemaphore = new Semaphore(5);

/**
 * Send a webhook with automatic retry (exponential backoff) and concurrency limiting.
 *
 * @param url         - Target webhook URL
 * @param payload     - JSON-serialisable request body
 * @param headers     - Additional HTTP headers (Content-Type is always set)
 * @param options     - Retry count and optional audit-log context
 */
export async function sendWebhook(
  url: string,
  payload: unknown,
  headers: Record<string, string> = {},
  options: SendWebhookOptions = {}
): Promise<void> {
  const { retries = 3, taskId, organizationId, botId, eventType } = options;
  const body = JSON.stringify(payload);

  await webhookSemaphore.acquire();
  try {
    let lastError: unknown;

    for (let attempt = 0; attempt < retries; attempt++) {
      if (attempt > 0) {
        // Exponential backoff: 2 s, 4 s, 8 s, …
        const delayMs = Math.pow(2, attempt) * 1000;
        await new Promise(resolve => setTimeout(resolve, delayMs));
      }

      try {
        const response = await fetch(url, {
          method: 'POST',
          headers: { 'Content-Type': 'application/json', ...headers },
          body,
        });

        if (response.ok) {
          return; // success
        }

        const text = await response.text().catch(() => '');
        lastError = new Error(`HTTP ${response.status}: ${text}`);
        console.error(
          `[webhook] Attempt ${attempt + 1}/${retries} failed (HTTP ${response.status}) — ${url}`
        );
      } catch (err) {
        lastError = err;
        console.error(
          `[webhook] Attempt ${attempt + 1}/${retries} failed (network) — ${url}:`,
          err
        );
      }
    }

    // All retries exhausted
    const errorMessage =
      lastError instanceof Error ? lastError.message : String(lastError);
    console.error(
      `[webhook] Delivery permanently failed after ${retries} attempts — ${url}: ${errorMessage}`
    );

    // Record failure in task audit log when task context is available
    if (taskId != null && organizationId != null) {
      storage
        .addTaskAuditLog({
          taskId,
          organizationId,
          action: 'webhook.failed',
          fieldName: 'webhook',
          newValue: url,
          changedBy: null,
          changedByName: 'system',
          metadata: {
            url,
            botId: botId ?? null,
            eventType: eventType ?? null,
            error: errorMessage,
            attempts: retries,
          },
        })
        .catch(err =>
          console.error('[webhook] Failed to write audit log entry:', err)
        );
    }
  } finally {
    webhookSemaphore.release();
  }
}