import { Injectable } from '@nestjs/common';
import { Agent, Dispatcher } from 'undici';
import { OutboundUrlGuard } from './outbound-url.guard';

export const OUTBOUND_REQUEST_TIMEOUT_MS = 10_000;

export type OutboundTlsOptions = {
  caCert?: string; // PEM encoded
  rejectUnauthorized?: boolean; // Defaults to true; self-hosted only when false.
};

export type AgentLease = {
  dispatcher: Dispatcher;
  release: () => Promise<void>;
};

export type IOutboundAgentFactory = {
  lease(url: string, tls?: OutboundTlsOptions): Promise<AgentLease>;
};

/** Creates a per-request agent pinned to the address validated by the SSRF guard. */
@Injectable()
export class OutboundAgentFactory implements IOutboundAgentFactory {
  constructor(private readonly urlGuard: OutboundUrlGuard) {}

  async lease(url: string, tls?: OutboundTlsOptions): Promise<AgentLease> {
    const pinned = await this.urlGuard.validate(url);

    const lookup = (_hostname: string, options: any, callback: any) => {
      if (options?.all) {
        callback(null, [{ address: pinned.address, family: pinned.family }]);
      } else {
        callback(null, pinned.address, pinned.family);
      }
    };

    const agent = new Agent({
      connect: {
        ca: tls?.caCert || undefined,
        rejectUnauthorized: tls?.rejectUnauthorized ?? true,
        lookup: lookup as any,
        timeout: OUTBOUND_REQUEST_TIMEOUT_MS,
      },
      headersTimeout: OUTBOUND_REQUEST_TIMEOUT_MS,
      bodyTimeout: OUTBOUND_REQUEST_TIMEOUT_MS,
    });

    return {
      dispatcher: agent,
      release: async () => {
        await agent.close();
      },
    };
  }
}