/**
 * @module event/signing
 * @description Event signing and verification utilities for Nostr
 */

import { schnorr } from '@noble/curves/secp256k1.js';
import { bytesToHex, hexToBytes } from '@noble/hashes/utils.js';
import { logger } from '../utils/logger';
import { getEventHash } from './creation';
import type { NostrEvent, SignedNostrEvent } from '../types';

/**
 * Signs a Nostr event with a private key (NIP-01)
 * @param event - Event to sign
 * @param privateKey - Private key in hex format
 * @returns Signed event
 */
export async function signEvent(
  event: NostrEvent, 
  privateKey: string
): Promise<SignedNostrEvent> {
  try {
    const hash = await getEventHash(event);
    const sig = schnorr.sign(hexToBytes(hash), hexToBytes(privateKey));
    
    return {
      ...event,
      id: hash,
      sig: bytesToHex(sig),
    };
  } catch (error) {
    logger.error({ error }, 'Failed to sign event');
    throw error;
  }
}

/**
 * Verifies the signature of a signed Nostr event (NIP-01)
 * @param event - Event to verify
 * @returns True if signature is valid
 */
export function verifySignature(event: SignedNostrEvent): boolean {
  try {
    return schnorr.verify(
      hexToBytes(event.sig),
      hexToBytes(event.id),
      hexToBytes(event.pubkey)
    );
  } catch (error) {
    logger.error({ error }, 'Failed to verify signature');
    return false;
  }
}

/**
 * Validates a Nostr event
 * @param event - Event to validate
 * @returns True if event is valid
 */
export function validateEvent(event: SignedNostrEvent): boolean {
  try {
    // Check required fields
    if (!event.id || !event.pubkey || !event.sig) {
      return false;
    }

    // Verify signature
    return verifySignature(event);
  } catch (error) {
    logger.error({ error }, 'Error validating event');
    return false;
  }
}

/**
 * Calculates the event ID for a Nostr event
 * @param event - Event to calculate ID for
 * @returns Event ID
 */
export function calculateEventId(event: NostrEvent): Promise<string> {
  return getEventHash(event);
}