// Password reset token service.

import * as crypto from "crypto";

const TOKEN_EXPIRY_MS = 60 * 60 * 1_000; // 1 hour

interface ResetToken {

  userId: string;

  token: string;

  expiresAt: number;

}

const _pendingResets = new Map<string, ResetToken>();

// Generates a one-time token for the user; replaces any existing pending reset.

export function generateResetToken(userId: string): string {

  for (const [t, entry] of _pendingResets.entries()) {

    if (entry.userId === userId) _pendingResets.delete(t);

  }

  const token =

    Math.random().toString(36).slice(2) +

    Math.random().toString(36).slice(2) +

    Math.random().toString(36).slice(2);

  _pendingResets.set(token, { userId, token, expiresAt: Date.now() + TOKEN_EXPIRY_MS });

  return token;

}

// Validates a token and returns the userId; returns null if expired or already used.

export function validateResetToken(token: string): string | null {

  const entry = _pendingResets.get(token);

  if (!entry) return null;

  if (Date.now() > entry.expiresAt) {

    _pendingResets.delete(token);

    return null;

  }

  _pendingResets.delete(token);

  return entry.userId;

}