import { NextResponse } from 'next/server';

import { validateEmail, isDisposableEmail } from '@gridpilot/identity/domain/value-objects/EmailAddress';
import { checkRateLimit, getClientIp } from '@/lib/rate-limit';

const SIGNUP_DEV_STORE = new Map<string, { email: string; createdAt: number; ip: string }>();
const SIGNUP_KV_HASH_KEY = 'signups:emails';

const isDev = !process.env.KV_REST_API_URL;

function jsonError(status: number, message: string, extra: Record<string, unknown> = {}) {
  return NextResponse.json(
    {
      error: message,
      ...extra,
    },
    { status },
  );
}

export async function POST(request: Request) {
  let body: unknown;

  try {
    body = await request.json();
  } catch {
    return jsonError(400, 'Invalid request body');
  }

  const email =
    typeof body === 'object' && body !== null && 'email' in body
      ? (body as { email: unknown }).email
      : undefined;

  if (typeof email !== 'string' || !email.trim()) {
    return jsonError(400, 'Invalid email address');
  }

  const validation = validateEmail(email);

  if (!validation.success) {
    return jsonError(400, validation.error || 'Invalid email address');
  }

  const normalizedEmail = validation.email;

  if (isDisposableEmail(normalizedEmail)) {
    return jsonError(400, 'Disposable email addresses are not allowed');
  }

  const ip = getClientIp(request);

  try {
    const rateResult = await checkRateLimit(ip);

    if (!rateResult.allowed) {
      const retryAfterSeconds = Math.max(0, Math.round((rateResult.resetAt - Date.now()) / 1000));

      return jsonError(429, 'Too many signups, please try again later.', {
        retryAfter: retryAfterSeconds,
      });
    }
  } catch {
    return jsonError(503, 'Temporarily unable to accept signups.');
  }

  try {
    if (isDev) {
      const existing = SIGNUP_DEV_STORE.get(normalizedEmail);

      if (existing) {
        return jsonError(409, 'You are already on the list.');
      }

      SIGNUP_DEV_STORE.set(normalizedEmail, {
        email: normalizedEmail,
        createdAt: Date.now(),
        ip,
      });
    } else {
      const { kv } = await import('@vercel/kv');

      const existing = await kv.hget<{ email: string; createdAt: number; ip: string }>(
        SIGNUP_KV_HASH_KEY,
        normalizedEmail,
      );

      if (existing) {
        return jsonError(409, 'You are already on the list.');
      }

      await kv.hset(SIGNUP_KV_HASH_KEY, {
        [normalizedEmail]: {
          email: normalizedEmail,
          createdAt: Date.now(),
          ip,
        },
      });
    }
  } catch (error) {
    console.error('Signup storage error:', error);
    return jsonError(503, 'Temporarily unable to accept signups.');
  }

  return NextResponse.json(
    {
      ok: true,
      message: 'You are on the grid! We will be in touch soon.',
    },
    {
      status: 201,
    },
  );
}