interface SignInRequest {
  email: string;
  password: string;
}

interface SignInResponse {
  token: string;
  user: {
    id: string;
    name: string;
    email: string;
    createdAt: string;
  };
}

async function signIn(credentials: SignInRequest): Promise<SignInResponse> {
  const response = await fetch('https://api.yourstore.com/v1/signin', {
    method: 'POST',
    headers: {
      'x-api-key': process.env.NEXT_PUBLIC_API_KEY!,
      'Content-Type': 'application/json',
    },
    body: JSON.stringify(credentials),
  });

  if (!response.ok) {
    const error = await response.json();
    throw new Error(error.message || 'Sign in failed');
  }

  return response.json();
}

// Usage
try {
  const result = await signIn({
    email: '[email protected]',
    password: 'SecurePass123',
  });
  
  console.log('Logged in:', result.user.name);
  // Store token and user data in cookies/localStorage
} catch (error) {
  console.error('Sign in error:', error);
}

async function signIn(credentials) {
  const response = await fetch('https://api.yourstore.com/v1/signin', {
    method: 'POST',
    headers: {
      'x-api-key': process.env.NEXT_PUBLIC_API_KEY,
      'Content-Type': 'application/json',
    },
    body: JSON.stringify(credentials),
  });

  if (!response.ok) {
    const error = await response.json();
    throw new Error(error.message || 'Sign in failed');
  }

  return response.json();
}

// Usage
signIn({
  email: '[email protected]',
  password: 'SecurePass123',
})
  .then(result => {
    console.log('Logged in:', result.user.name);
    // Store token and user data
  })
  .catch(error => {
    console.error('Sign in error:', error);
  });

'use server'

import { cookies } from 'next/headers';
import { redirect } from 'next/navigation';

export async function signInAction(formData: FormData) {
  const email = formData.get('email') as string;
  const password = formData.get('password') as string;

  try {
    const response = await fetch('https://api.yourstore.com/v1/signin', {
      method: 'POST',
      headers: {
        'x-api-key': process.env.BACKEND_API_KEY!,
        'Content-Type': 'application/json',
      },
      body: JSON.stringify({ email, password }),
    });

    if (!response.ok) {
      return { error: 'Invalid credentials' };
    }

    const data = await response.json();
    
    // Store auth token
    const cookieStore = await cookies();
    cookieStore.set('auth_token', data.token, {
      httpOnly: true,
      secure: process.env.NODE_ENV === 'production',
      sameSite: 'lax',
      maxAge: 60 * 60 * 24 * 90, // 90 days
    });

    // Store user data
    cookieStore.set('user_data', JSON.stringify(data.user), {
      httpOnly: true,
      secure: process.env.NODE_ENV === 'production',
      sameSite: 'lax',
      maxAge: 60 * 60 * 24 * 90,
    });

    // Clear guest token if exists
    cookieStore.delete('guest_token');

  } catch (error) {
    return { error: 'Something went wrong' };
  }

  redirect('/dashboard');
}