interface Entry
{
  count: number;
  windowStart: number;
}

function makeRateLimiter( maxAttempts: number, windowMs: number )
{
  const store = new Map<string, Entry>();

  return function check( ip: string ): { blocked: boolean }
  {
    const now   = Date.now();
    let   entry = store.get( ip );

    if ( !entry || now - entry.windowStart > windowMs )
      entry = { count: 0, windowStart: now };

    entry.count++;
    store.set( ip, entry );

    return { blocked: entry.count > maxAttempts };
  };
}

// forgot-password — strict, with escalating delay to prevent email spam
const FORGOT_WINDOW_MS    = 20 * 60 * 1000;
const FORGOT_MAX_ATTEMPTS = 20;
const forgotStore = new Map<string, Entry>();

function forgotDelayMs( count: number ): number
{
  if ( count <= 5  ) return  5_000;
  if ( count <= 10 ) return 15_000;
  return 30_000;
}

export function checkForgotPasswordRate( ip: string ): { blocked: boolean; delay: number }
{
  const now   = Date.now();
  let   entry = forgotStore.get( ip );

  if ( !entry || now - entry.windowStart > FORGOT_WINDOW_MS )
    entry = { count: 0, windowStart: now };

  entry.count++;
  forgotStore.set( ip, entry );

  if ( entry.count > FORGOT_MAX_ATTEMPTS ) return { blocked: true, delay: 0 };
  return { blocked: false, delay: forgotDelayMs( entry.count ) };
}

// login — 10 attempts per 15 min, small delay after 5
const loginStore = new Map<string, Entry>();
const LOGIN_WINDOW_MS    = 15 * 60 * 1000;
const LOGIN_MAX_ATTEMPTS = 10;

function loginDelayMs( count: number ): number
{
  if ( count <= 5 ) return 0;
  return 3_000;
}

export function checkLoginRate( ip: string ): { blocked: boolean; delay: number }
{
  const now   = Date.now();
  let   entry = loginStore.get( ip );

  if ( !entry || now - entry.windowStart > LOGIN_WINDOW_MS )
    entry = { count: 0, windowStart: now };

  entry.count++;
  loginStore.set( ip, entry );

  if ( entry.count > LOGIN_MAX_ATTEMPTS ) return { blocked: true, delay: 0 };
  return { blocked: false, delay: loginDelayMs( entry.count ) };
}

// register — 5 attempts per hour, no delay
export const checkRegisterRate = makeRateLimiter( 5, 60 * 60 * 1000 );

export function sleep( ms: number ): Promise<void>
{
  return new Promise( resolve => setTimeout( resolve, ms ) );
}