package main

import (
	"sync"
	"time"
)

type loginEntry struct {
	window time.Time
	count  int
	seen   time.Time
}

type LoginLimiter struct {
	mu      sync.Mutex
	entries map[string]loginEntry
	limit   int
	window  time.Duration
	maxKeys int
}

func NewLoginLimiter(limit int, window time.Duration) *LoginLimiter {
	return &LoginLimiter{entries: make(map[string]loginEntry), limit: limit, window: window, maxKeys: 10000}
}

func (limiter *LoginLimiter) Allow(key string, now time.Time) bool {
	limiter.mu.Lock()
	defer limiter.mu.Unlock()
	_, known := limiter.entries[key]
	if !known && len(limiter.entries) >= limiter.maxKeys {
		cutoff := now.Add(-2 * limiter.window)
		for item, entry := range limiter.entries {
			if entry.seen.Before(cutoff) {
				delete(limiter.entries, item)
			}
		}
		if len(limiter.entries) >= limiter.maxKeys {
			return false
		}
	}
	entry := limiter.entries[key]
	if entry.window.IsZero() || now.Sub(entry.window) >= limiter.window {
		entry.window, entry.count = now, 0
	}
	entry.seen = now
	if entry.count >= limiter.limit {
		limiter.entries[key] = entry
		return false
	}
	entry.count++
	limiter.entries[key] = entry
	return true
}