package main

import (
	"sync"
	"time"
)

// rateLimiter is a minimal in-memory fixed-window limiter keyed by string
// (bearer-token subject for the TMDB proxy). It blunts runaway clients abusing
// the shared API key; it is not a full DoS defense.
type rateLimiter struct {
	mu     sync.Mutex
	limit  int
	window time.Duration
	counts map[string]rateEntry
}

type rateEntry struct {
	windowStart time.Time
	count       int
}

func newRateLimiter(limit int, per time.Duration) *rateLimiter {
	return &rateLimiter{limit: limit, window: per, counts: map[string]rateEntry{}}
}

func (r *rateLimiter) allow(key string) bool {
	r.mu.Lock()
	defer r.mu.Unlock()

	now := time.Now()
	e, ok := r.counts[key]
	if !ok || now.Sub(e.windowStart) >= r.window {
		// Occasionally garbage-collect stale keys so the map stays bounded.
		if len(r.counts) > 10_000 {
			for k, v := range r.counts {
				if now.Sub(v.windowStart) >= r.window {
					delete(r.counts, k)
				}
			}
		}
		r.counts[key] = rateEntry{windowStart: now, count: 1}
		return true
	}
	e.count++
	r.counts[key] = e
	return e.count <= r.limit
}