cache-valkey/rate_limiter_store.go

package cachevalkey

import (
	"context"
	"time"
)

// rateLimiterStoreShape mirrors web/mw.RateLimiterStore for compile-time duck-type verification.
// Cache-valkey must not import web (D-1), so the shape is defined locally.
type rateLimiterStoreShape interface {
	Allow(ctx context.Context, key string) (bool, error)
}

var _ rateLimiterStoreShape = (*RateLimiterStore)(nil)

// RateLimiterStore is a Valkey-backed fixed-window rate limiter.
// Satisfies web/mw.RateLimiterStore via duck typing — no import of that package required.
//
// window is the length of the time window; limit is the maximum number of requests
// allowed within that window. When the store is temporarily unavailable, Allow returns
// (false, err); the web middleware fails open on non-nil errors.
type RateLimiterStore struct {
	provider Provider
	window   time.Duration
	limit    int64
}

// NewRateLimiterStore returns a RateLimiterStore backed by p.
// window is the rate limit window; limit is the maximum requests per window.
func NewRateLimiterStore(p Provider, window time.Duration, limit int64) *RateLimiterStore {
	return &RateLimiterStore{provider: p, window: window, limit: limit}
}

// Allow reports whether the request identified by key is within the rate limit.
// Uses a fixed-window counter stored in Valkey (atomically via Lua).
func (s *RateLimiterStore) Allow(ctx context.Context, key string) (bool, error) {
	count, err := s.provider.IncrWithTTL(ctx, key, s.window)
	if err != nil {
		return false, err
	}
	return count <= s.limit, nil
}