Initial open source release

internal/store/redisstore/ratelimit.go

@@ -0,0 +1,57 @@
+package redisstore
+
+import (
+	"context"
+	"fmt"
+	"math"
+	"time"
+
+	"github.com/redis/go-redis/v9"
+)
+
+// RateLimiter 用 Redis INCR + TTL 实现固定窗口限流。
+type RateLimiter struct {
+	c *redis.Client
+}
+
+// NewRateLimiter 创建 Redis-backed RateLimiter。
+func NewRateLimiter(c *redis.Client) *RateLimiter {
+	return &RateLimiter{c: c}
+}
+
+func rateLimitKey(key string) string {
+	return "ratelimit:" + key
+}
+
+func (l *RateLimiter) Allow(ctx context.Context, key string, limit int, window time.Duration) (bool, int, error) {
+	if limit <= 0 {
+		return true, 0, nil
+	}
+	if window <= 0 {
+		window = time.Second
+	}
+	if l == nil || l.c == nil {
+		return false, 0, fmt.Errorf("redis rate limiter: nil client")
+	}
+	redisKey := rateLimitKey(key)
+	count, err := l.c.Incr(ctx, redisKey).Result()
+	if err != nil {
+		return false, 0, fmt.Errorf("redis incr rate limit: %w", err)
+	}
+	if count == 1 {
+		if err := l.c.Expire(ctx, redisKey, window).Err(); err != nil {
+			return false, 0, fmt.Errorf("redis expire rate limit: %w", err)
+		}
+	}
+	if count <= int64(limit) {
+		return true, 0, nil
+	}
+	ttl, err := l.c.TTL(ctx, redisKey).Result()
+	if err != nil {
+		return false, 0, fmt.Errorf("redis ttl rate limit: %w", err)
+	}
+	if ttl <= 0 {
+		ttl = window
+	}
+	return false, int(math.Ceil(ttl.Seconds())), nil
+}