Merge pull request #14 from augustus281/sliding

[sliding window]: redis

Author: augustus281

internal/algorithms/sliding_window.go

@@ -1 +1,56 @@
 package algorithms
+
+import (
+	"context"
+	"fmt"
+	"sync"
+	"time"
+
+	"github.com/redis/go-redis/v9"
+)
+
+type SlidingWindow struct {
+	client *redis.Client
+	window time.Duration
+	limit  int
+	mu     sync.Mutex
+}
+
+func NewSlidingWindow(client *redis.Client, window time.Duration, limit int) *SlidingWindow {
+	return &SlidingWindow{
+		client: client,
+		window: window,
+		limit:  limit,
+	}
+}
+
+func (sw *SlidingWindow) Allow(ctx context.Context, key string) (bool, error) {
+	sw.mu.Lock()
+	defer sw.mu.Unlock()
+
+	now := time.Now().UnixMilli()
+	redisKey := fmt.Sprintf("sw:%s", key)
+
+	windowStart := now - sw.window.Milliseconds()
+
+	pipe := sw.client.TxPipeline()
+
+	pipe.ZRemRangeByScore(ctx, redisKey, "0", fmt.Sprintf("%d", windowStart))
+
+	countCmd := pipe.ZCard(ctx, redisKey)
+
+	pipe.ZAdd(ctx, redisKey, redis.Z{Score: float64(now), Member: now})
+
+	pipe.Expire(ctx, redisKey, sw.window)
+
+	_, err := pipe.Exec(ctx)
+	if err != nil {
+		return false, err
+	}
+
+	if countCmd.Val() >= int64(sw.limit) {
+		return false, nil
+	}
+
+	return true, nil
+}