[fixed window]: add redis

Author: augustus

fixed_window_counter.go

@@ -1 +1,53 @@
-package algorithms
+package algorithms
+
+import (
+	"context"
+	"fmt"
+	"sync"
+	"time"
+
+	"github.com/redis/go-redis/v9"
+)
+
+type FixedWindow struct {
+	client *redis.Client
+	window time.Duration
+	limit  int
+	mu     sync.Mutex
+}
+
+func NewFixedWindow(client *redis.Client, window time.Duration, limit int) *FixedWindow {
+	return &FixedWindow{
+		client: client,
+		window: window,
+		limit:  limit,
+	}
+}
+
+func (fw *FixedWindow) Allow(ctx context.Context, key string) (bool, error) {
+	fw.mu.Lock()
+	defer fw.mu.Unlock()
+
+	currentTime := time.Now().Unix()
+
+	windowStart := currentTime - (currentTime % int64(fw.window.Seconds()))
+
+	redisKey := fmt.Sprintf("fw:%s:%d", key, windowStart)
+
+	pipe := fw.client.TxPipeline()
+
+	count := pipe.Incr(ctx, redisKey)
+
+	pipe.Expire(ctx, redisKey, fw.window)
+
+	_, err := pipe.Exec(ctx)
+	if err != nil {
+		return false, err
+	}
+
+	if count.Val() > int64(fw.limit) {
+		return false, nil
+	}
+
+	return true, nil
+}