Implement redisstore

Author: Pavan-Rana

internal/store/redis.go

@@ -1 +1,51 @@
-// internal/store/redis.go
+package store
+
+import (
+	"context"
+	"time"
+
+	"github.com/redis/go-redis/v9"
+	"github.com/Pavan-Rana/redis-rate-limiter/internal/limiter"
+)
+
+type RedisStore struct {
+	client    	*redis.Client
+	scripts		*LuaScripts
+}
+
+func NewRedisStore(addr string) (*RedisStore, error) {
+	client := redis.NewClient(&redis.Options{Addr: addr})
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+
+	if err := client.Ping(ctx).Err(); err != nil {
+		return nil, err
+	}
+
+	scripts, err := LoadScripts(ctx, client)
+	if err != nil {
+		return nil, err
+	}
+
+	return &RedisStore{client: client, scripts: scripts}, nil
+}
+
+// Single round-trip; no TOCTOU race possible across replicas.
+func (r *RedisStore) AllowRequest(ctx context.Context, key string, policy limiter.Policy) (bool, error) {
+	nowMs := time.Now().UnixMilli()
+	windowMs := policy.Window.Milliseconds()
+
+	result, err := r.client.EvalSha(ctx, r.scripts.SlidingWindowSHA, []string{key},
+		nowMs, windowMs, policy.Limit
+	).Int()
+
+	if err != nil {
+		return false, err
+	}
+
+	return result == 1, nil
+}
+
+func (r *RedisStore) Ping(ctx context.Context) error {
+	return r.client.Ping(ctx).Err()
+}