feat: implement RAG-based chatbot service with daily usage rate limiting and background index worker

internal/repositories/usageRepository.go

@@ -0,0 +1,55 @@
+package repositories
+
+import (
+	"context"
+	"fmt"
+	"history-api/pkg/cache"
+	"history-api/pkg/constants"
+	"time"
+)
+
+type UsageRepository interface {
+	GetAIUsage(ctx context.Context, userID string) (int, error)
+	IncrementAIUsage(ctx context.Context, userID string) (int, error)
+}
+
+type usageRepository struct {
+	c cache.Cache
+}
+
+func NewUsageRepository(c cache.Cache) UsageRepository {
+	return &usageRepository{
+		c: c,
+	}
+}
+
+func (r *usageRepository) getUsageKey(userID string) string {
+	dateStr := time.Now().Format("20060102")
+	return fmt.Sprintf("usage:ai:%s:%s", userID, dateStr)
+}
+
+func (r *usageRepository) GetAIUsage(ctx context.Context, userID string) (int, error) {
+	key := r.getUsageKey(userID)
+	var count int
+	err := r.c.Get(ctx, key, &count)
+	if err != nil {
+		return 0, nil
+	}
+	return count, nil
+}
+
+func (r *usageRepository) IncrementAIUsage(ctx context.Context, userID string) (int, error) {
+	key := r.getUsageKey(userID)
+	rdb := r.c.GetRawClient()
+
+	count, err := rdb.Incr(ctx, key).Result()
+	if err != nil {
+		return 0, err
+	}
+
+	if count == 1 {
+		rdb.Expire(ctx, key, constants.UsageExpiration)
+	}
+
+	return int(count), nil
+}