package main

import (
	"context"
	"fmt"

	"go.mongodb.org/mongo-driver/bson"
	"go.mongodb.org/mongo-driver/mongo"
	"go.mongodb.org/mongo-driver/mongo/options"
)

var mongoClient *mongo.Client

func connect() error {
	clientOptions := options.Client().
		ApplyURI("******").
		SetAuth(options.Credential{
			Username: "******",
			Password: "******",
		})

	client, err := mongo.Connect(context.TODO(), clientOptions)
	if err != nil {
		return fmt.Errorf("connect mongodb err: %w", err)
	}

	err = client.Ping(context.TODO(), nil)
	if err != nil {
		return fmt.Errorf("ping mongodb err: %w", err)
	}

	mongoClient = client

	return nil
}

func main() {
	if err := connect(); err != nil {
		panic(err)
	}

	// empty slice is ok
	test([]string{})

	// nil slice will panic
	var list []string
	test(list)
}

func test(list []string) {
	filter := bson.M{"any": bson.M{"$in": list}}
	_, err := mongoClient.Database("any").Collection("any").Find(context.TODO(), filter, nil)
	if err != nil {
		panic(err)
	}
}

func test(list []string) {
	if list == nil {
		list = []string{}
	}

	filter := bson.M{"any": bson.M{"$in": list}}
	_, err := mongoClient.Database("any").Collection("any").Find(context.TODO(), filter, nil)
	if err != nil {
		panic(err)
	}
}