package operator

import (
	"fmt"

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

type Unset string

func (u Unset) MarshalBSON() ([]byte, error) {
	return opMarshal("$unset", string(u), "")
}

type PopIf struct {
	Key    string
	Filter interface{}
}

func (pi PopIf) MarshalBSON() ([]byte, error) {
	return opMarshal("$pull", pi.Key, pi.Filter)
}

type Set struct {
	Key   string
	Value interface{}
}

func (s Set) MarshalBSON() ([]byte, error) {
	return opMarshal("$set", s.Key, s.Value)
}

type Push struct {
	Key   string
	Value interface{}
}

func (p Push) MarshalBSON() ([]byte, error) {
	return opMarshal("$push", p.Key, p.Value)
}

func opMarshal(op, key string, value interface{}) ([]byte, error) {
	marshalable := opMarshalable(op, key, value)
	if len(marshalable) == 0 {
		return nil, fmt.Errorf("failed marshalling op")
	}
	return bson.Marshal(marshalable)
}

func opMarshalable(op, key string, value interface{}) map[string]map[string]interface{} {
	if len(key) == 0 {
		return nil
	}
	return map[string]map[string]interface{}{
		op: map[string]interface{}{
			key: value,
		},
	}
}