package operator

import (
	"context"
	"goflink/core"
)

type KeySelector[IN any] func(in IN) string
type KeyByOperator[IN any] struct {
	selector KeySelector[IN]
}

func NewKeyByOperator[IN any](selector KeySelector[IN]) *KeyByOperator[IN] {
	return &KeyByOperator[IN]{selector: selector}
}

func (k *KeyByOperator[IN]) Open(ctx context.Context) error {
	return nil
}

func (k *KeyByOperator[IN]) Process(ctx context.Context, record core.StreamRecord[IN], out Emitter[IN]) error {
	if record.Type != core.RecordData {
		return out.Emit(ctx, record)
	}

	record.Key = k.selector(record.Value)
	return out.Emit(ctx, record)
}

func (k *KeyByOperator[IN]) Close(ctx context.Context) error {
	return nil
}