// FILE: ./internal/normalizers/common/finalize.go
package common

import (
	"time"

	"gitea.maximumdirect.net/ejr/feedkit/event"
)

// Finalize builds the output event envelope by copying the input and applying the
// canonical schema/payload, plus (optionally) EffectiveAt.
//
// Important behavior:
//   - ID/Kind/Source/EmittedAt are preserved by copying the input event.
//   - EffectiveAt is only overwritten when effectiveAt is non-zero.
//     If effectiveAt is zero, any existing in.EffectiveAt is preserved.
func Finalize(in event.Event, outSchema string, outPayload any, effectiveAt time.Time) (*event.Event, error) {
	out := in
	out.Schema = outSchema
	out.Payload = outPayload

	if !effectiveAt.IsZero() {
		t := effectiveAt.UTC()
		out.EffectiveAt = &t
	}

	if err := out.Validate(); err != nil {
		return nil, err
	}

	return &out, nil
}