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

import (
	"encoding/json"
	"fmt"

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

// PayloadBytes extracts a JSON-ish payload into bytes suitable for json.Unmarshal.
//
// Supported payload shapes (weatherfeeder convention):
//   - json.RawMessage  (recommended for raw events)
//   - []byte
//   - string           (assumed to contain JSON)
//   - map[string]any   (re-marshaled to JSON)
//
// If you add other raw representations later, extend this function.
func PayloadBytes(e event.Event) ([]byte, error) {
	if e.Payload == nil {
		return nil, fmt.Errorf("payload is nil")
	}

	switch v := e.Payload.(type) {
	case json.RawMessage:
		if len(v) == 0 {
			return nil, fmt.Errorf("payload is empty json.RawMessage")
		}
		return []byte(v), nil

	case []byte:
		if len(v) == 0 {
			return nil, fmt.Errorf("payload is empty []byte")
		}
		return v, nil

	case string:
		if v == "" {
			return nil, fmt.Errorf("payload is empty string")
		}
		return []byte(v), nil

	case map[string]any:
		b, err := json.Marshal(v)
		if err != nil {
			return nil, fmt.Errorf("marshal map payload: %w", err)
		}
		return b, nil

	default:
		return nil, fmt.Errorf("unsupported payload type %T", e.Payload)
	}
}