package securechat

import "encoding/json"

// Event es el sobre estándar de los webhooks (docs/06-WEBHOOKS.md §2). `Data` depende de EventType.
type Event struct {
	Version         string          `json:"version"`
	EventID         string          `json:"eventId"`
	EventType       string          `json:"eventType"`
	OccurredAt      string          `json:"occurredAt"`
	CompanyID       string          `json:"companyId"`
	ConversationID  string          `json:"conversationId"`
	ExternalUserRef string          `json:"externalUserRef"`
	Metadata        json.RawMessage `json:"metadata"`
	Data            json.RawMessage `json:"data"`
}

// MessageCreated es `data` de message.created.
type MessageCreated struct {
	MessageID       string   `json:"messageId"`
	SenderType      string   `json:"senderType"`
	SenderID        string   `json:"senderId"`
	ContentType     string   `json:"contentType"`
	Encryption      Envelope `json:"encryption"`
	ConversationKey Wrap     `json:"conversationKey"`
	Attachment      *struct {
		AttachmentID string `json:"attachmentId"`
		Size         int    `json:"size"`
	} `json:"attachment"`
}

// ConversationStarted es `data` de conversation.started.
type ConversationStarted struct {
	UserID          string  `json:"userId"`
	UserPublicKey   string  `json:"userPublicKey"`
	ConversationKey Wrap    `json:"conversationKey"`
	InviteBinding   *string `json:"inviteBinding"`
	IsReinvite      bool    `json:"isReinvite"`
}

// DecryptEvent descifra un message.created: abre data.conversationKey con tus llaves
// [actual, anteriores…] y descifra data.encryption con senderType fijado en "user".
// Devuelve el texto, K (para responder sin otro GET) y su keyVersion.
func DecryptEvent(ev Event, companyKeys []KeyPair) (text string, key []byte, keyVersion int, err error) {
	var d MessageCreated
	if err := json.Unmarshal(ev.Data, &d); err != nil {
		return "", nil, 0, fail(ErrInvalidInput, "data de message.created inválido")
	}
	key, err = OpenWithAnyKey(d.ConversationKey, ev.ConversationID, companyKeys)
	if err != nil {
		return "", nil, 0, err
	}
	text, err = DecryptMessage(key, ev.ConversationID, "user", d.Encryption)
	if err != nil {
		return "", nil, 0, err
	}
	return text, key, d.ConversationKey.KeyVersion, nil
}