message

type Attachment struct {
	// ID is a unique identifier for the attachment within the message.
	// REQUIRED when attachments are referenced by other parts of the message.
	ID string `json:"id,omitempty"`

	// Description is a human-readable description. OPTIONAL.
	Description string `json:"description,omitempty"`

	// Filename is a hint about the filename. OPTIONAL.
	Filename string `json:"filename,omitempty"`

	// MediaType is the MIME type of the attachment content. OPTIONAL.
	MediaType string `json:"media_type,omitempty"`

	// Format describes the format of the attachment if not evident from media_type. OPTIONAL.
	Format string `json:"format,omitempty"`

	// LastModTime is the last modification time. OPTIONAL.
	// Unix timestamp in seconds.
	LastModTime *int64 `json:"lastmod_time,omitempty"`

	// ByteCount is the size in bytes. OPTIONAL.
	ByteCount *int64 `json:"byte_count,omitempty"`

	// Data contains the attachment data. REQUIRED.
	Data AttachmentData `json:"data"`
}

type AttachmentData struct {
	// JWS is a JSON Web Signature wrapping the content.
	// Provides integrity and optional authentication.
	JWS json.RawMessage `json:"jws,omitempty"`

	// Hash is a multihash of the content for integrity checking.
	// Used when content is retrieved via Links.
	Hash string `json:"hash,omitempty"`

	// Links is a list of URIs where the content can be fetched.
	Links []string `json:"links,omitempty"`

	// Base64 is base64url-encoded content.
	Base64 string `json:"base64,omitempty"`

	// JSON is embedded JSON content.
	JSON any `json:"json,omitempty"`
}

type Message struct {
	// ID is a unique identifier for the message. REQUIRED.
	// MUST be unique to the sender.
	ID string `json:"id"`

	// Type is the message type URI. REQUIRED.
	// Defines the protocol and message semantics.
	Type string `json:"type"`

	// From is the sender's DID. OPTIONAL for anonymous messages.
	// When present, the message can be authenticated.
	From string `json:"from,omitempty"`

	// To is the list of recipient DIDs. OPTIONAL but typically present.
	// Messages may omit To when the recipient is implicit.
	To []string `json:"to,omitempty"`

	// ThID is the thread identifier. OPTIONAL.
	// Groups related messages together.
	ThID string `json:"thid,omitempty"`

	// PThID is the parent thread identifier. OPTIONAL.
	// Links a thread to a parent thread.
	PThID string `json:"pthid,omitempty"`

	// CreatedTime is when the message was created. OPTIONAL.
	// Unix timestamp in seconds.
	CreatedTime *int64 `json:"created_time,omitempty"`

	// ExpiresTime is when the message expires. OPTIONAL.
	// Unix timestamp in seconds.
	ExpiresTime *int64 `json:"expires_time,omitempty"`

	// Body is the message-type-specific content. OPTIONAL.
	// Structure depends on the message type.
	Body any `json:"body,omitempty"`

	// Attachments is a list of attachments. OPTIONAL.
	Attachments []Attachment `json:"attachments,omitempty"`

	// FromPrior is a JWT for sender key rotation. OPTIONAL.
	// Proves continuity when the sender's DID or keys change.
	FromPrior string `json:"from_prior,omitempty"`

	// PleaseAck requests acknowledgment of this message. OPTIONAL.
	// Contains a list of message IDs that should trigger an ack.
	PleaseAck []string `json:"please_ack,omitempty"`

	// Ack acknowledges receipt of previous messages. OPTIONAL.
	// Contains message IDs being acknowledged.
	Ack []string `json:"ack,omitempty"`

	// CustomHeaders contains additional headers not in the spec.
	// These are serialized at the top level of the message JSON.
	CustomHeaders map[string]any `json:"-"`
}

type Option func(*Message)