historyinfo

type Diversion struct {
	URI         string
	Reason      string // free-form per RFC 5806; commonly one of DiversionXxx
	Counter     int    // hop counter; missing → 0; we increment when extending
	Privacy     string // "full" / "name" / "uri" / "off" / ...
	Limit       int    // hop limit (counter <= limit before drop); 0 = unset
	Screen      string // "yes" / "no" — was the diversion source verified
	ExtraParams []string
}

type Entry struct {
	// URI is the bare target URI (e.g. "sip:+8613800138000@trust.example").
	// Whether/not angle-bracketed, we normalise on parse to no brackets.
	URI string

	// Index is the dotted-decimal index per RFC 7044 §4.1. We always
	// emit flat integers like "1", "2", "3" (no forking).
	Index string

	// ReasonHeader optionally carries a SIP Reason header value
	// embedded in the Request-URI's hi-target-param `Reason=...`. RFC
	// 7044 §4.2: the param is percent-encoded; we decode on parse and
	// re-encode on format. Common values for our case:
	//   "SIP;cause=302;text=\"Moved Temporarily\""  — generic retarget
	//   "SIP;cause=480;text=\"AI Transfer\""         — transfer to agent
	//   "SIP;cause=487;text=\"Cancelled\""           — caller hung up
	// Empty = no reason param (legal, just less informative downstream).
	ReasonHeader string

	// PrivacyHeader: history-info-targeted-toparam Privacy value
	// (RFC 7044 §4.3). Rare; we currently don't emit but parse for
	// round-tripping.
	PrivacyHeader string

	// Extra opaque params we encountered on parse but don't model.
	// Carried through on format so we don't strip carrier annotations.
	Extra []string
}