add string type enums and retry config

pkg/types/readsb/aircraft.go

@@ -32,7 +32,7 @@ type Aircraft struct {
 	// indicates a non-ICAO address (TIS-B).
 	Hex string `json:"hex"`
 	// Type is the message source/type, e.g. "adsb_icao", "mode_s", "mlat".
-	Type string `json:"type"`
+	Type MessageType `json:"type"`
 	// Flight is the callsign. readsb space-pads it; use Callsign for a trimmed value.
 	Flight string `json:"flight,omitempty"`
 	// Registration (r) and aircraft type (t) come from an optional database.
@@ -61,9 +61,9 @@ type Aircraft struct {
 	// Squawk is the Mode A code as 4 octal digits.
 	Squawk string `json:"squawk,omitempty"`
 	// Emergency is the emergency/priority status; "none" when not declared.
-	Emergency string `json:"emergency,omitempty"`
+	Emergency EmergencyStatus `json:"emergency,omitempty"`
 	// Category is the emitter category, e.g. "A0".."A7", "B0".. (see README-json).
-	Category string `json:"category,omitempty"`
+	Category EmitterCategory `json:"category,omitempty"`
 
 	// Lat/Lon are the last known position in decimal degrees.
 	Lat float64 `json:"lat,omitempty"`
@@ -89,14 +89,14 @@ type Aircraft struct {
 	NavModes       []string `json:"nav_modes,omitempty"`
 
 	// ADS-B version and quality/accuracy indicators.
-	Version int    `json:"version,omitempty"`
-	NICBaro int    `json:"nic_baro,omitempty"`
-	NACP    int    `json:"nac_p,omitempty"`
-	NACV    int    `json:"nac_v,omitempty"`
-	SIL     int    `json:"sil,omitempty"`
-	SILType string `json:"sil_type,omitempty"`
-	GVA     int    `json:"gva,omitempty"`
-	SDA     int    `json:"sda,omitempty"`
+	Version int     `json:"version,omitempty"`
+	NICBaro int     `json:"nic_baro,omitempty"`
+	NACP    int     `json:"nac_p,omitempty"`
+	NACV    int     `json:"nac_v,omitempty"`
+	SIL     int     `json:"sil,omitempty"`
+	SILType SILType `json:"sil_type,omitempty"`
+	GVA     int     `json:"gva,omitempty"`
+	SDA     int     `json:"sda,omitempty"`
 
 	// Alert and special position identification flags.
 	Alert int `json:"alert,omitempty"`
@@ -133,7 +133,7 @@ func (a Aircraft) HasPosition() bool { return a.Lat != 0 || a.Lon != 0 }
 
 // InEmergency reports whether a non-routine emergency/priority code is set.
 func (a Aircraft) InEmergency() bool {
-	return a.Emergency != "" && a.Emergency != "none"
+	return a.Emergency != "" && a.Emergency != EmergencyNone
 }
 
 // SeenFor returns the time since the last message was received.

pkg/types/readsb/enums.go

@@ -0,0 +1,96 @@
+package readsb
+
+// MessageType is the source/type of an aircraft's data (the "type" field). It is
+// a named string so callers can compare against typed constants; it decodes from
+// and encodes to JSON exactly like a plain string. readsb lists these values in
+// descending order of trustworthiness in README-json.md.
+type MessageType string
+
+const (
+	TypeADSBICAO      MessageType = "adsb_icao"      // Mode S/ADS-B transponder, ICAO address
+	TypeADSBICAONT    MessageType = "adsb_icao_nt"   // ADS-B non-transponder emitter, ICAO address
+	TypeADSRICAO      MessageType = "adsr_icao"      // ADS-B rebroadcast (e.g. UAT), ICAO address
+	TypeTISBICAO      MessageType = "tisb_icao"      // TIS-B about a non-ADS-B target, ICAO address
+	TypeADSC          MessageType = "adsc"           // ADS-C via satellite downlink
+	TypeMLAT          MessageType = "mlat"           // position from multilateration
+	TypeOther         MessageType = "other"          // miscellaneous Basestation/SBS data
+	TypeModeS         MessageType = "mode_s"         // Mode S only, no position
+	TypeADSBOther     MessageType = "adsb_other"     // ADS-B transponder, non-ICAO address
+	TypeADSROther     MessageType = "adsr_other"     // ADS-B rebroadcast, non-ICAO address
+	TypeTISBOther     MessageType = "tisb_other"     // TIS-B about a non-ADS-B target, non-ICAO address
+	TypeTISBTrackfile MessageType = "tisb_trackfile" // TIS-B keyed by track/file id (radar)
+)
+
+// EmitterCategory is the ADS-B emitter category (the "category" field): a class
+// letter A-D and a digit 0-7. The A0/B0/C0/D0 codes mean "no category info"; the
+// remaining D codes and a few others are reserved. Decodes/encodes as a string.
+type EmitterCategory string
+
+const (
+	CatNoInfo EmitterCategory = "A0" // also B0/C0/D0: no category information
+
+	CatLight      EmitterCategory = "A1" // < 15,500 lb
+	CatSmall      EmitterCategory = "A2" // 15,500-75,000 lb
+	CatLarge      EmitterCategory = "A3" // 75,000-300,000 lb
+	CatHighVortex EmitterCategory = "A4" // high-vortex large, e.g. B757
+	CatHeavy      EmitterCategory = "A5" // > 300,000 lb
+	CatHighPerf   EmitterCategory = "A6" // > 5g and > 400 kt
+	CatRotorcraft EmitterCategory = "A7"
+
+	CatGlider         EmitterCategory = "B1" // glider / sailplane
+	CatLighterThanAir EmitterCategory = "B2"
+	CatParachutist    EmitterCategory = "B3" // parachutist / skydiver
+	CatUltralight     EmitterCategory = "B4" // ultralight / hang-glider / paraglider
+	CatUAV            EmitterCategory = "B6" // unmanned aerial vehicle
+	CatSpace          EmitterCategory = "B7" // space / transatmospheric vehicle
+
+	CatSurfaceEmergency EmitterCategory = "C1" // surface vehicle, emergency
+	CatSurfaceService   EmitterCategory = "C2" // surface vehicle, service
+	CatPointObstacle    EmitterCategory = "C3" // point obstacle (incl. tethered balloons)
+	CatClusterObstacle  EmitterCategory = "C4"
+	CatLineObstacle     EmitterCategory = "C5"
+)
+
+// catDescriptions maps every defined emitter code (including reserved ones) to a
+// human label. Codes absent from the map are undefined.
+var catDescriptions = map[EmitterCategory]string{
+	"A0": "no information", "A1": "light", "A2": "small", "A3": "large",
+	"A4": "high-vortex large", "A5": "heavy", "A6": "high performance", "A7": "rotorcraft",
+	"B0": "no information", "B1": "glider/sailplane", "B2": "lighter-than-air",
+	"B3": "parachutist", "B4": "ultralight", "B5": "reserved",
+	"B6": "unmanned aerial vehicle", "B7": "space/transatmospheric",
+	"C0": "no information", "C1": "surface emergency vehicle", "C2": "surface service vehicle",
+	"C3": "point obstacle", "C4": "cluster obstacle", "C5": "line obstacle",
+	"C6": "reserved", "C7": "reserved",
+	"D0": "no information", "D1": "reserved", "D2": "reserved", "D3": "reserved",
+	"D4": "reserved", "D5": "reserved", "D6": "reserved", "D7": "reserved",
+}
+
+// Description returns the human-readable label for the emitter category, or ""
+// if the code is not a defined A0-D7 value.
+func (c EmitterCategory) Description() string { return catDescriptions[c] }
+
+// EmergencyStatus is the emergency/priority status (the "emergency" field).
+// EmergencyNone means no emergency is declared. Decodes/encodes as a string.
+type EmergencyStatus string
+
+const (
+	EmergencyNone      EmergencyStatus = "none"
+	EmergencyGeneral   EmergencyStatus = "general"
+	EmergencyLifeguard EmergencyStatus = "lifeguard" // medical/lifeguard flight
+	EmergencyMinFuel   EmergencyStatus = "minfuel"   // minimum fuel
+	EmergencyNoRadio   EmergencyStatus = "nordo"     // no radio communication
+	EmergencyUnlawful  EmergencyStatus = "unlawful"  // unlawful interference
+	EmergencyDowned    EmergencyStatus = "downed"    // downed aircraft
+	EmergencyReserved  EmergencyStatus = "reserved"
+)
+
+// SILType describes how the SIL (source integrity level) probability is scaled
+// (the "sil_type" field): per flight hour or per sample. Decodes/encodes as a string.
+type SILType string
+
+const (
+	SILUnknown   SILType = "unknown"
+	SILPerHour   SILType = "perhour"
+	SILPerSample SILType = "persample"
+)

pkg/types/readsb/filter.go

@@ -66,16 +66,16 @@ func WithSquawk(codes ...string) AircraftFilter {
 	return func(a *Aircraft) bool { return set[strings.ToLower(a.Squawk)] }
 }
 
-// WithCategory keeps aircraft of any of the given emitter categories (e.g. "A3").
-func WithCategory(cats ...string) AircraftFilter {
-	set := lowerSet(nil, cats, "")
-	return func(a *Aircraft) bool { return set[strings.ToLower(a.Category)] }
+// WithCategory keeps aircraft of any of the given emitter categories (e.g. CatLarge).
+func WithCategory(cats ...EmitterCategory) AircraftFilter {
+	set := lowerSet(nil, strs(cats), "")
+	return func(a *Aircraft) bool { return set[strings.ToLower(string(a.Category))] }
 }
 
-// WithType keeps aircraft of any of the given source types (e.g. "adsb_icao", "mlat").
-func WithType(types ...string) AircraftFilter {
-	set := lowerSet(nil, types, "")
-	return func(a *Aircraft) bool { return set[strings.ToLower(a.Type)] }
+// WithType keeps aircraft of any of the given source types (e.g. TypeADSBICAO, TypeMLAT).
+func WithType(types ...MessageType) AircraftFilter {
+	set := lowerSet(nil, strs(types), "")
+	return func(a *Aircraft) bool { return set[strings.ToLower(string(a.Type))] }
 }
 
 // InEmergency keeps only aircraft squawking a non-routine emergency/priority code.
@@ -138,6 +138,15 @@ func Any(filters ...AircraftFilter) AircraftFilter {
 
 // lowerSet builds a lowercased lookup set, optionally pre-processing each value
 // with trim(value, cut) when trim is non-nil.
+// strs widens a slice of any string-kind type to []string for the set helpers.
+func strs[T ~string](in []T) []string {
+	out := make([]string, len(in))
+	for i, v := range in {
+		out[i] = string(v)
+	}
+	return out
+}
+
 func lowerSet(trim func(string, string) string, values []string, cut string) map[string]bool {
 	set := make(map[string]bool, len(values))
 	for _, v := range values {