protocol/aprs: refactored

protocol/aprs/data.go

@@ -0,0 +1,119 @@
+package aprs
+
+import (
+	"fmt"
+	"regexp"
+	"strconv"
+	"time"
+)
+
+type decoder interface {
+	CanDecode(*Frame) bool
+	Decode(*Frame) (Data, error)
+}
+
+var decoders []decoder
+
+func init() {
+	decoders = []decoder{
+		positionDecoder{},
+		micEDecoder{},
+		messageDecoder{},
+		queryDecoder{},
+	}
+}
+
+// Raw is the string encoded raw frame payload.
+type Raw string
+
+func (p Raw) Type() Type {
+	var t Type
+	if len(p) > 0 {
+		t = Type(p[0])
+	}
+	return t
+}
+
+// Data represents a decoded payload data.
+type Data interface {
+	String() string
+}
+
+// Type of payload.
+type Type byte
+
+var typeName = map[Type]string{
+	0x1c: "Current Mic-E Data (Rev 0 beta)",
+	0x1d: "Old Mic-E Data (Rev 0 beta)",
+	'!':  "Position without timestamp (no APRS messaging), or Ultimeter 2000 WX Station",
+	'#':  "Peet Bros U-II Weather Station",
+	'$':  "Raw GPS data or Ultimeter 2000",
+	'%':  "Agrelo DFJr / MicroFinder",
+	'"':  "Old Mic-E Data (but Current data for TM-D700)",
+	')':  "Item",
+	'*':  "Peet Bros U-II Weather Station",
+	',':  "Invalid data or test data",
+	'/':  "Position with timestamp (no APRS messaging)",
+	':':  "Message",
+	';':  "Object",
+	'<':  "Station Capabilities",
+	'=':  "Position without timestamp (with APRS messaging)",
+	'>':  "Status",
+	'?':  "Query",
+	'@':  "Position with timestamp (with APRS messaging)",
+	'T':  "Telemetry data",
+	'[':  "Maidenhead grid locator beacon (obsolete)",
+	'_':  "Weather Report (without position)",
+	'`':  "Current Mic-E Data (not used in TM-D700)",
+	'{':  "User-Defined APRS packet format",
+	'}':  "Third-party traffic",
+}
+
+func (t Type) String() string {
+	if s, ok := typeName[t]; ok {
+		return s
+	}
+	return fmt.Sprintf("unknown %02x", byte(t))
+}
+
+func (t Type) IsMessage() bool {
+	return t == ':'
+}
+
+func (t Type) IsThirdParty() bool {
+	return t == '}'
+}
+
+var matchTimestamp = regexp.MustCompile(`^[0-9]{6}[zh/]`)
+
+func hasTimestamp(s string) bool {
+	return matchTimestamp.MatchString(s)
+}
+
+func parseTimestamp(s string) (t time.Time, comment string, err error) {
+	// log.Printf("parse timestamp %q", s)
+	var hh, mm, ss int
+	if hh, err = strconv.Atoi(s[0:2]); err != nil {
+		return
+	}
+	if mm, err = strconv.Atoi(s[2:4]); err != nil {
+		return
+	}
+	if ss, err = strconv.Atoi(s[4:6]); err != nil {
+		return
+	}
+
+	now := time.Now()
+	switch s[6] {
+	case 'z': // DDHHMMz zulu time
+		now = now.UTC()
+		return time.Date(now.Year(), now.Month(), hh, mm, ss, 0, 0, time.UTC), s[7:], nil
+	case '/': // DDHHMM/ local time
+		return time.Date(now.Year(), now.Month(), hh, mm, ss, 0, 0, now.Location()), s[7:], nil
+	case 'h': // HHMMSSh zulu time
+		now = now.UTC()
+		return time.Date(now.Year(), now.Month(), now.Day(), hh, mm, ss, 0, time.UTC), s[7:], nil
+	default:
+		return time.Time{}, "", fmt.Errorf("aprs: invalid/unknown timestamp marker %q", s[6])
+	}
+}