fix(decodes): a decode's mode is a marker, not a mode name

Every station on an already-worked band was flagged NEW MODE.

A WSJT-X Decode does not carry the mode's name. It carries the
one-character marker from the decode line - "~" for FT8, "+" for FT4 - and
that character was passed straight through as though it were a mode. The
status resolver then compared "~" against the modes worked for the entity,
matched nothing, and concluded the mode had never been worked. Same cause
put "~ -07" in the comment of every decode spot pushed to the FlexRadio
panadapter, which nobody had traced back.

Resolved through a marker table, with the mode from the sender's last
Status as the fallback - Status is the message that carries the real name.
So an unlisted or future marker degrades to correct rather than to
nonsense, and a sender that puts the name in the field directly is believed
as-is. With neither available the mode is left empty, which makes the
resolver answer "worked": the safe side, since a wrong mode invents a
new-mode flag exactly as the marker did.

internal/integrations/udp/decodemode_test.go

@@ -0,0 +1,59 @@
+package udp
+
+import "testing"
+
+// A Decode does not carry the mode's NAME. It carries the one-character marker
+// from the decode line — "~" for FT8, "+" for FT4 — and that character used to
+// be passed on as if it were a mode. Everything downstream compared it against
+// the modes in the log, matched nothing, and reported every station on an
+// already-worked band as a NEW MODE.
+func TestDecodeModeNameResolvesTheMarker(t *testing.T) {
+	for raw, want := range map[string]string{
+		"~": "FT8",
+		"+": "FT4",
+		"#": "JT65",
+		"@": "JT9",
+	} {
+		if got := DecodeModeName(raw, "FT8"); got != want {
+			t.Errorf("DecodeModeName(%q) = %q, want %q", raw, got, want)
+		}
+	}
+}
+
+// A sender that puts the real name in the field is believed as-is — several do,
+// and the marker table must not get in their way.
+func TestDecodeModeNameKeepsARealName(t *testing.T) {
+	for _, raw := range []string{"FT8", "ft4", "JS8", "Q65"} {
+		if got := DecodeModeName(raw, ""); got == "" || got != upper(raw) {
+			t.Errorf("DecodeModeName(%q) = %q, want the name itself", raw, got)
+		}
+	}
+}
+
+// The safety net: an unknown marker falls back to the mode from the sender's
+// last Status, which always carries the real name. This is what keeps a future
+// or unlisted marker degrading to correct rather than to nonsense.
+func TestDecodeModeNameFallsBackToStatus(t *testing.T) {
+	if got := DecodeModeName("%", "FT4"); got != "FT4" {
+		t.Errorf("unknown marker resolved to %q, want the Status mode FT4", got)
+	}
+	if got := DecodeModeName("", "FT8"); got != "FT8" {
+		t.Errorf("empty mode resolved to %q, want the Status mode FT8", got)
+	}
+	// Nothing known at all is empty rather than a guess: an empty mode makes the
+	// status resolver answer "worked", which is the safe side — a wrong mode
+	// would invent a new-mode flag exactly as the marker did.
+	if got := DecodeModeName("%", ""); got != "" {
+		t.Errorf("with no Status mode the result was %q, want empty", got)
+	}
+}
+
+func upper(s string) string {
+	out := []rune(s)
+	for i, r := range out {
+		if r >= 'a' && r <= 'z' {
+			out[i] = r - 32
+		}
+	}
+	return string(out)
+}

internal/integrations/udp/server.go

@@ -183,6 +183,9 @@ type Server struct {
 	// lastFrom is the address each program's packets arrive from — where a Reply
 	// has to be sent. See SendReply.
 	lastFrom map[string]*net.UDPAddr
+	// lastMode is the mode NAME from each program's last Status, used to resolve
+	// a Decode's one-character mode marker.
+	lastMode map[string]string
 	lastDX   string // WSJT: last non-empty DX Call seen, to detect a clear
 
 	// badPkts counts datagrams this listener could not parse, so the diagnostic
@@ -436,6 +439,14 @@ func (s *Server) handle(pkt []byte, remote *net.UDPAddr) {
 				}
 				s.trPeriod[w.ProgramID] = w.TRPeriod
 			}
+			// The mode NAME, which only Status carries: a Decode gives the
+			// one-character marker instead. See DecodeModeName.
+			if w.Mode != "" {
+				if s.lastMode == nil {
+					s.lastMode = map[string]string{}
+				}
+				s.lastMode[w.ProgramID] = w.Mode
+			}
 			s.mu.Unlock()
 		}
 		if !w.IsDecode && (w.TxMessage != "" || w.DECall != "") {
@@ -452,6 +463,7 @@ func (s *Server) handle(pkt []byte, remote *net.UDPAddr) {
 			s.mu.Lock()
 			dial := s.dialHz[w.ProgramID]
 			tr := s.trPeriod[w.ProgramID]
+			statusMode := s.lastMode[w.ProgramID]
 			s.mu.Unlock()
 			if dial <= 0 {
 				// No Status from THIS instance yet. Guessing with another
@@ -464,7 +476,7 @@ func (s *Server) handle(pkt []byte, remote *net.UDPAddr) {
 			ev.DecodeFreqHz = dial + w.DeltaFreqHz
 			ev.DecodeSNR = w.SNR
 			ev.DecodeCQ = w.IsCQ
-			ev.Mode = w.Mode
+			ev.Mode = DecodeModeName(w.Mode, statusMode)
 			ev.DecodeMsg = w.DecodeMsg
 			ev.DecodeAt = decodeTime(w.DecodeMsSinceMidnight)
 			ev.DecodeTRPeriod = tr

internal/integrations/udp/wsjt.go

@@ -453,3 +453,50 @@ func readQString(r *bytes.Reader) (string, error) {
 	}
 	return string(buf), nil
 }
+
+// decodeModeChar maps the single character WSJT-X puts in a Decode's mode field
+// to the mode it stands for.
+//
+// A Decode does NOT carry the mode's name. It carries the one-character marker
+// that appears in the decode line and in ALL.TXT — "~" for FT8, "+" for FT4 —
+// and that character was being passed straight through as if it were a mode.
+// Everything downstream then compared "~" against the modes in the log, matched
+// nothing, and called every station on an already-worked band a new MODE.
+//
+// The table covers what is common; anything missing falls back to the mode from
+// the sender's last Status, which carries the real name — so an unlisted or
+// future marker degrades to correct rather than to nonsense.
+var decodeModeChar = map[string]string{
+	"~": "FT8",
+	"+": "FT4",
+	"#": "JT65",
+	"@": "JT9",
+	"&": "MSK144",
+	":": "Q65",
+	"`": "FST4",
+}
+
+// DecodeModeName resolves a Decode's mode field to a real mode name. statusMode
+// is the mode from the same program's last Status, used when the field is a
+// marker we do not know, or empty.
+func DecodeModeName(raw, statusMode string) string {
+	raw = strings.TrimSpace(raw)
+	if m, ok := decodeModeChar[raw]; ok {
+		return m
+	}
+	// A mode name is at least two alphanumeric characters ("FT8", "JS8", "Q65").
+	// Anything shorter, or carrying punctuation, is a marker rather than a name.
+	if len(raw) >= 2 {
+		named := true
+		for _, r := range raw {
+			if !(r >= 'A' && r <= 'Z') && !(r >= 'a' && r <= 'z') && !(r >= '0' && r <= '9') {
+				named = false
+				break
+			}
+		}
+		if named {
+			return strings.ToUpper(raw)
+		}
+	}
+	return strings.ToUpper(strings.TrimSpace(statusMode))
+}