feat(sat): PstRotator can point the antenna too

It handles azimuth and elevation, and a great many stations already run
it in front of a controller OpsLog has never heard of. For those,
OpsLog talking to the controller itself would be a second program
fighting PstRotator over the same cable — so it hands over the bearing
instead, and lets PstRotator turn the mast.

Both kinds sit behind one small interface, chosen in Settings. Neither is
more correct than the other: the right one is whichever the station
already has working.

The 450° overlap is deliberately NOT applied on the PstRotator path.
PstRotator knows which machine is on the other end and does its own; two
programs each deciding to go the long way round is exactly how an antenna
unwinds in the middle of a pass.

Position queries are asked at most every three seconds rather than on
every tick. A PstRotator query binds a socket and waits up to a second
and a half, and many setups answer nothing at all — so one silence is
enough and it stops asking, reporting the commanded position instead and
saying that is what it is.

app_sat_rotator.go

@@ -0,0 +1,140 @@
+package main
+
+// The two ways a satellite station points its antenna.
+//
+// Some operators drive their az/el rotator directly — EasyComm II, what
+// SatPC32 and Gpredict speak. Others already run PstRotator, which sits between
+// them and a dozen different controllers and handles az AND el; for those,
+// OpsLog talking to the controller itself would be a second program fighting
+// PstRotator over the same cable.
+//
+// So both, behind one small interface, chosen in Settings. Neither is more
+// "correct" than the other: the right one is whichever the station already has
+// working.
+
+import (
+	"fmt"
+	"math"
+	"strings"
+	"sync"
+
+	"hamlog/internal/rotator/easycomm"
+	"hamlog/internal/rotator/pst"
+)
+
+// satRotator is what the tracker needs of an antenna: point it, ask where it
+// is, and let go of it at the end of the pass.
+type satRotator interface {
+	Point(az, el float64) error
+	// Heading reports where the antenna is. live is false when the answer is
+	// the last commanded position rather than a reading — a stuck rotator must
+	// not be able to hide behind an order it never carried out.
+	Heading() (az, el float64, live bool, err error)
+	Close()
+}
+
+// The rotator kinds, as stored.
+const (
+	satRotEasycomm = "easycomm"
+	satRotPst      = "pstrotator"
+)
+
+// newSatRotator builds the configured controller.
+func newSatRotator(s SatSettings) (satRotator, error) {
+	switch s.RotType {
+	case satRotPst:
+		if strings.TrimSpace(s.RotHost) == "" && s.RotPort <= 0 {
+			return nil, fmt.Errorf("no address for PstRotator")
+		}
+		return &pstSatRotator{c: pst.New(s.RotHost, s.RotPstPort), maxAz: s.RotMaxAz}, nil
+	default:
+		if s.RotTransport == "tcp" {
+			if strings.TrimSpace(s.RotHost) == "" {
+				return nil, fmt.Errorf("no address for the rotator")
+			}
+			return easycomm.New(s.RotHost, s.RotPort, s.RotMaxAz), nil
+		}
+		if strings.TrimSpace(s.RotCOM) == "" {
+			return nil, fmt.Errorf("no COM port for the rotator")
+		}
+		return easycomm.NewSerial(s.RotCOM, s.RotBaud, s.RotMaxAz), nil
+	}
+}
+
+// pstSatRotator points the antenna through PstRotator.
+//
+// PstRotator takes whole degrees and does its own overlap handling for a 450°
+// rotator — it knows which controller is on the other end, and OpsLog does not.
+// So the azimuth is sent plainly, and the 450° logic that EasyComm needs is
+// deliberately NOT applied here: two programs each deciding to go the long way
+// round is how an antenna ends up unwinding in the middle of a pass.
+type pstSatRotator struct {
+	c     *pst.Client
+	maxAz int
+
+	mu sync.Mutex
+	// lastAz/lastEl are what was commanded, for the display when PstRotator
+	// does not answer a position query — which is the usual case for the many
+	// setups whose controller reports nothing back to it either.
+	lastAz, lastEl float64
+	commanded      bool
+	azSilent       bool // the azimuth query went unanswered; stop asking
+	elSilent       bool // likewise for elevation, and far more common
+}
+
+func (p *pstSatRotator) Point(az, el float64) error {
+	a := math.Mod(az, 360)
+	if a < 0 {
+		a += 360
+	}
+	if el < 0 {
+		el = 0
+	}
+	if el > 180 {
+		el = 180
+	}
+	if err := p.c.GoTo(int(math.Round(a)), true, int(math.Round(el))); err != nil {
+		return err
+	}
+	p.mu.Lock()
+	p.lastAz, p.lastEl, p.commanded = a, el, true
+	p.mu.Unlock()
+	return nil
+}
+
+func (p *pstSatRotator) Heading() (float64, float64, bool, error) {
+	p.mu.Lock()
+	azSilent, elSilent, la, le, commanded := p.azSilent, p.elSilent, p.lastAz, p.lastEl, p.commanded
+	p.mu.Unlock()
+
+	az, el, live := la, le, false
+	if !azSilent {
+		if v, _, err := p.c.Heading(); err == nil {
+			az, live = float64(v), true
+		} else {
+			// One silence is enough. Each query binds a socket and waits a second
+			// and a half; repeating that every few seconds for a setup that will
+			// never answer is a stall per poll for nothing.
+			p.mu.Lock()
+			p.azSilent = true
+			p.mu.Unlock()
+		}
+	}
+	if !elSilent {
+		if v, _, err := p.c.Elevation(); err == nil {
+			el = float64(v)
+		} else {
+			p.mu.Lock()
+			p.elSilent = true
+			p.mu.Unlock()
+		}
+	}
+	if !live && !commanded {
+		return 0, 0, false, fmt.Errorf("PstRotator does not report the antenna position")
+	}
+	return az, el, live, nil
+}
+
+// Close: nothing to release. Every PstRotator command is one datagram, and the
+// socket lives for the length of a single write.
+func (p *pstSatRotator) Close() {}