package cat

// Native Kenwood CAT — TS-590, TS-890, TS-2000 and the many rigs that speak the
// same dialect (Elecraft K3/K4, and the "Kenwood/Elecraft" setting on Flex and
// SunSDR). Plain ASCII, every command terminated by ';', same shape as Yaesu but
// a different vocabulary.
//
// The dialect is already proven in this repository from the other side:
// internal/catemu ANSWERS these commands, pretending to be a TS-2000 so an ACOM
// amplifier follows OpsLog. The frame layouts here and there are the same ones.
//
// Commands used:
//
//	FA;            → FA00014025000;  VFO A frequency, ELEVEN digits, Hz
//	FB;            → FB00014030000;  VFO B frequency
//	IF;            → 38-char status frame: frequency, RX/TX, mode, VFO, split —
//	                 the whole operating state in ONE round trip, which is why it
//	                 is the poll rather than asking four separate questions.
//	MD;            → MD3;            mode (1=LSB 2=USB 3=CW 4=FM 5=AM 6=FSK
//	                 7=CW-R 9=FSK-R)
//	FR0;/FR1;                        receive VFO — 0 = A, 1 = B
//	FT0;/FT1;                        transmit VFO (split = the two differ)
//	TX;/RX;                          key / unkey
//	ID;            → ID020;          model number
//	AI0;                             silence unsolicited status reports
//
// Why not OmniRig: the same reason the Yaesu backend exists. Every Kenwood
// fault reported through OmniRig came from its interpretation layer rather than
// from the radio, and the rig file decides what a "Freq" property means.

import (
	"fmt"
	"strconv"
	"strings"
	"sync"
	"time"

	"go.bug.st/serial"
)

// Kenwood is the native backend. One serial port, one mutex: a command and its
// reply are never interleaved with another exchange.
type Kenwood struct {
	portName string
	baud     int
	digital  string // mode name logged for data (FT8 by default)

	mu   sync.Mutex
	port serial.Port

	// dialPort, when set, replaces serial.Open. It exists so the backend can be
	// driven against internal/catemu — which already SPEAKS this dialect to
	// satisfy an ACOM amplifier — without a radio, a COM port or a null-modem
	// pair. Written for a Kenwood backend nobody here owns a rig to test.
	dialPort func() (serial.Port, error)

	model     string
	curFreq   int64
	curRXFreq int64
	curVFO    string // "A" or "B"
	// Commands this rig answered "?;" to — asked once, then never again.
	unsupported map[string]bool
}

func NewKenwood(portName string, baud int, digital string) *Kenwood {
	if baud <= 0 {
		baud = 9600 // TS-590 factory default; TS-890 ships at 115200
	}
	if strings.TrimSpace(digital) == "" {
		digital = "FT8"
	}
	return &Kenwood{portName: strings.TrimSpace(portName), baud: baud, digital: digital, curVFO: "A"}
}

func (k *Kenwood) Name() string { return "kenwood" }

func (k *Kenwood) Connect() error {
	k.mu.Lock()
	defer k.mu.Unlock()
	if k.portName == "" {
		return fmt.Errorf("kenwood: no serial port configured")
	}
	// Close any handle still held before opening another: Connect runs again on
	// every reconnect, and Windows opens a serial port exclusively, so a leaked
	// handle makes the next open fail with "port busy" (the fault found in the
	// Yaesu backend — same shape here).
	if k.port != nil {
		_ = k.port.Close()
		k.port = nil
	}
	p, err := k.openPort()
	if err != nil {
		return fmt.Errorf("kenwood: open %s @ %d baud: %w", k.portName, k.baud, err)
	}
	p.SetReadTimeout(300 * time.Millisecond)
	k.port = p
	k.unsupported = map[string]bool{}

	// Silence unsolicited status reports: they interleave with our
	// request/response pairs and make a reply impossible to attribute. We poll.
	_ = k.write("AI0;")

	answered := false
	if id, err := k.ask("ID;"); err == nil && strings.HasPrefix(id, "ID") {
		answered = true
		code := strings.TrimSuffix(strings.TrimPrefix(id, "ID"), ";")
		if name, ok := kenwoodModels[code]; ok {
			k.model = name
		} else {
			k.model = "Kenwood (" + code + ")"
			debugLog.Printf("kenwood: unknown model id %q — add it to kenwoodModels", code)
		}
	}
	// IF is the command everything else depends on, so it is also the honest
	// test of whether a radio is really there.
	if r, err := k.ask("IF;"); err == nil && strings.HasPrefix(r, "IF") {
		answered = true
	}
	if !answered {
		k.model = ""
		return fmt.Errorf("kenwood: %s opened but the rig is not answering — check that it is switched on and set to %d baud", k.portName, k.baud)
	}
	debugLog.Printf("kenwood: connected on %s @ %d baud, model=%q", k.portName, k.baud, k.model)
	return nil
}

func (k *Kenwood) Disconnect() {
	k.mu.Lock()
	defer k.mu.Unlock()
	if k.port != nil {
		_ = k.port.Close()
		k.port = nil
	}
}

// ReadState polls the rig. IF carries frequency, mode, VFO, split and TX state
// in one frame; the other VFO is only asked for when split is actually on, so
// the common simplex case costs a single round trip.
func (k *Kenwood) ReadState() (RigState, error) {
	k.mu.Lock()
	defer k.mu.Unlock()
	if k.port == nil {
		return RigState{}, fmt.Errorf("kenwood: not connected")
	}
	raw, err := k.ask("IF;")
	if err != nil {
		return RigState{}, err
	}
	f, ok := parseKenwoodIF(raw)
	if !ok {
		return RigState{}, fmt.Errorf("kenwood: unparsable IF frame %q", raw)
	}

	s := RigState{Connected: true, Backend: "kenwood"}
	k.curVFO = f.VFO
	s.Vfo = f.VFO
	s.Mode = kenwoodModeToADIF(f.Mode, k.digital)
	s.Rig = k.model

	// IF reports the frequency of the VFO in USE (what the operator hears).
	rx := f.FreqHz
	tx := rx
	if f.Split {
		// The transmit VFO is the other one. Read it rather than assume, and fall
		// back to simplex if it cannot be read: a wrong TX frequency is written
		// into the log, which is worse than showing no split at all.
		other := "FB;"
		if f.VFO == "B" {
			other = "FA;"
		}
		if r, err := k.ask(other); err == nil {
			if hz, ok := parseKenwoodFreq(r, strings.TrimSuffix(other, ";")); ok && hz > 0 && hz != rx {
				tx = hz
			}
		}
	}
	if tx != rx {
		s.FreqHz = tx // ADIF: FREQ is the TRANSMIT frequency
		s.RxFreqHz = rx
		s.Split = true
	} else {
		s.FreqHz = rx
	}
	k.curFreq = s.FreqHz
	if s.Split {
		k.curRXFreq = s.RxFreqHz
	}
	return s, nil
}

// SetFrequency tunes the VFO the operator is actually on — writing FA blind is
// what makes a display disagree with the radio when they are on B.
func (k *Kenwood) SetFrequency(hz int64) error {
	k.mu.Lock()
	defer k.mu.Unlock()
	if k.port == nil {
		return fmt.Errorf("kenwood: not connected")
	}
	if hz <= 0 || hz > 99_999_999_999 {
		return fmt.Errorf("kenwood: frequency %d out of the 11-digit CAT range", hz)
	}
	cmd := "FA"
	if k.curVFO == "B" {
		cmd = "FB"
	}
	return k.write(fmt.Sprintf("%s%011d;", cmd, hz))
}

func (k *Kenwood) SetMode(mode string) error {
	k.mu.Lock()
	defer k.mu.Unlock()
	if k.port == nil {
		return fmt.Errorf("kenwood: not connected")
	}
	d := kenwoodModeDigit(mode, k.curFreq)
	if d == 0 {
		return fmt.Errorf("kenwood: no CAT mode for %q", mode)
	}
	return k.write(fmt.Sprintf("MD%c;", d))
}

func (k *Kenwood) SetPTT(on bool) error {
	k.mu.Lock()
	defer k.mu.Unlock()
	if k.port == nil {
		return fmt.Errorf("kenwood: not connected")
	}
	if on {
		return k.write("TX;")
	}
	return k.write("RX;")
}

func (k *Kenwood) write(cmd string) error {
	if k.port == nil {
		return fmt.Errorf("kenwood: not connected")
	}
	_, err := k.port.Write([]byte(cmd))
	return err
}

// ask sends a query and returns the reply belonging to THAT command. Anything
// else on the wire is discarded: a stray frame parsed as a frequency reads as
// "lost the rig" to the Manager, which then reconnects — the CAT link dropping
// for no reason (found the hard way on the Yaesu backend).
func (k *Kenwood) ask(cmd string) (string, error) {
	want := cmdPrefix(cmd)
	if k.unsupported[want] {
		return "", fmt.Errorf("kenwood: %s is not supported by this rig", want)
	}
	if err := k.write(cmd); err != nil {
		return "", err
	}
	buf := make([]byte, 0, 64)
	tmp := make([]byte, 64)
	deadline := time.Now().Add(600 * time.Millisecond)
	for time.Now().Before(deadline) {
		n, err := k.port.Read(tmp)
		if err != nil {
			return "", err
		}
		if n == 0 {
			continue // read timeout — the rig may still be composing its answer
		}
		buf = append(buf, tmp[:n]...)
		for {
			i := strings.IndexByte(string(buf), ';')
			if i < 0 {
				break
			}
			frame := string(buf[:i+1])
			buf = buf[i+1:]
			if frame == "?;" {
				// The rig rejected the command. Remember it so the poll loop stops
				// paying a 600 ms timeout for it on every cycle.
				k.unsupported[want] = true
				debugLog.Printf("kenwood: this rig does not support %q — not asking again", cmd)
				return "", fmt.Errorf("kenwood: %s rejected", want)
			}
			if strings.HasPrefix(frame, want) {
				return frame, nil
			}
			debugLog.Printf("kenwood: discarding %q while waiting for %s", frame, want)
		}
	}
	return "", fmt.Errorf("kenwood: timeout answering %q", cmd)
}

// ── Frame parsing ──────────────────────────────────────────────────────────

// kenwoodIF is what the 38-character IF status frame carries.
type kenwoodIF struct {
	FreqHz int64
	Mode   byte
	VFO    string // "A" or "B"
	Split  bool
	// TX is parsed even though RigState has no PTT field: it is one character of
	// the same frame, and having it here means a future "transmitting" indicator
	// costs no extra round trip.
	TX bool
}

// parseKenwoodIF reads the TS-2000/TS-590 status frame. Its layout — the same
// one internal/catemu emits — is:
//
//	IF | freq(11) | step(4) | RIT(±5) | RIT/XIT/bank(3) | mem(2) | rx-tx(1) |
//	mode(1) | VFO(1) | scan(1) | split(1) | tone(1) | tone#(2) | shift(1) | ;
//
// Fields are read by POSITION, so the length is checked first: a short frame
// means a truncated read, and indexing into it would panic or, worse, silently
// yield a wrong frequency.
func parseKenwoodIF(reply string) (kenwoodIF, bool) {
	r := strings.TrimSpace(reply)
	if !strings.HasPrefix(r, "IF") || len(r) < 38 {
		return kenwoodIF{}, false
	}
	hz, err := strconv.ParseInt(strings.TrimSpace(r[2:13]), 10, 64)
	if err != nil || hz <= 0 {
		return kenwoodIF{}, false
	}
	out := kenwoodIF{FreqHz: hz, Mode: r[29], VFO: "A", TX: r[28] == '1', Split: r[32] == '1'}
	if r[30] == '1' {
		out.VFO = "B"
	}
	return out, true
}

// parseKenwoodFreq reads an FA/FB reply — ELEVEN digits on Kenwood, where Yaesu
// uses nine. The prefix is checked so an FB reply is never accepted as FA.
func parseKenwoodFreq(reply, prefix string) (int64, bool) {
	r := strings.TrimSpace(reply)
	if !strings.HasPrefix(r, prefix) {
		return 0, false
	}
	digits := strings.TrimSuffix(strings.TrimPrefix(r, prefix), ";")
	if digits == "" {
		return 0, false
	}
	hz, err := strconv.ParseInt(digits, 10, 64)
	if err != nil || hz <= 0 {
		return 0, false
	}
	return hz, true
}

// ── Modes ──────────────────────────────────────────────────────────────────

// kenwoodModeDigit maps an ADIF mode to the Kenwood digit. The sideband follows
// the frequency by worldwide convention — a backend that puts USB on 40 m makes
// every SSB QSO in the log wrong.
func kenwoodModeDigit(mode string, hz int64) byte {
	m := strings.ToUpper(strings.TrimSpace(mode))
	switch m {
	case "":
		return 0
	case "LSB":
		return '1'
	case "USB":
		return '2'
	case "CW":
		return '3'
	case "CW-R", "CWR":
		return '7'
	case "FM":
		return '4'
	case "AM":
		return '5'
	case "RTTY", "FSK":
		return '6'
	case "RTTY-R", "FSK-R":
		return '9'
	case "SSB":
		if hz > 0 && hz < 10_000_000 {
			return '1'
		}
		return '2'
	}
	// Any other digital mode rides on the data sideband, which on Kenwood is
	// plain USB/LSB with the rig's DATA input selected.
	if hz > 0 && hz < 10_000_000 {
		return '1'
	}
	return '2'
}

// kenwoodModeToADIF turns the rig's mode digit into what the log records.
// Digital modes are indistinguishable from SSB over CAT — the rig only knows
// it is on USB — so the operator's configured digital mode is used, exactly as
// the other backends do.
func kenwoodModeToADIF(d byte, digital string) string {
	switch d {
	case '1':
		return "LSB"
	case '2':
		return "USB"
	case '3', '7':
		return "CW"
	case '4':
		return "FM"
	case '5':
		return "AM"
	case '6', '9':
		return "RTTY"
	}
	return ""
}

// kenwoodModels maps the ID reply to a name for the status bar. An unknown code
// is shown as-is rather than refused: the model name is cosmetic, and a rig that
// answers everything else must not be rejected over it.
var kenwoodModels = map[string]string{
	"017": "TS-570",
	"019": "TS-2000",
	"020": "TS-480",
	"021": "TS-590S",
	"023": "TS-590SG",
	"024": "TS-990S",
	"025": "TS-890S",
}

// openPort opens the serial link, or whatever dialPort provides in a test.
func (k *Kenwood) openPort() (serial.Port, error) {
	if k.dialPort != nil {
		return k.dialPort()
	}
	return serial.Open(k.portName, &serial.Mode{BaudRate: k.baud})
}