// Package rigctld shares OpsLog's CAT link with other programs.
//
// A native CAT backend owns the rig's serial port, and Windows gives a COM port
// to ONE process. So the moment OpsLog talks to the radio directly, WSJT-X,
// MSHV or JTDX can no longer reach it — the cost of dropping OmniRig, which was
// itself a sharing layer.
//
// The answer is the one wfview uses: OpsLog becomes the server. It speaks the
// Hamlib "net rigctl" protocol, which WSJT-X, JTDX, MSHV, Log4OM and CQRLOG all
// support natively (rig model "Hamlib NET rigctl", host:4532) with no driver to
// install. The other program asks us, and we relay to whichever backend is
// connected — OmniRig, Flex, Icom, TCI or Yaesu alike.
//
// ── The protocol ──────────────────────────────────────────────────────────
// Line-based ASCII. A lowercase letter reads, its uppercase counterpart writes,
// and long names are prefixed with a backslash. A write answers "RPRT 0" for
// success or "RPRT -n" for an error; a read answers the value(s), one per line.
//
//	f            → 14074000          get_freq
//	F 14074000   → RPRT 0            set_freq
//	m            → USB\n2400         get_mode (mode + passband)
//	M USB 2400   → RPRT 0            set_mode
//	t / T 1      → 0                 get/set PTT
//	s            → 0\nVFOB           get_split_vfo
//	v            → VFOA              get_vfo
//	\dump_state  → capability block  asked once by WSJT-X at connect
//
// WSJT-X will not proceed past connect without a well-formed dump_state, which
// is why that block is written out in full rather than stubbed.
package rigctld

import (
	"bufio"
	"fmt"
	"net"
	"strconv"
	"strings"
	"sync"
	"time"
)

// Rig is what the server needs from OpsLog's CAT manager. An interface, so this
// package stays testable without a radio and without importing internal/cat.
type Rig interface {
	Freq() int64          // current TX frequency in Hz, 0 if unknown
	Mode() string         // ADIF mode (SSB, CW, FT8…)
	Split() (bool, int64) // split on?, and the other VFO's frequency
	SetFreq(hz int64) error
	SetMode(mode string) error
	SetPTT(on bool) error
}

type Server struct {
	port int
	rig  Rig
	log  func(string, ...any)

	mu     sync.Mutex
	ln     net.Listener
	conns  map[net.Conn]struct{}
	closed bool
}

func New(port int, rig Rig, logf func(string, ...any)) *Server {
	if port <= 0 || port > 65535 {
		port = 4532 // the rigctld default every client pre-fills
	}
	if logf == nil {
		logf = func(string, ...any) {}
	}
	return &Server{port: port, rig: rig, log: logf, conns: map[net.Conn]struct{}{}}
}

func (s *Server) Start() error {
	s.mu.Lock()
	if s.ln != nil {
		s.mu.Unlock()
		return nil // already listening
	}
	s.closed = false
	s.mu.Unlock()

	ln, err := net.Listen("tcp", fmt.Sprintf(":%d", s.port))
	if err != nil {
		return fmt.Errorf("rigctld: listen on %d: %w", s.port, err)
	}
	s.mu.Lock()
	s.ln = ln
	s.mu.Unlock()
	s.log("rigctld: sharing CAT on port %d (Hamlib NET rigctl)", s.port)

	go func() {
		for {
			c, err := ln.Accept()
			if err != nil {
				s.mu.Lock()
				closed := s.closed
				s.mu.Unlock()
				if !closed {
					s.log("rigctld: accept failed: %v", err)
				}
				return
			}
			s.mu.Lock()
			s.conns[c] = struct{}{}
			s.mu.Unlock()
			go s.serve(c)
		}
	}()
	return nil
}

func (s *Server) Stop() {
	s.mu.Lock()
	s.closed = true
	ln := s.ln
	s.ln = nil
	conns := make([]net.Conn, 0, len(s.conns))
	for c := range s.conns {
		conns = append(conns, c)
	}
	s.conns = map[net.Conn]struct{}{}
	s.mu.Unlock()

	if ln != nil {
		_ = ln.Close()
	}
	// Close the live sessions too. Leaving them open would keep a client happily
	// talking to a server the operator has switched off.
	for _, c := range conns {
		_ = c.Close()
	}
}

func (s *Server) serve(c net.Conn) {
	defer func() {
		s.mu.Lock()
		delete(s.conns, c)
		s.mu.Unlock()
		_ = c.Close()
	}()
	s.log("rigctld: client connected from %s", c.RemoteAddr())
	r := bufio.NewReader(c)
	w := bufio.NewWriter(c)
	for {
		// No deadline: WSJT-X polls every few seconds but a client may legitimately
		// sit idle between band changes, and dropping it would look like a fault.
		line, err := r.ReadString('\n')
		if err != nil {
			s.log("rigctld: client %s disconnected", c.RemoteAddr())
			return
		}
		resp, quit := s.handle(strings.TrimSpace(line))
		if resp != "" {
			if _, err := w.WriteString(resp); err != nil {
				return
			}
			if err := w.Flush(); err != nil {
				return
			}
		}
		if quit {
			return
		}
	}
}

// handle answers one command line. Pure apart from the Rig calls, so the whole
// protocol is testable with a fake rig.
func (s *Server) handle(line string) (resp string, quit bool) {
	if line == "" {
		return "", false
	}
	// Extended mode: clients may prefix a command with '+' or '-' to ask for a
	// verbose reply. We answer in the plain format, which every client also
	// accepts, so the prefix is simply stripped.
	line = strings.TrimLeft(line, "+-")
	fields := strings.Fields(line)
	if len(fields) == 0 {
		return "", false
	}
	cmd, args := fields[0], stripVFOArg(fields[1:])

	switch cmd {
	case "\\dump_state", "dump_state":
		return dumpState, false
	case "\\chk_vfo", "chk_vfo":
		// "is VFO mode on?" — we answer for one VFO at a time, so: no.
		return "CHKVFO 0\n", false
	case "\\get_powerstat", "get_powerstat":
		return "1\n", false
	case "q", "Q", "\\quit":
		return "", true

	case "f", "\\get_freq":
		return fmt.Sprintf("%d\n", s.rig.Freq()), false
	case "F", "\\set_freq":
		if len(args) < 1 {
			return rprt(-1), false
		}
		hz, err := parseFreq(args[0])
		if err != nil {
			// Logged with the RAW line: a client that phrases a command in a
			// dialect we don't accept shows only "Invalid parameter" on its side,
			// which says nothing about what it actually sent.
			s.log("rigctld: cannot read a frequency from %q — client dialect not handled", line)
			return rprt(-1), false
		}
		if err := s.rig.SetFreq(hz); err != nil {
			s.log("rigctld: set_freq %d failed: %v", hz, err)
			return rprt(-9), false
		}
		return rprt(0), false

	case "m", "\\get_mode":
		// Passband width is required by the protocol. We do not read the rig's
		// filter, and a made-up number is harmless here: clients use it to display
		// a bandwidth, never to decide anything.
		return fmt.Sprintf("%s\n%d\n", adifToHamlib(s.rig.Mode()), passbandFor(s.rig.Mode())), false
	case "M", "\\set_mode":
		if len(args) < 1 {
			return rprt(-1), false
		}
		if err := s.rig.SetMode(hamlibToADIF(args[0])); err != nil {
			s.log("rigctld: set_mode %q failed: %v", args[0], err)
			return rprt(-9), false
		}
		return rprt(0), false

	case "t", "\\get_ptt":
		// We do not read PTT back from every backend, and answering "transmitting"
		// wrongly would make a client hold off for ever. Reporting RX is the safe
		// direction: the worst case is a client that transmits when we said it
		// could, which is what it was going to do anyway.
		return "0\n", false
	case "T", "\\set_ptt":
		if len(args) < 1 {
			return rprt(-1), false
		}
		on := args[0] != "0"
		if err := s.rig.SetPTT(on); err != nil {
			s.log("rigctld: set_ptt %v failed: %v", on, err)
			return rprt(-9), false
		}
		return rprt(0), false

	case "v", "\\get_vfo":
		return "VFOA\n", false
	case "V", "\\set_vfo":
		// Accepted and ignored: OpsLog follows the rig's own VFO selection, and
		// answering an error here makes WSJT-X abandon the connection entirely.
		return rprt(0), false

	case "s", "\\get_split_vfo":
		on, _ := s.rig.Split()
		n := 0
		if on {
			n = 1
		}
		return fmt.Sprintf("%d\nVFOB\n", n), false
	case "S", "\\set_split_vfo":
		return rprt(0), false // see set_vfo — split is driven from the rig
	case "i", "\\get_split_freq":
		_, tx := s.rig.Split()
		if tx <= 0 {
			tx = s.rig.Freq()
		}
		return fmt.Sprintf("%d\n", tx), false
	case "I", "\\set_split_freq":
		return rprt(0), false

	default:
		// RPRT -11 is "command not implemented". Answering something is essential:
		// a client waiting on a silent socket hangs rather than degrading.
		s.log("rigctld: unimplemented command %q", line)
		return rprt(-11), false
	}
}

func rprt(code int) string { return fmt.Sprintf("RPRT %d\n", code) }

// stripVFOArg drops a leading VFO name from a command's arguments.
//
// Hamlib has two dialects. In the plain one a client sends "F 14074000"; in VFO
// mode it names the target first — "F VFOA 14074000". MSHV uses the first and
// worked immediately; JTDX uses the second, so the frequency landed in the
// argument slot where a VFO was expected, the parse failed, and JTDX showed
// "Hamlib error: Invalid parameter while setting frequency" (our RPRT -1).
//
// Accepting both costs nothing here: OpsLog follows the rig's own VFO
// selection, so the name carries no information we act on — dropping it is not
// losing anything, and refusing it locks out a whole family of clients.
func stripVFOArg(args []string) []string {
	if len(args) == 0 {
		return args
	}
	switch strings.ToUpper(args[0]) {
	case "VFOA", "VFOB", "VFOC", "VFO", "CURRVFO", "CURR", "MAIN", "SUB", "MEM", "A", "B":
		return args[1:]
	}
	return args
}

// parseFreq accepts both the integer Hz and the "14074000.000000" form clients
// send interchangeably.
func parseFreq(s string) (int64, error) {
	s = strings.TrimSpace(s)
	if i := strings.IndexByte(s, '.'); i >= 0 {
		s = s[:i]
	}
	hz, err := strconv.ParseInt(s, 10, 64)
	if err != nil || hz <= 0 {
		return 0, fmt.Errorf("rigctld: bad frequency %q", s)
	}
	return hz, nil
}

// adifToHamlib maps our mode vocabulary to Hamlib's. Every digital sub-mode
// becomes PKTUSB: that is what a client expects to see when the rig is in DATA,
// and it is what WSJT-X sets when it takes control.
func adifToHamlib(mode string) string {
	switch strings.ToUpper(strings.TrimSpace(mode)) {
	case "SSB", "USB":
		return "USB"
	case "LSB":
		return "LSB"
	case "CW":
		return "CW"
	case "AM":
		return "AM"
	case "FM":
		return "FM"
	case "RTTY":
		return "RTTY"
	case "":
		return "USB"
	default:
		return "PKTUSB"
	}
}

// hamlibToADIF is the reverse. PKTUSB/PKTLSB/DATA become "DATA": the CAT backend
// then applies the operator's configured digital mode, so a client switching the
// rig to data does not silently relabel their QSOs as FT8 when they run JS8.
func hamlibToADIF(mode string) string {
	switch strings.ToUpper(strings.TrimSpace(mode)) {
	case "USB":
		return "USB"
	case "LSB":
		return "LSB"
	case "CW", "CWR":
		return "CW"
	case "AM":
		return "AM"
	case "FM", "FMN", "WFM":
		return "FM"
	case "RTTY", "RTTYR":
		return "RTTY"
	case "PKTUSB", "PKTLSB", "PKTFM", "DATA", "DIGU", "DIGL":
		return "DATA"
	default:
		return strings.ToUpper(strings.TrimSpace(mode))
	}
}

func passbandFor(mode string) int {
	switch adifToHamlib(mode) {
	case "CW":
		return 500
	case "RTTY", "PKTUSB":
		return 3000
	case "AM":
		return 6000
	case "FM":
		return 15000
	default:
		return 2400
	}
}

// dumpState is the capability block Hamlib clients read once at connect. WSJT-X
// refuses to go further without it, and parses it positionally — the field
// ORDER is the contract, so this is kept as one literal rather than assembled.
//
// It declares protocol version 0, a generic rig, and one 150 kHz–1500 MHz range
// with the common modes. The numbers are deliberately permissive: they say what
// a client may ASK for, and OpsLog's backend refuses anything the radio cannot
// really do.
const dumpState = `0
1
2
150000.000000 1500000000.000000 0x1ff -1 -1 0x10000003 0x3
0 0 0 0 0 0 0
150000.000000 1500000000.000000 0x1ff -1 -1 0x10000003 0x3
0 0 0 0 0 0 0
0 0
0 0
0x1ff 1
0x1ff 0
0 0
0x1e 2400
0x2 500
0x1 8000
0x1 2400
0x20 15000
0x20 8000
0x40 230000
0 0
9990
9990
10000
0
10
10 20 30
0x3effffff
0x3effffff
0x7fffffff
0x7fffffff
0x7fffffff
0x7fffffff
`

// dialTimeout is only used by tests, kept here so the value is one place.
const dialTimeout = 2 * time.Second