// Package cluster provides a multi-server DX cluster client (telnet) —
// connects concurrently to several AR-Cluster / CC-Cluster / DXSpider
// nodes, logs in with the operator's callsign, optionally sends an init
// command list, and streams DX spots back to the UI via a callback.
//
// Spot parsing is tolerant of the dozens of slight format variations
// between cluster flavours (the prompt, the trailing locator, the time
// format). Anything that doesn't match the spot regex is treated as
// banner/chat noise and ignored, not surfaced as an error.
package cluster

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

	"hamlog/internal/applog"
)

// ServerConfig is the persisted shape of one cluster node. Mirrors the
// columns of the cluster_servers table; the frontend SettingsPanel
// pushes one of these per row.
type ServerConfig struct {
	ID            int64  `json:"id"`
	Name          string `json:"name"`
	Host          string `json:"host"`
	Port          int    `json:"port"`
	LoginOverride string `json:"login_override"`
	Password      string `json:"password,omitempty"`
	InitCommands  string `json:"init_commands"` // newline-separated, sent post-login
	Enabled       bool   `json:"enabled"`
	SortOrder     int    `json:"sort_order"`
}

// Spot is a single DX spot as parsed from the cluster stream.
// Country/Continent are filled by the caller (app.go) before the spot
// is emitted to the UI, so the table never has empty country cells
// flickering in for a few hundred ms.
type Spot struct {
	SourceID   int64     `json:"source_id"`              // ID of the cluster server this came from
	SourceName string    `json:"source_name"`            // display name (handy in the UI when multiple servers)
	Spotter    string    `json:"spotter"`                // DE field
	DXCall     string    `json:"dx_call"`                // the DX station heard
	FreqKHz    float64   `json:"freq_khz"`
	FreqHz     int64     `json:"freq_hz"`
	Band       string    `json:"band,omitempty"`
	Comment    string    `json:"comment,omitempty"`
	Locator    string    `json:"locator,omitempty"`      // spotter grid (optional)
	TimeUTC    string    `json:"time_utc,omitempty"`
	Country    string    `json:"country,omitempty"`      // DXCC entity name (cty.dat)
	Continent  string    `json:"continent,omitempty"`    // 2-letter continent
	CQZone     int       `json:"cqz,omitempty"`          // DXCC entity CQ zone
	ITUZone    int       `json:"ituz,omitempty"`         // DXCC entity ITU zone
	DistanceKm int       `json:"distance_km,omitempty"`  // great-circle km from operator's grid
	ShortPath  int       `json:"sp_deg,omitempty"`       // azimuth (deg) short path from operator
	LongPath   int       `json:"lp_deg,omitempty"`       // azimuth (deg) long path = SP + 180 mod 360
	ReceivedAt time.Time `json:"received_at"`
	Raw        string    `json:"raw"`
	// Historical marks a spot recovered from a SH/DX table rather than heard live.
	// It belongs in the grid, but must NOT fire alerts or reach the panadapter:
	// replaying 100 past spots would spam both, and a station spotted three hours
	// ago is not on the air now.
	Historical bool `json:"historical,omitempty"`
	POTARef    string    `json:"pota_ref,omitempty"`  // park id if this station is activating (api.pota.app)
	POTAName   string    `json:"pota_name,omitempty"` // park name
}

// State enumerates the per-server lifecycle.
type State string

const (
	StateDisconnected State = "disconnected"
	StateConnecting   State = "connecting"
	StateConnected    State = "connected"
	StateReconnecting State = "reconnecting"
	StateError        State = "error"
)

// ServerStatus is one row of the runtime status table — one entry per
// active session.
type ServerStatus struct {
	ServerID    int64     `json:"server_id"`
	Name        string    `json:"name"`
	Host        string    `json:"host"`
	Port        int       `json:"port"`
	State       State     `json:"state"`
	Login       string    `json:"login,omitempty"`
	Error       string    `json:"error,omitempty"`
	ConnectedAt time.Time `json:"connected_at,omitempty"`
	SpotsCount  int       `json:"spots_count,omitempty"`
	Retries     int       `json:"retries,omitempty"`
}

// session is one telnet connection bound to a single server config.
// Line is one raw line of cluster traffic: everything the server says, plus the
// commands we send (echoed, so the console reads as a conversation).
//
// Spots are PARSED OUT of this stream — but everything else used to be silently
// dropped. You could type SH/DX/100 or WHO and never see the answer, which made
// the command box look broken. The raw stream is the fix: the console shows what
// the server actually said, spot or not.
type Line struct {
	ServerID   int64  `json:"server_id"`
	ServerName string `json:"server_name"`
	Text       string `json:"text"`
	Sent       bool   `json:"sent"` // true = a command WE sent
	At         string `json:"at"`   // HH:MM:SS, local
}

// Internal — callers use Manager. The onStatus callback is fire-and-
// forget: it tells the manager something changed; the frontend fetches
// the new aggregate via Status() rather than receiving per-server diffs.
type session struct {
	cfg      ServerConfig
	login    string
	onSpot   func(Spot)
	onLine   func(Line)
	onStatus func()

	mu        sync.RWMutex
	status    ServerStatus
	conn      net.Conn
	stopCh    chan struct{}
	doneCh    chan struct{}
	stopped   bool // guards against double-stop on the same session
	spotsCnt  int
	dbgN      int // diagnostic: how many raw lines logged this connection
}

// Manager owns N sessions, one per enabled server. Safe for concurrent
// use from any goroutine; I/O is on per-session background goroutines.
type Manager struct {
	mu       sync.RWMutex
	sessions map[int64]*session
	onSpot   func(Spot)
	onLine   func(Line)
	onStatus func()
}

// NewManager builds an empty manager. emitSpot is called for each parsed
// spot (with the source server filled in). emitStatusChanged is called
// whenever ANY server's status changes — the frontend then re-fetches
// the aggregate Status() via a Wails binding.
func NewManager(emitSpot func(Spot), emitStatusChanged func(), emitLine func(Line)) *Manager {
	return &Manager{
		sessions: make(map[int64]*session),
		onSpot:   emitSpot,
		onLine:   emitLine,
		onStatus: emitStatusChanged,
	}
}

// Status returns a snapshot of every running session's status.
func (m *Manager) Status() []ServerStatus {
	m.mu.RLock()
	defer m.mu.RUnlock()
	out := make([]ServerStatus, 0, len(m.sessions))
	for _, s := range m.sessions {
		out = append(out, s.snapshot())
	}
	return out
}

// StartServer launches a session for cfg. login is the resolved callsign
// to send (empty = anonymous). If a session for the same ID is already
// running it is restarted with the new config.
func (m *Manager) StartServer(cfg ServerConfig, login string) {
	m.StopServer(cfg.ID)
	if !cfg.Enabled || cfg.Host == "" {
		return
	}
	s := &session{
		cfg:      cfg,
		login:    login,
		onSpot:   m.onSpot,
		onLine:   m.onLine,
		onStatus: m.emitStatus,
		stopCh:   make(chan struct{}),
		doneCh:   make(chan struct{}),
		status: ServerStatus{
			ServerID: cfg.ID, Name: cfg.Name, Host: cfg.Host, Port: cfg.Port,
			Login: login, State: StateConnecting,
		},
	}
	m.mu.Lock()
	m.sessions[cfg.ID] = s
	m.mu.Unlock()
	s.emitStatus()
	go s.run()
}

// StopServer terminates the session for the given ID (if any) and waits
// for its goroutine to exit.
func (m *Manager) StopServer(id int64) {
	m.mu.Lock()
	s, ok := m.sessions[id]
	if ok {
		delete(m.sessions, id)
	}
	m.mu.Unlock()
	if !ok {
		return
	}
	s.stop()
	m.emitStatus()
}

// StopAll closes every running session.
func (m *Manager) StopAll() {
	m.mu.Lock()
	all := make([]*session, 0, len(m.sessions))
	for _, s := range m.sessions {
		all = append(all, s)
	}
	m.sessions = make(map[int64]*session)
	m.mu.Unlock()
	for _, s := range all {
		s.stop()
	}
	m.emitStatus()
}

// SendCommand writes raw text (a CRLF is appended) to the session for
// the given server ID. Used for "show last 30", "set/skimmer", etc.
func (m *Manager) SendCommand(serverID int64, cmd string) error {
	m.mu.RLock()
	s, ok := m.sessions[serverID]
	m.mu.RUnlock()
	if !ok {
		return fmt.Errorf("no active session for server %d", serverID)
	}
	return s.send(cmd)
}

func (m *Manager) emitStatus() {
	if m.onStatus != nil {
		m.onStatus()
	}
}

// ---------- session ----------

func (s *session) snapshot() ServerStatus {
	s.mu.RLock()
	defer s.mu.RUnlock()
	return s.status
}

func (s *session) emitStatus() {
	if s.onStatus != nil {
		s.onStatus()
	}
}

func (s *session) send(cmd string) error {
	s.mu.RLock()
	conn := s.conn
	s.mu.RUnlock()
	if conn == nil {
		return fmt.Errorf("session %q not connected", s.cfg.Name)
	}
	_ = conn.SetWriteDeadline(time.Now().Add(5 * time.Second))
	_, err := conn.Write([]byte(strings.TrimRight(cmd, "\r\n") + "\r\n"))
	if err == nil {
		// Echo it into the console, so the operator sees WHAT was sent and can pair
		// it with the reply that follows. A console that only shows one side of the
		// conversation is barely better than none.
		s.emitLine(cmd, true)
	}
	return err
}

func (s *session) stop() {
	// Critical: do NOT nil out s.stopCh — the supervisor goroutine reads
	// `<-s.stopCh` in its select. Setting the field to nil would make
	// `<-nil` block forever, leaving the supervisor stuck on its backoff
	// timer and then re-dialing → a "deleted" cluster keeps spotting.
	// We just close() the channel and let the goroutine see the broadcast.
	s.mu.Lock()
	if s.stopped {
		s.mu.Unlock()
		return
	}
	s.stopped = true
	stop, done := s.stopCh, s.doneCh
	conn := s.conn
	s.mu.Unlock()
	if conn != nil {
		_ = conn.Close()
	}
	if stop != nil {
		close(stop)
	}
	if done != nil {
		<-done
	}
}

// run is the per-session supervisor: keeps trying to connect until
// Stop is called. Backoff caps at 60s, resets after a 30s healthy link.
func (s *session) run() {
	defer close(s.doneCh)
	backoff := []time.Duration{2, 5, 10, 30, 60}
	attempt := 0
	for {
		select {
		case <-s.stopCh:
			return
		default:
		}
		connectedAt, err := s.runOnce()
		select {
		case <-s.stopCh:
			return
		default:
		}
		if !connectedAt.IsZero() && time.Since(connectedAt) > 30*time.Second {
			attempt = 0
		}
		idx := attempt
		if idx >= len(backoff) {
			idx = len(backoff) - 1
		}
		delay := backoff[idx] * time.Second
		attempt++

		s.mu.Lock()
		s.status.State = StateReconnecting
		if err != nil {
			s.status.Error = err.Error()
		}
		s.status.Retries = attempt
		s.mu.Unlock()
		s.emitStatus()

		select {
		case <-s.stopCh:
			return
		case <-time.After(delay):
		}
	}
}

// runOnce dials, optionally logs in, sends init commands, parses spots.
// Returns the moment we marked the link "connected" (zero if dial failed)
// and the error that ended the session (nil if stopCh).
func (s *session) runOnce() (time.Time, error) {
	addr := net.JoinHostPort(s.cfg.Host, fmt.Sprintf("%d", s.cfg.Port)) // IPv6-safe
	conn, err := net.DialTimeout("tcp", addr, 10*time.Second)
	if err != nil {
		return time.Time{}, fmt.Errorf("dial %s: %w", addr, err)
	}
	s.mu.Lock()
	s.conn = conn
	s.mu.Unlock()
	defer func() {
		s.mu.Lock()
		if s.conn == conn {
			s.conn = nil
		}
		s.mu.Unlock()
		_ = conn.Close()
	}()

	// Login: send on first prompt OR blindly after 1.5s. Many DXSpider
	// nodes accept the callsign without re-prompting.
	loginSent := false
	if s.login != "" {
		go func() {
			select {
			case <-s.stopCh:
				return
			case <-time.After(1500 * time.Millisecond):
				if !loginSent {
					_, _ = conn.Write([]byte(s.login + "\r\n"))
				}
			}
		}()
	}

	// Init commands, once per connection (so they replay after a reconnect).
	//
	// Timing: the cluster needs a moment after login before it will take commands,
	// hence the lead-in wait; then they are PACED, because a DXSpider/AR-Cluster
	// happily swallows a burst of back-to-back lines and silently ignores half of
	// them. A fast-but-dropped command is worse than a slow one.
	//
	// They go through s.send() — NOT a raw conn.Write, which is what they used to
	// do. That matters for two reasons: the raw write skipped the write deadline
	// (a wedged server could hang this goroutine forever), and it skipped the
	// console echo, so there was no way to SEE whether your init commands had
	// actually been applied. Now you watch them go out and the reply come back.
	initFired := false
	fireInitCommands := func() {
		if initFired || strings.TrimSpace(s.cfg.InitCommands) == "" {
			return
		}
		initFired = true
		go func() {
			time.Sleep(initCommandLeadIn)
			for _, line := range strings.Split(s.cfg.InitCommands, "\n") {
				line = strings.TrimSpace(strings.TrimRight(line, "\r"))
				if line == "" || strings.HasPrefix(line, "//") {
					continue
				}
				select {
				case <-s.stopCh:
					return
				default:
				}
				if err := s.send(line); err != nil {
					s.emitLine("init command failed: "+line+" — "+err.Error(), false)
					return
				}
				time.Sleep(initCommandGap)
			}
		}()
	}

	var connectedAt time.Time
	rd := bufio.NewReader(conn)
	for {
		select {
		case <-s.stopCh:
			return connectedAt, nil
		default:
		}

		_ = conn.SetReadDeadline(time.Now().Add(120 * time.Second))
		line, err := rd.ReadString('\n')
		if err != nil {
			return connectedAt, fmt.Errorf("read: %w", err)
		}
		line = strings.TrimRight(line, "\r\n")
		// Strip terminal BELLs (\a) and other control bytes that some nodes
		// (e.g. F5LEN) append to spot lines — "DX de …0935Z KN04\a\a" — which
		// would otherwise break the parser's end-of-line anchor. Tabs → spaces.
		line = strings.Map(func(r rune) rune {
			if r == '\t' {
				return ' '
			}
			if r < 0x20 || r == 0x7f {
				return -1
			}
			return r
		}, line)
		if line == "" {
			continue
		}

		// Safety net: warn (rate-limited) about DX lines the parser still can't
		// read, so a future format drift is visible in the log.
		if strings.Contains(line, "DX de") && s.dbgN < 10 {
			if _, ok := parseSpot(line); !ok {
				s.dbgN++
				applog.Printf("cluster[%s] UNPARSED spot: %q", s.cfg.Name, line)
			}
		}

		// Login on explicit prompt.
		if !loginSent && s.login != "" && isLoginPrompt(line) {
			_, _ = conn.Write([]byte(s.login + "\r\n"))
			loginSent = true
			continue
		}
		// Password on prompt (rare).
		if loginSent && s.cfg.Password != "" && isPasswordPrompt(line) {
			_, _ = conn.Write([]byte(s.cfg.Password + "\r\n"))
			continue
		}

		// Mark connected once we've sent login OR seen a welcome banner.
		if s.snapshot().State != StateConnected && (loginSent || isWelcome(line)) {
			connectedAt = time.Now()
			s.mu.Lock()
			s.status.State = StateConnected
			s.status.ConnectedAt = connectedAt
			s.status.Error = ""
			s.mu.Unlock()
			s.emitStatus()
			fireInitCommands()
		}

		// EVERY line goes to the console — spot or not. This is the whole point:
		// SH/DX, WHO, the MOTD and error replies are not spots, and dropping them
		// (which is what happened before) made the command box look inert.
		s.emitLine(line, false)

		// Live broadcast first; then the SH/DX table form. Without the second, a
		// SH/DX reply arrived, matched nothing, and vanished — which is exactly why
		// "SH/DX/100" looked like it did nothing at all.
		spot, ok := parseSpot(line)
		if !ok {
			spot, ok = parseShowDX(line)
		}
		if ok {
			spot.SourceID = s.cfg.ID
			spot.SourceName = s.cfg.Name
			s.mu.Lock()
			// Historical spots are a replay of the past, not new traffic — counting
			// them would inflate the server's "spots received" figure.
			if !spot.Historical {
				s.spotsCnt++
				s.status.SpotsCount = s.spotsCnt
			}
			s.mu.Unlock()
			if s.onSpot != nil {
				s.onSpot(spot)
			}
		}
	}
}

// emitLine hands one line of traffic to the console. Blank lines are dropped —
// clusters send plenty and they'd only pad the scrollback.
func (s *session) emitLine(text string, sent bool) {
	if s.onLine == nil || strings.TrimSpace(text) == "" {
		return
	}
	s.onLine(Line{
		ServerID:   s.cfg.ID,
		ServerName: s.cfg.Name,
		Text:       strings.TrimRight(text, "\r\n"),
		Sent:       sent,
		At:         time.Now().Format("15:04:05"),
	})
}

// ---------- parsing ----------

// spotRE matches "DX de SPOTTER: FREQ DXCALL COMMENT TIME [LOC]".
var spotRE = regexp.MustCompile(
	`^\s*DX\s+de\s+([A-Z0-9/#\-]+):?\s+(\d+\.?\d*)\s+([A-Z0-9/]+)\s+(.*?)\s+(\d{4}Z?)(?:\s+([A-R]{2}\d{2}(?:[A-X]{2})?))?\s*$`,
)

// Pacing for the per-server init commands.
//
// A cluster is not ready to take commands the instant the login line goes out —
// it is still printing its banner — so we wait before the first one. And they are
// spaced, because DXSpider / AR-Cluster will happily accept a burst of
// back-to-back lines and silently apply only some of them: the connection stays
// up, no error is returned, your filters just aren't set. A command that is
// dropped is far worse than one that is slow.
const (
	initCommandLeadIn = 1500 * time.Millisecond
	initCommandGap    = 700 * time.Millisecond
)

// showDXRE matches the reply to SH/DX — which is a TABLE, not the "DX de …"
// broadcast format, and therefore matched nothing at all:
//
//	  14195.0  EA8DHH       3-Jul-2026 1234Z  CQ DX              <F5ABC>
//	  freq     dxcall       date       time   comment            <spotter>
//
// This is why "SH/DX/100 does nothing": the 100 lines arrive, fail the broadcast
// regex, and get dropped. The decimal point in the frequency is required — it is
// what keeps ordinary prose out of the spot grid.
var showDXRE = regexp.MustCompile(
	`^\s*(\d{3,7}\.\d+)\s+([A-Z0-9]{1,3}[0-9][A-Z0-9/]*)\s+(\d{1,2}-[A-Za-z]{3}-\d{4})\s+(\d{4})Z?\s*(.*?)\s*(?:<\s*([A-Z0-9/#\-]+)\s*>)?\s*$`,
)

// parseShowDX turns one line of a SH/DX table into a Spot. The result is flagged
// Historical: these are PAST spots, so they belong in the grid but must not fire
// alerts or land on the panadapter — replaying 100 of them would spam both, and a
// station spotted three hours ago is not on the air now.
func parseShowDX(line string) (Spot, bool) {
	if strings.Contains(strings.ToUpper(line), "DX DE") {
		return Spot{}, false // that's the broadcast form; spotRE owns it
	}
	m := showDXRE.FindStringSubmatch(line)
	if m == nil {
		return Spot{}, false
	}
	khz, err := strconv.ParseFloat(m[1], 64)
	if err != nil || khz <= 0 {
		return Spot{}, false
	}
	hz := int64(khz * 1000)
	return Spot{
		Spotter:    strings.ToUpper(m[6]),
		DXCall:     strings.ToUpper(m[2]),
		FreqKHz:    khz,
		FreqHz:     hz,
		Band:       bandFromHz(hz),
		Comment:    strings.TrimSpace(m[5]),
		TimeUTC:    m[4] + "Z",
		ReceivedAt: time.Now(),
		Raw:        line,
		Historical: true,
	}, true
}

func parseSpot(line string) (Spot, bool) {
	m := spotRE.FindStringSubmatch(line)
	if m == nil {
		return Spot{}, false
	}
	freqKHz, err := strconv.ParseFloat(m[2], 64)
	if err != nil {
		return Spot{}, false
	}
	freqHz := int64(freqKHz*1000 + 0.5)
	return Spot{
		Spotter:    strings.ToUpper(m[1]),
		FreqKHz:    freqKHz,
		FreqHz:     freqHz,
		Band:       bandFromHz(freqHz),
		DXCall:     strings.ToUpper(m[3]),
		Comment:    strings.TrimSpace(m[4]),
		TimeUTC:    m[5],
		Locator:    strings.ToUpper(m[6]),
		ReceivedAt: time.Now(),
		Raw:        line,
	}, true
}

func isLoginPrompt(s string) bool {
	low := strings.ToLower(s)
	return strings.Contains(low, "login:") ||
		strings.Contains(low, "please enter your call") ||
		strings.Contains(low, "your call:") ||
		strings.HasSuffix(strings.TrimSpace(low), "callsign:")
}

func isPasswordPrompt(s string) bool {
	low := strings.ToLower(s)
	return strings.Contains(low, "password:") || strings.Contains(low, "pwd:")
}

func isWelcome(s string) bool {
	low := strings.ToLower(s)
	return strings.Contains(low, "welcome") ||
		strings.Contains(low, "logged in") ||
		strings.Contains(low, "started")
}

func bandFromHz(hz int64) string {
	mhz := float64(hz) / 1_000_000
	switch {
	case mhz >= 1.8 && mhz <= 2.0:
		return "160m"
	case mhz >= 3.5 && mhz <= 4.0:
		return "80m"
	case mhz >= 5.3 && mhz <= 5.5:
		return "60m"
	case mhz >= 7.0 && mhz <= 7.3:
		return "40m"
	case mhz >= 10.1 && mhz <= 10.15:
		return "30m"
	case mhz >= 14.0 && mhz <= 14.35:
		return "20m"
	case mhz >= 18.068 && mhz <= 18.168:
		return "17m"
	case mhz >= 21.0 && mhz <= 21.45:
		return "15m"
	case mhz >= 24.89 && mhz <= 24.99:
		return "12m"
	case mhz >= 28.0 && mhz <= 29.7:
		return "10m"
	case mhz >= 50.0 && mhz <= 54.0:
		return "6m"
	case mhz >= 70.0 && mhz <= 70.5:
		return "4m"
	case mhz >= 144.0 && mhz <= 148.0:
		return "2m"
	case mhz >= 222.0 && mhz <= 225.0:
		return "1.25m"
	case mhz >= 420.0 && mhz <= 450.0:
		return "70cm"
	case mhz >= 902.0 && mhz <= 928.0:
		return "33cm"
	case mhz >= 1240.0 && mhz <= 1300.0:
		return "23cm"
	}
	return ""
}