package main

import (
	"fmt"
	"log"
	"strings"
	"sync"
	"time"

	"go.bug.st/serial"
	"tinygo.org/x/bluetooth"
)

const (
	hostTransportNone = "none"
	hostTransportUART = "uart"
	hostTransportBLE  = "ble"
)

// errHostBusy is returned when the link is held for OTA (UART only).
var errHostBusy = errUARTBusy

// managedHost is a reconnecting UART or BLE host link for serve/CLI.
type managedHost struct {
	quiet  bool
	baud   int
	settle time.Duration

	mu          sync.Mutex
	transport   string // none|uart|ble
	endpoint    string // port path or BLE address string
	bleName     string // last connected BLE local name (optional)
	sp          *serialPort
	ble         *bleLink
	otaActive   bool
	uartPort    string // remembered UART port for reconnect
}

func newManagedHost(baud int) *managedHost {
	if baud <= 0 {
		baud = defaultBaud
	}
	return &managedHost{
		baud:      baud,
		transport: hostTransportNone,
		settle:    time.Second,
	}
}

// newManagedSerial keeps the old constructor name for call sites during migrate.
func newManagedSerial(portName string, baud int) *managedHost {
	m := newManagedHost(baud)
	if portName != "" {
		m.uartPort = portName
		m.endpoint = portName
		m.transport = hostTransportUART
	}
	return m
}

func (m *managedHost) Transport() string {
	m.mu.Lock()
	defer m.mu.Unlock()
	if m.transport == "" {
		return hostTransportNone
	}
	return m.transport
}

func (m *managedHost) Endpoint() string {
	m.mu.Lock()
	defer m.mu.Unlock()
	return m.endpoint
}

func (m *managedHost) Close() error {
	m.mu.Lock()
	defer m.mu.Unlock()
	return m.disconnectLocked()
}

func (m *managedHost) IsConnected() bool {
	m.mu.Lock()
	defer m.mu.Unlock()
	switch m.transport {
	case hostTransportUART:
		return m.sp != nil
	case hostTransportBLE:
		return m.ble != nil
	default:
		return false
	}
}

func (m *managedHost) disconnectLocked() error {
	var err error
	if m.sp != nil {
		err = m.sp.port.Close()
		m.sp = nil
	}
	if m.ble != nil {
		e := m.ble.Close()
		if err == nil {
			err = e
		}
		m.ble = nil
	}
	m.transport = hostTransportNone
	return err
}

func (m *managedHost) Disconnect() error {
	m.mu.Lock()
	defer m.mu.Unlock()
	ep := m.endpoint
	err := m.disconnectLocked()
	if !m.quiet && ep != "" {
		log.Printf("host disconnected (%s)", ep)
	}
	return err
}

func (m *managedHost) ConnectUART(port string, baud int) error {
	if port == "" {
		return fmt.Errorf("UART port required")
	}
	if baud <= 0 {
		baud = m.baud
	}
	m.mu.Lock()
	defer m.mu.Unlock()
	if m.otaActive {
		return errHostBusy
	}
	_ = m.disconnectLocked()
	m.baud = baud
	m.uartPort = port
	m.endpoint = port
	m.transport = hostTransportUART
	if err := m.openUARTLocked(); err != nil {
		m.transport = hostTransportNone
		m.endpoint = ""
		return err
	}
	return nil
}

func (m *managedHost) ConnectBLE(address string, name string) error {
	if address == "" && name == "" {
		return fmt.Errorf("BLE address or name required")
	}
	m.mu.Lock()
	defer m.mu.Unlock()
	if m.otaActive {
		return errHostBusy
	}
	_ = m.disconnectLocked()

	var link *bleLink
	var err error
	settle := m.settle
	m.mu.Unlock()
	if address != "" {
		link, err = openBLEAddress(address, settle)
	} else {
		link, err = openBLE(name, settle)
	}
	m.mu.Lock()
	if err != nil {
		return err
	}
	link.quiet = m.quiet
	m.ble = link
	m.transport = hostTransportBLE
	if address != "" {
		m.endpoint = address
	} else {
		m.endpoint = name
	}
	m.bleName = name
	if !m.quiet {
		log.Printf("BLE host connected (%s)", m.endpoint)
	}
	return nil
}

func (m *managedHost) openUARTLocked() error {
	sp, err := openSerial(m.uartPort, m.baud)
	if err != nil {
		return err
	}
	sp.quiet = m.quiet
	m.sp = sp
	if !m.quiet {
		log.Printf("UART %s connected (%d baud)", m.uartPort, m.baud)
	}
	return nil
}

func (m *managedHost) openLocked() error {
	return m.openUARTLocked()
}

func (m *managedHost) closeLocked() error {
	return m.disconnectLocked()
}

func (m *managedHost) invalidateLocked(reason error) {
	if m.sp == nil && m.ble == nil {
		return
	}
	if !m.quiet {
		log.Printf("host %s disconnected: %v", m.endpoint, reason)
	}
	_ = m.disconnectLocked()
	// remember transport intent for UART reconnect
	if m.uartPort != "" && m.transport == hostTransportNone {
		// after invalidate, leave as none; poller will try Connect again via open
		m.transport = hostTransportUART
		m.endpoint = m.uartPort
	}
}

func (m *managedHost) withPort(fn func(*serialPort) error) error {
	return m.withPortLocked(false, fn)
}

func (m *managedHost) withPortPoll(fn func(*serialPort) error) error {
	return m.withPortLocked(true, fn)
}

func (m *managedHost) withPortLocked(poll bool, fn func(*serialPort) error) error {
	m.mu.Lock()
	defer m.mu.Unlock()
	if m.otaActive {
		return errHostBusy
	}
	if m.transport == hostTransportBLE {
		return fmt.Errorf("operation requires UART host (DIP8=0)")
	}
	if m.transport != hostTransportUART && m.uartPort == "" {
		return fmt.Errorf("not connected")
	}
	if m.transport == hostTransportNone && m.uartPort != "" {
		m.transport = hostTransportUART
		m.endpoint = m.uartPort
	}
	if m.sp == nil {
		if err := m.openUARTLocked(); err != nil {
			return fmt.Errorf("%s: %w", m.uartPort, err)
		}
	}
	err := fn(m.sp)
	if err != nil {
		m.invalidateLocked(err)
	}
	return err
}

func (m *managedHost) recoverAfterMasterRestart() {
	const bootWait = 6 * time.Second
	m.mu.Lock()
	tr := m.transport
	m.disconnectLocked()
	if tr == hostTransportUART {
		m.transport = hostTransportUART
		m.endpoint = m.uartPort
	}
	m.mu.Unlock()

	log.Printf("host: master restart — waiting %s for boot", bootWait)
	time.Sleep(bootWait)

	m.mu.Lock()
	defer m.mu.Unlock()
	if m.transport == hostTransportUART {
		if err := m.openUARTLocked(); err != nil {
			log.Printf("UART reconnect after master restart: %v", err)
			return
		}
		flushSerialInput(m.sp)
		log.Printf("UART %s ready after master restart", m.uartPort)
	}
}

func (m *managedHost) exchangePayload(payload []byte, cmdName string) ([]byte, error) {
	return m.exchangePayloadMode(false, payload, cmdName, readTimeout)
}

func (m *managedHost) exchangePayloadPoll(payload []byte, cmdName string) ([]byte, error) {
	return m.exchangePayloadMode(true, payload, cmdName, readTimeout)
}

func (m *managedHost) exchangePayloadMode(poll bool, payload []byte, cmdName string, timeout time.Duration) ([]byte, error) {
	m.mu.Lock()
	defer m.mu.Unlock()
	if m.otaActive {
		return nil, errHostBusy
	}
	switch m.transport {
	case hostTransportBLE:
		if m.ble == nil {
			return nil, fmt.Errorf("BLE not connected")
		}
		resp, err := m.ble.exchangePayload(payload, cmdName)
		if err != nil {
			m.invalidateLocked(err)
		}
		return resp, err
	case hostTransportUART, hostTransportNone:
		if m.uartPort == "" && m.sp == nil {
			return nil, fmt.Errorf("not connected")
		}
		if m.transport == hostTransportNone {
			m.transport = hostTransportUART
			m.endpoint = m.uartPort
		}
		if m.sp == nil {
			if err := m.openUARTLocked(); err != nil {
				return nil, fmt.Errorf("%s: %w", m.uartPort, err)
			}
		}
		resp, err := m.sp.exchangePayloadLocked(payload, cmdName, timeout)
		if err != nil {
			m.invalidateLocked(err)
		}
		return resp, err
	default:
		return nil, fmt.Errorf("not connected")
	}
}

func (m *managedHost) exchange(cmdID byte, cmdName string) ([]byte, error) {
	return m.exchangePayload([]byte{cmdID}, cmdName)
}

func (m *managedHost) exchangePoll(cmdID byte, cmdName string) ([]byte, error) {
	return m.exchangePayloadPoll([]byte{cmdID}, cmdName)
}

func (m *managedHost) exchangePayloadVia(
	portFn func(func(*serialPort) error) error,
	payload []byte, cmdName string,
) ([]byte, error) {
	// Prefer transport-aware path (works for BLE too).
	_ = portFn
	return m.exchangePayload(payload, cmdName)
}

func (m *managedHost) exchangeVia(
	portFn func(func(*serialPort) error) error,
	cmdID byte, cmdName string,
) ([]byte, error) {
	_ = portFn
	return m.exchange(cmdID, cmdName)
}

func (m *managedHost) NextStreamTick(timeout time.Duration) ([]byte, error) {
	m.mu.Lock()
	ble := m.ble
	tr := m.transport
	m.mu.Unlock()
	if tr != hostTransportBLE || ble == nil {
		return nil, fmt.Errorf("BLE stream ticks require BLE host")
	}
	return ble.NextStreamTick(timeout)
}

func (m *managedHost) HostStatus() map[string]any {
	m.mu.Lock()
	defer m.mu.Unlock()
	connected := false
	switch m.transport {
	case hostTransportUART:
		connected = m.sp != nil
	case hostTransportBLE:
		connected = m.ble != nil
	}
	return map[string]any{
		"transport": m.transportOrNone(),
		"endpoint":  m.endpoint,
		"connected": connected,
		"ble_name":  m.bleName,
	}
}

func (m *managedHost) transportOrNone() string {
	if m.transport == "" {
		return hostTransportNone
	}
	return m.transport
}

func listSerialPorts() ([]string, error) {
	ports, err := serial.GetPortsList()
	if err != nil {
		return nil, err
	}
	if ports == nil {
		return []string{}, nil
	}
	return ports, nil
}

type bleScanDevice struct {
	Address string `json:"address"`
	Name    string `json:"name"`
	RSSI    int    `json:"rssi"`
}

func scanBLEDevices(timeout time.Duration, nameFilter string) ([]bleScanDevice, error) {
	if timeout <= 0 {
		timeout = 5 * time.Second
	}
	adapter := bluetooth.DefaultAdapter
	if err := adapter.Enable(); err != nil {
		return nil, fmt.Errorf("enable bluetooth: %w", err)
	}

	seen := map[string]bleScanDevice{}
	var mu sync.Mutex
	go func() {
		time.Sleep(timeout)
		_ = adapter.StopScan()
	}()
	filter := strings.TrimSpace(nameFilter)
	_ = adapter.Scan(func(a *bluetooth.Adapter, result bluetooth.ScanResult) {
		name := result.LocalName()
		if filter != "" && !strings.Contains(strings.ToLower(name), strings.ToLower(filter)) {
			return
		}
		addr := result.Address.String()
		mu.Lock()
		seen[addr] = bleScanDevice{
			Address: addr,
			Name:    name,
			RSSI:    int(result.RSSI),
		}
		mu.Unlock()
	})
	// StopScan ends Scan; ignore error and return whatever was found.
	mu.Lock()
	defer mu.Unlock()
	out := make([]bleScanDevice, 0, len(seen))
	for _, d := range seen {
		out = append(out, d)
	}
	return out, nil
}

func disconnectedState(portName string, err error) DashboardState {
	msg := "host disconnected"
	if err != nil {
		msg = err.Error()
	}
	return DashboardState{
		UpdatedAt:     time.Now().Format(time.RFC3339),
		SerialPort:    portName,
		HostEndpoint:  portName,
		UARTConnected: false,
		HostConnected: false,
		HostTransport: hostTransportNone,
		SerialOK:      false,
		SerialError:   msg,
		Master:        MasterView{OK: false, Error: msg},
		Clients:       []ClientView{},
	}
}