package iwd

import (
	"log"
	"sync"

	"github.com/godbus/dbus/v5"
)

// SignalMonitor monitors D-Bus signals from iwd
type SignalMonitor struct {
	conn    *dbus.Conn
	station *Station

	// Signal channel
	signalChan chan *dbus.Signal

	// Callbacks
	onStateChange  func(state StationState, ssid string)
	onScanComplete func()

	// Control
	stopChan chan struct{}
	stopOnce sync.Once
	mu       sync.RWMutex
	running  bool

	// State tracking
	lastScanning bool
}

// NewSignalMonitor creates a new signal monitor
func NewSignalMonitor(conn *dbus.Conn, station *Station) *SignalMonitor {
	return &SignalMonitor{
		conn:       conn,
		station:    station,
		signalChan: make(chan *dbus.Signal, 100),
		stopChan:   make(chan struct{}),
	}
}

// OnStateChange registers a callback for state changes
func (sm *SignalMonitor) OnStateChange(callback func(state StationState, ssid string)) {
	sm.mu.Lock()
	defer sm.mu.Unlock()
	sm.onStateChange = callback
}

// OnScanComplete registers a callback for scan completion
func (sm *SignalMonitor) OnScanComplete(callback func()) {
	sm.mu.Lock()
	defer sm.mu.Unlock()
	sm.onScanComplete = callback
}

// Start begins monitoring D-Bus signals
func (sm *SignalMonitor) Start() error {
	sm.mu.Lock()
	if sm.running {
		sm.mu.Unlock()
		return nil
	}
	sm.running = true
	sm.mu.Unlock()

	// Subscribe to PropertiesChanged signals for Station interface
	stationPath := sm.station.GetPath()

	// Add signal match for PropertiesChanged on Station interface
	matchOptions := []dbus.MatchOption{
		dbus.WithMatchObjectPath(stationPath),
		dbus.WithMatchInterface("org.freedesktop.DBus.Properties"),
		dbus.WithMatchMember("PropertiesChanged"),
	}

	if err := sm.conn.AddMatchSignal(matchOptions...); err != nil {
		sm.mu.Lock()
		sm.running = false
		sm.mu.Unlock()
		return err
	}

	// Register signal channel
	sm.conn.Signal(sm.signalChan)

	// Get initial scanning state
	scanning, err := sm.station.IsScanning()
	if err == nil {
		sm.lastScanning = scanning
	}

	// Start monitoring goroutine
	go sm.monitor()

	log.Printf("D-Bus signal monitoring started for station %s", stationPath)
	return nil
}

// Stop stops monitoring D-Bus signals. Idempotent: stopOnce guards the
// channel close so concurrent Stop() callers do not panic on double-close.
func (sm *SignalMonitor) Stop() {
	sm.mu.Lock()
	if !sm.running {
		sm.mu.Unlock()
		return
	}
	sm.running = false
	sm.mu.Unlock()

	sm.stopOnce.Do(func() { close(sm.stopChan) })

	// Remove signal channel
	sm.conn.RemoveSignal(sm.signalChan)

	log.Printf("D-Bus signal monitoring stopped")
}

// monitor is the main signal processing loop
func (sm *SignalMonitor) monitor() {
	for {
		select {
		case sig := <-sm.signalChan:
			sm.handleSignal(sig)
		case <-sm.stopChan:
			return
		}
	}
}

// handleSignal processes a D-Bus signal
func (sm *SignalMonitor) handleSignal(sig *dbus.Signal) {
	// Only process PropertiesChanged signals
	if sig.Name != "org.freedesktop.DBus.Properties.PropertiesChanged" {
		return
	}

	// Verify signal is from Station interface
	if len(sig.Body) < 2 {
		return
	}

	interfaceName, ok := sig.Body[0].(string)
	if !ok || interfaceName != StationInterface {
		return
	}

	// Parse changed properties
	changedProps, ok := sig.Body[1].(map[string]dbus.Variant)
	if !ok {
		return
	}

	// Check for State property change
	if stateVariant, ok := changedProps["State"]; ok {
		if state, ok := stateVariant.Value().(string); ok {
			sm.handleStateChange(StationState(state))
		}
	}

	// Check for Scanning property change
	if scanningVariant, ok := changedProps["Scanning"]; ok {
		if scanning, ok := scanningVariant.Value().(bool); ok {
			sm.handleScanningChange(scanning)
		}
	}

	// Check for ConnectedNetwork property change
	if _, ok := changedProps["ConnectedNetwork"]; ok {
		// Network connection changed, trigger state update
		sm.handleConnectionChange()
	}
}

// handleStateChange processes a state change
func (sm *SignalMonitor) handleStateChange(state StationState) {
	sm.mu.RLock()
	callback := sm.onStateChange
	sm.mu.RUnlock()

	if callback == nil {
		return
	}

	// Get connected SSID if connected
	ssid := ""
	if state == StateConnected {
		network, err := sm.station.GetConnectedNetwork()
		if err == nil {
			props, err := network.GetProperties()
			if err == nil {
				ssid = props.Name
			}
		}
	}

	callback(state, ssid)
}

// handleScanningChange processes scanning state changes
func (sm *SignalMonitor) handleScanningChange(scanning bool) {
	// Detect scan completion (transition from true to false)
	if sm.lastScanning && !scanning {
		sm.mu.RLock()
		callback := sm.onScanComplete
		sm.mu.RUnlock()

		if callback != nil {
			callback()
		}
	}

	sm.lastScanning = scanning
}

// handleConnectionChange processes connection changes
func (sm *SignalMonitor) handleConnectionChange() {
	// Get current state and trigger state change callback
	state, err := sm.station.GetState()
	if err != nil {
		return
	}

	sm.handleStateChange(state)
}