// Package miot provides MIoT core client for Xiaomi Home devices.
// miot_network.go — network status monitor ported from py-miot/miot_network.py.
package miot

import (
	"fmt"
	"net"
	"net/http"
	"os/exec"
	"runtime"
	"strings"
	"sync"
	"time"

	"github.com/sirupsen/logrus"
)

// ============================================================================
// InterfaceStatus — network interface change event type
// ============================================================================

// InterfaceStatus describes what changed on a network interface.
type InterfaceStatus int

const (
	// InterfaceAdd means a new interface appeared.
	InterfaceAdd InterfaceStatus = 0
	// InterfaceUpdate means an existing interface's IP/mask changed.
	InterfaceUpdate InterfaceStatus = 1
	// InterfaceRemove means an interface was removed.
	InterfaceRemove InterfaceStatus = 2
)

// String returns the string representation of InterfaceStatus.
func (s InterfaceStatus) String() string {
	switch s {
	case InterfaceAdd:
		return "add"
	case InterfaceUpdate:
		return "update"
	case InterfaceRemove:
		return "remove"
	default:
		return "unknown"
	}
}

// ============================================================================
// NetworkInfo — information about a network interface
// ============================================================================

// NetworkInfo holds details about a single network interface.
type NetworkInfo struct {
	Name    string // interface name (e.g., "eth0", "wlan0")
	IP      string // IPv4 address
	Netmask string // IPv4 netmask
	NetSeg  string // network segment (CIDR network address)
}

// String returns a debug representation.
func (n *NetworkInfo) String() string {
	return fmt.Sprintf("%s: %s/%s (%s)", n.Name, n.IP, n.Netmask, n.NetSeg)
}

// ============================================================================
// MIoTNetwork — network status monitor
// ============================================================================

// MIoTNetwork monitors network connectivity using ping + HTTP detection,
// periodically refreshes network interface info, and notifies subscribers.
type MIoTNetwork struct {
	mu sync.Mutex

	// Detection addresses with cached response times (seconds)
	ipAddrMap   map[string]float64
	httpAddrMap map[string]float64

	// HTTP client for detection
	httpClient *http.Client

	// Refresh interval
	refreshInterval time.Duration

	// Current state
	networkStatus bool
	networkInfo   map[string]*NetworkInfo

	// Subscribers
	statusSubs map[string]func(status bool)
	infoSubs   map[string]func(status InterfaceStatus, info *NetworkInfo)

	// Timer control
	stopCh chan struct{}
	doneCh chan struct{}
}

// Default network detection addresses.
var (
	defaultIPAddrs = []string{
		"1.2.4.8", // CNNIC sDNS
		"8.8.8.8", // Google Public DNS
		"9.9.9.9", // Quad9
	}
	defaultHTTPAddrs = []string{
		"https://www.bing.com",
		"https://www.google.com",
		"https://www.baidu.com",
	}
	defaultDetectTimeout   = 6 * time.Second
	defaultRefreshInterval = 30 * time.Second
)

// NewMIoTNetwork creates a new MIoTNetwork monitor.
// ipAddrList and urlAddrList can be nil to use defaults.
func NewMIoTNetwork(ipAddrList, urlAddrList []string, refreshInterval time.Duration) *MIoTNetwork {
	if ipAddrList == nil {
		ipAddrList = defaultIPAddrs
	}
	if urlAddrList == nil {
		urlAddrList = defaultHTTPAddrs
	}
	if refreshInterval <= 0 {
		refreshInterval = defaultRefreshInterval
	}

	n := &MIoTNetwork{
		ipAddrMap:       make(map[string]float64),
		httpAddrMap:     make(map[string]float64),
		httpClient:      &http.Client{Timeout: defaultDetectTimeout},
		refreshInterval: refreshInterval,
		networkStatus:   false,
		networkInfo:     make(map[string]*NetworkInfo),
		statusSubs:      make(map[string]func(status bool)),
		infoSubs:        make(map[string]func(status InterfaceStatus, info *NetworkInfo)),
		stopCh:          make(chan struct{}),
		doneCh:          make(chan struct{}),
	}

	for _, ip := range ipAddrList {
		n.ipAddrMap[ip] = float64(defaultDetectTimeout.Seconds())
	}
	for _, url := range urlAddrList {
		n.httpAddrMap[url] = float64(defaultDetectTimeout.Seconds())
	}

	return n
}

// Init starts the network monitor.
func (n *MIoTNetwork) Init() {
	// Initial refresh
	n.refresh()

	// Start periodic timer
	go n.loop()
}

// Deinit stops the network monitor and cleans up.
func (n *MIoTNetwork) Deinit() {
	close(n.stopCh)
	<-n.doneCh

	n.httpClient.CloseIdleConnections()

	n.mu.Lock()
	defer n.mu.Unlock()
	n.networkStatus = false
	n.networkInfo = make(map[string]*NetworkInfo)
	n.statusSubs = make(map[string]func(status bool))
	n.infoSubs = make(map[string]func(status InterfaceStatus, info *NetworkInfo))
}

// GetNetworkStatus returns the current network connectivity status.
func (n *MIoTNetwork) GetNetworkStatus() bool {
	n.mu.Lock()
	defer n.mu.Unlock()
	return n.networkStatus
}

// GetNetworkInfo returns the current network interface info.
func (n *MIoTNetwork) GetNetworkInfo() map[string]*NetworkInfo {
	n.mu.Lock()
	defer n.mu.Unlock()
	// Return a copy
	result := make(map[string]*NetworkInfo, len(n.networkInfo))
	for k, v := range n.networkInfo {
		result[k] = &NetworkInfo{
			Name:    v.Name,
			IP:      v.IP,
			Netmask: v.Netmask,
			NetSeg:  v.NetSeg,
		}
	}
	return result
}

// SubNetworkStatus subscribes to network status changes.
// key is a unique subscriber identifier.
func (n *MIoTNetwork) SubNetworkStatus(key string, handler func(status bool)) {
	n.mu.Lock()
	defer n.mu.Unlock()
	n.statusSubs[key] = handler
}

// UnsubNetworkStatus unsubscribes from network status changes.
func (n *MIoTNetwork) UnsubNetworkStatus(key string) {
	n.mu.Lock()
	defer n.mu.Unlock()
	delete(n.statusSubs, key)
}

// SubNetworkInfo subscribes to network interface changes.
// key is a unique subscriber identifier.
func (n *MIoTNetwork) SubNetworkInfo(key string, handler func(status InterfaceStatus, info *NetworkInfo)) {
	n.mu.Lock()
	defer n.mu.Unlock()
	n.infoSubs[key] = handler
}

// UnsubNetworkInfo unsubscribes from network interface changes.
func (n *MIoTNetwork) UnsubNetworkInfo(key string) {
	n.mu.Lock()
	defer n.mu.Unlock()
	delete(n.infoSubs, key)
}

// Refresh triggers an immediate refresh of network status and info.
func (n *MIoTNetwork) Refresh() {
	n.refresh()
}

// loop runs the periodic refresh timer.
func (n *MIoTNetwork) loop() {
	defer close(n.doneCh)

	ticker := time.NewTicker(n.refreshInterval)
	defer ticker.Stop()

	for {
		select {
		case <-n.stopCh:
			return
		case <-ticker.C:
			n.refresh()
		}
	}
}

// refresh performs a full refresh: network status detection + interface info.
func (n *MIoTNetwork) refresh() {
	newStatus := checkNetworkStatus(n)
	newInfo := n.getNetworkInterfaces()

	n.mu.Lock()
	oldStatus := n.networkStatus
	oldInfo := n.networkInfo

	// Update cached addresses with latest response times
	for ip, ts := range n.ipAddrMap {
		_ = ip
		n.ipAddrMap[ip] = ts
	}
	for url, ts := range n.httpAddrMap {
		_ = url
		n.httpAddrMap[url] = ts
	}

	// Status changed?
	if oldStatus != newStatus {
		n.networkStatus = newStatus
		handlers := make([]func(bool), 0, len(n.statusSubs))
		for _, h := range n.statusSubs {
			handlers = append(handlers, h)
		}
		n.mu.Unlock()

		// Notify outside lock
		for _, h := range handlers {
			if h != nil {
				h(newStatus)
			}
		}
	} else {
		n.mu.Unlock()
	}

	// Check for interface changes
	n.mu.Lock()
	for name := range oldInfo {
		if newInfoInfo, ok := newInfo[name]; ok {
			// Update
			old := oldInfo[name]
			if old.IP != newInfoInfo.IP || old.Netmask != newInfoInfo.Netmask {
				n.networkInfo[name] = newInfoInfo
				delete(newInfo, name)
				n.notifyInfoSubsLocked(InterfaceUpdate, newInfoInfo)
			} else {
				delete(newInfo, name) // no change
			}
		} else {
			// Remove
			removed := n.networkInfo[name]
			delete(n.networkInfo, name)
			n.notifyInfoSubsLocked(InterfaceRemove, removed)
		}
	}
	// Add new interfaces
	for _, info := range newInfo {
		n.networkInfo[info.Name] = info
		n.notifyInfoSubsLocked(InterfaceAdd, info)
	}

	// Collect handlers
	handlers := make([]func(InterfaceStatus, *NetworkInfo), 0, len(n.infoSubs))
	for _, h := range n.infoSubs {
		handlers = append(handlers, h)
	}
	n.mu.Unlock()

	// For new interfaces we already notified inside lock above
	_ = handlers
}

// notifyInfoSubsLocked sends info change notifications. Must hold mu.
func (n *MIoTNetwork) notifyInfoSubsLocked(status InterfaceStatus, info *NetworkInfo) {
	for _, handler := range n.infoSubs {
		if handler != nil {
			handler(status, info)
		}
	}
}

// ============================================================================
// Network detection functions
// ============================================================================

// checkNetworkStatus detects if the network is reachable.
// Strategy: try the fastest known IP first, then fastest HTTP, then all.
func checkNetworkStatus(n *MIoTNetwork) bool {
	n.mu.Lock()
	ipAddrs := make([]string, 0, len(n.ipAddrMap))
	ipTimes := make(map[string]float64)
	for ip, ts := range n.ipAddrMap {
		ipAddrs = append(ipAddrs, ip)
		ipTimes[ip] = ts
	}
	httpAddrs := make([]string, 0, len(n.httpAddrMap))
	httpTimes := make(map[string]float64)
	for url, ts := range n.httpAddrMap {
		httpAddrs = append(httpAddrs, url)
		httpTimes[url] = ts
	}
	n.mu.Unlock()

	timeout := float64(defaultDetectTimeout.Seconds())

	// Try fastest IP first
	fastestIP := ""
	fastestIPTime := timeout
	for ip, ts := range ipTimes {
		if ts < fastestIPTime {
			fastestIP = ip
			fastestIPTime = ts
		}
	}
	if fastestIPTime < timeout && fastestIP != "" {
		if pingAddr(fastestIP) {
			return true
		}
	}

	// Try fastest HTTP first
	fastestHTTP := ""
	fastestHTTPTime := timeout
	for url, ts := range httpTimes {
		if ts < fastestHTTPTime {
			fastestHTTP = url
			fastestHTTPTime = ts
		}
	}
	if fastestHTTPTime < timeout && fastestHTTP != "" {
		if httpCheck(fastestHTTP) {
			return true
		}
	}

	// Full detection: ping all
	pingResults := pingMulti(ipAddrs)
	// Update cached times
	n.mu.Lock()
	for ip, ts := range pingResults {
		n.ipAddrMap[ip] = ts
	}
	n.mu.Unlock()
	for _, ok := range pingResults {
		if ok < timeout {
			return true
		}
	}

	// Full detection: HTTP all
	httpResults := httpMulti(httpAddrs)
	n.mu.Lock()
	for url, ts := range httpResults {
		n.httpAddrMap[url] = ts
	}
	n.mu.Unlock()
	for _, ok := range httpResults {
		if ok < timeout {
			return true
		}
	}

	return false
}

// pingAddr pings a single IP address and returns true if reachable.
func pingAddr(ip string) bool {
	return pingSingle(ip) < float64(defaultDetectTimeout.Seconds())
}

// pingSingle pings an IP and returns the response time in seconds, or the timeout value on failure.
func pingSingle(ip string) float64 {
	start := time.Now()
	timeout := defaultDetectTimeout

	var cmd *exec.Cmd
	if runtime.GOOS == "windows" {
		// Windows: ping -n 1 -w <ms> <ip>
		cmd = exec.Command("ping", "-n", "1", "-w", fmt.Sprintf("%d", int(timeout.Seconds()*1000)), ip)
	} else {
		// Linux: ping -c 1 -W <seconds> <ip>
		cmd = exec.Command("ping", "-c", "1", "-W", fmt.Sprintf("%d", int(timeout.Seconds())), ip)
	}

	if err := cmd.Run(); err != nil {
		return float64(timeout.Seconds())
	}
	return time.Since(start).Seconds()
}

// pingMulti pings multiple IPs concurrently and returns response times.
func pingMulti(ips []string) map[string]float64 {
	results := make(map[string]float64)
	type result struct {
		ip string
		ts float64
	}
	ch := make(chan result, len(ips))

	for _, ip := range ips {
		go func(addr string) {
			ch <- result{addr, pingSingle(addr)}
		}(ip)
	}

	for range ips {
		r := <-ch
		results[r.ip] = r.ts
	}
	return results
}

// httpCheck performs an HTTP HEAD request and returns true if successful.
func httpCheck(url string) bool {
	client := &http.Client{Timeout: defaultDetectTimeout}
	start := time.Now()

	resp, err := client.Head(url)
	if err != nil {
		// Fallback to GET
		resp, err = client.Get(url)
		if err != nil {
			return false
		}
	}
	defer resp.Body.Close()
	_ = start
	return resp.StatusCode < 500
}

// httpMulti checks multiple HTTP URLs concurrently and returns response times.
func httpMulti(urls []string) map[string]float64 {
	results := make(map[string]float64)
	type result struct {
		url string
		ts  float64
	}
	ch := make(chan result, len(urls))
	timeout := float64(defaultDetectTimeout.Seconds())

	for _, url := range urls {
		go func(addr string) {
			start := time.Now()
			client := &http.Client{Timeout: defaultDetectTimeout}
			resp, err := client.Head(addr)
			if err != nil {
				// Fallback to GET
				resp, err = client.Get(addr)
			}
			if err != nil || resp.StatusCode >= 500 {
				ch <- result{addr, timeout}
				return
			}
			resp.Body.Close()
			ch <- result{addr, time.Since(start).Seconds()}
		}(url)
	}

	for range urls {
		r := <-ch
		results[r.url] = r.ts
	}
	return results
}

// ============================================================================
// Network interface detection
// ============================================================================

// getNetworkInterfaces returns all non-loopback, non-docker IPv4 interfaces.
func (n *MIoTNetwork) getNetworkInterfaces() map[string]*NetworkInfo {
	results := make(map[string]*NetworkInfo)

	ifaces, err := net.Interfaces()
	if err != nil {
		logrus.Warnf("[network] get interfaces error: %v", err)
		return results
	}

	for _, iface := range ifaces {
		name := iface.Name
		// Skip loopback, docker, hassio interfaces
		if name == "lo" || name == "hassio" || strings.HasPrefix(name, "docker") {
			continue
		}

		addrs, err := iface.Addrs()
		if err != nil {
			continue
		}

		for _, addr := range addrs {
			ipNet, ok := addr.(*net.IPNet)
			if !ok {
				continue
			}
			ip := ipNet.IP
			// IPv4 only, skip loopback
			if ip.To4() == nil || ip.IsLoopback() {
				continue
			}

			mask := net.IP(ipNet.Mask)
			netSeg := ip.Mask(ipNet.Mask)

			results[name] = &NetworkInfo{
				Name:    name,
				IP:      ip.String(),
				Netmask: fmt.Sprintf("%d.%d.%d.%d", mask[0], mask[1], mask[2], mask[3]),
				NetSeg:  netSeg.String(),
			}
			break // only first valid IPv4 per interface
		}
	}

	return results
}

// UpdateAddrList updates the ping and HTTP detection address lists.
func (n *MIoTNetwork) UpdateAddrList(ipAddrList, urlAddrList []string) {
	n.mu.Lock()
	defer n.mu.Unlock()

	if ipAddrList != nil {
		newIPMap := make(map[string]float64)
		for _, ip := range ipAddrList {
			if ts, ok := n.ipAddrMap[ip]; ok {
				newIPMap[ip] = ts
			} else {
				newIPMap[ip] = float64(defaultDetectTimeout.Seconds())
			}
		}
		n.ipAddrMap = newIPMap
	}

	if urlAddrList != nil {
		newURLMap := make(map[string]float64)
		for _, url := range urlAddrList {
			if ts, ok := n.httpAddrMap[url]; ok {
				newURLMap[url] = ts
			} else {
				newURLMap[url] = float64(defaultDetectTimeout.Seconds())
			}
		}
		n.httpAddrMap = newURLMap
	}
}