package main

import (
	"bufio"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"log"
	"net/http"
	"os"
	"os/exec"
	"runtime"
	"strconv"
	"strings"
	"sync"
	"time"

	"github.com/gorilla/websocket"
)

// APIServer handles HTTP API requests
type APIServer struct {
	daemon   *Daemon
	upgrader websocket.Upgrader

	// Recent events (ring buffer)
	recentBLE  []interface{}
	recentWiFi []interface{}
	recentMu   sync.RWMutex

	// WebSocket clients
	wsClients   map[*websocket.Conn]bool
	wsClientsMu sync.Mutex

	// Session management
	sessions   map[string]time.Time
	sessionsMu sync.RWMutex
}

// StatusResponse is the response for /api/status
type StatusResponse struct {
	DeviceID   string         `json:"device_id"`
	Registered bool           `json:"registered"`
	Mode       string         `json:"mode"`
	Uptime     int64          `json:"uptime_sec"`
	Network    NetworkStatus  `json:"network"`
	Scanners   ScannerStatus  `json:"scanners"`
	Counters   CounterStatus  `json:"counters"`
	ServerOK   bool           `json:"server_ok"`
}

type NetworkStatus struct {
	Eth0IP       string `json:"eth0_ip,omitempty"`
	Eth0RX       int64  `json:"eth0_rx,omitempty"`
	Eth0TX       int64  `json:"eth0_tx,omitempty"`
	Wlan0IP      string `json:"wlan0_ip,omitempty"`
	Wlan0SSID    string `json:"wlan0_ssid,omitempty"`
	Wlan0Signal  int    `json:"wlan0_signal,omitempty"`
	Wlan0Channel int    `json:"wlan0_channel,omitempty"`
	Wlan0Gateway string `json:"wlan0_gateway,omitempty"`
	Wlan0DNS     string `json:"wlan0_dns,omitempty"`
	Wlan0RX      int64  `json:"wlan0_rx,omitempty"`
	Wlan0TX      int64  `json:"wlan0_tx,omitempty"`
	Gateway      string `json:"gateway,omitempty"`
	DNS          string `json:"dns,omitempty"`
	NTP          string `json:"ntp,omitempty"`
	APActive     bool   `json:"ap_active"`
}

type ScannerStatus struct {
	BLERunning  bool `json:"ble_running"`
	WiFiRunning bool `json:"wifi_running"`
}

type CounterStatus struct {
	BLEEvents  uint64 `json:"ble_events"`
	WiFiEvents uint64 `json:"wifi_events"`
	Uploads    uint64 `json:"uploads"`
	Errors     uint64 `json:"errors"`
}

// MetricsResponse is the response for /api/metrics
type MetricsResponse struct {
	CPUPercent  float64 `json:"cpu_percent"`
	MemUsedMB   float64 `json:"mem_used_mb"`
	MemTotalMB  float64 `json:"mem_total_mb"`
	Temperature float64 `json:"temperature"`
	LoadAvg     float64 `json:"load_avg"`
}

// SettingsRequest is the request for /api/settings
type SettingsRequest struct {
	Password string          `json:"password"`
	Settings SettingsPayload `json:"settings"`
}

// SettingsPayload contains the actual settings
type SettingsPayload struct {
	Mode        string `json:"mode"`
	WifiSSID    string `json:"wifi_ssid"`
	WifiPSK     string `json:"wifi_psk"`
	Eth0Mode    string `json:"eth0_mode"`
	Eth0IP      string `json:"eth0_ip"`
	Eth0Gateway string `json:"eth0_gateway"`
	Eth0DNS     string `json:"eth0_dns"`
	NTPServers  string `json:"ntp_servers"`
}

// NewAPIServer creates a new API server
func NewAPIServer(daemon *Daemon) *APIServer {
	return &APIServer{
		daemon: daemon,
		upgrader: websocket.Upgrader{
			CheckOrigin: func(r *http.Request) bool {
				return true // Allow all origins for local access
			},
		},
		recentBLE:  make([]interface{}, 0, 100),
		recentWiFi: make([]interface{}, 0, 100),
		wsClients:  make(map[*websocket.Conn]bool),
		sessions:   make(map[string]time.Time),
	}
}

// Start starts the HTTP server
func (s *APIServer) Start(addr string) error {
	mux := http.NewServeMux()

	// API endpoints
	mux.HandleFunc("/api/status", s.handleStatus)
	mux.HandleFunc("/api/metrics", s.handleMetrics)
	mux.HandleFunc("/api/ble/recent", s.handleBLERecent)
	mux.HandleFunc("/api/wifi/recent", s.handleWiFiRecent)
	mux.HandleFunc("/api/config", s.handleConfig)
	mux.HandleFunc("/api/settings", s.handleSettings)
	mux.HandleFunc("/api/unlock", s.handleUnlock)
	mux.HandleFunc("/api/logs", s.handleLogs)
	mux.HandleFunc("/api/ws", s.handleWebSocket)

	// Serve static files for dashboard
	mux.Handle("/", http.FileServer(http.Dir("/opt/mybeacon/www")))

	log.Printf("[api] Starting HTTP server on %s", addr)
	return http.ListenAndServe(addr, s.corsMiddleware(mux))
}

// corsMiddleware adds CORS headers
func (s *APIServer) corsMiddleware(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Access-Control-Allow-Origin", "*")
		w.Header().Set("Access-Control-Allow-Methods", "GET, POST, OPTIONS")
		w.Header().Set("Access-Control-Allow-Headers", "Content-Type, Authorization")

		if r.Method == "OPTIONS" {
			w.WriteHeader(http.StatusOK)
			return
		}

		next.ServeHTTP(w, r)
	})
}

// handleStatus returns device status
func (s *APIServer) handleStatus(w http.ResponseWriter, r *http.Request) {
	s.daemon.mu.Lock()
	defer s.daemon.mu.Unlock()

	eth0rx, eth0tx := getInterfaceStats("eth0")
	wlan0rx, wlan0tx := getInterfaceStats("wlan0")

	wlanInfo := getWlanInfo()

	// Gateway and DNS are shared, but wlan0 might have its own
	gateway := getDefaultGateway()
	dns := getDNS()

	status := StatusResponse{
		DeviceID:   s.daemon.state.DeviceID,
		Registered: s.daemon.state.DeviceToken != "",
		Mode:       "cloud", // TODO: implement mode switching
		Uptime:     getUptime(),
		Network: NetworkStatus{
			Eth0IP:       getInterfaceIP("eth0"),
			Eth0RX:       eth0rx,
			Eth0TX:       eth0tx,
			Wlan0IP:      getInterfaceIP("wlan0"),
			Wlan0SSID:    wlanInfo.ssid,
			Wlan0Signal:  wlanInfo.signal,
			Wlan0Channel: wlanInfo.channel,
			Wlan0Gateway: gateway, // same gateway for now
			Wlan0DNS:     dns,     // same DNS for now
			Wlan0RX:      wlan0rx,
			Wlan0TX:      wlan0tx,
			Gateway:      gateway,
			DNS:          dns,
			NTP:          "pool.ntp.org",
		},
		Scanners: ScannerStatus{
			BLERunning:  s.daemon.scanners.IsBLERunning(),
			WiFiRunning: s.daemon.scanners.IsWiFiRunning(),
		},
		ServerOK: s.daemon.state.DeviceToken != "",
	}

	s.jsonResponse(w, status)
}

// handleMetrics returns system metrics
func (s *APIServer) handleMetrics(w http.ResponseWriter, r *http.Request) {
	metrics := MetricsResponse{
		CPUPercent:  getCPUPercent(),
		MemUsedMB:   getMemUsedMB(),
		MemTotalMB:  getMemTotalMB(),
		Temperature: getTemperature(),
		LoadAvg:     getLoadAvg(),
	}

	s.jsonResponse(w, metrics)
}

// handleBLERecent returns recent BLE events
func (s *APIServer) handleBLERecent(w http.ResponseWriter, r *http.Request) {
	s.recentMu.RLock()
	events := make([]interface{}, len(s.recentBLE))
	copy(events, s.recentBLE)
	s.recentMu.RUnlock()

	s.jsonResponse(w, events)
}

// handleWiFiRecent returns recent WiFi events
func (s *APIServer) handleWiFiRecent(w http.ResponseWriter, r *http.Request) {
	s.recentMu.RLock()
	events := make([]interface{}, len(s.recentWiFi))
	copy(events, s.recentWiFi)
	s.recentMu.RUnlock()

	s.jsonResponse(w, events)
}

// handleLogs returns recent daemon log lines
func (s *APIServer) handleLogs(w http.ResponseWriter, r *http.Request) {
	logFile := "/var/log/mybeacon.log"
	data, err := os.ReadFile(logFile)
	if err != nil {
		s.jsonResponse(w, []string{})
		return
	}

	lines := strings.Split(string(data), "\n")
	// Return last 500 lines
	if len(lines) > 500 {
		lines = lines[len(lines)-500:]
	}

	// Filter out empty lines
	var result []string
	for _, line := range lines {
		if strings.TrimSpace(line) != "" {
			result = append(result, line)
		}
	}

	s.jsonResponse(w, result)
}

// handleConfig returns current config (without secrets)
func (s *APIServer) handleConfig(w http.ResponseWriter, r *http.Request) {
	s.daemon.mu.Lock()
	cfg := *s.daemon.cfg
	s.daemon.mu.Unlock()

	// Remove secrets
	cfg.SSHTunnel.KeyPath = ""

	s.jsonResponse(w, cfg)
}

// handleSettings handles settings updates (requires password)
func (s *APIServer) handleSettings(w http.ResponseWriter, r *http.Request) {
	if r.Method != "POST" {
		http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
		return
	}

	var req SettingsRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		http.Error(w, "Invalid JSON", http.StatusBadRequest)
		return
	}

	// Verify password
	if !s.verifyPassword(req.Password) {
		http.Error(w, "Invalid password", http.StatusUnauthorized)
		return
	}

	s.daemon.mu.Lock()

	// Apply mode change
	if req.Settings.Mode != "" && (req.Settings.Mode == "cloud" || req.Settings.Mode == "lan") {
		if s.daemon.cfg.Mode != req.Settings.Mode {
			log.Printf("[api] Mode changed: %s -> %s", s.daemon.cfg.Mode, req.Settings.Mode)
			s.daemon.cfg.Mode = req.Settings.Mode
		}
	}

	// Apply NTP settings
	if req.Settings.NTPServers != "" {
		servers := strings.Split(req.Settings.NTPServers, ",")
		for i := range servers {
			servers[i] = strings.TrimSpace(servers[i])
		}
		s.daemon.cfg.Network.NTPServers = servers
		log.Printf("[api] NTP servers updated: %v", servers)
	}

	// Apply eth0 settings (always local, never from server)
	if req.Settings.Eth0Mode == "static" {
		s.daemon.cfg.Network.Eth0.Static = true
		s.daemon.cfg.Network.Eth0.Address = req.Settings.Eth0IP
		s.daemon.cfg.Network.Eth0.Gateway = req.Settings.Eth0Gateway
		s.daemon.cfg.Network.Eth0.DNS = req.Settings.Eth0DNS
		log.Printf("[api] eth0 static IP configured: %s", req.Settings.Eth0IP)
	} else if req.Settings.Eth0Mode == "dhcp" {
		s.daemon.cfg.Network.Eth0.Static = false
		log.Printf("[api] eth0 set to DHCP")
	}

	// Save local config
	SaveConfig(s.daemon.configPath, s.daemon.cfg)

	s.daemon.mu.Unlock()

	// Apply WiFi settings if provided (this may take time)
	if req.Settings.WifiSSID != "" {
		// Also save to local config
		s.daemon.mu.Lock()
		s.daemon.cfg.WiFi.SSID = req.Settings.WifiSSID
		s.daemon.cfg.WiFi.PSK = req.Settings.WifiPSK
		s.daemon.cfg.WiFi.ClientEnabled = true
		SaveConfig(s.daemon.configPath, s.daemon.cfg)
		s.daemon.mu.Unlock()

		if err := applyWiFiSettings(req.Settings.WifiSSID, req.Settings.WifiPSK); err != nil {
			log.Printf("[api] Failed to apply WiFi settings: %v", err)
			http.Error(w, "Failed to apply WiFi settings: "+err.Error(), http.StatusInternalServerError)
			return
		}
		log.Printf("[api] WiFi settings applied: SSID=%s", req.Settings.WifiSSID)
	}

	s.jsonResponse(w, map[string]bool{"success": true})
}

// handleUnlock verifies password and creates session
func (s *APIServer) handleUnlock(w http.ResponseWriter, r *http.Request) {
	if r.Method != "POST" {
		http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
		return
	}

	var req struct {
		Password string `json:"password"`
	}
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		http.Error(w, "Invalid JSON", http.StatusBadRequest)
		return
	}

	if !s.verifyPassword(req.Password) {
		http.Error(w, "Invalid password", http.StatusUnauthorized)
		return
	}

	// Create session token (simple implementation)
	token := generateToken(32)
	s.sessionsMu.Lock()
	s.sessions[token] = time.Now().Add(30 * time.Minute)
	s.sessionsMu.Unlock()

	s.jsonResponse(w, map[string]string{"token": token})
}

// handleWebSocket handles WebSocket connections for live updates
func (s *APIServer) handleWebSocket(w http.ResponseWriter, r *http.Request) {
	conn, err := s.upgrader.Upgrade(w, r, nil)
	if err != nil {
		log.Printf("[api] WebSocket upgrade error: %v", err)
		return
	}
	defer conn.Close()

	s.wsClientsMu.Lock()
	s.wsClients[conn] = true
	s.wsClientsMu.Unlock()

	defer func() {
		s.wsClientsMu.Lock()
		delete(s.wsClients, conn)
		s.wsClientsMu.Unlock()
	}()

	// Keep connection alive and read messages
	for {
		_, _, err := conn.ReadMessage()
		if err != nil {
			break
		}
	}
}

// AddBLEEvent adds a BLE event to recent list and broadcasts to WebSocket
func (s *APIServer) AddBLEEvent(event interface{}) {
	s.recentMu.Lock()
	s.recentBLE = append(s.recentBLE, event)
	if len(s.recentBLE) > 100 {
		s.recentBLE = s.recentBLE[1:]
	}
	s.recentMu.Unlock()

	s.broadcast(map[string]interface{}{
		"type":  "ble",
		"event": event,
	})
}

// AddWiFiEvent adds a WiFi event to recent list and broadcasts to WebSocket
func (s *APIServer) AddWiFiEvent(event interface{}) {
	s.recentMu.Lock()
	s.recentWiFi = append(s.recentWiFi, event)
	if len(s.recentWiFi) > 100 {
		s.recentWiFi = s.recentWiFi[1:]
	}
	s.recentMu.Unlock()

	s.broadcast(map[string]interface{}{
		"type":  "wifi",
		"event": event,
	})
}

// broadcast sends a message to all WebSocket clients
func (s *APIServer) broadcast(msg interface{}) {
	data, err := json.Marshal(msg)
	if err != nil {
		return
	}

	s.wsClientsMu.Lock()
	defer s.wsClientsMu.Unlock()

	for conn := range s.wsClients {
		if err := conn.WriteMessage(websocket.TextMessage, data); err != nil {
			conn.Close()
			delete(s.wsClients, conn)
		}
	}
}

// verifyPassword checks if password matches device password
func (s *APIServer) verifyPassword(password string) bool {
	s.daemon.mu.Lock()
	devicePassword := s.daemon.state.DevicePassword
	s.daemon.mu.Unlock()

	// Use default password "admin" if no password set (device not registered)
	if devicePassword == "" {
		devicePassword = "admin"
	}

	return password != "" && password == devicePassword
}

// jsonResponse sends a JSON response
func (s *APIServer) jsonResponse(w http.ResponseWriter, data interface{}) {
	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(data)
}

// Helper functions for system metrics

func getUptime() int64 {
	data, err := os.ReadFile("/proc/uptime")
	if err != nil {
		return 0
	}
	var uptime float64
	if err := parseFloat(string(data), &uptime); err != nil {
		return 0
	}
	return int64(uptime)
}

func parseFloat(s string, f *float64) error {
	parts := strings.Fields(s)
	if len(parts) == 0 {
		return nil
	}
	return json.Unmarshal([]byte(parts[0]), f)
}

func getCPUPercent() float64 {
	// Simplified - read from /proc/stat
	return 0 // TODO: implement proper CPU usage
}

func getMemUsedMB() float64 {
	var m runtime.MemStats
	runtime.ReadMemStats(&m)
	return float64(m.Alloc) / 1024 / 1024
}

func getMemTotalMB() float64 {
	data, err := os.ReadFile("/proc/meminfo")
	if err != nil {
		return 0
	}
	scanner := bufio.NewScanner(strings.NewReader(string(data)))
	for scanner.Scan() {
		line := scanner.Text()
		if strings.HasPrefix(line, "MemTotal:") {
			var total int64
			if err := parseMemInfo(line, &total); err == nil {
				return float64(total) / 1024
			}
		}
	}
	return 0
}

func parseMemInfo(line string, value *int64) error {
	parts := strings.Fields(line)
	if len(parts) >= 2 {
		return json.Unmarshal([]byte(parts[1]), value)
	}
	return nil
}

func getTemperature() float64 {
	data, err := os.ReadFile("/sys/class/thermal/thermal_zone0/temp")
	if err != nil {
		return 0
	}
	var temp int64
	if err := json.Unmarshal([]byte(strings.TrimSpace(string(data))), &temp); err != nil {
		return 0
	}
	return float64(temp) / 1000
}

func getLoadAvg() float64 {
	data, err := os.ReadFile("/proc/loadavg")
	if err != nil {
		return 0
	}
	var load float64
	if err := parseFloat(string(data), &load); err != nil {
		return 0
	}
	return load
}

func generateToken(length int) string {
	const chars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
	b := make([]byte, length)
	for i := range b {
		b[i] = chars[time.Now().UnixNano()%int64(len(chars))]
		time.Sleep(time.Nanosecond)
	}
	return string(b)
}

func getInterfaceStats(name string) (rx, tx int64) {
	rxPath := "/sys/class/net/" + name + "/statistics/rx_bytes"
	txPath := "/sys/class/net/" + name + "/statistics/tx_bytes"

	if data, err := os.ReadFile(rxPath); err == nil {
		json.Unmarshal([]byte(strings.TrimSpace(string(data))), &rx)
	}
	if data, err := os.ReadFile(txPath); err == nil {
		json.Unmarshal([]byte(strings.TrimSpace(string(data))), &tx)
	}
	return
}

func getDefaultGateway() string {
	data, err := os.ReadFile("/proc/net/route")
	if err != nil {
		return ""
	}
	scanner := bufio.NewScanner(strings.NewReader(string(data)))
	for scanner.Scan() {
		fields := strings.Fields(scanner.Text())
		if len(fields) >= 3 && fields[1] == "00000000" {
			gw := fields[2]
			if len(gw) == 8 {
				b, _ := hex.DecodeString(gw)
				if len(b) == 4 {
					// Little-endian: reverse bytes
					return fmt.Sprintf("%d.%d.%d.%d", b[3], b[2], b[1], b[0])
				}
			}
		}
	}
	return ""
}

func getDNS() string {
	data, err := os.ReadFile("/etc/resolv.conf")
	if err != nil {
		return ""
	}
	var servers []string
	scanner := bufio.NewScanner(strings.NewReader(string(data)))
	for scanner.Scan() {
		line := scanner.Text()
		if strings.HasPrefix(line, "nameserver ") {
			servers = append(servers, strings.TrimPrefix(line, "nameserver "))
		}
	}
	return strings.Join(servers, ", ")
}

type wlanInfoResult struct {
	ssid    string
	signal  int
	channel int
}

func getWlanInfo() wlanInfoResult {
	var info wlanInfoResult

	// Get SSID, signal, channel from iw dev wlan0 link
	out, err := exec.Command("iw", "dev", "wlan0", "link").Output()
	if err == nil {
		scanner := bufio.NewScanner(strings.NewReader(string(out)))
		for scanner.Scan() {
			line := strings.TrimSpace(scanner.Text())
			if strings.HasPrefix(line, "SSID:") {
				info.ssid = strings.TrimSpace(strings.TrimPrefix(line, "SSID:"))
			} else if strings.HasPrefix(line, "signal:") {
				// signal: -30 dBm
				parts := strings.Fields(line)
				if len(parts) >= 2 {
					if v, err := strconv.Atoi(parts[1]); err == nil {
						info.signal = v
					}
				}
			} else if strings.HasPrefix(line, "freq:") {
				// freq: 2462
				parts := strings.Fields(line)
				if len(parts) >= 2 {
					if f, err := strconv.Atoi(parts[1]); err == nil {
						info.channel = freqToChannel(f)
					}
				}
			}
		}
	}

	return info
}

// freqToChannel converts WiFi frequency (MHz) to channel number
func freqToChannel(freq int) int {
	if freq >= 2412 && freq <= 2484 {
		if freq == 2484 {
			return 14
		}
		return (freq - 2407) / 5
	}
	if freq >= 5170 && freq <= 5825 {
		return (freq - 5000) / 5
	}
	return 0
}

// applyWiFiSettings configures wpa_supplicant and connects to WiFi
func applyWiFiSettings(ssid, psk string) error {
	// Retry the whole connection up to 3 times
	var lastErr error
	for attempt := 1; attempt <= 3; attempt++ {
		log.Printf("[wifi] Connection attempt %d/3 to SSID=%s", attempt, ssid)

		if err := tryWiFiConnect(ssid, psk); err != nil {
			lastErr = err
			log.Printf("[wifi] Attempt %d failed: %v", attempt, err)
			if attempt < 3 {
				log.Printf("[wifi] Waiting 5s before retry...")
				time.Sleep(5 * time.Second)
			}
			continue
		}

		log.Println("[wifi] WiFi client connected successfully")
		return nil
	}

	return fmt.Errorf("all connection attempts failed: %w", lastErr)
}

func tryWiFiConnect(ssid, psk string) error {
	// Use external shell script for WiFi connection (more reliable)
	scriptPath := "/opt/mybeacon/bin/wifi-connect.sh"

	cmd := exec.Command(scriptPath, ssid, psk)
	output, err := cmd.CombinedOutput()
	if err != nil {
		return fmt.Errorf("wifi-connect.sh failed: %w (output: %s)", err, string(output))
	}

	log.Printf("[wifi] %s", strings.TrimSpace(string(output)))

	// Ensure wlan0 is configured in /etc/network/interfaces (for manual use)
	ensureWlan0Interface()

	return nil
}

func ensureWlan0Interface() error {
	interfacesPath := "/etc/network/interfaces"
	data, err := os.ReadFile(interfacesPath)
	if err != nil {
		return err
	}

	content := string(data)

	// Check if wlan0 is already configured (not commented out)
	lines := strings.Split(content, "\n")
	for _, line := range lines {
		trimmed := strings.TrimSpace(line)
		if !strings.HasPrefix(trimmed, "#") && strings.Contains(trimmed, "iface wlan0 inet") {
			return nil // Already configured
		}
	}

	// Add wlan0 configuration
	wlan0Config := `
# WiFi (managed by beacon-daemon)
auto wlan0
iface wlan0 inet dhcp
    pre-up wpa_supplicant -B -i wlan0 -c /etc/wpa_supplicant/wpa_supplicant.conf
    post-down killall wpa_supplicant 2>/dev/null || true
`

	if err := os.WriteFile(interfacesPath, []byte(content+wlan0Config), 0644); err != nil {
		return err
	}

	log.Println("[wifi] Added wlan0 configuration to /etc/network/interfaces")
	return nil
}

// disconnectWiFiClient disconnects from WiFi and stops wpa_supplicant
func disconnectWiFiClient() {
	log.Println("[wifi] Disconnecting WiFi client...")
	exec.Command("killall", "wpa_supplicant", "udhcpc", "dhcpcd").Run()
	exec.Command("ip", "addr", "flush", "dev", "wlan0").Run()
	os.RemoveAll("/var/run/wpa_supplicant/wlan0")
	log.Println("[wifi] WiFi client disconnected")
}