package main

import (
	"encoding/json"
	"fmt"
	"net/http"
	"os"
	"os/exec"
	"path/filepath"
	"runtime"
	"strconv"
	"strings"
	"sync"
	"time"
)

var cpuStat struct {
	sync.Mutex
	lastIdle  uint64
	lastTotal uint64
	usage     float64
}

var systemInfoCache struct {
	sync.RWMutex
	data map[string]any
}

func initCPUUsage() {
	updateCPUUsage()
}

func updateSystemInfoCache() {
	memPercent, memUsed, memTotal := getMemInfo()
	diskPercent, diskUsed, diskTotal := getDiskInfo()

	data := map[string]any{
		"cpu_usage": updateCPUUsage(),
		"cpu_cores": getCPUCore(),
		"cpu_freq":  getCPUFreq(),
		"cpu_temp":  getCPUTemperature(),

		"mem_percent": memPercent,
		"mem_used":    memUsed,
		"mem_total":   memTotal,

		"disk_percent": diskPercent,
		"disk_used":    diskUsed,
		"disk_total":   diskTotal,
	}

	systemInfoCache.Lock()
	systemInfoCache.data = data
	systemInfoCache.Unlock()
}

func startSystemInfoCache() {
	updateSystemInfoCache()
	go func() {
		ticker := time.NewTicker(5 * time.Second)
		defer ticker.Stop()

		for range ticker.C {
			updateSystemInfoCache()
		}
	}()
}

func systemInfoHandler(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Content-Type", "application/json; charset=utf-8")

	systemInfoCache.RLock()
	data := systemInfoCache.data
	systemInfoCache.RUnlock()

	json.NewEncoder(w).Encode(data)
}

func updateCPUUsage() float64 {
	cpuStat.Lock()
	defer cpuStat.Unlock()

	data, err := os.ReadFile("/proc/stat")
	if err != nil {
		return cpuStat.usage
	}

	fields := strings.Fields(strings.SplitN(string(data), "\n", 2)[0])

	if len(fields) < 5 {
		return cpuStat.usage
	}

	var idle uint64
	var total uint64

	for i := 1; i < len(fields); i++ {
		v, err := strconv.ParseUint(fields[i], 10, 64)
		if err != nil {
			continue
		}

		total += v

		if i == 4 || i == 5 {
			idle += v
		}
	}

	if cpuStat.lastTotal == 0 {
		cpuStat.lastTotal = total
		cpuStat.lastIdle = idle
		return 0
	}

	deltaTotal := total - cpuStat.lastTotal
	deltaIdle := idle - cpuStat.lastIdle

	cpuStat.lastTotal = total
	cpuStat.lastIdle = idle

	if deltaTotal == 0 {
		return cpuStat.usage
	}

	cpuStat.usage = float64(deltaTotal-deltaIdle) * 100 / float64(deltaTotal)

	return cpuStat.usage
}

func getCPUCore() int {
	return runtime.NumCPU()
}

func getCPUFreq() string {
	var total, count int

	for i := 0; ; i++ {
		data, err := os.ReadFile(fmt.Sprintf("/sys/devices/system/cpu/cpu%d/cpufreq/scaling_cur_freq", i))
		if err != nil {
			break
		}

		freq, err := strconv.Atoi(strings.TrimSpace(string(data)))
		if err != nil {
			continue
		}

		total += freq / 1000
		count++
	}

	if count > 0 {
		return strconv.Itoa(total / count)
	}

	data, err := os.ReadFile("/proc/cpuinfo")
	if err == nil {
		for _, line := range strings.Split(string(data), "\n") {
			if strings.HasPrefix(line, "cpu MHz") {
				f := strings.Split(line, ":")
				if len(f) == 2 {
					v, err := strconv.ParseFloat(strings.TrimSpace(f[1]), 64)
					if err == nil {
						return strconv.Itoa(int(v))
					}
				}
			}
		}
	}

	return noValue
}

func getCPUTemperature() string {
	files, _ := filepath.Glob("/sys/class/thermal/thermal_zone*/temp")

	max := 0

	for _, f := range files {
		data, err := os.ReadFile(f)
		if err != nil {
			continue
		}

		temp, err := strconv.Atoi(strings.TrimSpace(string(data)))
		if err == nil && temp > max {
			max = temp
		}
	}

	if max == 0 {
		return noValue
	}

	return fmt.Sprintf("%d℃", max/1000)
}

func getMemInfo() (int, string, string) {
	data, err := os.ReadFile("/proc/meminfo")
	if err != nil {
		return 0, noValue, noValue
	}

	var total, avail uint64

	for _, line := range strings.Split(string(data), "\n") {
		f := strings.Fields(line)
		if len(f) < 2 {
			continue
		}

		switch f[0] {
		case "MemTotal:":
			total, _ = strconv.ParseUint(f[1], 10, 64)
		case "MemAvailable:":
			avail, _ = strconv.ParseUint(f[1], 10, 64)
		}
	}

	if total == 0 {
		return 0, noValue, noValue
	}

	used := total - avail

	return int(used * 100 / total), formatSize(used * 1024), formatSize(total * 1024)
}

func getDiskInfo() (int, string, string) {
	out, err := exec.Command("df", "-hP", "/").Output()
	if err != nil {
		return 0, noValue, noValue
	}

	lines := strings.Split(string(out), "\n")
	if len(lines) < 2 {
		return 0, noValue, noValue
	}

	f := strings.Fields(lines[1])
	if len(f) < 5 {
		return 0, noValue, noValue
	}

	percent, err := strconv.Atoi(strings.TrimSuffix(f[4], "%"))
	if err != nil {
		percent = 0
	}

	return percent, f[2], f[1]
}

func formatSize(size uint64) string {
	const (
		KB = 1024
		MB = KB * 1024
		GB = MB * 1024
	)

	switch {
	case size >= GB:
		return fmt.Sprintf("%.1fGB", float64(size)/GB)
	case size >= MB:
		return fmt.Sprintf("%.0fMB", float64(size)/MB)
	case size >= KB:
		return fmt.Sprintf("%.0fKB", float64(size)/KB)
	default:
		return fmt.Sprintf("%dB", size)
	}
}

func systemLoadAverageHandler(w http.ResponseWriter, r *http.Request) {
	data, err := os.ReadFile("/proc/loadavg")
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}

	fields := strings.Fields(string(data))

	if len(fields) < 4 {
		http.Error(w, "invalid /proc/loadavg", http.StatusInternalServerError)
		return
	}

	boot, uptime := noValue, noValue
	if b, err := os.ReadFile("/proc/uptime"); err == nil {
		if fields := strings.Fields(string(b)); len(fields) > 0 {
			if sec, err := strconv.ParseFloat(fields[0], 64); err == nil {
				d := time.Duration(sec) * time.Second
				boot = time.Now().Add(-d).Format("2006-01-02 15:04:05")
				day := int(d.Hours() / 24)
				if day > 0 {
					uptime = fmt.Sprintf("%d天 %02d:%02d:%02d",
						int(d.Hours()/24), int(d.Hours())%24, int(d.Minutes())%60, int(d.Seconds())%60)
				} else {
					uptime = fmt.Sprintf("%02d:%02d:%02d",
						int(d.Hours())%24, int(d.Minutes())%60, int(d.Seconds())%60)
				}
			}
		}
	}

	resp := struct {
		Load1m   string `json:"load1m"`
		Load5m   string `json:"load5m"`
		Load15m  string `json:"load15m"`
		RunQueue string `json:"runQueue"`
		BootTime string `json:"bootTime"`
		UpTime   string `json:"uptime"`
	}{
		Load1m:   formatLoad(fields[0]),
		Load5m:   formatLoad(fields[1]),
		Load15m:  formatLoad(fields[2]),
		RunQueue: fields[3],
		BootTime: boot,
		UpTime:   uptime,
	}

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(resp)
}

func formatLoad(v string) string {
	f, err := strconv.ParseFloat(v, 64)
	if err != nil {
		return noValue
	}

	return strconv.FormatFloat(f, 'f', 2, 64)
}

var services = []struct {
	name string
	dir  string
	bin  string
}{
	{"yfkj-networkd.service", "/opt/yfkj/networkd.service", "networkd"},
	{"yfkj-timesyncd.service", "/opt/yfkj/timesyncd.service", "timesyncd"},
	{"yfkj-gnss.service", "/opt/yfkj/gnss.service", "gnss"},
	{"yfkj-sshd-mqtt-bridge.service", "/opt/yfkj/sshd-mqtt-bridge.service", "sshd-mqtt-bridge"},
	{"yfkj-camera-capture.service", "/opt/yfkj/camera-capture.service", "camera-capture"},
	{"yfkj-app-install.service", "/opt/yfkj/app-install.service", "app-install"},
	{"yfkj-web-ui.service", "/opt/yfkj/web-ui.service", "web-ui"},
	{"yfkj-frp-client.service", "/opt/yfkj/frp-client.service", "frpc"},
	{"yfkj-upgrade.service", "/opt/yfkj/upgrade.service", "upgrade"},
	{"yfkj-local-startup.service", "/opt/yfkj/local-startup.service", "startup.sh"},
}

var serviceStatusActive struct {
	sync.Mutex
	lastAccess time.Time
}

var serviceStatusCache struct {
	sync.RWMutex
	data map[string]string
}

func updateServiceStatus() {
	data := make(map[string]string, len(services)*2)

	args := []string{"show",
		"-p", "Id",
		"-p", "LoadState",
		"-p", "ActiveState",
		"-p", "SubState",
		"-p", "Result",
	}

	for _, s := range services {
		args = append(args, s.name)
	}

	statusMap := make(map[string]string, len(services))

	out, _ := exec.Command("systemctl", args...).CombinedOutput()

	var name, loadState, activeState, subState, result string

	save := func() {
		if name == "" {
			return
		}

		status := noValue

		switch {
		case activeState == "active" && subState == "running":
			status = "🟢运行中"
		case activeState == "active" && subState == "exited":
			status = "🔵已完成"
		case loadState == "loaded" && activeState == "inactive":
			status = "🟡已停止"
		case activeState == "failed" && result == "timeout":
			status = "🔴超时停"
		case activeState == "failed":
			status = "🔴异常停"
		}

		statusMap[name] = status
	}

	for line := range strings.SplitSeq(string(out), "\n") {
		if line == "" { // Empty line indicates the end of a service status block
			save() ///// Save the previous service status before starting a new one

			name = ""
			loadState = ""
			activeState = ""
			subState = ""
			result = ""

			continue
		}

		if v, ok := strings.CutPrefix(line, "Id="); ok {
			name = v
		} else if v, ok := strings.CutPrefix(line, "LoadState="); ok {
			loadState = v
		} else if v, ok := strings.CutPrefix(line, "ActiveState="); ok {
			activeState = v
		} else if v, ok := strings.CutPrefix(line, "SubState="); ok {
			subState = v
		} else if v, ok := strings.CutPrefix(line, "Result="); ok {
			result = v
		}
	}

	save() // Save the last service status

	for i, s := range services {
		n := i + 1

		if v, ok := statusMap[s.name]; ok {
			data[fmt.Sprintf("var%d", n)] = v
		} else {
			data[fmt.Sprintf("var%d", n)] = noValue
		}

		if v, err := os.ReadFile(filepath.Join(s.dir, "version.txt")); err == nil {
			data[fmt.Sprintf("var%d%d", n, n)] = "v" + strings.TrimSpace(string(v))
		} else {
			data[fmt.Sprintf("var%d%d", n, n)] = noValue
		}
	}

	serviceStatusCache.Lock()
	serviceStatusCache.data = data
	serviceStatusCache.Unlock()
}

func startServiceCache() {
	go func() {
		ticker := time.NewTicker(5 * time.Second)
		defer ticker.Stop()

		for range ticker.C {
			serviceStatusActive.Lock()

			if !serviceStatusActive.lastAccess.IsZero() && time.Since(serviceStatusActive.lastAccess) >= 10*time.Second {
				serviceStatusActive.lastAccess = time.Time{}
			}

			active := !serviceStatusActive.lastAccess.IsZero()

			serviceStatusActive.Unlock()

			if active {
				updateServiceStatus()
			}
		}
	}()
}

func serviceStatusHandler(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}

	serviceStatusActive.Lock()
	first := serviceStatusActive.lastAccess.IsZero() || time.Since(serviceStatusActive.lastAccess) >= 10*time.Second
	serviceStatusActive.lastAccess = time.Now()
	serviceStatusActive.Unlock()

	if first {
		updateServiceStatus()
	}

	serviceStatusCache.RLock()
	data := serviceStatusCache.data
	serviceStatusCache.RUnlock()

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(data)
}

type VersionSwitchReq struct {
	Service  string `json:"service"`
	Action   string `json:"action"`
	Password string `json:"password"`
}

type VersionResp struct {
	Status  string `json:"status"`
	Message string `json:"message,omitempty"`
}

var versionSwitchLock sync.Mutex

func serviceVersionSwitchHandler(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}

	versionSwitchLock.Lock()
	defer versionSwitchLock.Unlock()

	var req VersionSwitchReq
	if json.NewDecoder(r.Body).Decode(&req) != nil {
		json.NewEncoder(w).Encode(VersionResp{Status: "error", Message: "invalid request"})
		return
	}

	if req.Password != "yfkj123456" {
		json.NewEncoder(w).Encode(VersionResp{Status: "error", Message: "输入的密码不正确"})
		return
	}

	var cfg struct{ name, dir, bin string }
	for _, v := range services {
		if v.name == req.Service {
			cfg = v
			break
		}
	}

	if cfg.name == "" {
		json.NewEncoder(w).Encode(VersionResp{Status: "error", Message: "unknown service"})
		return
	}

	link := filepath.Join(cfg.dir, cfg.bin)

	oldLink, err := os.Readlink(link)
	if err != nil {
		json.NewEncoder(w).Encode(VersionResp{Status: "error", Message: "读取当前版本失败"})
		return
	}

	current := filepath.Base(filepath.Dir(oldLink))
	if current != "a" && current != "b" && current != "c" {
		json.NewEncoder(w).Encode(VersionResp{Status: "error", Message: "当前版本状态异常"})
		return
	}
	target := ""

	switch req.Action {
	case "factory":
		if current == "a" {
			json.NewEncoder(w).Encode(VersionResp{Status: "ok", Message: "当前已是出厂版本"})
			return
		}
		target = "a"
	case "previous":
		switch current {
		case "b":
			if info, err := os.Stat(filepath.Join(cfg.dir, "c", cfg.bin)); err == nil && !info.IsDir() && info.Size() > 0 && info.Mode().Perm()&0111 != 0 {
				target = "c"
			}
		case "c":
			if info, err := os.Stat(filepath.Join(cfg.dir, "b", cfg.bin)); err == nil && !info.IsDir() && info.Size() > 0 && info.Mode().Perm()&0111 != 0 {
				target = "b"
			}
		}
		if target == "" {
			json.NewEncoder(w).Encode(VersionResp{
				Status:  "error",
				Message: "当前没有可回退的上一版本",
			})
			return
		}
	default:
		json.NewEncoder(w).Encode(VersionResp{Status: "error", Message: "invalid action"})
		return
	}

	targetBin := filepath.Join(cfg.dir, target, cfg.bin)

	info, err := os.Stat(targetBin)
	if err != nil || info.IsDir() || info.Size() == 0 || info.Mode().Perm()&0111 == 0 {
		json.NewEncoder(w).Encode(VersionResp{Status: "error", Message: fmt.Sprintf("目标版本文件异常: %s", target)})
		return
	}

	if out, err := exec.Command("systemctl", "stop", req.Service).CombinedOutput(); err != nil {
		json.NewEncoder(w).Encode(VersionResp{Status: "error", Message: fmt.Sprintf("停止当前服务失败: %s", out)})
		return
	}

	tmp := filepath.Join(cfg.dir, cfg.bin+".tmp")
	os.Remove(tmp)

	if err := os.Symlink(filepath.Join(target, cfg.bin), tmp); err != nil {
		exec.Command("systemctl", "start", req.Service).Run()
		json.NewEncoder(w).Encode(VersionResp{Status: "error", Message: err.Error()})
		return
	}

	if err := os.Rename(tmp, link); err != nil {
		os.Remove(tmp)
		exec.Command("systemctl", "start", req.Service).Run()
		json.NewEncoder(w).Encode(VersionResp{Status: "error", Message: err.Error()})
		return
	}

	if out, err := exec.Command("systemctl", "start", req.Service).CombinedOutput(); err != nil {
		tmp := filepath.Join(cfg.dir, cfg.bin+".tmp")
		os.Remove(tmp)

		if e := os.Symlink(oldLink, tmp); e == nil {
			if e = os.Rename(tmp, link); e != nil {
				os.Remove(tmp)
			}
		}

		exec.Command("systemctl", "start", req.Service).Run()

		json.NewEncoder(w).Encode(VersionResp{
			Status:  "error",
			Message: fmt.Sprintf("目标版本启动失败，已恢复旧版本: %s", out),
		})
		return
	}

	json.NewEncoder(w).Encode(VersionResp{Status: "ok"})
}