// Package gsysctl 提供内核参数(sysctl)读写、持久化、快照备份/回滚、审计日志能力。
// 对应 Python 版 backend/app/services/sysctl.py。
package gsysctl

import (
	"encoding/json"
	"fmt"
	"os"
	"os/exec"
	"path/filepath"
	"regexp"
	"sort"
	"strings"
	"time"

	"github.com/user_TGPJp0KLpNsa5TAo/ddhv/core/consts"
)

// ErrSysctl 表示 sysctl 操作错误
type ErrSysctl struct{ Msg string }

func (e *ErrSysctl) Error() string { return e.Msg }

// NewErrSysctl 构造 sysctl 错误
func NewErrSysctl(msg string) error { return &ErrSysctl{Msg: msg} }

func newErr(format string, a ...any) error {
	return &ErrSysctl{Msg: fmt.Sprintf(format, a...)}
}

// Manager 内核参数管理器
type Manager struct {
	backupDir string // 快照备份目录
	logFile   string // 审计日志文件
}

// 持久化配置文件(独立文件，不污染系统默认配置)
const persistConf = "/etc/sysctl.d/99-gm-tune.conf"

// 需要同步的系统配置文件(避免 sysctl --system 重载时被旧值覆盖)
var systemConfFiles = []string{
	"/etc/sysctl.conf",
	"/etc/sysctl.d/99-sysctl.conf",
	"/etc/sysctl.d/99-bbr.conf",
}

// 快照前缀
const snapshotPrefix = "snapshot_"

// NewManager 创建管理器，确保目录存在
func NewManager() *Manager {
	backup := filepath.Join(consts.APP_DATA_PATH, "backups")
	logF := filepath.Join(consts.APP_DATA_PATH, "logs", "audit.log")
	os.MkdirAll(backup, 0o755)
	os.MkdirAll(filepath.Dir(logF), 0o755)
	return &Manager{backupDir: backup, logFile: logF}
}

// run 执行命令并返回 stdout
func run(cmd ...string) (string, error) {
	c := exec.Command(cmd[0], cmd[1:]...)
	out, err := c.Output()
	if err != nil {
		if ee, ok := err.(*exec.ExitError); ok {
			return "", newErr("命令执行失败: %s => %s", strings.Join(cmd, " "), strings.TrimSpace(string(ee.Stderr)))
		}
		return "", newErr("命令执行失败: %s => %v", strings.Join(cmd, " "), err)
	}
	return string(out), nil
}

// GetValue 读取单个内核参数当前值
func GetValue(key string) (string, error) {
	out, err := run("sysctl", "-n", key)
	if err != nil {
		return "", err
	}
	return strings.TrimSpace(out), nil
}

// GetAll 读取全部内核参数
func GetAll() (map[string]string, error) {
	out, err := run("sysctl", "-a")
	if err != nil {
		return nil, err
	}
	result := map[string]string{}
	for _, line := range strings.Split(out, "\n") {
		line = strings.TrimSpace(line)
		if line == "" || !strings.Contains(line, "=") {
			continue
		}
		parts := strings.SplitN(line, "=", 2)
		result[strings.TrimSpace(parts[0])] = strings.TrimSpace(parts[1])
	}
	return result, nil
}

// GetValues 批量读取指定参数
func GetValues(keys []string) (map[string]string, error) {
	result := map[string]string{}
	for _, k := range keys {
		v, err := GetValue(k)
		if err != nil {
			v = ""
		}
		result[k] = v
	}
	return result, nil
}

// SetValue 设置单个内核参数并持久化
func SetValue(key, value string, persist bool) error {
	if _, err := run("sysctl", "-w", fmt.Sprintf("%s=%s", key, value)); err != nil {
		return err
	}
	if persist {
		return persistValue(key, value)
	}
	return nil
}

// SetValues 批量设置，返回每个参数的执行结果
func SetValues(pairs map[string]string, persist bool) map[string]any {
	results := map[string]any{}
	for k, v := range pairs {
		if err := SetValue(k, v, persist); err != nil {
			results[k] = map[string]any{"ok": false, "error": err.Error()}
		} else {
			results[k] = map[string]any{"ok": true, "value": v}
		}
	}
	return results
}

// syncSystemConf 同步同名参数到系统配置文件(只更新已存在的同名非注释行)
func syncSystemConf(key, value string) {
	re := regexp.MustCompile(fmt.Sprintf(`^\s*%s\s*=`, regexp.QuoteMeta(key)))
	for _, path := range systemConfFiles {
		data, err := os.ReadFile(path)
		if err != nil {
			continue
		}
		lines := strings.Split(string(data), "\n")
		changed := false
		for i, line := range lines {
			trimmed := strings.TrimSpace(line)
			if re.MatchString(line) && !strings.HasPrefix(trimmed, "#") {
				lines[i] = fmt.Sprintf("%s = %s", key, value)
				changed = true
			}
		}
		if changed {
			os.WriteFile(path, []byte(strings.Join(lines, "\n")), 0o644)
		}
	}
}

// persistValue 将参数写入持久化配置并同步系统配置
func persistValue(key, value string) error {
	lines := []string{}
	if data, err := os.ReadFile(persistConf); err == nil {
		lines = strings.Split(string(data), "\n")
	}
	re := regexp.MustCompile(fmt.Sprintf(`^\s*%s\s*=`, regexp.QuoteMeta(key)))
	newLines := []string{}
	for _, line := range lines {
		if !re.MatchString(line) {
			newLines = append(newLines, line)
		}
	}
	newLines = append(newLines, fmt.Sprintf("%s = %s", key, value))
	os.MkdirAll(filepath.Dir(persistConf), 0o755)
	if err := os.WriteFile(persistConf, []byte(strings.Join(newLines, "\n")+"\n"), 0o644); err != nil {
		return newErr("写入持久化配置失败: %v", err)
	}
	syncSystemConf(key, value)
	return nil
}

// RemovePersist 从持久化配置中移除参数
func RemovePersist(key string) error {
	data, err := os.ReadFile(persistConf)
	if err != nil {
		return nil
	}
	re := regexp.MustCompile(fmt.Sprintf(`^\s*%s\s*=`, regexp.QuoteMeta(key)))
	lines := []string{}
	for _, line := range strings.Split(string(data), "\n") {
		if !re.MatchString(line) {
			lines = append(lines, line)
		}
	}
	return os.WriteFile(persistConf, []byte(strings.Join(lines, "\n")), 0o644)
}

// SnapshotMeta 快照元信息
type SnapshotMeta struct {
	Name       string `json:"name"`
	CreatedAt  string `json:"created_at"`
	Reason     string `json:"reason"`
	Kind       string `json:"kind"`
	ParamCount int    `json:"param_count"`
}

// CreateSnapshot 创建当前全部内核参数快照
func (m *Manager) CreateSnapshot(reason, kind string) (SnapshotMeta, error) {
	ts := time.Now().Format("20060102_150405")
	name := snapshotPrefix + ts
	dir := filepath.Join(m.backupDir, name)
	if err := os.MkdirAll(dir, 0o755); err != nil {
		return SnapshotMeta{}, err
	}
	// 全部参数快照
	params, err := GetAll()
	if err != nil {
		return SnapshotMeta{}, err
	}
	keys := make([]string, 0, len(params))
	for k := range params {
		keys = append(keys, k)
	}
	sort.Strings(keys)
	var sb strings.Builder
	for _, k := range keys {
		sb.WriteString(fmt.Sprintf("%s = %s\n", k, params[k]))
	}
	os.WriteFile(filepath.Join(dir, "sysctl_all.conf"), []byte(sb.String()), 0o644)
	// 持久化配置副本
	if data, err := os.ReadFile(persistConf); err == nil {
		os.WriteFile(filepath.Join(dir, "persist.conf.bak"), data, 0o644)
	}
	// 元信息
	meta := SnapshotMeta{
		Name: name, CreatedAt: time.Now().Format("2006-01-02 15:04:05"),
		Reason: reason, Kind: kind, ParamCount: len(params),
	}
	mb, _ := json.MarshalIndent(meta, "", "  ")
	os.WriteFile(filepath.Join(dir, "meta.json"), mb, 0o644)
	return meta, nil
}

// ListSnapshots 列出所有快照(按时间倒序)
func (m *Manager) ListSnapshots() []SnapshotMeta {
	snapshots := []SnapshotMeta{}
	entries, err := os.ReadDir(m.backupDir)
	if err != nil {
		return snapshots
	}
	for _, e := range entries {
		if !e.IsDir() || !strings.HasPrefix(e.Name(), snapshotPrefix) {
			continue
		}
		meta := SnapshotMeta{Name: e.Name(), Kind: "manual"}
		if data, err := os.ReadFile(filepath.Join(m.backupDir, e.Name(), "meta.json")); err == nil {
			json.Unmarshal(data, &meta)
		}
		snapshots = append(snapshots, meta)
	}
	sort.Slice(snapshots, func(i, j int) bool { return snapshots[i].Name > snapshots[j].Name })
	return snapshots
}

// RestoreSnapshot 回滚到指定快照
func (m *Manager) RestoreSnapshot(name string) (map[string]any, error) {
	dir := filepath.Join(m.backupDir, name)
	confPath := filepath.Join(dir, "sysctl_all.conf")
	if _, err := os.Stat(confPath); err != nil {
		return nil, newErr("快照不存在: %s", name)
	}
	data, err := os.ReadFile(confPath)
	if err != nil {
		return nil, err
	}
	restored := map[string]string{}
	failed := map[string]string{}
	for _, line := range strings.Split(string(data), "\n") {
		line = strings.TrimSpace(line)
		if line == "" || strings.HasPrefix(line, "#") || !strings.Contains(line, "=") {
			continue
		}
		parts := strings.SplitN(line, "=", 2)
		k, v := strings.TrimSpace(parts[0]), strings.TrimSpace(parts[1])
		if _, err := run("sysctl", "-w", fmt.Sprintf("%s=%s", k, v)); err != nil {
			failed[k] = err.Error()
		} else {
			restored[k] = v
		}
	}
	// 恢复持久化配置
	persistBackup := filepath.Join(dir, "persist.conf.bak")
	if _, err := os.Stat(persistBackup); err == nil {
		if pb, err := os.ReadFile(persistBackup); err == nil {
			os.WriteFile(persistConf, pb, 0o644)
			for k, v := range restored {
				syncSystemConf(k, v)
			}
		}
	}
	return map[string]any{
		"snapshot": name, "restored_count": len(restored), "failed_count": len(failed), "failed": failed,
	}, nil
}

// LogAction 记录操作审计日志
func (m *Manager) LogAction(action string, detail map[string]any) {
	entry := map[string]any{"time": time.Now().Format("2006-01-02 15:04:05"), "action": action}
	for k, v := range detail {
		entry[k] = v
	}
	os.MkdirAll(filepath.Dir(m.logFile), 0o755)
	jb, _ := json.Marshal(entry)
	f, _ := os.OpenFile(m.logFile, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0o644)
	if f != nil {
		f.WriteString(string(jb) + "\n")
		f.Close()
	}
}

// AuditLogs 读取审计日志(最近 n 条，倒序)
func (m *Manager) AuditLogs(limit int) []map[string]any {
	lines := []string{}
	if data, err := os.ReadFile(m.logFile); err == nil {
		lines = strings.Split(strings.TrimSpace(string(data)), "\n")
	}
	// 倒序(最新在前)
	result := []map[string]any{}
	for i := len(lines) - 1; i >= 0 && len(result) < limit; i-- {
		line := strings.TrimSpace(lines[i])
		if line == "" {
			continue
		}
		var entry map[string]any
		if json.Unmarshal([]byte(line), &entry) == nil {
			result = append(result, entry)
		}
	}
	return result
}

// BoolToInt bool 转 int(0/1)，供前端逻辑使用
func BoolToInt(b bool) int {
	if b {
		return 1
	}
	return 0
}