package netplan

import (
	"fmt"
	"os"
	"path/filepath"

	"quickip/internal/model"

	"gopkg.in/yaml.v3"
)

type Service struct{}

type fileConfig struct {
	Network networkConfig `yaml:"network"`
}

type networkConfig struct {
	Version   int                       `yaml:"version,omitempty"`
	Ethernets map[string]*ethernetEntry `yaml:"ethernets,omitempty"`
}

type ethernetEntry struct {
	DHCP4       *bool             `yaml:"dhcp4,omitempty"`
	Addresses   []string          `yaml:"addresses,omitempty"`
	Gateway4    string            `yaml:"gateway4,omitempty"`
	Nameservers *nameserverConfig `yaml:"nameservers,omitempty"`
	Optional    *bool             `yaml:"optional,omitempty"`
	MTU         int               `yaml:"mtu,omitempty"`
	WakeOnLAN   *bool             `yaml:"wakeonlan,omitempty"`
}

type nameserverConfig struct {
	Addresses []string `yaml:"addresses,omitempty"`
}

func New() *Service { return &Service{} }

func (s *Service) FindSingleFile() (string, error) {
	files, err := filepath.Glob("/etc/netplan/*.yaml")
	if err != nil {
		return "", err
	}
	if len(files) == 0 {
		return "", fmt.Errorf("未找到 netplan 配置文件")
	}
	if len(files) > 1 {
		return "", fmt.Errorf("检测到多个 netplan 配置文件，首版暂不支持自动处理")
	}
	return files[0], nil
}

func (s *Service) Backup(path string) (string, error) {
	backupPath := path + ".quickip.bak"
	if _, err := os.Stat(backupPath); err == nil {
		return backupPath, nil
	}
	data, err := os.ReadFile(path)
	if err != nil {
		return "", err
	}
	if err := os.WriteFile(backupPath, data, 0600); err != nil {
		return "", err
	}
	return backupPath, nil
}

func (s *Service) Restore(path string, backupPath string) error {
	data, err := os.ReadFile(backupPath)
	if err != nil {
		return err
	}
	if err := os.WriteFile(path, data, 0600); err != nil {
		return err
	}
	_ = os.Remove(backupPath)
	return nil
}

func (s *Service) Write(path string, targetInterface string, input model.InterfaceConfig, managementInterface string, maintenanceCIDR string) error {
	data, err := os.ReadFile(path)
	if err != nil {
		return err
	}

	var cfg fileConfig
	if err := yaml.Unmarshal(data, &cfg); err != nil {
		return err
	}
	if cfg.Network.Version == 0 {
		cfg.Network.Version = 2
	}
	if cfg.Network.Ethernets == nil {
		cfg.Network.Ethernets = make(map[string]*ethernetEntry)
	}

	target := cfg.Network.Ethernets[targetInterface]
	if target == nil {
		target = &ethernetEntry{}
		cfg.Network.Ethernets[targetInterface] = target
	}
	dhcpFalse := false
	target.DHCP4 = &dhcpFalse
	target.Addresses = []string{fmt.Sprintf("%s/%d", input.IP, input.Prefix)}
	if input.Gateway != "" {
		target.Gateway4 = input.Gateway
	} else {
		target.Gateway4 = ""
	}
	if len(input.DNS) > 0 {
		target.Nameservers = &nameserverConfig{Addresses: input.DNS}
	} else {
		target.Nameservers = nil
	}

	mgmt := cfg.Network.Ethernets[managementInterface]
	if mgmt == nil {
		mgmt = &ethernetEntry{}
		cfg.Network.Ethernets[managementInterface] = mgmt
	}
	dhcpTrue := true
	mgmt.DHCP4 = &dhcpTrue
	if !contains(mgmt.Addresses, maintenanceCIDR) {
		mgmt.Addresses = append(uniqueNonEmpty(mgmt.Addresses), maintenanceCIDR)
	}

	output, err := yaml.Marshal(&cfg)
	if err != nil {
		return err
	}
	return os.WriteFile(path, output, 0600)
}

func contains(items []string, target string) bool {
	for _, item := range items {
		if item == target {
			return true
		}
	}
	return false
}

func uniqueNonEmpty(items []string) []string {
	seen := make(map[string]struct{})
	result := make([]string, 0, len(items))
	for _, item := range items {
		if item == "" {
			continue
		}
		if _, ok := seen[item]; ok {
			continue
		}
		seen[item] = struct{}{}
		result = append(result, item)
	}
	return result
}