package services

import (
	"encoding/json"
	"errors"
	"fmt"
	"os"
	"path/filepath"
	"slices"
)

type Server struct {
	ID   string `json:"id"`
	Name string `json:"name"`
	Host string `json:"host"`
}

type Config struct {
	Servers          []Server `json:"servers"`
	SelectedServerID string   `json:"selectedServerId"`
}

type ConfigService struct {
	path   string
	config Config
}

func NewConfigService() (*ConfigService, error) {
	configDir, err := os.UserConfigDir()
	if err != nil {
		return nil, fmt.Errorf("get config dir: %w", err)
	}

	dir := filepath.Join(configDir, "tailscale-vpn")
	if err := os.MkdirAll(dir, 0o700); err != nil {
		return nil, fmt.Errorf("create config dir: %w", err)
	}

	path := filepath.Join(dir, "settings.json")

	if _, err := os.Stat(path); errors.Is(err, os.ErrNotExist) {
		if err := os.WriteFile(path, []byte(`{"servers":[]}`), 0o600); err != nil {
			return nil, fmt.Errorf("create config file: %w", err)
		}
	}

	data, err := os.ReadFile(path)
	if err != nil {
		return nil, fmt.Errorf("read config file: %w", err)
	}

	var cfg Config
	if err := json.Unmarshal(data, &cfg); err != nil {
		return nil, fmt.Errorf("parse config: %w", err)
	}

	return &ConfigService{path: path, config: cfg}, nil
}

func (s *ConfigService) GetServers() []Server {
	return s.config.Servers
}

func (s *ConfigService) GetServer(id string) (Server, bool) {
	for _, srv := range s.config.Servers {
		if srv.ID == id {
			return srv, true
		}
	}
	return Server{}, false
}

func (s *ConfigService) AddServer(name, host string) error {
	srv := Server{
		ID:   host,
		Name: name,
		Host: host,
	}
	s.config.Servers = append(s.config.Servers, srv)
	return s.Save()
}

func (s *ConfigService) RemoveServer(id string) error {
	s.config.Servers = slices.DeleteFunc(s.config.Servers, func(srv Server) bool {
		return srv.ID == id
	})
	return s.Save()
}

func (s *ConfigService) GetSelectedServer() (Server, bool) {
	for _, srv := range s.config.Servers {
		if srv.ID == s.config.SelectedServerID {
			return srv, true
		}
	}
	return Server{}, false
}

func (s *ConfigService) SetSelectedServer(id string) error {
	for _, srv := range s.config.Servers {
		if srv.ID == id {
			s.config.SelectedServerID = id
			return s.Save()
		}
	}
	return fmt.Errorf("server not found")
}

func (s *ConfigService) UpdateServer(id, name, host string) error {
	for i, srv := range s.config.Servers {
		if srv.ID == id {
			s.config.Servers[i].Name = name
			s.config.Servers[i].Host = host
			s.config.Servers[i].ID = host
			return s.Save()
		}
	}
	return fmt.Errorf("server not found")
}

func (s *ConfigService) Save() error {
	data, err := json.MarshalIndent(s.config, "", "  ")
	if err != nil {
		return fmt.Errorf("marshal config: %w", err)
	}
	if err := os.WriteFile(s.path, data, 0o600); err != nil {
		return fmt.Errorf("write config: %w", err)
	}
	return nil
}