package main

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

	"gopkg.in/yaml.v3"
)

type Config struct {
	SMTP SMTPConfig `yaml:"smtp"`
	Web  WebConfig  `yaml:"web"`
}

type SMTPConfig struct {
	ListenAddress  string `yaml:"listen_address"`
	ListenPort     int    `yaml:"listen_port"`
	StorageDir     string `yaml:"storage_dir"`
	DomainName     string `yaml:"domain_name"`
	MaxMessageSize int64  `yaml:"max_message_size"`
	EnableAuth     bool   `yaml:"enable_auth"`
}

type WebConfig struct {
	Enabled   bool            `yaml:"enabled"`
	Port      int             `yaml:"port"`
	Directory string          `yaml:"directory"`
	BasicAuth BasicAuthConfig `yaml:"basic_auth"`
}

type BasicAuthConfig struct {
	Enabled  bool   `yaml:"enabled"`
	Username string `yaml:"username"`
	Password string `yaml:"password"`
}

func getExecutableDir() (string, error) {
	exe, err := os.Executable()
	if err != nil {
		return "", err
	}

	return filepath.Dir(exe), nil
}

func defaultConfig() *Config {
	return &Config{
		SMTP: SMTPConfig{
			ListenAddress:  "0.0.0.0",
			ListenPort:     1025,
			StorageDir:     "emails",
			DomainName:     "m.ric930.ru",
			MaxMessageSize: 50 * 1024 * 1024,
			EnableAuth:     true,
		},
		Web: WebConfig{
			Enabled:   true,
			Port:      8089,
			Directory: "web",
			BasicAuth: BasicAuthConfig{
				Enabled:  true,
				Username: "admin",
				Password: "admin",
			},
		},
	}
}

func resolveConfigPaths(cfg *Config, exeDir string) {
	if !filepath.IsAbs(cfg.SMTP.StorageDir) {
		cfg.SMTP.StorageDir = filepath.Join(exeDir, cfg.SMTP.StorageDir)
	}

	if !filepath.IsAbs(cfg.Web.Directory) {
		cfg.Web.Directory = filepath.Join(exeDir, cfg.Web.Directory)
	}
}

func validateConfig(cfg *Config) error {
	if cfg.SMTP.ListenPort < 1 || cfg.SMTP.ListenPort > 65535 {
		return fmt.Errorf("invalid smtp.listen_port: %d", cfg.SMTP.ListenPort)
	}

	if cfg.SMTP.StorageDir == "" {
		return fmt.Errorf("smtp.storage_dir must not be empty")
	}

	if cfg.SMTP.DomainName == "" {
		return fmt.Errorf("smtp.domain_name must not be empty")
	}

	if cfg.SMTP.MaxMessageSize <= 0 {
		return fmt.Errorf("smtp.max_message_size must be greater than zero")
	}

	if cfg.Web.Enabled {
		if cfg.Web.Port < 1 || cfg.Web.Port > 65535 {
			return fmt.Errorf("invalid web.port: %d", cfg.Web.Port)
		}

		if cfg.Web.Directory == "" {
			return fmt.Errorf("web.directory must not be empty")
		}

		if cfg.Web.BasicAuth.Enabled {
			if cfg.Web.BasicAuth.Username == "" {
				return fmt.Errorf("web.basic_auth.username must not be empty")
			}

			if cfg.Web.BasicAuth.Password == "" {
				return fmt.Errorf("web.basic_auth.password must not be empty")
			}
		}
	}

	return nil
}

func LoadConfig(configPath string) (*Config, error) {
	exeDir, err := getExecutableDir()
	if err != nil {
		log.Printf(
			"Warning: cannot get executable directory: %v, using current directory",
			err,
		)
		exeDir = "."
	}

	finalConfigPath := configPath
	if !filepath.IsAbs(finalConfigPath) {
		finalConfigPath = filepath.Join(exeDir, finalConfigPath)
	}

	data, err := os.ReadFile(finalConfigPath)
	if err != nil {
		if !os.IsNotExist(err) {
			return nil, fmt.Errorf("failed to read config: %w", err)
		}

		cfg := defaultConfig()

		cfgData, marshalErr := yaml.Marshal(cfg)
		if marshalErr != nil {
			return nil, fmt.Errorf(
				"failed to create default config data: %w",
				marshalErr,
			)
		}

		if writeErr := os.WriteFile(finalConfigPath, cfgData, 0600); writeErr != nil {
			return nil, fmt.Errorf(
				"failed to create default config: %w",
				writeErr,
			)
		}

		log.Printf("Created default config at %s", finalConfigPath)
		log.Printf(
			"WARNING: change the default web Basic Auth password in %s",
			finalConfigPath,
		)

		resolveConfigPaths(cfg, exeDir)

		if err := validateConfig(cfg); err != nil {
			return nil, err
		}

		return cfg, nil
	}

	var cfg Config

	if err := yaml.Unmarshal(data, &cfg); err != nil {
		return nil, fmt.Errorf(
			"failed to parse YAML config %s: %w",
			finalConfigPath,
			err,
		)
	}

	if err := validateConfig(&cfg); err != nil {
		return nil, fmt.Errorf(
			"invalid config %s: %w",
			finalConfigPath,
			err,
		)
	}

	resolveConfigPaths(&cfg, exeDir)

	return &cfg, nil
}