package config

import (
	"fmt"
	"os"

	"gopkg.in/yaml.v3"
)

// Config is the top-level server configuration.
type Config struct {
	Server  ServerConfig  `yaml:"server"`
	Auth    AuthConfig    `yaml:"auth"`
	Storage StorageConfig `yaml:"storage"`
	TLS     TLSConfig     `yaml:"tls"`
	Logging LoggingConfig `yaml:"logging"`
}

type ServerConfig struct {
	Host string `yaml:"host"`
	Port int    `yaml:"port"`
	// Base URL used in DAV responses (e.g. https://dav.example.com)
	BaseURL string `yaml:"base_url"`
}

type AuthConfig struct {
	// Realm shown in WWW-Authenticate header
	Realm string `yaml:"realm"`
}

type StorageConfig struct {
	// Root directory for all data
	DataDir string `yaml:"data_dir"`
}

type TLSConfig struct {
	Enabled  bool   `yaml:"enabled"`
	CertFile string `yaml:"cert_file"`
	KeyFile  string `yaml:"key_file"`
}

type LoggingConfig struct {
	Level  string `yaml:"level"`  // debug | info | warn | error
	Format string `yaml:"format"` // text | json
}

// Load reads and parses a YAML config file.
func Load(path string) (*Config, error) {
	data, err := os.ReadFile(path)
	if err != nil {
		return nil, fmt.Errorf("reading config %q: %w", path, err)
	}

	cfg := &Config{}
	if err := yaml.Unmarshal(data, cfg); err != nil {
		return nil, fmt.Errorf("parsing config %q: %w", path, err)
	}

	cfg.applyDefaults()

	return cfg, cfg.validate()
}

func (c *Config) applyDefaults() {
	if c.Server.Host == "" {
		c.Server.Host = "0.0.0.0"
	}
	if c.Server.Port == 0 {
		c.Server.Port = 8080
	}
	if c.Server.BaseURL == "" {
		scheme := "http"
		if c.TLS.Enabled {
			scheme = "https"
		}
		c.Server.BaseURL = fmt.Sprintf("%s://%s:%d", scheme, c.Server.Host, c.Server.Port)
	}
	if c.Auth.Realm == "" {
		c.Auth.Realm = "DAV Server"
	}
	if c.Storage.DataDir == "" {
		c.Storage.DataDir = "./data"
	}
	if c.Logging.Level == "" {
		c.Logging.Level = "info"
	}
	if c.Logging.Format == "" {
		c.Logging.Format = "text"
	}
}

func (c *Config) validate() error {
	if c.TLS.Enabled {
		if c.TLS.CertFile == "" || c.TLS.KeyFile == "" {
			return fmt.Errorf("tls.cert_file and tls.key_file are required when tls is enabled")
		}
	}
	return nil
}