package config

import (
	_ "embed"
	"errors"
	"fmt"
	"os"
	"path/filepath"
	"strings"

	"git.netflux.io/rob/octoplex/internal/domain"
	"gopkg.in/yaml.v3"
)

//go:embed data/config.example.yml
var exampleConfig []byte

// Service provides configuration services.
type Service struct {
	userConfigDir string
	appConfigDir  string
	appStateDir   string
}

// ConfigDirFunc is a function that returns the user configuration directory.
type ConfigDirFunc func() (string, error)

// NewDefaultService creates a new service with the default configuration file
// location.
func NewDefaultService() (*Service, error) {
	return NewService(os.UserConfigDir)
}

// NewService creates a new service with provided ConfigDirFunc.
//
// The app data directories (config and state) are created if they do not
// exist.
func NewService(configDirFunc ConfigDirFunc) (*Service, error) {
	configDir, err := configDirFunc()
	if err != nil {
		return nil, fmt.Errorf("user config dir: %w", err)
	}

	appConfigDir, err := createAppConfigDir(configDir)
	if err != nil {
		return nil, fmt.Errorf("app config dir: %w", err)
	}

	appStateDir, err := createAppStateDir()
	if err != nil {
		return nil, fmt.Errorf("app state dir: %w", err)
	}

	return &Service{
		userConfigDir: configDir,
		appConfigDir:  appConfigDir,
		appStateDir:   appStateDir,
	}, nil
}

// ReadOrCreateConfig reads the configuration from the file at the given path or
// creates it with default values.
func (s *Service) ReadOrCreateConfig() (cfg Config, _ error) {
	if _, err := os.Stat(s.Path()); os.IsNotExist(err) {
		return s.createConfig()
	} else if err != nil {
		return cfg, fmt.Errorf("stat: %w", err)
	}

	return s.readConfig()
}

func (s *Service) readConfig() (cfg Config, _ error) {
	contents, err := os.ReadFile(s.Path())
	if err != nil {
		return cfg, fmt.Errorf("read file: %w", err)
	}

	if err = yaml.Unmarshal(contents, &cfg); err != nil {
		return cfg, fmt.Errorf("unmarshal: %w", err)
	}

	s.setDefaults(&cfg)

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

	return cfg, nil
}

func (s *Service) createConfig() (Config, error) {
	if err := os.MkdirAll(s.appConfigDir, 0744); err != nil {
		return Config{}, fmt.Errorf("mkdir: %w", err)
	}

	if err := os.WriteFile(s.Path(), exampleConfig, 0644); err != nil {
		return Config{}, fmt.Errorf("write file: %w", err)
	}

	return Config{}, nil
}

func (s *Service) Path() string {
	return filepath.Join(s.appConfigDir, "config.yaml")
}

func (s *Service) setDefaults(cfg *Config) {
	if cfg.LogFile.Enabled && cfg.LogFile.Path == "" {
		cfg.LogFile.Path = filepath.Join(s.appStateDir, domain.AppName+".log")
	}

	for i := range cfg.Destinations {
		if strings.TrimSpace(cfg.Destinations[i].Name) == "" {
			cfg.Destinations[i].Name = fmt.Sprintf("Stream %d", i+1)
		}
	}
}

func validate(cfg Config) error {
	var err error

	for _, dest := range cfg.Destinations {
		if !strings.HasPrefix(dest.URL, "rtmp://") {
			err = errors.Join(err, fmt.Errorf("destination URL must start with rtmp://"))
		}
	}

	return err
}