vaultik/internal/config/config.go

package config

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

	"git.eeqj.de/sneak/smartconfig"
	"github.com/adrg/xdg"
	"go.uber.org/fx"
	"gopkg.in/yaml.v3"
)

const appName = "berlin.sneak.app.vaultik"

// expandTilde expands ~ at the start of a path to the user's home directory.
func expandTilde(path string) string {
	if path == "~" {
		home, _ := os.UserHomeDir()
		return home
	}
	if strings.HasPrefix(path, "~/") {
		home, _ := os.UserHomeDir()
		return filepath.Join(home, path[2:])
	}
	return path
}

// expandTildeInURL expands ~ in file:// URLs.
func expandTildeInURL(url string) string {
	if strings.HasPrefix(url, "file://~/") {
		home, _ := os.UserHomeDir()
		return "file://" + filepath.Join(home, url[9:])
	}
	return url
}

// Config represents the application configuration for Vaultik.
// It defines all settings for backup operations, including source directories,
// encryption recipients, storage configuration, and performance tuning parameters.
// Configuration is typically loaded from a YAML file.
type Config struct {
	AgeRecipients     []string      `yaml:"age_recipients"`
	AgeSecretKey      string        `yaml:"age_secret_key"`
	BackupInterval    time.Duration `yaml:"backup_interval"`
	BlobSizeLimit     Size          `yaml:"blob_size_limit"`
	ChunkSize         Size          `yaml:"chunk_size"`
	Exclude           []string      `yaml:"exclude"`
	FullScanInterval  time.Duration `yaml:"full_scan_interval"`
	Hostname          string        `yaml:"hostname"`
	IndexPath         string        `yaml:"index_path"`
	MinTimeBetweenRun time.Duration `yaml:"min_time_between_run"`
	S3                S3Config      `yaml:"s3"`
	SourceDirs        []string      `yaml:"source_dirs"`
	CompressionLevel  int           `yaml:"compression_level"`

	// StorageURL specifies the storage backend using a URL format.
	// Takes precedence over S3Config if set.
	// Supported formats:
	//   - s3://bucket/prefix?endpoint=host&region=us-east-1
	//   - file:///path/to/backup
	// For S3 URLs, credentials are still read from s3.access_key_id and s3.secret_access_key.
	StorageURL string `yaml:"storage_url"`
}

// S3Config represents S3 storage configuration for backup storage.
// It supports both AWS S3 and S3-compatible storage services.
// All fields except UseSSL and PartSize are required.
type S3Config struct {
	Endpoint        string `yaml:"endpoint"`
	Bucket          string `yaml:"bucket"`
	Prefix          string `yaml:"prefix"`
	AccessKeyID     string `yaml:"access_key_id"`
	SecretAccessKey string `yaml:"secret_access_key"`
	Region          string `yaml:"region"`
	UseSSL          bool   `yaml:"use_ssl"`
	PartSize        Size   `yaml:"part_size"`
}

// ConfigPath wraps the config file path for fx dependency injection.
// This type allows the config file path to be injected as a distinct type
// rather than a plain string, avoiding conflicts with other string dependencies.
type ConfigPath string

// New creates a new Config instance by loading from the specified path.
// This function is used by the fx dependency injection framework.
// Returns an error if the path is empty or if loading fails.
func New(path ConfigPath) (*Config, error) {
	if path == "" {
		return nil, fmt.Errorf("config path not provided")
	}

	cfg, err := Load(string(path))
	if err != nil {
		return nil, fmt.Errorf("failed to load config: %w", err)
	}

	return cfg, nil
}

// Load reads and parses the configuration file from the specified path.
// It applies default values for optional fields, performs environment variable
// substitution using smartconfig, and validates the configuration.
// The configuration file should be in YAML format. Returns an error if the file
// cannot be read, parsed, or if validation fails.
func Load(path string) (*Config, error) {
	// Load config using smartconfig for interpolation
	sc, err := smartconfig.NewFromConfigPath(path)
	if err != nil {
		return nil, fmt.Errorf("failed to load config file: %w", err)
	}

	cfg := &Config{
		// Set defaults
		BlobSizeLimit:     Size(10 * 1024 * 1024 * 1024), // 10GB
		ChunkSize:         Size(10 * 1024 * 1024),        // 10MB
		BackupInterval:    1 * time.Hour,
		FullScanInterval:  24 * time.Hour,
		MinTimeBetweenRun: 15 * time.Minute,
		IndexPath:         filepath.Join(xdg.DataHome, appName, "index.sqlite"),
		CompressionLevel:  3,
	}

	// Convert smartconfig data to YAML then unmarshal
	configData := sc.Data()
	yamlBytes, err := yaml.Marshal(configData)
	if err != nil {
		return nil, fmt.Errorf("failed to marshal config data: %w", err)
	}

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

	// Expand tilde in all path fields
	cfg.IndexPath = expandTilde(cfg.IndexPath)
	cfg.StorageURL = expandTildeInURL(cfg.StorageURL)
	for i, dir := range cfg.SourceDirs {
		cfg.SourceDirs[i] = expandTilde(dir)
	}

	// Check for environment variable override for IndexPath
	if envIndexPath := os.Getenv("VAULTIK_INDEX_PATH"); envIndexPath != "" {
		cfg.IndexPath = expandTilde(envIndexPath)
	}

	// Get hostname if not set
	if cfg.Hostname == "" {
		hostname, err := os.Hostname()
		if err != nil {
			return nil, fmt.Errorf("failed to get hostname: %w", err)
		}
		cfg.Hostname = hostname
	}

	// Set default S3 settings
	if cfg.S3.Region == "" {
		cfg.S3.Region = "us-east-1"
	}
	if cfg.S3.PartSize == 0 {
		cfg.S3.PartSize = Size(5 * 1024 * 1024) // 5MB
	}

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

	return cfg, nil
}

// Validate checks if the configuration is valid and complete.
// It ensures all required fields are present and have valid values:
// - At least one age recipient must be specified
// - At least one source directory must be configured
// - Storage must be configured (either storage_url or s3.* fields)
// - Chunk size must be at least 1MB
// - Blob size limit must be at least the chunk size
// - Compression level must be between 1 and 19
// Returns an error describing the first validation failure encountered.
func (c *Config) Validate() error {
	if len(c.AgeRecipients) == 0 {
		return fmt.Errorf("at least one age_recipient is required")
	}

	if len(c.SourceDirs) == 0 {
		return fmt.Errorf("at least one source directory is required")
	}

	// Validate storage configuration
	if err := c.validateStorage(); err != nil {
		return err
	}

	if c.ChunkSize.Int64() < 1024*1024 { // 1MB minimum
		return fmt.Errorf("chunk_size must be at least 1MB")
	}

	if c.BlobSizeLimit.Int64() < c.ChunkSize.Int64() {
		return fmt.Errorf("blob_size_limit must be at least chunk_size")
	}

	if c.CompressionLevel < 1 || c.CompressionLevel > 19 {
		return fmt.Errorf("compression_level must be between 1 and 19")
	}

	return nil
}

// validateStorage validates storage configuration.
// If StorageURL is set, it takes precedence. S3 URLs require credentials.
// File URLs don't require any S3 configuration.
// If StorageURL is not set, legacy S3 configuration is required.
func (c *Config) validateStorage() error {
	if c.StorageURL != "" {
		// URL-based configuration
		if strings.HasPrefix(c.StorageURL, "file://") {
			// File storage doesn't need S3 credentials
			return nil
		}
		if strings.HasPrefix(c.StorageURL, "s3://") {
			// S3 storage needs credentials
			if c.S3.AccessKeyID == "" {
				return fmt.Errorf("s3.access_key_id is required for s3:// URLs")
			}
			if c.S3.SecretAccessKey == "" {
				return fmt.Errorf("s3.secret_access_key is required for s3:// URLs")
			}
			return nil
		}
		return fmt.Errorf("storage_url must start with s3:// or file://")
	}

	// Legacy S3 configuration
	if c.S3.Endpoint == "" {
		return fmt.Errorf("s3.endpoint is required (or set storage_url)")
	}

	if c.S3.Bucket == "" {
		return fmt.Errorf("s3.bucket is required (or set storage_url)")
	}

	if c.S3.AccessKeyID == "" {
		return fmt.Errorf("s3.access_key_id is required")
	}

	if c.S3.SecretAccessKey == "" {
		return fmt.Errorf("s3.secret_access_key is required")
	}

	return nil
}

// Module exports the config module for fx dependency injection.
// It provides the Config type to other modules in the application.
var Module = fx.Module("config",
	fx.Provide(New),
)