package b2

import (
	"os"
	"path"
	"regexp"
	"strings"

	"github.com/restic/restic/internal/backend"
	"github.com/restic/restic/internal/errors"
	"github.com/restic/restic/internal/options"
)

// Config contains all configuration necessary to connect to an b2 compatible
// server.
type Config struct {
	AccountID string
	Key       options.SecretString
	Bucket    string
	Prefix    string

	Connections uint `option:"connections" help:"set a limit for the number of concurrent connections (default: 5)"`
}

// NewConfig returns a new config with default options applied.
func NewConfig() Config {
	return Config{
		Connections: 5,
	}
}

func init() {
	options.Register("b2", Config{})
}

var bucketName = regexp.MustCompile("^[a-zA-Z0-9-]+$")

// checkBucketName tests the bucket name against the rules at
// https://help.backblaze.com/hc/en-us/articles/217666908-What-you-need-to-know-about-B2-Bucket-names
func checkBucketName(name string) error {
	if name == "" {
		return errors.New("bucket name not found")
	}

	if len(name) < 6 {
		return errors.New("bucket name is too short")
	}

	if len(name) > 50 {
		return errors.New("bucket name is too long")
	}

	if !bucketName.MatchString(name) {
		return errors.New("bucket name contains invalid characters, allowed are: a-z, 0-9, dash (-)")
	}

	return nil
}

// ParseConfig parses the string s and extracts the b2 config. The supported
// configuration format is b2:bucketname/prefix. If no prefix is given the
// prefix "restic" will be used.
func ParseConfig(s string) (*Config, error) {
	if !strings.HasPrefix(s, "b2:") {
		return nil, errors.New("invalid format, want: b2:bucket-name[:path]")
	}

	s = s[3:]
	bucket, prefix, _ := strings.Cut(s, ":")
	if err := checkBucketName(bucket); err != nil {
		return nil, err
	}

	if len(prefix) > 0 {
		prefix = strings.TrimPrefix(path.Clean(prefix), "/")
	}

	cfg := NewConfig()
	cfg.Bucket = bucket
	cfg.Prefix = prefix

	return &cfg, nil
}

var _ backend.ApplyEnvironmenter = &Config{}

// ApplyEnvironment saves values from the environment to the config.
func (cfg *Config) ApplyEnvironment(prefix string) {
	if cfg.AccountID == "" {
		cfg.AccountID = os.Getenv(prefix + "B2_ACCOUNT_ID")
	}
	if cfg.Key.String() == "" {
		cfg.Key = options.NewSecretString(os.Getenv(prefix + "B2_ACCOUNT_KEY"))
	}
}