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short.go
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short.go
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package short
import (
"context"
"errors"
"fmt"
"net/url"
"strings"
)
type ShortenedURL interface {
GetUrl() string
}
type Shortener interface {
// CreateShortenedUrl creates a shortened url for `url`.
CreateShortenedUrl(ctx context.Context, url string, config ...UrlConfig) (ShortenedURL, error)
// GetUrlFromShortenedUrl receives a shortened url `surl` and returns the original url.
// E.g.: https://short.com/abCD123
GetUrlFromShortenedUrl(ctx context.Context, surl string) (string, error)
// GetUrlFromShortenedUrl receives a shortened url `id` and returns the original url.
// E.g.: abCD123
GetUrlFromShortenedUrlId(ctx context.Context, id string) (string, error)
}
type shortner struct {
host string
store Store
}
type shortenedUrl struct {
url string
}
func (s *shortenedUrl) GetUrl() string {
return s.url
}
// NewShortener creates a new shortener.
// If no configuration is passed uses the default configuration (see: `DefaultConfig()`)
func NewShortener(config ...Config) (Shortener, error) {
var c Config
var err error
if len(config) > 1 {
return nil, errors.New("passed multiple configuration instances")
}
if len(config) == 0 {
c = DefaultConfig()
} else {
c = config[0]
}
ci := c.getConfig()
if ci.err != nil {
return nil, ci.err
}
var s shortner
s.host = ci.host
s.store, err = newStore(ci.mongoUri, ci.host)
if err != nil {
return nil, err
}
return &s, nil
}
func newShortenedUrl(id string, host string) ShortenedURL {
scheme := "https://"
if strings.HasPrefix(host, "localhost") {
scheme = "http://"
}
return &shortenedUrl{
url: scheme + host + "/" + id,
}
}
func (s *shortner) insert(ctx context.Context, ic *insertConfig) (ShortenedURL, error) {
if err := s.store.Insert(ctx, ic); err != nil {
return nil, fmt.Errorf("failed to insert an entry for a shortened url: %w", err)
}
return newShortenedUrl(ic.id, s.host), nil
}
// CreateShortenedUrl creates a shortened url.
// If no configuration is passed uses the default configuration (see: `DefaultUrlConfig()`)
func (s *shortner) CreateShortenedUrl(ctx context.Context, url string, config ...UrlConfig) (ShortenedURL, error) {
if err := validateUrl(url); err != nil {
return nil, err
}
var uc UrlConfig
if len(config) > 1 {
return nil, errors.New("passed multiple configuration instances")
}
if len(config) == 0 {
uc = DefaultUrlConfig()
} else {
uc = config[0]
}
uci := uc.getConfig()
if uci.err != nil {
return nil, uci.err
}
if len(uci.alias) > 0 {
return s.insert(ctx, &insertConfig{
url: url, id: uci.alias, override: uci.overrideAlias, expiration: uci.expirationDate,
})
}
for {
id, err := generateRandomId()
if err != nil {
return nil, err
}
shortenedUrl, err := s.insert(ctx, &insertConfig{
url: url, id: id, override: false, expiration: uci.expirationDate,
})
if err != nil {
// In rare cases (statistically) a conflict may occur. Generate a new random id.
if errors.Is(err, &ConflictError{}) {
continue
}
return nil, err
}
return shortenedUrl, nil
}
}
func (s *shortner) GetUrlFromShortenedUrl(ctx context.Context, surl string) (string, error) {
su, err := url.ParseRequestURI(surl)
if err != nil {
return "", fmt.Errorf("invalid short url %s: %w", surl, err)
}
id := strings.Trim(su.Path, "/")
return s.GetUrlFromShortenedUrlId(ctx, id)
}
func (s *shortner) GetUrlFromShortenedUrlId(ctx context.Context, id string) (string, error) {
if len(id) == 0 || !isAlphaNumeric(id) {
return "", fmt.Errorf("invalid short url path %s", id)
}
return s.store.GetUrl(ctx, id)
}