URL Shortener. https://fsh.ee/
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// A URL Shortener called Link.
// Copyright (C) 2021 i@fsh.ee
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.
package main
import (
"crypto/md5"
_ "embed"
"errors"
"flag"
"fmt"
"hash/maphash"
"html/template"
"io/ioutil"
"log"
"net/http"
"net/url"
"os"
"strconv"
"strings"
"time"
"gorm.io/driver/sqlite"
"gorm.io/gorm"
"gorm.io/gorm/logger"
)
//go:embed index.html
var indexTemplate string
type Retry struct {
retryAttemptCount int
}
func NewRetry(retryAttemptCount int) (Retry, error) {
if retryAttemptCount < 1 {
return Retry{}, errors.New("retry attempt count must be greater than zero")
}
return Retry{retryAttemptCount}, nil
}
func (r Retry) Do(f func() error) (err error) {
for i := 0; i < r.retryAttemptCount; i++ {
err = f()
if err == nil {
return nil
}
}
return err
}
type DB struct {
*gorm.DB
log *log.Logger
hashSeed string
retry Retry
}
func NewDB(l *log.Logger, dbFilePath, hashSeed string, retry Retry) (DB, error) {
_, err := os.Stat(dbFilePath)
if os.IsNotExist(err) {
err := ioutil.WriteFile(dbFilePath, []byte{}, 0600)
if err != nil {
return DB{}, err
}
}
db, err := gorm.Open(sqlite.Open(dbFilePath), &gorm.Config{
NowFunc: func() time.Time { return time.Now().UTC() },
Logger: logger.Default.LogMode(logger.Silent),
})
if err != nil {
return DB{}, err
}
return DB{db, l, hashSeed, retry}, db.AutoMigrate(&Link{})
}
type Link struct {
gorm.Model
Big string
Smol string `gorm:"unique"`
Del string `gorm:"unique"`
}
func (db DB) getHashShortLink(s fmt.Stringer) (string, error) {
var (
h = maphash.Hash{}
_, err = h.WriteString(s.String())
)
if err != nil {
return "", err
}
return strings.TrimSpace(strings.TrimLeft(fmt.Sprintf("%#x\n", h.Sum64()), "0x")), nil
}
func (db DB) getHashDeleteKey(s fmt.Stringer) string {
return strings.TrimSpace(fmt.Sprintf("%x", md5.Sum([]byte(db.hashSeed+s.String()+strconv.FormatInt(time.Now().Unix(), 10)))))
}
func (db DB) NewLink(u *url.URL) (Link, error) {
h, err := db.getHashShortLink(u)
if err != nil {
return Link{}, err
}
return db.NewLinkWithShortLink(u, h)
}
func (db DB) NewLinkWithShortLink(u *url.URL, hash string) (link Link, err error) {
// Retry for unique errors.
err = db.retry.Do(func() error {
link = Link{Big: u.String(), Smol: hash, Del: db.getHashDeleteKey(u)}
return db.Create(&link).Error
})
return
}
func (db DB) GetLink(smol string) (l Link, e error) {
res := db.Where(&Link{Smol: smol}).First(&l)
return l, res.Error
}
func (db DB) DelLink(smol, del string) error {
link, err := db.GetLink(smol)
if err != nil {
return err
}
res := db.Where(&Link{Del: del}).Delete(&link)
if res.RowsAffected < 1 {
return gorm.ErrRecordNotFound
}
return res.Error
}
type controller struct {
log *log.Logger
db DB
demo bool
url, copy string
tmpl *template.Template
}
func NewController(logger *log.Logger, db DB, demo bool, url, copy string, tmpl *template.Template) controller {
return controller{logger, db, demo, strings.TrimRight(url, "/"), copy, tmpl}
}
func (c controller) Err(rw http.ResponseWriter, r *http.Request, err error) {
if errors.Is(err, gorm.ErrRecordNotFound) {
rw.WriteHeader(http.StatusNotFound)
fmt.Fprintf(rw, "%s", err)
return
}
c.log.Println(err)
rw.WriteHeader(http.StatusInternalServerError)
fmt.Fprintf(rw, "%s", err)
}
func (c controller) ServeHTTP(rw http.ResponseWriter, r *http.Request) {
switch r.Method {
case http.MethodGet:
switch strings.TrimRight(r.URL.Path, "/") {
case "":
data := map[string]interface{}{
"URL": c.url,
"Demo": c.demo,
"Copy": c.copy,
}
if err := c.tmpl.Execute(rw, data); err != nil {
c.Err(rw, r, err)
return
}
return
case "/favicon.ico":
http.NotFound(rw, r)
return
default:
link, err := c.db.GetLink(strings.TrimLeft(r.URL.Path, "/"))
if err != nil {
c.Err(rw, r, err)
return
}
http.Redirect(rw, r, link.Big, http.StatusPermanentRedirect)
return
}
case http.MethodPost:
b, err := ioutil.ReadAll(r.Body)
if err != nil {
c.Err(rw, r, err)
return
}
u, err := url.Parse(string(b))
if err != nil {
c.Err(rw, r, err)
return
}
if u.Scheme != "http" && u.Scheme != "https" {
rw.WriteHeader(http.StatusBadRequest)
fmt.Fprintf(rw, "URL must contain scheme. E.G. missing `http://` or `https://`.")
return
}
var (
link Link
h = strings.Trim(r.URL.Path, "/")
)
if h != "" {
link, err = c.db.NewLinkWithShortLink(u, h)
} else {
link, err = c.db.NewLink(u)
}
if err != nil {
c.Err(rw, r, err)
return
}
rw.Header().Set("X-Delete-With", link.Del)
rw.WriteHeader(http.StatusFound)
fmt.Fprintf(rw, "%s/%s", c.url, link.Smol)
return
case http.MethodDelete:
b, err := ioutil.ReadAll(r.Body)
if err != nil {
c.Err(rw, r, err)
return
}
if len(b) < 1 {
rw.WriteHeader(http.StatusBadRequest)
fmt.Fprintf(rw, "Must include deletion key in DELETE body.")
return
}
var (
smol = strings.TrimSpace(strings.TrimLeft(r.URL.Path, "/"))
del = strings.TrimSpace(string(b))
)
if err := c.db.DelLink(smol, del); err != nil {
c.Err(rw, r, err)
return
}
rw.WriteHeader(http.StatusNoContent)
return
}
http.NotFound(rw, r)
}
func main() {
var (
logPrefix = "link: "
startupLogger = log.New(os.Stdout, logPrefix, 0)
applicationLogger = log.New(ioutil.Discard, logPrefix, 0)
v = flag.Bool("v", false, "verbose logging")
demo = flag.Bool("demo", false, "turn on demo mode")
port = flag.Uint("port", 8080, "port to listen on")
dbFilePath = flag.String("db", "", "sqlite database filepath: required")
url = flag.String("url", "", "service url: required")
hashSeed = flag.String("seed", "", "hash seed: required")
copy = flag.String("copy", "", "copyright information")
)
flag.Parse()
if *dbFilePath == "" || *url == "" || *hashSeed == "" {
flag.Usage()
return
}
if *v {
applicationLogger = log.New(os.Stdout, logPrefix, 0)
}
retry, err := NewRetry(3)
if err != nil {
startupLogger.Fatal(err)
return
}
db, err := NewDB(applicationLogger, *dbFilePath, *hashSeed, retry)
if err != nil {
startupLogger.Fatal(err)
return
}
tmpl, err := template.New("").Parse(indexTemplate)
if err != nil {
startupLogger.Fatal(err)
return
}
http.Handle("/", NewController(applicationLogger, db, *demo, *url, *copy, tmpl))
startupLogger.Println("listening on port", *port)
startupLogger.Fatal(http.ListenAndServe(fmt.Sprintf(":%d", *port), nil))
}