My script for downloading images I've posted to Imgur

imgur-assets-dl.go

package main

import (
  "errors"
  "flag"
  "fmt"
  "io"
  "net/http"
  "os"
  "path/filepath"
  "strings"
  "time"
)

var (
  defaultDir = "/var/www/assets.c7.se/imgur"
  defaultURL = "https://assets.c7.se/imgur/"
  defaultRaw = false
)

const (
  iImgurCom = `https://i.imgur.com/`
  firefoxUA = `Mozilla/5.0 (X11; Linux i686; rv:135.0) Gecko/20100101 Firefox/135.0`
)

type config struct {
  dir string
  url string
  src string
  img string
  raw bool
}

func (cfg config) path() string {
  return filepath.Join(cfg.dir, cfg.img)
}

func (cfg config) out() string {
  return cfg.url + cfg.img
}

func main() {
  if err := run(os.Args, os.Stdout); err != nil {
    fmt.Fprintf(os.Stderr, "❌ %s\n", err)
    os.Exit(1)
  }
}

func run(args []string, w io.Writer) error {
  cfg, err := parse(args)
  if err != nil {
    return err
  }

  client := &http.Client{
    Timeout: time.Minute,
  }

  if err := download(cfg, client); err != nil {
    return err
  }

  return output(w, cfg)
}

func request(cfg config) (*http.Request, error) {
  req, err := http.NewRequest(http.MethodGet, cfg.src, nil)
  if err != nil {
    return nil, err
  }

  req.Header.Set("User-Agent", firefoxUA)

  return req, nil
}

func download(cfg config, client *http.Client) error {
  name := cfg.path()

  if _, err := os.Stat(name); !errors.Is(err, os.ErrNotExist) {
    return fmt.Errorf("file already exists, served on %s", cfg.out())
  }

  req, err := request(cfg)
  if err != nil {
    return err
  }

  resp, err := client.Do(req)
  if err != nil {
    return err
  }
  defer resp.Body.Close()

  if resp.StatusCode != http.StatusOK {
    return fmt.Errorf("bad status: %s", resp.Status)
  }

  dst, err := os.Create(name)
  if err != nil {
    return err
  }
  defer dst.Close()

  _, err = io.Copy(dst, resp.Body)

  return err
}

func output(w io.Writer, cfg config) error {
  if cfg.raw {
    return fprintf(w, "%s\n", cfg.out())
  }

  return fprintf(w, "✅ file downloaded, served on %s\n", cfg.out())
}

func fprintf(w io.Writer, format string, a ...any) error {
  _, err := fmt.Fprintf(w, format, a...)

  return err
}

func parse(args []string) (config, error) {
  var cfg config

  flags := flag.NewFlagSet(args[0], flag.ExitOnError)

  flags.StringVar(&cfg.dir, "dir", defaultDir, "Local directory to download to")
  flags.StringVar(&cfg.url, "url", defaultURL, "URL to construct links from")
  flags.BoolVar(&cfg.raw, "raw", defaultRaw, "If to output just the link URL")

  if err := flags.Parse(args[1:]); err != nil {
    return cfg, err
  }

  cfg.src = strings.Join(flags.Args(), "")

  switch {
  case cfg.src == "":
    return cfg, fmt.Errorf("no URL provided")
  case !strings.HasPrefix(cfg.src, iImgurCom):
    return cfg, fmt.Errorf("provided source %q does not have the required prefix %q", cfg.src, iImgurCom)
  }

  cfg.img = filepath.Base(cfg.src)

  return cfg, nil
}