Flickr 短縮 URL

https://www.flickr.com/photos/spiegel/52462249619

package main

import (
    "flag"
    "fmt"
    "net/url"
    "os"
    "strings"

    "github.com/itchyny/base58-go"
)

func FlickrShortURL(s string) string {
    u, err := url.Parse(s)
    if err != nil {
        return s
    }
    if !strings.HasSuffix(u.Hostname(), "flickr.com") {
        return s
    }
    var photoId string
    elms := strings.Split(strings.TrimSuffix(u.EscapedPath(), "/"), "/")[1:]
    if len(elms) == 3 && strings.EqualFold(elms[0], "photos") {
        photoId = elms[2]
    }
    if len(photoId) == 0 || !isDigitString(photoId) {
        return s
    }
    b, err := base58.FlickrEncoding.Encode([]byte(photoId))
    if err != nil {
        return s
    }
    return "https://flic.kr/p/" + string(b)
}

func isDigitString(s string) bool {
    return strings.IndexFunc(s, func(c rune) bool {
        return c < '0' || '9' < c
    }) < 0
}

func main() {
    flag.Parse()
    args := flag.Args()
    if len(args) == 0 {
        fmt.Fprintln(os.Stderr, os.ErrInvalid)
        return
    }
    fmt.Println(FlickrShortURL(args[0]))
}

$ go run sample.go https://www.flickr.com/photos/spiegel/52462249619/
https://flic.kr/p/2nVUK4a