Simple script to turn a webpage into an epub

main.go

package main

import (
	"log"
	"net/http"
	"net/url"
	"os"
	"path/filepath"
	"strings"

	"github.com/bmaupin/go-epub"
	"github.com/cixtor/readability"
	"golang.org/x/net/html"
)

func main() {
	if len(os.Args) != 3 {
		log.Fatalf("usage: %v URL output.epub", os.Args[0])
	}
	url := os.Args[1]
	r := readability.New()
	res, err := http.Get(url)
	if err != nil {
		log.Fatal(err)
	}
	defer res.Body.Close()
	article, err := r.Parse(res.Body, url)
	if err != nil {
		log.Fatal(err)
	}
	d := newDocument()
	err = d.setMeta(&article)
	if err != nil {
		log.Fatal(err)
	}
	err = d.replaceImages(article.Node)
	if err != nil {
		log.Fatal(err)
	}
	var body strings.Builder
	err = html.Render(&body, article.Node)
	if err != nil {
		// handle error
		log.Fatal(err)
	}
	// Create a new EPUB
	d.AddSection(body.String(), "Content", "", "")
	err = d.Write(os.Args[2])
	if err != nil {
		log.Fatal(err)
	}

}

type document struct {
	*epub.Epub
	buf         strings.Builder
	currSection string
}

func newDocument() *document {
	return &document{
		Epub:        epub.NewEpub(""),
		buf:         strings.Builder{},
		currSection: "Preamble",
	}
}

func (d *document) setMeta(a *readability.Article) error {
	d.SetTitle(a.Title)
	d.SetDescription(a.Excerpt)
	d.SetAuthor(a.Byline)
	if a.Image != "" {
		img, err := d.AddImage(a.Image, "")
		if err != nil {
			return err
		}
		d.SetCover(img, "")
	}
	return nil
}

func (d *document) replaceImages(n *html.Node) error {
	if n.Type == html.ElementNode && n.Data == "img" {
		for i, a := range n.Attr {
			if a.Key == "src" {
				// get the filname
				u, err := url.Parse(a.Val)
				if err != nil {
					return err
				}
				f := filepath.Base(u.Path)
				img, err := d.AddImage(a.Val, f)
				if err != nil {
					return err
				}
				n.Attr[i].Val = img
			}
			// remove the srcset
			if a.Key == "srcset" {
				n.Attr[i] = n.Attr[len(n.Attr)-1]        // Copy last element to index i.
				n.Attr[len(n.Attr)-1] = html.Attribute{} // Erase last element (write zero value).
				n.Attr = n.Attr[:len(n.Attr)-1]          // Truncate slice.
			}
		}
	}
	for c := n.FirstChild; c != nil; c = c.NextSibling {
		err := d.replaceImages(c)
		if err != nil {
			return err
		}
	}
	return nil
}