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ebook.go
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ebook.go
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// Copyright 2022 Hal Canary
// Use of this program is governed by the file LICENSE.
package ebook
import (
"encoding/base64"
"encoding/xml"
"fmt"
"io"
"log"
"math/rand"
"net/http"
"net/url"
"strings"
"time"
"github.com/HalCanary/facility/dom"
"github.com/HalCanary/facility/zipper"
)
// One Chapter of an Ebook.
type Chapter struct {
Title string
Url string
Content *Node
Modified time.Time
}
// Ebook content and metadata.
type EbookInfo struct {
Authors string
Comments string
Title string
Source string
Language string
Chapters []Chapter
Modified time.Time
Cover []byte
}
const bookStyle = `
div p{text-indent:2em;margin-top:0;margin-bottom:0}
div p:first-child{text-indent:0;}
table, th, td { border:2px solid #808080; padding:3px; }
table { border-collapse:collapse; margin:3px; }
ol.flat {list-style-type:none;}
ol.flat li {list-style:none; display:inline;}
ol.flat li::after {content:"]";}
ol.flat li::before {content:"[";}
div.mid {margin: 0 auto;}
div.mid p {text-indent:0;}
div.center {margin-left:auto;margin-right:auto;}
`
const conatainer_xml = xml.Header + `<container version="1.0" xmlns="urn:oasis:names:tc:opendocument:xmlns:container">
<rootfiles>
<rootfile full-path="book/content.opf" media-type="application/oebps-package+xml"/>
</rootfiles>
</container>
`
// Return the time of most recently modified chapter.
func (info EbookInfo) CalculateLastModified() time.Time {
var result time.Time = info.Modified
for _, ch := range info.Chapters {
if !ch.Modified.IsZero() && ch.Modified.After(result) {
result = ch.Modified
}
}
return result
}
func meta(name, content string) *Node {
return dom.Element("meta", dom.Attr{"name": name, "content": content})
}
func head(title, style, comment string) *Node {
return dom.Elem("head",
dom.Element("meta", dom.Attr{
"http-equiv": "Content-Type", "content": "text/html; charset=utf-8"}),
dom.Comment(comment),
meta("viewport", "width=device-width, initial-scale=1.0"),
dom.Elem("title", dom.Text(title)),
dom.Elem("style", dom.Text(style)),
)
}
func nl() *Node {
return dom.Text("\n")
}
func dataUrl(src []byte) string {
return fmt.Sprintf("data:%s;base64,%s",
http.DetectContentType(src),
base64.StdEncoding.EncodeToString(src))
}
func (info *EbookInfo) Cleanup() {
for i, chapter := range info.Chapters {
info.Chapters[i].Content = Cleanup(chapter.Content)
if chUrl, _ := url.Parse(chapter.Url); chUrl != nil {
info.Chapters[i].Content = ResolveLinks(info.Chapters[i].Content, chUrl)
}
}
}
// Write the ebook as a single HTML file.
func (info EbookInfo) WriteHtml(dst io.Writer) error {
body := dom.Elem("body", nl())
if len(info.Cover) > 0 {
dom.Append(body,
dom.Element("div", dom.Attr{"style": "text-align:center"},
nl(),
imgElem(dataUrl(info.Cover), "[COVER]"),
nl()),
nl(),
dom.Elem("hr"),
nl(),
)
}
dom.Append(body,
dom.Elem("div", nl(),
dom.Elem("h1", dom.Text(info.Title)), nl(),
dom.Elem("div", dom.Text("Author: "+info.Authors)), nl(),
dom.Elem("div",
dom.Text("Source: "),
dom.Element("a", dom.Attr{"href": info.Source}, dom.Text(info.Source)),
), nl(),
), nl(),
dom.Elem("hr"), nl(),
)
for i, chapter := range info.Chapters {
attr := dom.Attr{"class": "chapter", "id": fmt.Sprintf("ch%03d", i)}
div := dom.Elem("div",
dom.Element("h2", attr, dom.Text(chapter.Title)), nl())
if chapter.Url != "" {
dom.Append(div, dom.Comment(fmt.Sprintf("\n%s\n", chapter.Url)), nl())
}
if !chapter.Modified.IsZero() {
dom.Append(div, dom.Elem("div", dom.Elem("em", dom.Text(chapter.Modified.Format("2006-01-02")))), nl())
}
dom.Append(div, nl(), dom.Elem("hr"), nl(), chapter.Content, nl(), dom.Elem("hr"), nl())
if i+1 == len(info.Chapters) {
dom.Append(div, dom.Elem("div", link(info.Source, info.Source)), nl(), dom.Elem("hr"), nl())
}
dom.Append(body, div, dom.Text("\n\n"))
}
description := info.Source
if len(info.Comments) > 0 {
description = description + "\n\n" + info.Comments
}
var dcDateModified *dom.Node
if !info.Modified.IsZero() {
dcDateModified = meta("DC.date.modified", info.Modified.Format("2006-01-02"))
}
htmlNode := dom.Element("html", dom.Attr{"lang": info.Language}, nl(),
dom.Elem("head", nl(),
dom.Element("meta", dom.Attr{"charset": "utf-8"}), nl(),
meta("viewport", "width=device-width, initial-scale=1.0"), nl(),
dom.Elem("title", dom.Text(info.Title)), nl(),
meta("DC.title", info.Title), nl(),
meta("DC.creator.aut", info.Authors), nl(),
meta("DC.description", description), nl(),
meta("DC.source", info.Source), nl(),
meta("DC.language", info.Language), nl(),
dcDateModified, nl(),
dom.Elem("style", dom.Text(bookStyle)), nl(),
),
nl(), body, nl(),
)
err := dom.RenderHTML(htmlNode, dst)
for _, chapter := range info.Chapters {
dom.Remove(chapter.Content)
}
return err
}
// Print information about the book.
func (info EbookInfo) Print(dst io.Writer) {
fmt.Fprintf(dst, "Authors: %q\n", info.Authors)
fmt.Fprintf(dst, "Comments: %q\n", info.Comments)
fmt.Fprintf(dst, "Title: %q\n", info.Title)
fmt.Fprintf(dst, "Source: %q\n", info.Source)
fmt.Fprintf(dst, "Language: %q\n", info.Language)
fmt.Fprintf(dst, "Cover: %d bytes\n", len(info.Cover))
fmt.Fprintf(dst, "Modified: %s\n", info.Modified.Format(time.RFC3339))
fmt.Fprintf(dst, "Chapters: %d\n", len(info.Chapters))
for _, ch := range info.Chapters {
fmt.Fprintf(dst, "* Title: %q\n", ch.Title)
fmt.Fprintf(dst, " Url: %q\n", ch.Url)
fmt.Fprintf(dst, " Text: %d bytes\n", dom.TextBytes(ch.Content))
fmt.Fprintf(dst, " Mod: %s\n", ch.Modified.Format(time.RFC3339))
}
}
// Write the ebook as an Epub.
func (info EbookInfo) Write(dst io.Writer) error {
var (
uid string = randomUUID()
cover []byte
)
if len(info.Cover) > 0 {
var err error
cover, err = saveJpegWithScale(info.Cover, 400, 600)
if err != nil {
log.Printf("Cover error: %v", err)
cover = nil
}
}
zw := zipper.Make(dst)
defer zw.Close()
modTime := info.Modified
if !modTime.IsZero() {
modTime = modTime.UTC()
}
if w := zw.CreateStore("mimetype", time.Time{}); w != nil {
_, zw.Error = w.Write([]byte("application/epub+zip"))
}
if w := zw.CreateDeflate("META-INF/container.xml", modTime); w != nil {
_, zw.Error = w.Write([]byte(conatainer_xml))
}
if w := zw.CreateDeflate("book/"+"toc.ncx", modTime); w != nil {
zw.Error = makeNCX(info, uid, w)
}
if w := zw.CreateDeflate("book/"+"content.opf", modTime); w != nil {
zw.Error = makePackage(info, uid, w, len(cover) > 0)
}
if w := zw.CreateDeflate("book/"+"frontmatter.xhtml", modTime); w != nil {
zw.Error = writeFrontmatter(info, w, len(cover) > 0)
}
if w := zw.CreateDeflate("book/"+"toc.xhtml", modTime); w != nil {
zw.Error = writeToc(info, w)
}
if len(cover) > 0 {
if w := zw.CreateStore("book/"+"cover.jpg", modTime); w != nil {
_, zw.Error = w.Write(cover)
}
}
for i, chapter := range info.Chapters {
if w := zw.CreateDeflate(fmt.Sprintf("book/"+"%04d.xhtml", i), chapter.Modified); w != nil {
var churl string
if i+1 == len(info.Chapters) {
churl = chapter.Url
}
zw.Error = writeChapter(chapter, churl, info.Language, w)
}
}
return zw.Error
}
func writeFrontmatter(info EbookInfo, dst io.Writer, cover bool) error {
description := dom.Elem("div")
for _, p := range strings.Split(info.Comments, "\n\n") {
pnode := dom.Elem("p")
for i, c := range strings.Split(p, "\n\n") {
if i > 0 {
dom.Append(pnode, dom.Elem("br"))
}
dom.Append(pnode, dom.Text(c))
}
dom.Append(description, pnode)
}
var img *dom.Node
if cover {
img = dom.Element("img", dom.Attr{"src": "cover.jpg", "alt": "[COVER]"})
}
htmlNode := dom.Element("html", dom.Attr{"xmlns": "http://www.w3.org/1999/xhtml", "xml:lang": info.Language},
head(info.Title, bookStyle, ""),
dom.Elem("body",
dom.Elem("h1", dom.Text(info.Title)),
img,
dom.Elem("div", dom.Text(info.Authors)),
dom.Elem("div", dom.Text(info.Source)),
dom.Elem("div", dom.Elem("em", dom.Text(info.Modified.Format("2006-01-02")))),
description,
),
)
return dom.RenderXHTMLDoc(htmlNode, dst)
}
func writeChapter(chapter Chapter, url, lang string, dst io.Writer) error {
body := dom.Elem("body")
if chapter.Url != "" {
dom.Append(body, dom.Comment(fmt.Sprintf("\n%s\n", chapter.Url)))
}
dom.Append(body, dom.Element("h2", dom.Attr{"class": "chapter"}, dom.Text(chapter.Title)))
if !chapter.Modified.IsZero() {
dom.Append(body, dom.Elem("p", dom.Elem("em", dom.Text(chapter.Modified.Format("2006-01-02")))))
}
dom.Append(body, dom.Elem("hr"), chapter.Content, dom.Elem("hr"))
if url != "" {
dom.Append(body, dom.Elem("div", link(url, url)), dom.Elem("hr"))
}
htmlNode := dom.Element("html",
dom.Attr{"xmlns": "http://www.w3.org/1999/xhtml", "xml:lang": lang},
head(chapter.Title, bookStyle, ""),
body,
)
return dom.RenderXHTMLDoc(htmlNode, dst)
}
func writeToc(info EbookInfo, dst io.Writer) error {
links := dom.Element("ol", dom.Attr{"class": "flat"})
for i, ch := range info.Chapters {
label := fmt.Sprintf("%d. %s", i+1, ch.Title)
dom.Append(links, dom.Elem("li", link(fmt.Sprintf("%04d.xhtml", i), label)))
}
htmlNode := dom.Element("html",
dom.Attr{
"xmlns": "http://www.w3.org/1999/xhtml",
"xml:lang": info.Language,
"xmlns:epub": "http://www.idpf.org/2007/ops",
},
head(info.Title, bookStyle, ""),
dom.Elem("body",
dom.Element("nav",
dom.Attr{"epub:type": "toc", "style": "display:none;"},
dom.Elem("h2", dom.Text("Contents")),
links),
),
)
return dom.RenderXHTMLDoc(htmlNode, dst)
}
func link(url, text string) *Node {
if url == "" {
return nil
}
return dom.Element("a", dom.Attr{"href": url}, dom.Text(text))
}
func imgElem(url, alt string) *Node {
if url == "" {
return nil
}
return dom.Element("img", dom.Attr{"src": url, "alt": alt})
}
func randomUUID() string {
var v [16]byte
rand.Read(v[:])
return fmt.Sprintf("%x-%x-%x-%x-%x", v[0:4], v[4:6], v[6:8], v[8:10], v[10:16])
}