trantor/lib/reader.go

package trantor

import (
	log "github.com/cihub/seelog"

	"io"
	"net/http"
	"strconv"
	"strings"

	"github.com/gorilla/mux"
	"github.com/meskio/epubgo"
	"gitlab.com/trantor/trantor/lib/database"
	"gitlab.com/trantor/trantor/lib/storage"
)

type chapter struct {
	Label  string
	Link   string
	Depth  int
	Active bool
	In     []bool // one level in depth
	Out    []bool // one level out depth
}

type readData struct {
	S        Status
	Book     database.Book
	Content  string
	Chapters []chapter
	Next     string
	Prev     string
	Back     string
}

func cleanHtml(html string) string {
	str := strings.Split(html, "<body")
	if len(str) < 2 {
		return html
	}
	str = strings.SplitN(str[1], ">", 2)
	if len(str) < 2 {
		return str[0]
	}

	return "<div " + str[0] + ">" + strings.Split(str[1], "</body>")[0] + "</div>"
}

func genLink(id string, base string, link string) string {
	return base + id + "/" + link
}

func cleanLink(link string) string {
	for i := 0; i < len(link); i++ {
		if link[i] == '%' {
			c, _ := strconv.ParseInt(link[i+1:i+3], 16, 0)
			link = link[:i] + string(c) + link[i+3:]
		}
	}
	return link
}

func getNextPrev(e *epubgo.Epub, file string, id string, base string) (string, string) {
	spine, err := e.Spine()
	if err != nil {
		return "", ""
	}

	prev := ""
	next := ""
	for err == nil {
		if cleanLink(spine.URL()) == file {
			break
		}
		prev = spine.URL()
		err = spine.Next()
	}
	if err != nil {
		return "", ""
	}

	if prev != "" {
		prev = genLink(id, base, prev)
	}
	if spine.Next() == nil {
		next = genLink(id, base, spine.URL())
	}
	return next, prev
}

func getChapters(e *epubgo.Epub, file string, id string, base string) []chapter {
	nav, err := e.Navigation()
	if err != nil {
		return nil
	}
	chapters := listChapters(nav, 0)

	for i, c := range chapters {
		chapters[i].Link = genLink(id, base, c.Link)
		if cleanLink(c.Link) == file {
			chapters[i].Active = true
		}
	}
	return chapters
}

func listChapters(nav *epubgo.NavigationIterator, depth int) []chapter {
	var chapters []chapter
	var err error
	for err == nil {
		var c chapter
		c.Label = nav.Title()
		c.Link = nav.URL()
		c.Depth = depth
		chapters = append(chapters, c)

		if nav.HasChildren() {
			nav.In()
			children := listChapters(nav, depth+1)
			chapters = append(chapters, children...)
			nav.Out()
		}
		err = nav.Next()
	}
	chapters[0].In = append(chapters[0].In, true)
	chapters[len(chapters)-1].Out = append(chapters[len(chapters)-1].Out, true)
	return chapters
}

func readStartHandler(h handler) {
	id := mux.Vars(h.r)["id"]
	e := openReadEpub(id, h.store)
	if e == nil {
		log.Warn("Open epub returns an empty file")
		notFound(h)
		return
	}
	defer e.Close()

	it, err := e.Spine()
	if err != nil {
		log.Warn("No spine in the epub")
		notFound(h)
		return
	}
	http.Redirect(h.w, h.r, "/read/"+id+"/"+it.URL(), http.StatusTemporaryRedirect)
}

func readHandler(h handler) {
	id := mux.Vars(h.r)["id"]
	file := mux.Vars(h.r)["file"]
	e := openReadEpub(id, h.store)
	if e == nil {
		notFound(h)
		return
	}
	defer e.Close()

	var data readData
	data.S = GetStatus(h)

	book, err := h.db.GetBookID(id)
	if err != nil {
		notFound(h)
		return
	}
	author := ""
	if len(book.Authors) > 0 {
		author = " by " + book.Authors[0]
	}
	data.S.Title = book.Title + author + " -- Read -- " + data.S.Title

	data.Book = book
	if !book.Active {
		data.Back = "/new/"
	} else {
		data.Back = "/book/" + id
	}

	data.Next, data.Prev = getNextPrev(e, file, id, "/read/")
	data.Chapters = getChapters(e, file, id, "/read/")
	data.Content = genLink(id, "/content/", file)
	h.load("read", data)
}

func openReadEpub(id string, store storage.Store) *epubgo.Epub {
	f, err := store.Get(id, epubFile)
	if err != nil {
		return nil
	}
	defer f.Close()

	info, err := f.Stat()
	if err != nil {
		return nil
	}

	e, err := epubgo.Load(f, info.Size())
	if err != nil {
		return nil
	}
	return e
}

func contentHandler(h handler) {
	vars := mux.Vars(h.r)
	id := vars["id"]
	file := vars["file"]
	if file == "" || id == "" {
		notFound(h)
		return
	}

	err := openEpubFile(h, id, file)
	if err != nil {
		notFound(h)
		return
	}
}

func openEpubFile(h handler, id string, file string) error {
	f, err := h.store.Get(id, epubFile)
	if err != nil {
		return err
	}
	defer f.Close()

	info, err := f.Stat()
	if err != nil {
		return err
	}

	e, err := epubgo.Load(f, info.Size())
	if err != nil {
		return err
	}
	defer e.Close()

	html, err := e.OpenFile(file)
	if err != nil {
		return err
	}
	defer html.Close()

	addCacheControlHeader(h.w, false)
	io.Copy(h.w, html)
	return nil
}