kepub.go

package quarto

import (
	"context"
	"regexp"
)

var (
	xhtmlRe = regexp.MustCompile(`(?i)\.x?html?$`)
	navRe   = regexp.MustCompile(`epub:type=["']toc["']`)
)

// ToKepub converts a standard EPUB into a Kobo kepub in memory. It's the
// equivalent of running kepubify, with no external binary required.
//
// Every content document is rewritten with Kobo reading-location spans and
// the book-columns/book-inner wrappers. The navigation document is left
// untouched. The returned bytes should be written with a .kepub.epub
// extension so Kobo devices recognise the enhanced format.
func ToKepub(data []byte) ([]byte, error) {
	entries, err := unzipEpub(data)
	if err != nil {
		return nil, err
	}

	files := make([]fileEntry, 0, len(entries))
	for _, entry := range entries {
		if entry.path == "mimetype" {
			continue // re-added (stored, first) by zipEpub
		}
		if xhtmlRe.MatchString(entry.path) {
			// Skip the navigation document; Kobo builds its TOC from it
			// directly.
			if !navRe.Match(entry.data) {
				entry.data = []byte(kepubifyXhtml(string(entry.data)))
			}
		}
		files = append(files, entry)
	}

	return zipEpub(files)
}

// GenerateKepub is a convenience that builds an EPUB3 from in and converts it
// to a Kobo kepub in one call (equivalent to ToKepub(Generate(ctx, in))). It
// is the common path for callers targeting Kobo devices; use Generate and
// ToKepub separately when you need the intermediate EPUB3.
func GenerateKepub(ctx context.Context, in Input) ([]byte, error) {
	epub, err := Generate(ctx, in)
	if err != nil {
		return nil, err
	}
	return ToKepub(epub)
}