@ocelot-consulting/hummus-toc/index.js

An extension for HummusJS to add Table of Contents (including bookmarks).

const hummus = require('hummus')
const writeOutline = require('./src/writeOutline')
const addTOCPages = require('./src/addTOCPages')
const countPages = require('./src/countPages')
const countOutline = require('./src/countOutline')
const getTOCText = require('./src/getTOCText')
const translatePageNumbers = require('./src/translatePageNumbers')
const writeLinks = require('./src/writeLinks')

module.exports = (inFile, outFile, origOutline, font = null) => {
  // Start new PDF to contain TOC pages only
  const newPDFWriter = hummus.createWriter(outFile)
  const outlineSize = countOutline(origOutline)
  const howManyPages = countPages(outlineSize)
  const tocText = getTOCText(origOutline, howManyPages)
  const tocPageSize = addTOCPages(newPDFWriter, tocText, font)
  newPDFWriter.appendPDFPagesFromPDF(inFile)
  newPDFWriter.end()
  // End TOC PDF

  // Start final PDF containing bookmarks as well as TOC pages
  const mergingWriter = hummus.createWriterToModify(outFile)
  const ctx = mergingWriter.getObjectsContext()
  const events = mergingWriter.getEvents()
  const copyCtx = mergingWriter.createPDFCopyingContextForModifiedFile()
  const parser = copyCtx.getSourceDocumentParser()

  // translate numbers from index to PDF object IDs
  const translatedOutline = origOutline.map(childOutline => translatePageNumbers(parser, childOutline, howManyPages))

  // write bookmarks
  const outline = writeOutline(ctx, translatedOutline)

  // create link annotations for TOC to locations in file
  for (let i = 0; i < howManyPages; i++) {
    writeLinks(ctx, copyCtx, parser, i, tocText, howManyPages, tocPageSize)
  }

  // before writer closes, add outline to PDF
  events.on('OnCatalogWrite', e => {
    let d = e.catalogDictionaryContext
    if (outline !== null) {
      d.writeKey('Outlines')
        .writeObjectReferenceValue(outline)
        .writeKey('PageMode')
        .writeNameValue('UseOutlines')
    }
  })

  // force update, in case it is necessary
  mergingWriter.requireCatalogUpdate()
  mergingWriter.end()
  // End Final PDF
}