api.js

const express = require('express')
const path = require('path')
const fs = require('fs')
const crypto = require('crypto')
const cache = require('memory-cache')
const convert = require('xml-js')

const lib = require('./lib.js')

// Settings
const DIR = 'letters'
const app = express()
const PORT = 3000

function loadDocAsJson (filepath) {
  /*
   * TODO: Maybe check if XML is valid?
   * Reads XML file and transforms it to JSON
   */

  let data = {}

  try {
    let xml = fs.readFileSync(filepath, 'utf8')
    data = convert.xml2js(xml, {compact: true})
  } catch (err) {
    console.log('> Error while loading ' + filepath)
    console.log(err)
    return data
  }

  return data
}

function inCacheFormat (docname, docobj) {
  /*
   * Create some metadata for document cache representation
   */

  let hash = crypto.createHmac('sha256', JSON.stringify(docobj)).digest('hex')

  return {
    link: '/letters/' + docname.slice(0, -4),
    collection: docobj.TEI.teiHeader.fileDesc.titleStmt.collection._text,
    url: '/api/letters/' + docname.slice(0, -4),
    name: docname.replace(/_/g, ' '),
    hash: hash,
    object: docobj
  }
}

function loadDocumentsToCache (dir) {
  /*
   * Load all documents to cache
   */

  try {
    var documents = fs.readdirSync(dir)
  } catch (err) {
    console.log('> Error while loading files from ' + dir)
    console.log(err)
  }

  for (let docname of documents) {
    // We just want the XML documents
    if (!docname.endsWith('.xml')) {
      continue
    }
    let docjs = loadDocAsJson(path.join(dir, docname))
    cache.put(docname, inCacheFormat(docname, docjs))