"non-destructive" injecting of file content into markdown files

Readme.md

Test

This is a test

Examples

An example:

example.js

after.js

[ 'markdown',
  [ 'header', { level: 1 }, 'Test' ],
  [ 'para',
    'This is a ',
    [ 'link',
      { href: 'test' },
      'test' ] ],
  [ 'header',
    { level: 3 },
    'Examples' ],
  [ 'para', 'An example:' ],
  [ 'para',
    [ 'inlinecode',
      'js\nconsole.log(\'Hello\')\n' ],
    '\n',
    [ 'link',
      { href: 'example.js', title: '^' },
      'example.js' ] ] ]

before.js

[ 'markdown',
  [ 'header', { level: 1 }, 'Test' ],
  [ 'para',
    'This is a ',
    [ 'link',
      { href: 'test' },
      'test' ] ],
  [ 'header',
    { level: 3 },
    'Examples' ],
  [ 'para', 'An example:' ],
  [ 'para',
    [ 'inlinecode', 'js\n' ],
    '\n',
    [ 'link',
      { href: 'example.js', title: '^' },
      'example.js' ] ] ]

example.js

console.log('Hello')

index.js

"use strict"

var fs = require('fs')
var path = require('path')
var md = require('markdown').markdown

module.exports = function(file, options) {
  var dirName = path.dirname(file)
  options = options || {gfm: true}
  var input = fs.readFileSync(file, 'utf8')
  var ast = md.parse(input)
  var injects = findInjects(ast)
  injects.forEach(function(inject) {
    var injectFile = inject.link[1].href
    var ext = path.extname(injectFile).slice(1)
    inject.code[1] = [
      ext,
      fs.readFileSync(path.resolve(dirName, injectFile), 'utf8')
    ].join('\n')
  })
  // ast is now modified but wtf do I do with it?
  console.log(ast) // ??? 
}

function findInjects(node, links) {
  links = links || []
  if (!Array.isArray(node)) return links
  var foundCode = null
  node.forEach(function(node) {
    if (!Array.isArray(node)) return
    if (foundCode) {
      if (node[0] === 'link') {
        if (node[1].title && node[1].title[0] === '^') {
          links.push({
            code: foundCode,
            link: node
          })
        }
      }
      foundCode = false
    } else {
      if (node[0] === 'inlinecode') foundCode = node
    }
    findInjects(node, links)
  })
  return links
}