latex_parser.rb

#!/usr/bin/env ruby
require 'tempfile'
require 'open3'

INF = 10000000000 

def ap(file)
  File.absolute_path file
end

def convert_file(text)
  infile = Tempfile.new("latex")
  outfile = Tempfile.new("latex")
  errfile = Tempfile.new("latex")
  output = []
  while text =~ /\(\$[^$].*[^$]\$\)/m or text =~ /\[\$[^$].*[^$]\$\]/m
    round_index = (text.index /\(\$[^$]/) || INF
    square_index = (text.index /\[\$[^$]/) || INF
    if round_index < square_index then
      c = text[text.index(/\(\$[^$]/) + 2]
      first_bit, middle = text.split(/\(\$[^$]/, 2)
      middle = c + middle
      c = middle[middle.index(/[^$]\$\)/)]
      middle, last_bit = middle.split(/[^$]\$\)/, 2)
      middle += c
      flags = ""
    else
      c = text[text.index(/\[\$[^$]/) + 2]
      first_bit, middle = text.split(/\[\$[^$]/, 2)
      middle = c + middle
      c = middle[middle.index(/[^$]\$\]/)]
      middle, last_bit = middle.split(/[^$]\$\]/, 2)
      middle += c
      flags = "-d"
    end

    File.write(infile, middle)

    converted = ""
    if system("katex #{flags} -i #{ap infile} -o #{ap outfile} 2> #{ap errfile}")
      converted = File.read outfile
      output << first_bit << converted
      text = last_bit
    else
      puts middle
      STDERR.puts (File.read errfile)
      exit 1
    end
  end
  output << text
  output.join
    .gsub("($$", "($")
    .gsub("$$)", "$)")
    .gsub("[$$", "[$")
    .gsub("$$]", "$]")
end

Dir.glob("*.md").each do |filepath|
  txt = convert_file(File.read(filepath))
  File.write(File.join("hugo-site/content", filepath), txt)
end