convert_md_to_text.rb

out_filename_suffix = '.text'
conversions = [
  { from: '  ', to: '　' },
  { from: /^## (.*)/, to: "\\1\n------------------------------" },
  { from: /^### /, to: '■ ' },
]

in_filename = ARGV.shift
out_filename = in_filename + out_filename_suffix
buf = ''

File.open(in_filename, 'r') do |f|
  buf = f.read
  conversions.each { |c| buf.gsub!(c[:from], c[:to]) }
end

File.open(out_filename, 'w') do |f|
  f.write(buf)
end