#!/usr/bin/env ruby
require 'paru/pandoc'

USAGE = <<~EOU
  markdown2html.rb converts a markdown file to html

  Usage:

      markdown2html.rb [input [output]]

  - If no argument is given, markdown2html converts STDIN to STDOUT
  - If one argument is given, markdown2html treats the argument as a
    path and converts it to STDOUT
  - If two arguments are given, markdown2html treats both as paths
    and converts the first path to the second
EOU

begin
  output = $stdout
  case ARGV.length
  when 0
    # Convert STDIN to STDOUT
    markdown = $stdin.read
  when 1
    # Treat only argument as path to input file
    markdown = File.read(ARGV.first)
  when 2
    # Treat first argument as input file and second as output file
    markdown = File.read(ARGV.first)
    output = File.open(ARGV.last, 'w')
  else
    warn 'Error: Too many arguments'
    warn USAGE
    exit
  end

  html = Paru::Pandoc.new do
    from 'markdown'
    to 'html5'
    standalone
    toc
    # add any pandoc option you like
  end << markdown

  output.puts html
ensure
  output.close
end