#!/usr/bin/env ruby

require 'mustache'
require 'yaml'

if STDIN.stat.size > 0
  doc = STDIN.read
  if doc =~ /^(\s*---(.*)---\s*)/m
    yaml = $2.strip
    template = doc.sub($1, '')
    
    YAML.each_document(yaml) do |data|
      puts Mustache.render(template, data)
    end
  else
    puts doc
  end
else
  puts <<-usage
Usage: cat data.yml template.mustache | mustache

Expects a single Mustache template on STDIN complete with YAML
frontmatter.

Runs template.mustache through Mustache, using the data in data.yml to
replace sections and variables. Useful when developing templates
before hooking them into your website or whatnot.

The data.yml file should start with --- on a single line and end with
--- on a single line, e.g.

    ---
    names: [ {name: chris}, {name: mark}, {name: scott} ]
    ---

The converted document will be printed on STDOUT.

You can include multiple documents in your YAML frontmatter if you
like. Then the template is evaluated once for each of them.

    ---
    name: chris
    ---
    name: mark
    ---
    name: scott
    ---
usage
end