gistfile1.rb

require 'json'

# Parse CMD Args
template_file = ARGV.first
data_json = ARGV[1]
output_file = ARGV.last

# Read Files
data = JSON.parse open(data_json).read()
template = open(template_file).read()


# Provide dot syntax for hashes
def dot_access(hash, route)
  route.split('.').reduce(hash){|hash, key| hash[key]}
end

# returns the MatchData Object for the closing tag of the first directive
def find_closing_tag(template)
  matches = template.to_enum(:scan, /<\* ([A-Z]+)(.*?|.?) \*>/m).map{Regexp.last_match}

# iterate through the matches and look out for enclosed directives
  count = 0
  for match in matches
    count += 1 if match[1] == matches.first[1]
    count -= 1 if match[1] == "END" + matches.first[1]
    return match if count == 0
  end
end

# recursive parsing
def parse_template(template, context)
  return_string = ""

  # iterate through the string and find template directives
  while match = template.match(/<\* (.*?) \*>/m)

    # match behavior on tag name
    case match[1]
    when /EACH ([a-z\d\.]*) ([a-z\d]*)/

      # add non-tag template part
      return_string += match.pre_match

      # find the corresponding closing tag
      closing_tag = find_closing_tag(template)
      
      # loop through the appropriate object and parse recursively
      for obj in dot_access(context, $1)
        new_context = context.dup
        new_context[$2] = obj
        return_string += parse_template(template.slice(match.end(0)..find_closing_tag(template).begin(0)-1), new_context)
      end

      # remove directive part of template
      template.slice!(0..closing_tag.end(0)-1)
    
    else
      # simple value insert
      return_string += match.pre_match
      return_string += dot_access(context, match[1])
      template = match.post_match
    end
  end

  # append the rest of the template
  return_string += template
  return return_string
end

# write to file
File.open(output_file, 'w') {|f| f.write(parse_template(template, data)) }