jsonpipe in ruby

jsonpipe.rb

#!/usr/local/bin/ruby

require 'yajl'
require 'awesome_print'
require 'optparse'

module JsonPipe
  DEFAULTS = {in: $stdin, out: $stdout, sep: '/', v_sep: "\t", no_root: false}

  class Pipe
    def initialize(obj, opts = {})
      opts = DEFAULTS.merge(opts)

      @obj     = obj
      @out     = opts[:out]
      @sep     = opts[:sep]
      @v_sep   = opts[:v_sep]
      @no_root = opts[:no_root]

      @context = []
    end

    def print
      print_obj(@obj)
    end

    private

    def print_obj(json)
      @out.print @sep unless @no_root
      @out.print @context.join(@sep)
      @out.print @v_sep unless @context.empty? && @no_root
      case json
      when Hash
        @out.puts "{}"
        json.each do |k, v|
          @context.push k
          print_obj(v)
          @context.pop
        end
      when Array
        @out.puts "[]"
        json.each_with_index do |v, idx|
          @context.push idx
          print_obj(v)
          @context.pop
        end
      else
        Yajl::Encoder.encode(json, @out)
        @out.puts
      end
    end
  end

  class Unpipe
    def initialize(opts = {})
      opts = DEFAULTS.merge(opts)

      @sep     = Regexp.escape(opts[:sep])
      @v_sep   = Regexp.escape(opts[:v_sep])
      @no_root = opts[:no_root]
      @out     = opts[:out]
      @in      = opts[:in]
    end

    def parse
      obj = nil
      @in.each do |line|
        line.chomp!

        if @no_root && !obj
          pointer = nil
          value = line
        else
          m = /^(.+?)#@v_sep([^#@v_sep]+)$/.match(line)
          raise "Parsing error #{@in.lineno}: #{line}" unless m
          elm, value = m.captures
          parts = elm.split(/#@sep/).map do |p|
            p =~ /^\d+$/ ? p.to_i : p
          end
          *parents, child = parts
          parents.shift unless @no_root
          pointer = parents.inject(obj){|o, p| o[p]}
        end

        value = Yajl::Parser.parse value
        if pointer
          pointer[child] = value
        else
          obj = value
        end
      end
      Yajl::Encoder.encode(obj, @out)
      @out.puts
    end
  end
end



if __FILE__ == $PROGRAM_NAME
  $format = :simple
  $decode = false
  options = {}
  opt = OptionParser.new do |opts|
    opts.banner = "Usage: #$0 [options]"
    opts.separator ""
    opts.separator "Options:"
    opts.on('-h', '--help', 'Show help message') do
      puts opts
      exit
    end
    opts.on('-f', '--format [TYPE]', [:simple, :awesome],  "Select format simple(default) or awesome") do |f|
      $format = f
    end
    opts.separator 'The following options are valid for simple format only:'
    opts.on('-s', '--separator SEP', 'Specify path separator') do |sep|
      options[:sep] = eval "\"#{sep}\""
    end
    opts.on('-v', '--value-separator SEP', 'Specify value separator') do |sep|
      options[:v_sep] = eval "\"#{sep}\""
    end
    opts.on('-r' ,'--no-root', "Don't print root path") do
      options[:no_root] = true
    end
    opts.on('-u', '--unpipe', "Decode json from the jsonpipe output") do
      $decode = true
    end
  end

  begin
    opt.parse!

    if $decode
      JsonPipe::Unpipe.new(options).parse
    else
      parser = Yajl::Parser.new
      obj = parser.parse($stdin)

      case $format
      when :simple
        JsonPipe::Pipe.new(obj, options).print
      when :awesome
        ap obj
      end
    end
  rescue OptionParser::MissingArgument
    $stderr.puts $!.message
    puts opt
    exit -1
  rescue StandardError
    $stderr.puts $!.message
    exit -1
  rescue Exception
    exit -1
  end
end