Script for finding old code.

oldies

#! /usr/bin/env ruby
#
# Find really old code.
#
# Author: Jon-Michael Deldin
# Date:   2013-12-13
#
# Usage:
#   oldies [DIR]
#

require 'parallel'
require 'optparse'

$LONGEST_FILENAME = 45
$FMT = "%-#{$LONGEST_FILENAME + 5}s %-12s %-12s"

FileEntry = Struct.new(:filename, :oldest_line_date, :newest_line_date)

def parse_args(argv)
  options = {}

  parser = OptionParser.new do |opts|
    opts.on('--e LIST', '--exclude', 'Comma-delimited list of directories to exclude') do |exclude|
      options[:exclude] = exclude.split(/,/)
    end

    opts.on('-h', '--help', 'show this screen') do
      STDERR.puts opts
      abort
    end

    opts.on('-j PROCESSES', '--processes', 'Number of processes to run') do |j|
      options[:processes] = Integer(j)
    end
  end

  parser.parse!(argv)

  options[:dir] = argv.first || Dir.getwd

  options
end

def dir_regexp(dirs)
  return nil unless dirs
  pattern = '^(' + dirs.join('|') + ')'

  /#{pattern}/
end

def blame(dir, exclude, processes)
  pattern = dir_regexp(exclude)

  Parallel.map(Dir.glob('**/*.rb'), :in_processes => processes) { |file|
    next if pattern && file =~ pattern

    blames = `git blame #{file} 2>/dev/null`
    next unless $?.success?

    blames = blames.split(/\n/).map { |line| line[/\d{4}-\d{2}-\d{2}/] }.compact.sort

    $LONGEST_FILENAME = file.length if file.length > $LONGEST_FILENAME

    FileEntry.new(file, blames.first, blames.last)
  }.compact
end

if $0 == __FILE__
  options = parse_args(ARGV)
  dir = options.fetch(:dir)

  abort("#{dir} does not exist") unless Dir.exists?(dir)
  Dir.chdir(dir)

  entries = blame(dir, options.fetch(:exclude, []), options.fetch(:processes, 2))

  hdr = $FMT % %w(filename oldest_line newest_line)
  puts hdr, "-" * hdr.length
  entries.sort_by { |e| e.oldest_line_date }.each do |e|
    puts $FMT % [e.filename, e.oldest_line_date, e.newest_line_date]
  end
end