align-table

#!/usr/bin/env ruby
#
# Vertically aligns multiple columns, which are
# delimited by a user-defined regular expression,
# that are present in the input given on STDIN.
#
# For example, the following input:
#
#   short text    =            foo = hello
#   really long text = bar =     world
#   wide operator  <=>  moz   <=> again
#
# yields the following output:
#
#   short text        =  foo
#   really long text  =  bar
#   wide operator    <=> moz
#
#--
# Written in 2007 by Suraj N. Kurapati

def align_table lines, delimiter, selector, rejector, justifier
  delim_regexp = /#{delimiter}/

  # determine columns widths
  widths = Hash.new(0)

  rows = lines.map do |line|
    line.chomp!

    if line =~ selector and line !~ rejector and line =~ delim_regexp
      fields = line.split(delim_regexp)
      fields.each {|f| f.strip! }
      fields.unshift line[/\A[ \t]*/] # whitespace margin

      delims = line.scan(delim_regexp)
      delims[0..-2].each {|d| d << ' ' }
      delims[1..-1].each {|d| d.insert(0, ' ') }
      #delims.each {|d| d.insert(0, ' ') << ' ' }
      delims.unshift nil

      cols = fields.zip(delims).flatten.compact
      cols.each_with_index do |c, i|
        widths[i] = [c.length, widths[i]].max
      end
    else
      line
    end
  end

  # equalize column widths
  rows.map! do |row|
    if row.is_a? Array
      cols = []

      row.each_with_index do |col, i|
        cols[i] = col.send(justifier, widths[i])
      end

      cols.join.rstrip
    else
      row
    end
  end

  rows.join("\n")
end


if $0 == __FILE__
  require 'optparse'
  parser = OptionParser.new

  parser.on '-h', '--help', 'show this help message' do
              puts File.read(__FILE__).split(/^$/).first, nil, parser
              exit
            end

  parser.on '-d', '--delimiter REGEXP', 'input column delimiter',
            "(default: #{(delimiter = /[[:punct:]]*=[[:punct:]]*/).inspect})\n",
            String do |arg| delimiter = arg end

  parser.on '-j', '--justify METHOD', 'justify text inside columns',
            '(choices: ljust, rjust, or center)',
            "(default: #{justifier = 'center'})",
            String do |arg| justifier = arg end

  parser.on '-m', '--select REGEXP', 'only wrap lines that match REGEXP',
            "(default: #{(selector = //).inspect})",
            Regexp do |arg| selector = arg end

  parser.on '-M', '--reject REGEXP', 'do not wrap lines that match REGEXP',
            "(default: #{(rejector = nil).inspect})",
            Regexp do |arg| rejector = arg end

  parser.parse ARGV

  puts align_table(STDIN.readlines, delimiter, selector, rejector, justifier)
end