table_format - a ascii table formatter (nc) (tabs→spaces)

# -*- coding: utf-8 -*-
require 'active_support/core_ext/object/blank'

module Helpers
  # Formats a supplied array into a list or table.
  # @author Mark Seymour ('Azure') (mark.seymour.ns@gmail.com)
  #
  # @param [Array] The source array.
  # @param [Hash] params Options for generating the table.
  # @option params [String] :splitchars ('\t') Characters to split each individual item on.
  # @option params [Regexp] :regexp (nil) A Regexp to split each individual item on. If one is supplied, then :splitchars is ignored.
  # @option params [Symbol] :justify (:left) Changes the justification of table items., `:left` or `:right`
  # @option params [Array] :headers ([]) Sets the names for the table column headers. If left unset, no headers will be generated.
  # @option params [Integer] :gutter (4) Sets the gutter size between columns and optionally the left gutter.
  # @option params [Boolean] :left_gutter (false) Generates a gutter on the left side of the generated table, equal to the same length as column gutters.
  # @todo Have :justify be set on individual columns.
  # @todo Have the ability to output either an array or string (params[:array]?)
  # @return [String] The formatted string with line endings.
  def Helpers.table_format array, params={}
    params = {
      splitchars: "\t",
      regexp: nil,
      justify: :left, # :left, :right
      headers: [], # ary (ex: ["a","b","c"])
      gutter: 4,
      left_gutter: false
    }.merge!(params)

    source = array.dup # We cannot be altering our original object now, can we?

    # We use the str.tr method if our regexp param is nil.
    # Otherwise, we just use regexp.
    source.map! {|e| params[:regexp].nil? ? e.tr(params[:splitchars], "\t").split("\t") : e.match(params[:regexp])[1..-1].map {|e| e.nil? ? "" : e; } }

    # calculating the maximum length of each column
    column_lengths = []
    source.dup.unshift(params[:headers]).each {|e|
      e.each_with_index {|item,index|
        column_lengths[index] = [] if column_lengths[index].blank?
        column_lengths[index] << item.size
      }
    }
    column_lengths.map! {|e| e.sort.last }

    data = []

    # Generating table headers
    if !params[:headers].blank?
      # Generating the headers, separators, etc.
      s_header = []
      s_separator = s_header.dup
      params[:headers].each_with_index {|e,i|
        s_header << "%#{"-" if params[:justify] == :left}#{column_lengths[i]}s" % e.to_s
        s_separator << "-"*column_lengths[i]
      }
      data << s_header.join(" "*params[:gutter]) << s_separator.join(" "*params[:gutter])
    end

    # Generating formatted table rows
    source.each {|e|
      line = []
      e.each_with_index {|item,index|
        line << "%#{"-" if params[:justify] == :left}#{column_lengths[index]}s" % item.to_s
      }
      data << line.join(" "*params[:gutter])
    }

    # Adding a gutter to the left side
    if params[:left_gutter] === true then data.map! {|e| " "*params[:gutter] + e } end

    data.join("\n")
  end
end