Bootstrap 3 -> 4 simplistic migration script (Rails based paths and file types)

Bootstrap4migration.md

1. Run against code base to make the most labor intensive work
2. Totally redo navigation from scratch
3. maybe add -xs stuff, like col-xs- or btn-xs, thats missing from BS4

migration.rb

RULES = {
  '.panel-heading' => '.card-header',
  '.panel.panel-default' => '.card',
  '.panel-title' => '.card-title',
  '.panel-body' => '.card-body',
  '.panel-footer' => '.card-footer',
  '.panel-primary' => '.card.bg-primary.text-white',
  '.panel-success' => '.card.bg-success.text-white',
  '.panel-info' => '.card.text-white.bg-info',
  '.panel-warning' => '.card.bg-warning',
  '.panel-danger' => '.card.bg-danger.text-white',
  '.pull-right' => '.float-right',
  '.pull-left' => '.float-left',
  '.hidden-xs' => '.d-none',
  '.hidden-sm' => '.d-sm-none',
  '.hidden-md' => '.d-md-none',
  '.hidden-lg' => '.d-lg-none',
  '.visible-xs' => '.d-block.d-sm-none',
  '.visible-sm' => '.d-none.d-sm-block.d-md-none',
  '.visible-md' => '.d-none.d-md-block.d-lg-none',
  '.visible-lg' => '.d-none.d-lg-block.d-xl-none',
  '.badge' => '.badge.badge-pill',
  '.label' => '.badge',
  '.col-xs-' => 'col-',
  '.table-condensed' => '.table-sm',
  '.well' => '.card.card-body',
  '.thumbnail' =>       '.card.card-body',
  '.btn-default' =>     '.btn-secondary',
  '.img-responsive' =>  '.img-fluid',
  '.img-circle' => '.rounded-circle',
  '.img-rounded' =>     '.rounded',
}.freeze

paths = [
  'app/views/**/*.slim',
  'app/views/**/*.haml',
  'app/views/**/*.erb',
  'app/assets/**/*.scss',
  'app/assets/**/*.js',
  'app/assets/**/*.sass',
  'app/assets/**/*.coffee',
]
uses_dot_syntax = /slim|haml|css|sass/
Dir[*paths].each do |view_file|
  input = File.read(view_file)
  work = input.dup
  RULES.each do |from, to|
    if view_file[uses_dot_syntax]
      unless view_file[to]
        work.gsub!(from, to)
      end
    else
      work.gsub!(from.sub('.', ''), to.gsub('.', ' ').strip)
    end
  end
  if work != input
    puts "migrated #{view_file}"
    File.write(view_file, work)
  end
end