manual_import_migrations.rb

# usage:
#   ruby manual_import_migrations.rb ../path/to/project/db/migrate/**/*.rb

require 'optparse'
require 'fileutils'
require 'ripper'

def omit_pos(token)
  if token.size == 3 &&
      token[-1].is_a?(Array) && token[-1].size == 2 &&
      token[-1][0].is_a?(Integer) && token[-1][1].is_a?(Integer)
    token[-1] = nil
  end

  token.each do |t|
    next unless t.is_a?(Array)
    omit_pos(t)
  end
end

def sexp(str)
  s = Ripper.sexp(str)
  omit_pos(s)
  s
end

def get_migrations(dir)
  migrations = {}

  Dir[File.join(dir, '**/*')].each do |fname|
    next unless FileTest.file?(fname)

    s = sexp(File.read(fname))
    sf = s.flatten
    migrations[fname] = [s, sf, sf.size]
  end

  migrations
end

def find_migration(fname, migrations)
  s = sexp(File.read(fname))
  found = nil

  migrations.each do |fn, x|
    if s == x[0]
      found = fn
      break
    end
  end

  unless found
    sf = s.flatten
    sf_size = sf.size

    sims = migrations.map do |fn, x|
      d1 = sf - x[1]
      d2 = x[1] - sf
      [(sf_size + x[2])/(d1.size + d2.size), fn]
    end.sort_by {|ratio, fn| ratio }

    if sims.last[0] > 20
      sim = sims.last[1]
    end
  end

  [found, sim]
end

def copy_migration(src, migrate_dir, opts)
  n = File.basename(src)
  to = File.join(migrate_dir, n).sub(/\.rb\z/, '.manual_import.rb')

  if File.exists?(to)
    warn "already exists `#{to}' for `#{src}'"
  else
    FileUtils.cp(src, to,
      noop: opts[:dryrun],
      verbose: opts[:verbose])
  end
end

opts = {
  list: true,
  copy: false,
  dryrun: false,
  verbose: true,
}
OptionParser.new do |o|
  o.on('-l', '--[no-]list', 'suppress list') do |v|
    opts[:list] = v
  end
  o.on('-c', '--copy', 'copy missing migrations') do
    opts[:copy] = true
  end
  o.on('-n', '--dry-run', 'show copy instructions') do
    opts[:dryrun] = true
  end
  o.on('-q', '--quiet', 'suppress output') do
    opts[:verbose] = false
  end

  o.on_tail('-h', '--help') do
    puts o
    exit
  end
end.parse!

migrate_dir = 'db/migrate'
migrations = get_migrations(migrate_dir)
copy = []
ARGV.each do |fname|
  found, sim = find_migration(fname, migrations)

  if found
    puts "#{fname} == #{found}" if opts[:list]
  elsif sim
    puts "#{fname} =~ #{sim}" if opts[:list]
  else
    puts "#{fname}: --" if opts[:list]
    copy << fname if opts[:copy]
  end
end

copy.each do |src|
  copy_migration(src, migrate_dir, opts)
end