update_gem

#!/usr/bin/env ruby

class GemUpdater
  attr_reader :gem_name

  def initialize(gem_name)
    @gem_name = gem_name
  end

  def update
    log "Starting the update process for gem #{gem_name}"

    abort("You need the bundler gem before continuing (run: [sudo] gem install bundler)") if !bundler_gem_installed?

    create_new_git_branch
    update_gem
    commit_and_push

    create_pr if hub_installed?

    log("All done")
  end

  private

  def update_gem
    run("bundle update #{gem_name}")
  end

  # If there's no bundler gem, the command still returns a newline.
  def bundler_gem_installed?
    !`gem list "^bundler$"`.chomp.empty?
  end

  # Time is appended to avoid branch name clashes
  def create_new_git_branch
    run("git checkout -b update_#{gem_name}_gem_#{Time.now.to_i}")
  end

  def commit_and_push
    git_add_gemfile_lock
    git_commit
    git_push
  end

  def git_add_gemfile_lock
    run("git add Gemfile.lock")
  end

  def git_commit(message=nil)
    message ||= "Updated #{gem_name}"
    run("git commit -m '#{message}'")
  end

  def git_push
    run("git push")
  end

  def hub_installed?
    `hub`
    true
  rescue Errno::ENOENT
    false
  end

  def create_pr(message=nil)
    message ||= "Updated #{gem_name}"
    puts run("hub pull-request -m '#{message}'")

    # Delete branch after successful PR creation?
  end

  def log(msg)
    puts msg
  end

  def run(command)
    log("Running:  #{command}")
    `#{command}`
  end

end

GemUpdater.new(ARGV[0]).update