karma.rake

require 'pry'

namespace :karma  do
  task :start => :environment do
    with_tmp_config :start
  end

  task :run => :environment do
    exit with_tmp_config :start, "--single-run"
  end

  private

  def with_tmp_config(command, args = nil)
    # by default karma looks for a file name "karma.conf.js" so let's not reinvent the wheel here
    File.open(Rails.root.join('karma.conf.js'), 'w') do |f|
      f.write unit_js(application_spec_files)
      f.flush
      # karma.conf.js should be in root directory that the command is run in.
      # supplying the file path may work locally, but was giving me issues on 
      # a remote builder
      system "./node_modules/karma/bin/karma #{command} #{args}"
    end
  end

  def application_spec_files
    Rails.application.assets.each_file.select { |pathname| pathname.match(/spec\/javascripts\/app/) }
  end

  def unit_js(files)
    unit_js = File.open('spec/javascripts/karma/config/unit.js', 'r').read
    unit_js.gsub "APPLICATION_SPEC", "\"#{files.join("\",\n\"")}\""
  end
end