error_handler.rb

require_relative 'constants'

module Rack
  class ErrorHandler
    def initialize(app)
      @app = app
    end

    def log_error(env, error)
      error_stream = env[RACK_ERRORS]
      # Exception#full_message was introduced in Ruby 2.5+. If it's not
      # available, we fall back to the old behavior of just printing the
      # exception message.
      if error.respond_to?(:full_message)
        error_stream.puts(error.full_message)
      else
        error_stream.puts(error.message)
      end
    end

    def bad_request(error)
      [400, {}, ["Bad Request"]]
    end

    def internal_server_error(error)
      [500, {}, ["Internal Server Error"]]
    end

    def call(env)
      @app.call(env)
    rescue BadRequest => error
      log_error(env, error)
      return bad_request(error)
    rescue ScriptError, StandardError => error
      log_error(env, error)
      return internal_server_error(error)
    end
  end
end