rack middleware to catch exceptions

except_catcher

module Rack
  class ExceptCatcher
    def initialize(app, mailer)
      @app = app
      @mailer = mailer
      @ignore = [404]
      @hash_blacklist = %w(rack.session.options)
    end

    def call(env)
      @env = env
      begin
        @status, @headers, @response = @app.call(@env)
      rescue Exception => e
        send_email(build_hash(e, @env))
        raise
      end

      if framework_exception
        send_email(build_hash(framework_exception, @env))
      end

      [@status, @headers, @response]
    end

    def framework_exception
      @env['sinatra.error']
    end

    def build_hash(e, env)
      hash = {
        name: e.to_s,
        timestamp: Time.now,
        backtrace: e.backtrace,
        backtrace_summary: e.backtrace[0..3],
        status: @status,
        env: build_env
      } 
    end

    def build_env
      env = []
      @env.each do |key, value|
        next if @hash_blacklist.include?(key)
        env << {'key' => key.to_s, 'value' => value.to_s}
      end
      env
    end

    def ignore_status(status)
      @ignore.include?(status)
    end

    def send_email(hash)
      hash.merge!({
        to: 'someemail'
      })
      @mailer.mail(hash) unless ignore_status(hash[:status])
    end
  end
end