Module: AwsApiGatewayEventHandler

Defined in:
lib/lambda/aws_lambda_handler.rb

Constant Summary collapse

NUMBER_REGEX = 
/\A[+-]?\d+(\.[\d]+)?\z/

Class Method Summary collapse

Class Method Details

.call(event:, context:) ⇒ Object 



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# File 'lib/lambda/aws_lambda_handler.rb', line 32

def call(event:, context:)
  wrapper_params = {}

  if ENV['wrapper_name']
    # module init
    require Pathname.getwd.join(ENV['wrapper_path']).to_s
    wrapper = Object.const_get(ENV['wrapper_name'])
    mod_method = ENV['wrapper_method']

    # check arity
    if wrapper.method(mod_method).parameters != [[:keyreq, :event], [:keyreq, :context]]
      raise("#{wrapper}.#{mod_method} should accept event and context keyword arguments")
    end

    # print call info
    puts "Calling wrapper #{wrapper}.#{mod_method}"
    wrapper_result = wrapper.send(mod_method, event: event, context: context)

    if wrapper_result.is_a?(Hash)
      # block with custom status and body
      return {
        statusCode: wrapper_result[:status],
        body: JSON.generate(wrapper_result[:body])
      } if wrapper_result[:status]

      # or set params
      wrapper_params = wrapper_result

    elsif !wrapper_result
      # block if result is false/nil
      return {
        statusCode: 403,
        body: JSON.generate(forbidden: "#{wrapper}.#{mod_method}")
      } if !wrapper_result
    end
  end

  # module init
  require Pathname.getwd.join(ENV['module_path']).to_s
  mod = Object.const_get(ENV['module_name'])
  mod_method = ENV['module_method']

  # gateway def
  verb = ENV['gateway_verb']
  path = ENV['gateway_path']

  # print call info
  method_signature = mod.method(mod_method).parameters
  puts "Resolving #{verb.to_s.upcase} #{path} to #{mod}.#{mod_method} with #{method_signature}"

  # cast path parameters to numbers
  path_params = event['pathParameters'].each_with_object({}) do |(key, value), params|
    if matcher = NUMBER_REGEX.match(value)
      value = matcher[1] ? Float(value) : value.to_i
    end
    params[key] = value
  end

  # merge wrapper params
  path_params.merge!(wrapper_params)

  # call the module method
  result =
  if ['GET', 'DELETE'].include?(verb)
    mod.send(mod_method, *path_params.values)

  elsif verb == 'POST'
    payload = AwsLambdaHandler.symbolize_keys(JSON.parse(event['body']))
    method_signature.each do |arg_type, arg_name|         # [[:req, :id], [:key, :pet]]
      payload = {arg_name => payload} if arg_type == :key # scope payload to first named argument
    end

    # we can override GET to POST without payload, ruby will break if **payload is resolved from {}
    if payload.any?
      mod.send(mod_method, *path_params.values, **payload)
    else
      mod.send(mod_method, *path_params.values)
    end

  else
    raise 'Verb should be GET, POST or DELETE'
  end

  # set status and body values
  if result.nil?
    status  = 404
    body    = nil # it will print json null string
  else
    status  = result[:status] ? result[:status] : 200
    body    = result[:body] ? result[:body] : result
  end

  # return result
  return {statusCode: status, body: JSON.generate(body)}

  # print and return error
  rescue => e
    puts output = {
      statusCode: 500,
      body: JSON.generate(
        error: {
          class: e.class,
          message: e.message
        }.merge(ENV['debug'] ? {backtrace: e.backtrace.take(20)} : {})
      )
    }
    output
end