WIP - Syntax Parser

app/lib/exceptions/invalid_environment_variable.rb

@@ -0,0 +1,4 @@
+# frozen_string_literal: true
+
+class InvalidEnvironmentVariable < StandardError
+end

app/lib/exceptions/invalid_payload_key.rb

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+# frozen_string_literal: true
+
+class InvalidPayloadKey < StandardError
+end

app/lib/json_web_token.rb

@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative './exceptions/jwt_expired_token'
+require_relative './exceptions/jwt/expired_web_token'
 
 class JsonWebToken
   SECRET_KEY = Rails.application.secrets.secret_key_base.to_s

app/lib/request_deconstructor.rb

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+# frozen_string_literal: true
+
+require_relative './exceptions'
+
+# TODO: Build
+#
+# Deconstructs the request & response from us & service B. Replaces
+# any headers that contain environment variables with placeholder values
+# to prevent data leakage.
+class RequestDeconstructor
+end

app/lib/request_handler.rb

@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+require_relative './exceptions'
+
+# TODO: Build or delete
+#
+# Thinking some EventWorker functionality will be moved into here.
+# SyntaxParser & RequestDeconstructor would be attributes and aid
+# in setting up & properly saving requests/responses.
+class RequestHandler
+end

app/lib/syntax_parser.rb

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+# frozen_string_literal: true
+
+require_relative './exceptions/invalid_environment_variable'
+require_relative './exceptions/invalid_payload_key'
+
+# This class parses user defined headers & payloads into the values we expect
+# to send to the outbound service.
+#
+# Example:
+#
+# ```ruby
+# custom_user_payload = {
+#   'hello' => '$payload.top_level_key',
+#   'environment_variable' => '$env.API_KEY',
+#   'did_you' => '$payload.nested_key_1.nested_key_2.nested_key_3'
+# }
+#
+# incoming_request_from_service_a = {
+#   'top_level_key' => 'world',
+#   'nested_key_1' => {
+#     'nested_key_2' => {
+#       'nested_key_3' => 'make it!'
+#     }
+#   }
+# }
+#
+# bridge = Bridge.where(user_id: @current_user.id)
+#
+# syntax_parser = SyntaxParser.new(bridge)
+#
+# syntax_parser.parse_payload(
+#  incoming_request_from_service_a,
+#  custom_user_payload
+# ) # => Hash(String, String) where $payload & $env are replaced with their respective values
+#
+# syntax_parser.parse_headers # => Array(Hash(String, String)) where $env is
+# replaced with decrypted environment variable value
+# ```
+class SyntaxParser
+  # Set bridge headers & env's.
+  #
+  # @param [Bridge] bridge
+  def initialize(bridge)
+    @headers = bridge.headers
+    @environment_variables = bridge.environment_variables
+  end
+
+  # Parses the user's custom payload replacing any values containing `$env`
+  # or `$payload` with the respective value
+  #
+  # @param [Hash(String, String)] incoming_request
+  # @param [Hash(String, String)] user_data
+  #
+  # @return [Hash(String, String)]
+  def parse_payload(incoming_request, user_data)
+    @incoming_request = incoming_request
+    @user_data = user_data
+
+    parse_payload!
+
+    outbound_request
+  end
+
+  # Parses the user's headers replacing any values containing `$env`
+  # with the decrypted environment variable value
+  #
+  # @return [Array(Hash(String, String))]
+  def parse_headers
+    parse_headers!
+
+    outbound_headers
+  end
+
+  private
+
+  attr_reader :user_data,        # User defined payload (bridge.data['payload'])
+              :outbound_request, # Parsed request returned from `parse_payload`
+              :incoming_request, # Inbound request from service A
+              :outbound_headers, # Parsed headers returned from `parse_headers`
+              :environment_variables,
+              :headers
+
+  # Iterates through user defined payload and parse values containing `$env` or `$payload`
+  # Reinitializes & mutates `outbound_request`
+  def parse_payload!
+    @outbound_request = {} # Reset
+
+    user_data.each do |key, val|
+      outbound_request[key] = if val.include?('$env')
+                                fetch_environment_variable(val)
+                              elsif val.include?('$payload')
+                                fetch_payload_data(val)
+                              else
+                                val
+                              end
+    end
+  end
+
+  # Iterates through user defined payload and parse values containing `$env`
+  # Reinitializes & mutates `outbound_headers`
+  def parse_headers!
+    @outbound_headers = [] # Reset
+    headers.each do |header|
+      parsed_header = {}
+      parsed_header[header.key] = if header.value.include?('$env')
+                                    fetch_environment_variable(header.value)
+                                  else
+                                    header.value
+                                  end
+
+      outbound_headers << parsed_header
+    end
+  end
+
+  def fetch_environment_variable(value)
+    key = value.split('.').last
+    environment_variable = environment_variables.where(key: key)
+    raise InvalidEnvironmentVariable unless environment_variable
+
+    environment_variable.decrypt
+  end
+
+  def fetch_payload_data(value)
+    values = value.split('.')
+    data = incoming_request # Set data to the incoming request
+
+    values.each_with_index do |val, idx|
+      next if idx.zero? # skip the $payload
+
+      data = data[val] # dig deeper into the request on each iteration
+      raise InvalidPayloadKey if data.nil?
+    end
+
+    data
+  end
+end