module Appsignal
  class Aggregator
    module Middleware
      class ActiveRecordSanitizer
        TARGET_EVENT_NAME = 'sql.active_record'.freeze

        SINGLE_QUOTE       = /\\'/.freeze
        DOUBLE_QUOTE       = /\\"/.freeze
        QUOTED_DATA        = /(?:"[^"]+"|'[^']+')/.freeze
        SINGLE_QUOTED_DATA = /(?:'[^']+')/.freeze
        IN_ARRAY           = /(IN \()[^\)]+(\))/.freeze
        NUMERIC_DATA       = /\b\d+\b/.freeze

        SANITIZED_VALUE = '\1?\2'.freeze

        def call(event)
          if event.name == TARGET_EVENT_NAME
            unless schema_query?(event) || adapter_uses_prepared_statements?
              query_string = event.payload[:sql]
              if query_string
                if adapter_uses_double_quoted_table_names?
                  query_string.gsub!(SINGLE_QUOTE, SANITIZED_VALUE)
                  query_string.gsub!(SINGLE_QUOTED_DATA, SANITIZED_VALUE)
                else
                  query_string.gsub!(SINGLE_QUOTE, SANITIZED_VALUE)
                  query_string.gsub!(DOUBLE_QUOTE, SANITIZED_VALUE)
                  query_string.gsub!(QUOTED_DATA, SANITIZED_VALUE)
                end
                query_string.gsub!(IN_ARRAY, SANITIZED_VALUE)
                query_string.gsub!(NUMERIC_DATA, SANITIZED_VALUE)
              end
            end
            event.payload.delete(:connection_id)
            event.payload.delete(:binds)
          end
          yield
        end

        def schema_query?(event)
          event.payload[:name] == 'SCHEMA'
        end

        def connection_config
          @connection_config ||= if ActiveRecord::Base.respond_to?(:connection_config)
            ActiveRecord::Base.connection_config
          else
            ActiveRecord::Base.connection_pool.spec.config
          end
        end

        def adapter_uses_double_quoted_table_names?
          adapter = connection_config[:adapter]
          adapter =~ /postgres/ || adapter =~ /sqlite/
        end

        def adapter_uses_prepared_statements?
          return false unless adapter_uses_double_quoted_table_names?
          return true if connection_config[:prepared_statements].nil?
          connection_config[:prepared_statements]
        end
      end
    end
  end
end