# encoding: utf-8

require 'one_apm/configuration'
require 'yaml'
require 'erb'

module OneApm
  module Configuration
    class YamlSource < OneApm::Support::DottedHash

      attr_accessor :file_path

      def initialize(path, env)
        config = {}

        begin
          @file_path = validate_config_file_path(path)
          return unless @file_path

          OneApm::Agent.logger.info("Reading configuration from #{path} (#{Dir.pwd})")
          raw_file = File.read(@file_path)
          erb_file = process_erb(raw_file)
          config   = process_yaml(erb_file, env, config, @file_path)
        rescue ScriptError, StandardError => e
          ::OneApm::Agent.logger.error("Failed to read or parse configuration file at #{path}", e)
        end

        substitute_transaction_threshold(config)
        booleanify_values(config, 'agent_enabled', 'enabled', 'monitor_daemons')

        super(config, true)
      end

      protected

      def validate_config_file_path(path)
        expanded_path = File.expand_path(path)

        if path.empty? || !File.exists?(expanded_path)
          warn_missing_config_file(expanded_path)
          return
        end

        expanded_path
      end

      def warn_missing_config_file(path)
        based_on        = 'unknown'
        source          = ::OneApm::Agent.config.source(:config_path)
        candidate_paths = [path]

        case source
        when DefaultSource
          based_on = 'defaults'
          candidate_paths = OneApm::Agent.config[:config_search_paths].map do |p|
            File.expand_path(p)
          end
        when EnvironmentSource
          based_on = 'environment variable'
        when ManualSource
          based_on = 'API call'
        end

        OneApm::Agent.logger.warn(
          "No configuration file found. Working directory = #{Dir.pwd}",
          "Looked in these locations (based on #{based_on}): #{candidate_paths.join(", ")}"
        )
      end

      def process_erb(file)
        begin
          # Exclude lines that are commented out so failing Ruby code in an
          # ERB template commented at the YML level is fine. Leave the line,
          # though, so ERB line numbers remain correct.
          file.gsub!(/^\s*#.*$/, '#')

          # Next two are for populating the oneapm.yml via erb binding, necessary
          # when using the default oneapm.yml file
          generated_for_user = ''
          license_key = ''

          ERB.new(file).result(binding)
        rescue ScriptError, StandardError => e
          ::OneApm::Agent.logger.error("Failed ERB processing configuration file. This is typically caused by a Ruby error in <% %> templating blocks in your oneapm.yml file.", e)
          nil
        end
      end

      def process_yaml(file, env, config, path)
        if file
          confighash = with_yaml_engine { YAML.load(file) }
          ::OneApm::Agent.logger.error("Config file at #{path} doesn't include a '#{env}' section!") unless confighash.key?(env)

          config = confighash[env] || {}
        end

        config
      end

      def substitute_transaction_threshold(config)
        if config['transaction_tracer'] &&
            config['transaction_tracer']['transaction_threshold'] =~ /apdex_f/i
          # when value is "apdex_f" remove the config and defer to default
          config['transaction_tracer'].delete('transaction_threshold')
        end
      end

      def with_yaml_engine
        return yield unless OneApm::LanguageSupport.needs_syck?

        yamler = ::YAML::ENGINE.yamler
        ::YAML::ENGINE.yamler = 'syck'
        result = yield
        ::YAML::ENGINE.yamler = yamler
        result
      end

      def booleanify_values(config, *keys)
        # auto means defer ro default
        keys.each do |option|
          if config[option] == 'auto'
            config.delete(option)
          elsif !config[option].nil? && !is_boolean?(config[option])
            config[option] = !!(config[option] =~ /yes|on|true/i)
          end
        end
      end

      def is_boolean?(value)
        value == !!value
      end
    end
  end
end