# frozen_string_literal: true

module StatsD
  module Instrument
    # The environment module is used to detect, and initialize the environment in
    # which this library is active. It will use different default values based on the environment.
    class Environment
      class << self
        def current
          @current ||= StatsD::Instrument::Environment.new(ENV)
        end

        # @deprecated For backwards compatibility only. Use {StatsD::Instrument::Environment#environment}
        #   through {StatsD::Instrument::Environment.current} instead.
        def environment
          current.environment
        end

        # Sets default values for sample rate and logger.
        #
        # - Default sample rate is set to the value in the STATSD_SAMPLE_RATE environment variable,
        #   or 1.0 otherwise. See {StatsD#default_sample_rate}
        # - {StatsD#logger} is set to a logger that send output to stderr.
        #
        # If you are including this library inside a Rails environment, additional initialization will
        # be done as part of the {StatsD::Instrument::Railtie}.
        #
        # @return [void]
        def setup
          StatsD.logger = Logger.new($stderr)
        end
      end

      attr_reader :env

      def initialize(env)
        @env = env
      end

      # Detects the current environment, either by asking Rails, or by inspecting environment variables.
      #
      # - It will prefer the value set in <tt>ENV['STATSD_ENV']</tt>
      # - Within a Rails application, <tt>Rails.env</tt> is used.
      # - It will check the following environment variables in order:
      #   - <tt>RAILS_ENV</tt>,
      #   - <tt>RACK_ENV</tt>
      #   - <tt>ENV</tt>.
      # - If none of these are set, it will return <tt>development</tt>
      #
      # @return [String] The detected environment.
      def environment
        if env['STATSD_ENV']
          env['STATSD_ENV']
        elsif defined?(Rails) && Rails.respond_to?(:env)
          Rails.env.to_s
        else
          env['RAILS_ENV'] || env['RACK_ENV'] || env['ENV'] || 'development'
        end
      end

      def statsd_implementation
        env.fetch('STATSD_IMPLEMENTATION', 'datadog')
      end

      def statsd_sample_rate
        env.fetch('STATSD_SAMPLE_RATE', 1.0).to_f
      end

      def statsd_prefix
        env.fetch('STATSD_PREFIX', nil)
      end

      def statsd_addr
        env.fetch('STATSD_ADDR', 'localhost:8125')
      end

      def statsd_default_tags
        env.key?('STATSD_DEFAULT_TAGS') ? env.fetch('STATSD_DEFAULT_TAGS').split(',') : nil
      end

      def client
        StatsD::Instrument::Client.from_env(self)
      end

      def default_sink_for_environment
        case environment
        when 'production', 'staging'
          StatsD::Instrument::UDPSink.for_addr(statsd_addr)
        when 'test'
          StatsD::Instrument::NullSink.new
        else
          StatsD::Instrument::LogSink.new(StatsD.logger)
        end
      end
    end
  end
end

StatsD::Instrument::Environment.setup