require "ostruct"

module Sapience
  UnkownLogLevel = Class.new(StandardError)
  InvalidLogExecutor = Class.new(StandardError)

  # rubocop:disable ClassVars
  class Configuration
    attr_reader :default_level, :backtrace_level, :backtrace_level_index
    attr_writer :host
    attr_accessor :app_name, :ap_options, :appenders, :log_executor, :filter_parameters

    SUPPORTED_EXECUTORS = %i(single_thread_executor immediate_executor).freeze
    DEFAULT = {
      log_level:         :info,
      host:              nil,
      ap_options:        { multiline: false },
      appenders:         [{ stream: { io: STDOUT, formatter: :color } }],
      log_executor:      :single_thread_executor,
      filter_parameters: %w(password password_confirmation),
    }.freeze

    # Initial default Level for all new instances of Sapience::Logger
    def initialize(options = {}) # rubocop:disable AbcSize
      fail ArgumentError, "options need to be a hash #{options.inspect}" unless options.is_a?(Hash)
      @options             = DEFAULT.merge(options.dup.deep_symbolize_keyz!)
      @options[:log_executor] &&= @options[:log_executor].to_sym
      validate_log_executor!(@options[:log_executor])
      self.default_level     = @options[:log_level].to_sym
      self.backtrace_level   = @options[:log_level].to_sym
      self.host              = @options[:host]
      self.app_name          = @options[:app_name]
      self.ap_options        = @options[:ap_options]
      self.appenders         = @options[:appenders]
      self.log_executor      = @options[:log_executor]
      self.filter_parameters = @options[:filter_parameters]
    end

    # Sets the global default log level
    def default_level=(level)
      @default_level       = level
      # For performance reasons pre-calculate the level index
      @default_level_index = level_to_index(level)
    end

    # Returns the symbolic level for the supplied level index
    def index_to_level(level_index)
      LEVELS[level_index]
    end

    # Internal method to return the log level as an internal index
    # Also supports mapping the ::Logger levels to Sapience levels
    def level_to_index(level) # rubocop:disable AbcSize, PerceivedComplexity, CyclomaticComplexity
      return if level.nil?

      case level
      when Symbol
        LEVELS.index(level)
      when String
        LEVELS.index(level.downcase.to_sym)
      when Integer
        map_levels[level] || fail_with_unkown_log_level!(level)
      else
        fail_with_unkown_log_level!(level)
      end
    end

    def fail_with_unkown_log_level!(level)
      fail UnkownLogLevel,
        "Invalid level:#{level.inspect} being requested." \
        " Must be one of #{LEVELS.inspect}"
    end

    # Mapping of Rails and Ruby Logger levels to Sapience levels
    def map_levels
      return [] unless defined?(::Logger::Severity)
      @@map_levels ||=
        ::Logger::Severity.constants.each_with_object([]) do |constant, levels|
          levels[::Logger::Severity.const_get(constant)] = level_by_index_or_error(constant)
        end
    end

    def level_by_index_or_error(constant)
      LEVELS.find_index(constant.downcase.to_sym) || LEVELS.find_index(:error)
    end

    def default_level_index
      Thread.current[:sapience_silence] || @default_level_index
    end


    # Sets the level at which backtraces should be captured
    # for every log message.
    #
    # By enabling backtrace capture the filename and line number of where
    # message was logged can be written to the log file. Additionally, the backtrace
    # can be forwarded to error management services such as Bugsnag.
    #
    # Warning:
    #   Capturing backtraces is very expensive and should not be done all
    #   the time. It is recommended to run it at :error level in production.
    def backtrace_level=(level)
      @backtrace_level       = level
      # For performance reasons pre-calculate the level index
      @backtrace_level_index = level.nil? ? 65_535 : level_to_index(level)
    end

    # Returns [String] name of this host for logging purposes
    # Note: Not all appenders use `host`
    def host
      @host ||= Socket.gethostname
    end

    def validate_log_executor!(log_executor)
      return true if SUPPORTED_EXECUTORS.include?(log_executor)
      fail InvalidLogExecutor, "#{log_executor} is unsupported. Use (#{SUPPORTED_EXECUTORS.join(", ")})"
    end
  end
end