require 'logger'
require 'stringio'

module Immunio
  # Subclass global Logger class to add TRACE level
  class Logger < ::Logger
    module Severity
      TRACE = -1
    end
    include Severity

    def trace?; @level <= TRACE; end

    def trace(progname = nil, &block)
      add(TRACE, nil, progname, &block)
    end

    def format_severity(severity)
      SEV_LABEL[severity] || 'ANY'
    end

    SEV_LABEL = Array.new(::Logger::SEV_LABEL)
    SEV_LABEL[-1] = 'TRACE'
  end

  attr_reader :logger

  def self.create_startup_logger
    @startup_messages = StringIO.new
    @logger = Logger.new @startup_messages

    setup_logger_formatter
  end

  def self.setup_logger_formatter
    logger.formatter = proc do |severity, datetime, _progname, msg|
      "[#{datetime}] #{severity}: #{msg}\n"
    end
  end

  def self.switch_to_real_logger(log_file, log_level)
    # Have we already switched to real logger?
    return if !defined?(@startup_messages)

    if log_file == "STDOUT"
      @logger = Logger.new $stdout
    elsif log_file == "STDERR"
      @logger = Logger.new $stderr
    else
      path = Pathname.new(log_file)
      begin
        FileUtils.mkdir_p path.dirname unless File.exist? path.dirname

        file = File.open path, 'a'
        file.binmode
        file.sync = true

        @logger = Logger.new file
        log_file = path.realpath
      rescue StandardError => e
        logger.warn "Failed to open #{log_file} (#{path.realdirpath}) for logging (#{e.message})"
        @logger = Logger.new $stderr
        log_file = "STDERR"
      end
    end

    # Dump saved log messages during startup to real log
    logger << @startup_messages.string
    remove_instance_variable(:@startup_messages)

    setup_logger_formatter

    begin
      logger.level = Logger.const_get(log_level.to_s.upcase)
    rescue
      logger.level = Logger::DEBUG
      logger.debug "Failed to interpret log level #{log_level}, falling back to debug"
    end

    logger.debug "Logging to #{log_file}"
  end

  def self.logger
    @logger
  end
end