require 'logging'
require 'forwardable'

module Rackamole
  class Logger
    class ConfigurationError < StandardError ; end  #:nodoc:

    attr_reader :log #:nodoc:

    extend Forwardable
    def_delegators :@log, :debug, :warn, :info, :error, :fatal 
    def_delegators :@log, :level=, :level
    def_delegators :@log, :debug?, :warn?, :info?, :error?, :fatal?  
    def_delegators :@log, :add, :clear_appenders

    # there are more options here than are typically utilized for the
    # logger, they are made available if someone wants to utilize
    # them directly.  
    #
    def self.default_options #:nodoc:
      @default_options ||= {

        # log event layout pattern
        #    YYYY-MM-DDTHH:MM:SS 12345 LEVEL LoggerName : The Log message
        #
        :layout_pattern       => '%d %5p %5l %c : %m\n'.freeze  ,
        :logger_name          => 'Mole'                         ,
        :additive             => true                           ,

        # log file configuration options
        #   age        -> how often to rotate the logs if a file is used
        #   keep_count -> how many of the log files to keep
        :log_level            => :info          ,
        :log_file             => $stdout        ,
        :log_file_age         => 'daily'.freeze ,
        :log_file_keep_count  => 7              ,

        # email logging options
        #   buffsize -> number of log events used as a threshold to send an
        #               email.  If that is not reached before the program
        #               exists then the at_exit handler for logging will flush
        #               the log to smtp.
        :email_alerts_to      => nil    ,
        :email_alert_level    => :error ,
        :email_alert_server   => nil    ,
        :email_alert_buffsize => 200    ,
      }
    end

    # Creates a logger for mole usage by leveraging the most excellent logging gem.
    # This provides for a semi persistent storage for mole information, typically set up
    # for the console or a file. By default moled features will be sent out to the console.
    # Alternatively you can store the moled info to a file.
    #
    def initialize( opts = {} )
      @options = ::Rackamole::Logger.default_options.merge(opts)
      @log     = ::Logging::Logger[@options[:logger_name]]
      @layout  = ::Logging::Layouts::Pattern.new( { :pattern => @options[:layout_pattern] } )
     
      # add appenders explicitly, since this logger may already be defined and
      # already have loggers
      @appenders = []
      @appenders << log_file_appender if @options[:log_file]
      @appenders << email_appender if @options[:email_alerts_to]

      @log.appenders = @appenders
      @log.level = @options[:log_level]
      @log.additive = @options[:additive]
    end

    # File appender, this is either an IO appender or a RollingFile appender
    # depending on if an IO object or a String is passed in.
    #
    # a configuration error is raised in any other circumstance
    def log_file_appender  #:nodoc:
      appender_name = "#{@log.name}-log_file_appender"
      if String === @options[:log_file] then 
        ::Logging::Appenders::RollingFile.new( appender_name, 
                                             { :layout    => @layout,
                                               :filename  => @options[:log_file],
                                               :age       => @options[:log_file_age],
                                               :keep      => @options[:log_file_keep_count],
                                               :safe      => true  # make sure log files are rolled using lockfile
        })
      elsif @options[:log_file].respond_to?(:print) then
        ::Logging::Appenders::IO.new( appender_name, @options[:log_file],  :layout => @layout  )
      else
        raise ConfigurationError, "Invalid :log_file option [#{@options[:log_file].inspect}]"
      end
    end

    # an email appender that uses :email_alerts_to option to send emails to.
    # :email_alerts_to can either be a singe email address as a string or an
    # Array of email addresses.  Any other option for :email_alerts_to is
    # invalid and raises an error.
    #
    def email_appender #:nodoc:
      email_alerts_to = [ @options[:email_alerts_to] ].flatten.reject { |x| x == nil }
      raise ConfigurationError, "Invalid :email_alerts_to option [#{@options[:email_alerts_to].inspect}]" unless email_alerts_to.size > 0
      ::Logging::Appenders::Email.new("#{@log.name}-email_appender",
                                      {
                                        :level    => @options[:email_alert_level],
                                        :layout   => @layout,
                                        :from     => "#{@log.name}",
                                        :to       => "#{email_alerts_to.join(', ')}",
                                        :subject  => "Logging Alert from #{@log.name} on #{ENV['HOSTNAME']}",
                                        :server   => @options[:email_alert_server],
                                        :buffsize => @options[:email_alert_buffsize], # lines 
      })
    end

    # create a new logger thi logger has no options when it is created although 
    # more can be added with the logger instance that is returned.  The
    # appenders of the current instance of Logger will be set on the new
    # logger and the options of the current logger will be applied
    def for( arg ) #:nodoc:
      new_logger           = ::Logging::Logger[arg]
      new_logger.level     = @options[:level]
      new_logger.additive  = @options[:additive]
      new_logger.appenders = @appenders
      return new_logger
    end     
  end
end