# $Id: logger.rb 15 2007-01-15 19:03:45Z tim_pease $

require 'sync'
require 'logging'
require 'logging/appender'
require 'logging/log_event'
require 'logging/repository'


module Logging

  #
  # The +Logger+ class is the primary interface to the +Logging+ framework.
  # It provides the logging methods that will be called from user methods,
  # and it generates logging events that are sent to the appenders (the
  # appenders take care of sending the log events to the logging
  # destinations -- files, sockets, etc).
  #
  # +Logger+ instances are obtained from the +Repository+ and should
  # not be directly created by users.
  #
  # Example:
  #
  #    log = Logging::Logger['my logger']
  #    log.add( Logging::Appenders::StdOut.new )   # append to STDOUT
  #    log.level = :info                           # log 'info' and above
  #
  #    log.info 'starting foo operation'
  #    ...
  #    log.info 'finishing foo operation'
  #    ...
  #    log.fatal 'unknown exception', exception
  #
  class Logger

    @mutex = Sync.new  # :nodoc:

    class << self

      #
      # call-seq:
      #    Logger.root
      #
      # Returns the root logger.
      #
      def root
        ::Logging::Repository.instance[:root]
      end

      # :stopdoc:

      #
      # Overrides the new method such that only one Logger will be created
      # for any given logger name.
      #
      def new( *args )
        return super if args.empty?

        repo = ::Logging::Repository.instance
        name = repo.to_key(args.shift)

        @mutex.synchronize(:EX) do
          logger = repo[name]
          if logger.nil?
            logger = super(name, *args)
            repo[name] = logger
          end
          logger
        end
      end
      alias :[] :new

      #
      # This is where the actual logging methods are defined. Two methods
      # are created for each log level. The first is a query method used to
      # determine if that perticular logging level is enabled. The second is
      # the actual logging method that accepts a list of objects to be
      # logged or a block. If a block is given, then the object returned
      # from the block will be logged.
      #
      # Example
      #
      #    log = Logging::Logger['my logger']
      #    log.level = :warn
      #
      #    log.info?                               # => false
      #    log.warn?                               # => true
      #    log.warn 'this is your last warning'
      #    log.fatal 'I die!', exception
      #
      #    log.debug do
      #      # expensive method to construct log message
      #      msg
      #    end
      #
      def define_log_methods( logger )
        ::Logging::LEVELS.each do |name,num|
          code =  "undef :#{name}  if method_defined? :#{name}\n"
          code << "undef :#{name}? if method_defined? :#{name}?\n"

          if logger.level > num
            code << <<-CODE
              def #{name}?( ) false end
              def #{name}( *args ) false end
            CODE
          else
            code << <<-CODE
              def #{name}?( ) true end
              def #{name}( *args )
                args.push yield if block_given?
                log_event(::Logging::LogEvent.new(@name, #{num}, args, @trace)) unless args.empty?
                true
              end
            CODE
          end

          logger.meta_eval code
        end
      end
      # :startdoc:

    end  # class << self

    attr_reader :level, :name, :parent
    attr_accessor :additive, :trace

    #
    # call-seq:
    #    Logger.new( name )
    #    Logger[name]
    #
    # Returns the logger identified by _name_.
    #
    # When _name_ is a +String+ or a +Symbol+ it will be used "as is" to
    # retrieve the logger. When _name_ is a +Class+ the class name will be
    # used to retrieve the logger. When _name_ is an object the name of the
    # object's class will be used to retrieve the logger.
    #
    # Example:
    #
    #   obj = MyClass.new
    #
    #   log1 = Logger.new(obj)
    #   log2 = Logger.new(MyClass)
    #   log3 = Logger['MyClass']
    #
    #   log1.object_id == log2.object_id         # => true
    #   log2.object_id == log3.object_id         # => true
    #
    def initialize( name )
      case name
      when String:
        raise(ArgumentError, "logger must have a name") if name.empty?
      else raise(ArgumentError, "logger name must be a String") end

      repo = ::Logging::Repository.instance
      @name = name
      @parent = repo.parent(name)
      @appenders = []
      @additive = true
      @trace = false
      self.level = @parent.level

      repo.children(name).each {|c| c.parent = self}
    end

    #
    # call-seq:
    #    log <=> other
    #
    # Compares this logger by name to another logger. The normal return codes
    # for +String+ objects apply.
    #
    def <=>( other )
      case other
      when self: 0
      when ::Logging::RootLogger: 1
      when ::Logging::Logger: @name <=> other.name
      else raise ArgumentError, 'expecting a Logger instance' end
    end

    #
    # call-seq:
    #    log << "message"
    #
    # Log the given message without any formatting and without performing any
    # level checks. The message is logged to all appenders. The message is
    # passed up the logger tree if this logger's additivity is +true+.
    #
    def <<( msg )
      @appenders.each {|a| a << msg}
      @parent << msg if @additive
    end

    #
    # call-seq:
    #    level = :all
    #
    # Set the level for this logger. The level can be either a +String+, a
    # +Symbol+, or a +Fixnum+. An +ArgumentError+ is raised if this is not
    # the case.
    #
    # There are two special levels -- "all" and "off". The former will
    # enable log messages from this logger. The latter will disable all log
    # messages from this logger.
    #
    # Setting the logger level to +nil+ will cause the parent's logger level
    # to be used.
    #
    # Example:
    #
    #    log.level = :debug
    #    log.level = "INFO"
    #    log.level = 4
    #    log.level = 'off'
    #    log.level = :all
    #
    # These prodcue an +ArgumentError+
    #
    #    log.level = Object
    #    log.level = -1
    #    log.level = 1_000_000_000_000
    #
    def level=( level )
      lvl = case level
            when String, Symbol: ::Logging::level_num(level)
            when Fixnum: level
            when nil: @parent.level
            else
              raise ArgumentError,
                    "level must be a String, Symbol, or Integer"
            end
      if lvl.nil? or lvl < 0 or lvl > ::Logging::LEVELS.length
        raise ArgumentError, "unknown level was given '#{level}'"
      end

      @level = lvl
      ::Logging::Logger.define_log_methods(self)
      @level
    end

    #
    # call-seq:
    #    appenders = app
    #
    # Clears the current list of appenders and replaces them with _app_,
    # where _app_ can be either a single appender or an array of appenders.
    #
    def appenders=( args )
      @appenders.clear
      add(*args) unless args.nil?
    end

    #
    # call-seq:
    #    add( appenders )
    #
    # Add the given _appenders_ to the list of appenders, where _appenders_
    # can be either a single appender or an array of appenders.
    #
    def add( *args )
      args.each do |arg|
        unless arg.kind_of? ::Logging::Appender
          raise TypeError,
                "#{arg.inspect} is not a kind of 'Logging::Appender'"
        end
        @appenders << arg unless @appenders.include? arg
      end
    end

    #
    # call-seq:
    #    remove( appenders )
    #
    # Remove the given _appenders_ from the list of appenders. The appenders
    # to remove can be identified either by name using a +String+ or by
    # passing the appender instance. _appenders_ can be a single appender or
    # an array of appenders.
    #
    def remove( *args )
      args.each do |arg|
        @appenders.delete_if do |a|
          case arg
          when String: arg == a.name
          when ::Logging::Appender: arg.object_id == a.object_id
          else
            raise TypeError, "#{arg.inspect} is not a 'Logging::Appender'"
          end
        end
      end
    end

    #
    # call-seq:
    #    clear
    #
    # Remove all appenders from this logger.
    #
    def clear( ) @appenders.clear end


    protected
    #
    # call-seq:
    #    parent = ParentLogger
    #
    # Set the parent logger for this logger. This method will be invoked by
    # the +Repository+ class when a parent or child is added to the
    # hierarchy.
    #
    def parent=( parent ) @parent = parent end

    #
    # call-seq:
    #    log_event( event )
    #
    # Send the given _event_ to the appenders for logging, and pass the
    # _event_ up to the parent if additive mode is enabled. The log level has
    # already been checked before this method is called.
    #
    def log_event( event )
      @appenders.each {|a| a.append(event)}
      @parent.log_event(event) if @additive
    end

    # :stopdoc:

    #
    # call-seq:
    #    meta_eval( code )
    #
    # Evaluates the given string of _code_ if the singleton class of this
    # Logger object.
    #
    def meta_eval( code )
      meta = class << self; self end
      meta.class_eval code
    end
    public :meta_eval
    # :startdoc:

  end  # class Logger
end  # module Logging

# EOF