# logger.rb - simple logging utility
# Copyright (C) 2000-2003, 2005, 2008, 2011  NAKAMURA, Hiroshi <nahi@ruby-lang.org>.
#
# Documentation:: NAKAMURA, Hiroshi and Gavin Sinclair
# License::
#   You can redistribute it and/or modify it under the same terms of Ruby's
#   license; either the dual license version in 2003, or any later version.
# Revision:: $Id: logger.rb 31641 2011-05-19 00:07:25Z nobu $
#
# A simple system for logging messages.  See Logger for more documentation.

require 'monitor'
require 'fileutils'
# == Description
#
# The Logger class provides a simple but sophisticated logging utility that
# you can use to output messages.
#
# The messages have associated levels, such as +INFO+ or +ERROR+ that indicate
# their importance.  You can then give the Logger a level, and only messages
# at that level of higher will be printed.
#
# The levels are:
#
# +FATAL+:: an unhandleable error that results in a program crash
# +ERROR+:: a handleable error condition
# +WARN+::  a warning
# +INFO+::  generic (useful) information about system operation
# +DEBUG+:: low-level information for developers
#
# For instance, in a production system, you may have your Logger set to
# +INFO+ or even +WARN+
# When you are developing the system, however, you probably
# want to know about the program's internal state, and would set the Logger to
# +DEBUG+.
#
# *Note*: Logger does not escape or sanitize any messages passed to it.
# Developers should be aware of when potentially malicious data (user-input)
# is passed to Logger, and manually escape the untrusted data:
#
#   logger.info("User-input: #{input.dump}")
#   logger.info("User-input: %p" % input)
#
# You can use #formatter= for escaping all data.
#
#   original_formatter = Logger::Formatter.new
#   logger.formatter = proc { |severity, datetime, progname, msg|
#     original_formatter.call(severity, datetime, progname, msg.dump)
#   }
#   logger.info(input)
#
# === Example
#
# This creates a logger to the standard output stream, with a level of +WARN+
#
#   log = Logger.new(STDOUT)
#   log.level = Logger::WARN
#
#   log.debug("Created logger")
#   log.info("Program started")
#   log.warn("Nothing to do!")
#
#   begin
#     File.each_line(path) do |line|
#       unless line =~ /^(\w+) = (.*)$/
#         log.error("Line in wrong format: #{line}")
#       end
#     end
#   rescue => err
#     log.fatal("Caught exception; exiting")
#     log.fatal(err)
#   end
#
# Because the Logger's level is set to +WARN+, only the warning, error, and
# fatal messages are recorded.  The debug and info messages are silently
# discarded.
#
# === Features
#
# There are several interesting features that Logger provides, like
# auto-rolling of log files, setting the format of log messages, and
# specifying a program name in conjunction with the message.  The next section
# shows you how to achieve these things.
#
#
# == HOWTOs
#
# === How to create a logger
#
# The options below give you various choices, in more or less increasing
# complexity.
#
# 1. Create a logger which logs messages to STDERR/STDOUT.
#
#      logger = Logger.new(STDERR)
#      logger = Logger.new(STDOUT)
#
# 2. Create a logger for the file which has the specified name.
#
#      logger = Logger.new('logfile.log')
#
# 3. Create a logger for the specified file.
#
#      file = File.open('foo.log', File::WRONLY | File::APPEND)
#      # To create new (and to remove old) logfile, add File::CREAT like;
#      #   file = open('foo.log', File::WRONLY | File::APPEND | File::CREAT)
#      logger = Logger.new(file)
#
# 4. Create a logger which ages logfile once it reaches a certain size.  Leave
#    10 "old log files" and each file is about 1,024,000 bytes.
#
#      logger = Logger.new('foo.log', 10, 1024000)
#
# 5. Create a logger which ages logfile daily/weekly/monthly.
#
#      logger = Logger.new('foo.log', 'daily')
#      logger = Logger.new('foo.log', 'weekly')
#      logger = Logger.new('foo.log', 'monthly')
#
# === How to log a message
#
# Notice the different methods (+fatal+, +error+, +info+) being used to log
# messages of various levels?  Other methods in this family are +warn+ and
# +debug+.  +add+ is used below to log a message of an arbitrary (perhaps
# dynamic) level.
#
# 1. Message in block.
#
#      logger.fatal { "Argument 'foo' not given." }
#
# 2. Message as a string.
#
#      logger.error "Argument #{ @foo } mismatch."
#
# 3. With progname.
#
#      logger.info('initialize') { "Initializing..." }
#
# 4. With severity.
#
#      logger.add(Logger::FATAL) { 'Fatal error!' }
#
# The block form allows you to create potentially complex log messages,
# but to delay their evaluation until and unless the message is
# logged.  For example, if we have the following:
#
#     logger.debug { "This is a " + potentially + " expensive operation" }
#
# If the logger's level is +INFO+ or higher, no debug messages will be logged,
# and the entire block will not even be evaluated.  Compare to this:
#
#     logger.debug("This is a " + potentially + " expensive operation")
#
# Here, the string concatenation is done every time, even if the log
# level is not set to show the debug message.
#
# === How to close a logger
#
#      logger.close
#
# === Setting severity threshold
#
# 1. Original interface.
#
#      logger.sev_threshold = Logger::WARN
#
# 2. Log4r (somewhat) compatible interface.
#
#      logger.level = Logger::INFO
#
#      DEBUG < INFO < WARN < ERROR < FATAL < UNKNOWN
#
#
# == Format
#
# Log messages are rendered in the output stream in a certain format by
# default.  The default format and a sample are shown below:
#
# Log format:
#   SeverityID, [Date Time mSec #pid] SeverityLabel -- ProgName: message
#
# Log sample:
#   I, [Wed Mar 03 02:34:24 JST 1999 895701 #19074]  INFO -- Main: info.
#
# You may change the date and time format via #datetime_format=
#
#   logger.datetime_format = "%Y-%m-%d %H:%M:%S"
#         # e.g. "2004-01-03 00:54:26"
#
# Or, you may change the overall format with #formatter= method.
#
#   logger.formatter = proc do |severity, datetime, progname, msg|
#     "#{datetime}: #{msg}\n"
#   end
#   # e.g. "Thu Sep 22 08:51:08 GMT+9:00 2005: hello world"
#
# class Logger
#   #具体内容请看https://bugs.ruby-lang.org/issues/7303
#   # Device used for logging messages.
#   class LogDevice
#     def shift_log_period(period_end)
#       postfix = period_end.strftime("%Y%m%d") # YYYYMMDD
#       age_file = "#{@filename}.#{postfix}"
#       if FileTest.exist?(age_file)
#         # try to avoid filename crash caused by Timestamp change.
#         idx = 0
#         # .99 can be overridden; avoid too much file search with 'loop do'
#         while idx < 100
#           idx += 1
#           age_file = "#{@filename}.#{postfix}.#{idx}"
#           break unless FileTest.exist?(age_file)
#         end
#       end
#       # @dev.close rescue nil
#       # File.rename("#{@filename}", age_file)
#       # @dev = create_logfile(@filename)
#       #覆盖原来lib库的方法，将上边三行删除，增加下边两行
#       FileUtils.cp(@filename, age_file)
#       reset_logfile(@dev) # see below for this new method return true
#       return true
#     end
#     #打开原来lib库，新增一个方法
#     def reset_logfile(logdev)
#       logdev.truncate( 0 )
#       logdev.sync = true
#       add_log_header(logdev)
#     end
#   end
# end
