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"""General logging facility

This module attempts to provide a simple programming API for logging
with a pluggable API for defining where log messages should go.

Programmers call the LOG function to log information.

The LOG function, in turn, calls the write_log method to actually write
logging information somewhere.  This module provides a very simple
write_log implementation.  It is intended that applications main
programs will replace this method with a method more suited to their needs.

The module provides a register_subsystem method that does nothing, but
provides a hook that logging management systems could use to collect information about subsystems being used.

The module defines several standard severities:

  BLATHER=-100 -- Somebody shut this app up.

  INFO=0       -- For things like startup and shutdown.

  PROBLEM=100  -- This isn't causing any immediate problems, but deserves
                  attention.

  ERROR=200    -- This is going to have adverse effects.

  PANIC=300    -- We're dead!

Also, looging facilities will normally ignore negative severities.

"""
import time

# Standard severities
BLATHER=-100
INFO=0      
PROBLEM=100             
ERROR=200   
PANIC=300

def severity_string(severity, mapping={
    -100: 'BLATHER',
    0: 'INFO',       
    100: 'PROBLEM', 
    200: 'ERROR',    
    300: 'PANIC', 
    }):
    """Convert a severity code to a string
    """
    s=int(severity)
    if mapping.has_key(s): s=mapping[s]
    else: s=''
    return "%s(%s)" % (s, severity)

def LOG(subsystem, severity, summary, detail='', error=None, reraise=None):
    """Log some information

    The required arguments are:

      subsystem -- The subsystem generating the message (e.g. ZODB)

      severity -- The "severity" of the event.  This may be an integer or
                  a floating point number.  Logging back ends may
                  consider the int() of this valua to be significant.
                  For example, a backend may consider any severity
                  whos integer value is WARNING to be a warning.

      summary -- A short summary of the event

      detail -- A detailed description

      error -- A three-element tuple consisting of an error type, value, and
               traceback.  If provided, then a summary of the error
               is added to the detail.

      reraise -- If provided with a true value, then the error given by
                 error is reraised.

    """
    log_write(subsystem, severity, summary, detail, error)
    if reraise and error:
        raise error[0], error[1], error[2]

def register_subsystem(subsystem):
    """Register a subsystem name

    A logging facility might replace this function to collect information about
    subsystems used in an application.
    """

def log_time():
    """Return a simple time string without spaces suitable for logging
    """
    return ("%4.4d-%2.2d-%2.2dT%2.2d:%2.2d:%2.2d"
            % time.gmtime(time.time())[:6])
    
_stupid_dest=None
_no_stupid_log=[]
def stupid_log_write(subsystem, severity, summary, detail, error):

    if severity < 0: return
    
    global _stupid_dest
    if _stupid_dest is None:
        import os
        if os.environ.has_key('STUPID_LOG_FILE'):
            f=os.environ['STUPID_LOG_FILE']
            if f: _stupid_dest=open(f,'a').write
            else:
                import sys
                _stupid_dest=sys.stderr.write
        else:
            _stupid_dest=_no_stupid_log
            
    if _stupid_dest is _no_stupid_log: return
               
    _stupid_dest(
        "------\n"
        "%s %s %s %s\n%s\n"
        %
        (log_time(),
         severity_string(severity),
         subsystem,
         summary,
         detail,
         )
        )

log_write=stupid_log_write