# logtoprocess.py - send ui.log() data to a subprocess

#

# Copyright 2016 Facebook, Inc.

#

# This software may be used and distributed according to the terms of the

# GNU General Public License version 2 or any later version.

"""send ui.log() data to a subprocess (EXPERIMENTAL)

This extension lets you specify a shell command per ui.log() event,

sending all remaining arguments to as environment variables to that command.

Positional arguments construct a log message, which is passed in the `MSG1`

environment variables. Each keyword argument is set as a `OPT_UPPERCASE_KEY`

variable (so the key is uppercased, and prefixed with `OPT_`). The original

event name is passed in the `EVENT` environment variable, and the process ID

of mercurial is given in `HGPID`.

So given a call `ui.log('foo', 'bar %s\n', 'baz', spam='eggs'), a script

configured for the `foo` event can expect an environment with `MSG1=bar baz`,

and `OPT_SPAM=eggs`.

Scripts are configured in the `[logtoprocess]` section, each key an event name.

For example::

  [logtoprocess]

  commandexception = echo "$MSG1" > /var/log/mercurial_exceptions.log

would log the warning message and traceback of any failed command dispatch.

Scripts are run asynchronously as detached daemon processes; mercurial will

not ensure that they exit cleanly.

"""

from __future__ import absolute_import

import os

from mercurial.utils import procutil

# Note for extension authors: ONLY specify testedwith = 'ships-with-hg-core' for

# extensions which SHIP WITH MERCURIAL. Non-mainline extensions should

# be specifying the version(s) of Mercurial they are tested with, or

# leave the attribute unspecified.

testedwith = b'ships-with-hg-core'

class processlogger(object):

    """Map log events to external commands

    Arguments are passed on as environment variables.

    """

    def __init__(self, ui):

        self._scripts = dict(ui.configitems(b'logtoprocess'))

    def tracked(self, event):

        return bool(self._scripts.get(event))

    def log(self, ui, event, msg, opts):

        script = self._scripts[event]

        maxmsg = 100000

        if len(msg) > maxmsg:

            # Each env var has a 128KiB limit on linux. msg can be long, in

            # particular for command event, where it's the full command line.

            # Prefer truncating the message than raising "Argument list too

            # long" error.

            msg = msg[:maxmsg] + b' (truncated)'

        env = {

            b'EVENT': event,

            b'HGPID': os.getpid(),

            b'MSG1': msg,

        }

        # keyword arguments get prefixed with OPT_ and uppercased

        env.update(

            (b'OPT_%s' % key.upper(), value) for key, value in opts.items()

        )

        fullenv = procutil.shellenviron(env)

        procutil.runbgcommand(script, fullenv, shell=True)

def uipopulate(ui):

    ui.setlogger(b'logtoprocess', processlogger(ui))