# pager.py - display output using a pager

#

# Copyright 2008 David Soria Parra <dsp@php.net>

#

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

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

#

# To load the extension, add it to your configuration file:

#

#   [extension]

#   pager =

#

# Run "hg help pager" to get info on configuration.

'''browse command output with an external pager

To set the pager that should be used, set the application variable::

  [pager]

  pager = LESS='FSRX' less

If no pager is set, the pager extensions uses the environment variable

$PAGER. If neither pager.pager, nor $PAGER is set, no pager is used.

If you notice "BROKEN PIPE" error messages, you can disable them by

setting::

  [pager]

  quiet = True

You can disable the pager for certain commands by adding them to the

pager.ignore list::

  [pager]

  ignore = version, help, update

You can also enable the pager only for certain commands using

pager.attend. Below is the default list of commands to be paged::

  [pager]

  attend = annotate, cat, diff, export, glog, log, qdiff

Setting pager.attend to an empty value will cause all commands to be

paged.

If pager.attend is present, pager.ignore will be ignored.

To ignore global commands like :hg:`version` or :hg:`help`, you have

to specify them in your user configuration file.

'''

import sys, os, signal, shlex, errno

from mercurial import dispatch, util, extensions

def _runpager(p):

    if not hasattr(os, 'fork'):

        sys.stderr = sys.stdout = util.popen(p, 'wb')

        return

    fdin, fdout = os.pipe()

    pid = os.fork()

    if pid == 0:

        os.close(fdin)

        os.dup2(fdout, sys.stdout.fileno())

        os.dup2(fdout, sys.stderr.fileno())

        os.close(fdout)

        return

    os.dup2(fdin, sys.stdin.fileno())

    os.close(fdin)

    os.close(fdout)

    try:

        os.execvp('/bin/sh', ['/bin/sh', '-c', p])

    except OSError, e:

        if e.errno == errno.ENOENT:

            # no /bin/sh, try executing the pager directly

            args = shlex.split(p)

            os.execvp(args[0], args)

        else:

            raise

def uisetup(ui):

    if ui.plain():

        return

    def pagecmd(orig, ui, options, cmd, cmdfunc):

        p = ui.config("pager", "pager", os.environ.get("PAGER"))

        if p and sys.stdout.isatty() and '--debugger' not in sys.argv:

            attend = ui.configlist('pager', 'attend', attended)

            if (cmd in attend or

                (cmd not in ui.configlist('pager', 'ignore') and not attend)):

                ui.setconfig('ui', 'formatted', ui.formatted())

                ui.setconfig('ui', 'interactive', False)

                _runpager(p)

                if ui.configbool('pager', 'quiet'):

                    signal.signal(signal.SIGPIPE, signal.SIG_DFL)

        return orig(ui, options, cmd, cmdfunc)

    extensions.wrapfunction(dispatch, '_runcommand', pagecmd)

attended = ['annotate', 'cat', 'diff', 'export', 'glog', 'log', 'qdiff']