# commandserver.py - communicate with Mercurial's API over a pipe

#

#  Copyright Matt Mackall <mpm@selenic.com>

#

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

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

from __future__ import absolute_import

import errno

import gc

import os

import random

import signal

import socket

import struct

import traceback

try:

    import selectors

    selectors.BaseSelector

except ImportError:

    from .thirdparty import selectors2 as selectors

from .i18n import _

from . import (

    encoding,

    error,

    util,

)

from .utils import (

    procutil,

)

logfile = None

def log(*args):

    if not logfile:

        return

    for a in args:

        logfile.write(str(a))

    logfile.flush()

class channeledoutput(object):

    """

    Write data to out in the following format:

    data length (unsigned int),

    data

    """

    def __init__(self, out, channel):

        self.out = out

        self.channel = channel

    @property

    def name(self):

        return '<%c-channel>' % self.channel

    def write(self, data):

        if not data:

            return

        # single write() to guarantee the same atomicity as the underlying file

        self.out.write(struct.pack('>cI', self.channel, len(data)) + data)

        self.out.flush()

    def __getattr__(self, attr):

        if attr in (r'isatty', r'fileno', r'tell', r'seek'):

            raise AttributeError(attr)

        return getattr(self.out, attr)

class channeledinput(object):

    """

    Read data from in_.

    Requests for input are written to out in the following format:

    channel identifier - 'I' for plain input, 'L' line based (1 byte)

    how many bytes to send at most (unsigned int),

    The client replies with:

    data length (unsigned int), 0 meaning EOF

    data

    """

    maxchunksize = 4 * 1024

    def __init__(self, in_, out, channel):

        self.in_ = in_

        self.out = out

        self.channel = channel

    @property

    def name(self):

        return '<%c-channel>' % self.channel

    def read(self, size=-1):

        if size < 0:

            # if we need to consume all the clients input, ask for 4k chunks

            # so the pipe doesn't fill up risking a deadlock

            size = self.maxchunksize

            s = self._read(size, self.channel)

            buf = s

            while s:

                s = self._read(size, self.channel)

                buf += s

            return buf

        else:

            return self._read(size, self.channel)

    def _read(self, size, channel):

        if not size:

            return ''

        assert size > 0

        # tell the client we need at most size bytes

        self.out.write(struct.pack('>cI', channel, size))

        self.out.flush()

        length = self.in_.read(4)

        length = struct.unpack('>I', length)[0]

        if not length:

            return ''

        else:

            return self.in_.read(length)

    def readline(self, size=-1):

        if size < 0:

            size = self.maxchunksize

            s = self._read(size, 'L')

            buf = s

            # keep asking for more until there's either no more or

            # we got a full line

            while s and s[-1] != '\n':

                s = self._read(size, 'L')

                buf += s

            return buf

        else:

            return self._read(size, 'L')

    def __iter__(self):

        return self

    def next(self):

        l = self.readline()

        if not l:

            raise StopIteration

        return l

    __next__ = next

    def __getattr__(self, attr):

        if attr in (r'isatty', r'fileno', r'tell', r'seek'):

            raise AttributeError(attr)

        return getattr(self.in_, attr)

class server(object):

    """

    Listens for commands on fin, runs them and writes the output on a channel

    based stream to fout.

    """

    def __init__(self, ui, repo, fin, fout):

        self.cwd = encoding.getcwd()

        # developer config: cmdserver.log

        logpath = ui.config("cmdserver", "log")

        if logpath:

            global logfile

            if logpath == '-':

                # write log on a special 'd' (debug) channel

                logfile = channeledoutput(fout, 'd')

            else:

                logfile = open(logpath, 'a')

        if repo:

            # the ui here is really the repo ui so take its baseui so we don't

            # end up with its local configuration

            self.ui = repo.baseui

            self.repo = repo

            self.repoui = repo.ui

        else:

            self.ui = ui

            self.repo = self.repoui = None

        self.cerr = channeledoutput(fout, 'e')

        self.cout = channeledoutput(fout, 'o')

        self.cin = channeledinput(fin, fout, 'I')

        self.cresult = channeledoutput(fout, 'r')

        self.client = fin

    def cleanup(self):

        """release and restore resources taken during server session"""

    def _read(self, size):

        if not size:

            return ''

        data = self.client.read(size)

        # is the other end closed?

        if not data:

            raise EOFError

        return data

    def _readstr(self):

        """read a string from the channel

        format:

        data length (uint32), data

        """

        length = struct.unpack('>I', self._read(4))[0]

        if not length:

            return ''

        return self._read(length)

    def _readlist(self):

        """read a list of NULL separated strings from the channel"""

        s = self._readstr()

        if s:

            return s.split('\0')

        else:

            return []

    def runcommand(self):

        """ reads a list of \0 terminated arguments, executes

        and writes the return code to the result channel """

        from . import dispatch  # avoid cycle

        args = self._readlist()

        # copy the uis so changes (e.g. --config or --verbose) don't

        # persist between requests

        copiedui = self.ui.copy()

        uis = [copiedui]

        if self.repo:

            self.repo.baseui = copiedui

            # clone ui without using ui.copy because this is protected

            repoui = self.repoui.__class__(self.repoui)

            repoui.copy = copiedui.copy # redo copy protection

            uis.append(repoui)

            self.repo.ui = self.repo.dirstate._ui = repoui

            self.repo.invalidateall()

        for ui in uis:

            ui.resetstate()

            # any kind of interaction must use server channels, but chg may

            # replace channels by fully functional tty files. so nontty is

            # enforced only if cin is a channel.

            if not util.safehasattr(self.cin, 'fileno'):

                ui.setconfig('ui', 'nontty', 'true', 'commandserver')

        req = dispatch.request(args[:], copiedui, self.repo, self.cin,

                               self.cout, self.cerr)

        try:

            ret = dispatch.dispatch(req) & 255

            self.cresult.write(struct.pack('>i', int(ret)))

        finally:

            # restore old cwd

            if '--cwd' in args:

                os.chdir(self.cwd)

    def getencoding(self):

        """ writes the current encoding to the result channel """

        self.cresult.write(encoding.encoding)

    def serveone(self):

        cmd = self.client.readline()[:-1]

        if cmd:

            handler = self.capabilities.get(cmd)

            if handler:

                handler(self)

            else:

                # clients are expected to check what commands are supported by

                # looking at the servers capabilities

                raise error.Abort(_('unknown command %s') % cmd)

        return cmd != ''

    capabilities = {'runcommand': runcommand,

                    'getencoding': getencoding}

    def serve(self):

        hellomsg = 'capabilities: ' + ' '.join(sorted(self.capabilities))

        hellomsg += '\n'

        hellomsg += 'encoding: ' + encoding.encoding

        hellomsg += '\n'

        hellomsg += 'pid: %d' % procutil.getpid()

        if util.safehasattr(os, 'getpgid'):

            hellomsg += '\n'

            hellomsg += 'pgid: %d' % os.getpgid(0)

        # write the hello msg in -one- chunk

        self.cout.write(hellomsg)

        try:

            while self.serveone():

                pass

        except EOFError:

            # we'll get here if the client disconnected while we were reading

            # its request

            return 1

        return 0

class pipeservice(object):

    def __init__(self, ui, repo, opts):

        self.ui = ui

        self.repo = repo

    def init(self):

        pass

    def run(self):

        ui = self.ui

        # redirect stdio to null device so that broken extensions or in-process

        # hooks will never cause corruption of channel protocol.

        with procutil.protectedstdio(ui.fin, ui.fout) as (fin, fout):

            try:

                sv = server(ui, self.repo, fin, fout)

                return sv.serve()

            finally:

                sv.cleanup()

def _initworkerprocess():

    # use a different process group from the master process, in order to:

    # 1. make the current process group no longer "orphaned" (because the

    #    parent of this process is in a different process group while

    #    remains in a same session)

    #    according to POSIX 2.2.2.52, orphaned process group will ignore

    #    terminal-generated stop signals like SIGTSTP (Ctrl+Z), which will

    #    cause trouble for things like ncurses.

    # 2. the client can use kill(-pgid, sig) to simulate terminal-generated

    #    SIGINT (Ctrl+C) and process-exit-generated SIGHUP. our child

    #    processes like ssh will be killed properly, without affecting

    #    unrelated processes.

    os.setpgid(0, 0)

    # change random state otherwise forked request handlers would have a

    # same state inherited from parent.

    random.seed()

def _serverequest(ui, repo, conn, createcmdserver):

    sv = None

    try:

        sv = createcmdserver(repo, conn, fin, fout)

        try:

            sv.serve()

        # handle exceptions that may be raised by command server. most of

        # known exceptions are caught by dispatch.

        except error.Abort as inst:

            ui.error(_('abort: %s\n') % inst)

        except IOError as inst:

            if inst.errno != errno.EPIPE:

                raise

        except KeyboardInterrupt:

            pass

        finally:

            sv.cleanup()

    except: # re-raises

        # also write traceback to error channel. otherwise client cannot

        # see it because it is written to server's stderr by default.

        if sv:

            cerr = sv.cerr

        else:

            cerr = channeledoutput(fout, 'e')

        traceback.print_exc(file=cerr)

        raise

    finally:

        fin.close()

        try:

            fout.close()  # implicit flush() may cause another EPIPE

        except IOError as inst:

            if inst.errno != errno.EPIPE:

                raise

class unixservicehandler(object):

    """Set of pluggable operations for unix-mode services

    Almost all methods except for createcmdserver() are called in the main

    process. You can't pass mutable resource back from createcmdserver().

    """

    pollinterval = None

    def __init__(self, ui):

        self.ui = ui

    def bindsocket(self, sock, address):

        util.bindunixsocket(sock, address)

        sock.listen(socket.SOMAXCONN)

        self.ui.status(_('listening at %s\n') % address)

        self.ui.flush()  # avoid buffering of status message

    def unlinksocket(self, address):

        os.unlink(address)