""" This is an implementation of an execnet protocol on top
of a transport layer provided by the greensock2 interface.

It has the same semantics, but does not use threads at all
(which makes it suitable for specific enviroments, like pypy-c).

There are some features lacking, most notable:
- callback support for channels
- socket gateway
- bootstrapping (there is assumption of pylib being available
  on remote side, which is not always true)
"""

import sys, os, py, inspect
from pygreen import greensock2
from pygreen.msgstruct import message, decodemessage

MSG_REMOTE_EXEC = 'r'
MSG_OBJECT      = 'o'
MSG_ERROR       = 'e'
MSG_CHAN_CLOSE  = 'c'
MSG_FATAL       = 'f'
MSG_CHANNEL  = 'n'

class Gateway(object):

    def __init__(self, input, output, is_remote=False):
        self.input  = input
        self.output = output
        self.nextchannum = int(is_remote)
        self.receivers = {}
        self.greenlet = greensock2.autogreenlet(self.serve_forever, is_remote)

    def remote_exec(self, remote_source):
        remote_source = py.code.Source(remote_source)
        chan = self.newchannel()
        msg = message(MSG_REMOTE_EXEC, chan.n, str(remote_source))
        self.output.sendall(msg)
        return chan

    def newchannel(self):
        n = self.nextchannum
        self.nextchannum += 2
        return self.make_channel(n)

    def make_channel(self, n):
        giver, accepter = greensock2.meetingpoint()
        assert n not in self.receivers
        self.receivers[n] = giver
        return Channel(self, n, accepter)

    def serve_forever(self, is_remote=False):
        try:
            buffer = ""
            while 1:
                msg, buffer = decodemessage(buffer)
                if msg is None:
                    buffer += self.input.recv(16384)
                else:
                    handler = HANDLERS[msg[0]]
                    handler(self, *msg[1:])
        except greensock2.greenlet.GreenletExit:
            raise
        except:
            if is_remote:
                msg = message(MSG_FATAL, format_error(*sys.exc_info()))
                self.output.sendall(msg)
            else:
                raise

    def msg_remote_exec(self, n, source):
        def do_execute(channel):
            try:
                d = {'channel': channel}
                exec source in d
            except:
                channel.report_error(*sys.exc_info())
            else:
                channel.close()
        greensock2.autogreenlet(do_execute, self.make_channel(n))

    def msg_object(self, n, objrepr):
        obj = eval(objrepr)
        if n in self.receivers:
            self.receivers[n].give_queued(obj)

    def msg_error(self, n, s):
        if n in self.receivers:
            self.receivers[n].give_queued(RemoteError(s))
            self.receivers[n].close()
            del self.receivers[n]

    def msg_chan_close(self, n):
        if n in self.receivers:
            self.receivers[n].close()
            del self.receivers[n]

    def msg_channel(self, n, m):
        if n in self.receivers:
            self.receivers[n].give_queued(self.make_channel(m))

    def msg_fatal(self, s):
        raise RemoteError(s)

HANDLERS = {
    MSG_REMOTE_EXEC: Gateway.msg_remote_exec,
    MSG_OBJECT:      Gateway.msg_object,
    MSG_ERROR:       Gateway.msg_error,
    MSG_CHAN_CLOSE:  Gateway.msg_chan_close,
    MSG_CHANNEL:     Gateway.msg_channel,
    MSG_FATAL:       Gateway.msg_fatal,
    }


class Channel(object):

    def __init__(self, gw, n, accepter):
        self.gw = gw
        self.n = n
        self.accepter = accepter

    def send(self, obj):
        if isinstance(obj, Channel):
            assert obj.gw is self.gw
            msg = message(MSG_CHANNEL, self.n, obj.n)
        else:
            msg = message(MSG_OBJECT, self.n, repr(obj))
        self.gw.output.sendall(msg)

    def receive(self):
        obj = self.accepter.accept()
        if isinstance(obj, RemoteError):
            raise obj
        else:
            return obj

    def close(self):
        try:
            self.gw.output.sendall(message(MSG_CHAN_CLOSE, self.n))
        except OSError:
            pass

    def report_error(self, exc_type, exc_value, exc_traceback=None):
        s = format_error(exc_type, exc_value, exc_traceback)
        try:
            self.gw.output.sendall(message(MSG_ERROR, self.n, s))
        except OSError:
            pass


class RemoteError(Exception):
    pass

def format_error(exc_type, exc_value, exc_traceback=None):
    import traceback, StringIO
    s = StringIO.StringIO()
    traceback.print_exception(exc_type, exc_value, exc_traceback, file=s)
    return s.getvalue()


class PopenCmdGateway(Gateway):
    action = "exec input()"

    def __init__(self, cmdline):
        from pygreen.pipe.fd import FDInput, FDOutput
        child_in, child_out = os.popen2(cmdline, 't', 0)
        fdin  = FDInput(child_out.fileno(), child_out.close)
        fdout = FDOutput(child_in.fileno(), child_in.close)
        fdout.sendall(self.get_bootstrap_code())
        super(PopenCmdGateway, self).__init__(input = fdin, output = fdout)

    def get_bootstrap_code():
        # XXX assumes that the py lib is installed on the remote side
        src = []
        src.append('from pygreen import greenexecnet')
        src.append('greenexecnet.PopenCmdGateway.run_server()')
        src.append('')
        return '%r\n' % ('\n'.join(src),)
    get_bootstrap_code = staticmethod(get_bootstrap_code)

    def run_server():
        from pygreen.pipe.fd import FDInput, FDOutput
        gw = Gateway(input = FDInput(os.dup(0)),
                     output = FDOutput(os.dup(1)),
                     is_remote = True)
        # for now, ignore normal I/O
        fd = os.open('/dev/null', os.O_RDWR)
        os.dup2(fd, 0)
        os.dup2(fd, 1)
        os.close(fd)
        greensock2._suspend_forever()
    run_server = staticmethod(run_server)

class PopenGateway(PopenCmdGateway):
    def __init__(self, python=sys.executable):
        cmdline = '"%s" -u -c "%s"' % (python, self.action)
        super(PopenGateway, self).__init__(cmdline)

class SshGateway(PopenCmdGateway):
    def __init__(self, sshaddress, remotepython='python', identity=None):
        self.sshaddress = sshaddress
        remotecmd = '%s -u -c "%s"' % (remotepython, self.action)
        cmdline = [sshaddress, remotecmd]
        # XXX Unix style quoting
        for i in range(len(cmdline)):
            cmdline[i] = "'" + cmdline[i].replace("'", "'\\''") + "'"
        cmd = 'ssh -C'
        if identity is not None: 
            cmd += ' -i %s' % (identity,)
        cmdline.insert(0, cmd) 
        super(SshGateway, self).__init__(' '.join(cmdline))


##f = open('LOG', 'a')
##import os; print >> f, '[%d] READY' % (os.getpid(),)
##f.close()