import ast
import collections
import json
import subprocess
import select
import time
import os
import base64
import zlib
import logging
from threading import Thread
from queue import Queue, Empty


def get_muxer(shell):
    # The full path of the Python interpreter.  Configured by CMake.
    pythonpath = "/usr/bin/python"

    muxer = r"""
import os,sys,subprocess,signal,select,json
TIMEOUT=120

def w(s):
	sys.stdout.write(repr(s) + "\n")
	sys.stdout.flush()

def exec_cmds(cmds):
	p=[]
	for i,cmd in enumerate(cmds):
		try:
			proc=subprocess.Popen(cmd,stdout=subprocess.PIPE,stderr=subprocess.PIPE __SHELL__)
			p.append((i,proc))
		except Exception as e:
			w((i,(1,'',str(e))))
	return p

w("ready")
commands=[]
signal.alarm(TIMEOUT)
for line in iter(sys.stdin.readline,"done\n"):
	commands.append(json.loads(line))

procs=exec_cmds(commands)
cmd_map={}
fd_map={}
fds=set()
for i,proc in procs:
	o={"idx":i, "proc":proc, "stdout":[], "stderr":[], "waiting":2}
	fd_map[proc.stdout]=o["stdout"]
	fd_map[proc.stderr]=o["stderr"]
	cmd_map[proc.stdout]=o
	cmd_map[proc.stderr]=o
	fds.update((proc.stdout,proc.stderr))

while fds:
	r,_,_=select.select(fds,[],[])
	for fd in r:
		output=os.read(fd.fileno(),1024)
		if output:
			fd_map[fd].append(output)
			continue

		cmd=cmd_map[fd]
		fds.remove(fd)
		cmd["waiting"]-=1
		if cmd["waiting"]:
			continue

		proc=cmd["proc"]
		status=proc.wait()
		out=b"".join(cmd["stdout"])
		err=b"".join(cmd["stderr"])
		w((cmd["idx"],(status,out,err)))

w("done")
"""

    if shell:
        muxer = muxer.replace("__SHELL__", ",shell=True")
    else:
        muxer = muxer.replace("__SHELL__", "")

    muxer = muxer.encode()
    muxer = base64.b64encode(zlib.compress(muxer))
    muxer = muxer.decode()
    muxer = "%s -c 'import zlib,base64; exec(zlib.decompress(base64.b64decode(b\"%s\")))'\n" % (pythonpath, muxer)
    muxer = muxer.encode()

    return muxer


CmdResult = collections.namedtuple("CmdResult", "status stdout stderr")

class SSHMaster:
    def __init__(self, host, localaddrs):
        # The BatchMode=yes disables interactive prompting.  The LogLevel=error
        # prevents seeing login banners but allows error messages from ssh.
        self.base_cmd = [
            "ssh",
            "-o", "BatchMode=yes",
            "-o", "LogLevel=error",
            host,
        ]
        self.host = host
        self.need_connect = True
        self.master = None
        self.localaddrs = localaddrs
        self.run_mux = get_muxer(False)
        self.run_mux_shell = get_muxer(True)

    def connect(self):
        if self.need_connect:
            if self.host in self.localaddrs:
                cmd = ["sh"]
            else:
                cmd = self.base_cmd + ["sh"]
            self.master = subprocess.Popen(cmd, bufsize=0, stdout=subprocess.PIPE, stdin=subprocess.PIPE, close_fds=True, preexec_fn=os.setsid)
            self.need_connect = False

    def readline_with_timeout(self, timeout):
        readable, _, _ = select.select([self.master.stdout], [], [], timeout)
        if not readable:
            return None
        jtxt = self.master.stdout.readline()
        jtxt = jtxt.decode()
        return jtxt

    def exec_command(self, cmd, shell=False, timeout=60):
        return self.exec_commands([cmd], shell, timeout)[0]

    def exec_commands(self, cmds, shell=False, timeout=60):
        self.send_commands(cmds, timeout, shell)
        return self.collect_results(timeout)

    def send_commands(self, cmds, timeout, shell=False):
        self.connect()
        if shell:
            self.master.stdin.write(self.run_mux_shell)
        else:
            self.master.stdin.write(self.run_mux)
        self.master.stdin.flush()

        # Wait until we receive the "ready" message from muxer script
        self.readline_with_timeout(timeout)

        for cmd in cmds:
            jcmd = "%s\n" % json.dumps(cmd)
            jcmd = jcmd.encode()
            self.master.stdin.write(jcmd)
        # Note: the "b" string prefix here for Py3 is ignored by Py2.6-2.7
        self.master.stdin.write(b"done\n")
        self.master.stdin.flush()
        self.sent_commands = len(cmds)

    def collect_results(self, timeout):
        outputs = [Exception("Command timeout on host %s" % self.host)] * self.sent_commands

        while True:
            line = self.readline_with_timeout(timeout)
            if not line:
                logging.debug("Command timeout on host %s", self.host)
                self.close()
                break
            resp = ast.literal_eval(line)
            if resp == "done":
                break
            idx, result = resp
            status, out, err = result

            out = out.decode(errors="replace")
            err = err.decode(errors="replace")

            outputs[idx] = CmdResult(status, out, err)
        return outputs

    def close(self):
        if not self.master:
            return
        self.master.stdin.close()
        try:
            self.master.kill()
        except OSError:
            pass
        self.master.wait()
        self.master = None
        self.need_connect = True
    __del__ = close


STOP_RUNNING = object()

class HostHandler(Thread):
    def __init__(self, host, localaddrs, timeout):
        self.host = host
        self.localaddrs = localaddrs
        self.timeout = timeout
        self.q = Queue()
        self.alive = False
        self.master = None
        Thread.__init__(self)

    def shutdown(self):
        self.q.put((STOP_RUNNING, None, None))

    def connect(self):
        if self.master:
            self.master.close()
        self.master = SSHMaster(self.host, self.localaddrs)

    def ping(self):
        # Error message should indicate whether or not ssh is being used.
        msgstr = "" if self.host in self.localaddrs else "ssh "

        # Error message shows if a connection was previously established.
        if self.alive:
            msg = "Lost %sconnection to host %s" % (msgstr, self.host)
        else:
            msg = "Failed to establish %sconnection to host %s" % (msgstr, self.host)

        # This will be set to True below only if the "ping" is received.
        self.alive = False

        try:
            resp = self.master.exec_command(["/bin/echo", "ping"], timeout=10)
        except Exception as e:
            # This happens most likely due to broken pipe (i.e., ssh
            # terminates, usually because it couldn't connect, or its own
            # timeout occurred).
            return "%s: %s" % (msg, e)

        try:
            ping_recvd = resp.stdout.strip() == "ping"
        except Exception:
            # This happens when there was a timeout in SSHMaster (in this
            # situation, that almost always means unable to establish
            # connection or a loss of connection).
            return msg

        if ping_recvd:
            self.alive = True
            return ""

        # This should probably never happen.
        return "Communication failure with host %s when checking connection" % self.host

    def connect_and_ping(self):
        if not self.alive:
            self.connect()
        return self.ping()

    def run(self):
        while True:
            if self.iteration():
                return

    def iteration(self):
        try:
            item, shell, rq = self.q.get(timeout=30)
        except Empty:
            self.connect_and_ping()
            return False

        if item is STOP_RUNNING:
            return True

        msg = self.connect_and_ping()
        if not self.alive:
            logging.debug(msg)
            resp = [Exception(msg)] * len(item)
            rq.put(resp)
            return False

        try:
            resp = self.master.exec_commands(item, shell, self.timeout)
        except Exception as e:
            self.alive = False
            msgstr = "" if self.host in self.localaddrs else "ssh "
            msg = "Lost %sconnection while running command on host %s: %s" % (msgstr, self.host, e)
            logging.debug(msg)
            resp = [Exception(msg)] * len(item)
            time.sleep(2)
        rq.put(resp)

        return False

    def send_commands(self, commands, shell, rq):
        self.q.put((commands, shell, rq))


class MultiMasterManager:
    def __init__(self, localaddrs=[]):
        self.masters = {}
        self.response_queues = {}
        self.localaddrs = localaddrs

    def setup(self, host, timeout):
        if host not in self.masters:
            self.masters[host] = HostHandler(host, self.localaddrs, timeout)
            self.masters[host].start()

    def send_commands(self, host, commands, timeout, shell=False):
        self.setup(host, timeout)
        rq = Queue()
        self.response_queues[host] = rq
        self.masters[host].send_commands(commands, shell, rq)

    def get_result(self, host, hosttimeout):
        # Add a few seconds to the host timeout in order to let the
        # command timeout happen first.
        hosttimeout += 5

        rq = self.response_queues[host]
        try:
            return rq.get(timeout=hosttimeout)
        except Empty:
            self.shutdown(host)
            # This can happen due to commands that take a while to run, a
            # loss of connectivity to remote host, or both.
            return [Exception("Timeout waiting for commands to finish on host %s" % host)] #FIXME: needs to be the right length

    def exec_command(self, host, command, timeout=30):
        return self.exec_commands(host, [command], timeout)[0]

    def exec_commands(self, host, commands, timeout=60):
        self.send_commands(host, commands, timeout)
        return self.get_result(host, timeout)

    def exec_multihost_commands(self, cmds, shell=False, timeout=60):
        hosts = collections.defaultdict(list)
        for host, cmd in cmds:
            hosts[host].append(cmd)

        for host, cmds in hosts.items():
            self.send_commands(host, cmds, timeout, shell)

        for host in hosts:
            for res in self.get_result(host, timeout):
                yield host, res

    def host_status(self):
        for h, o in self.masters.items():
            if h not in self.localaddrs:
                yield h, o.alive

    def shutdown(self, host):
        self.masters[host].shutdown()
        del self.masters[host]

    def shutdown_all(self):
        for handler in self.masters.values():
            handler.shutdown()
        self.masters = {}

    __del__ = shutdown_all

