# Copyright (c) 2012 Nicira Networks
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at:
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import copy
import errno
import os
import types

import ovs.daemon
import ovs.dirs
import ovs.jsonrpc
import ovs.stream
import ovs.util
import ovs.version
import ovs.vlog

Message = ovs.jsonrpc.Message
vlog = ovs.vlog.Vlog("unixctl")
commands = {}
strtypes = types.StringTypes


class _UnixctlCommand(object):
    def __init__(self, usage, min_args, max_args, callback, aux):
        self.usage = usage
        self.min_args = min_args
        self.max_args = max_args
        self.callback = callback
        self.aux = aux


def _unixctl_help(conn, unused_argv, unused_aux):
    assert isinstance(conn, UnixctlConnection)
    reply = "The available commands are:\n"
    command_names = sorted(commands.keys())
    for name in command_names:
        reply += "  "
        usage = commands[name].usage
        if usage:
            reply += "%-23s %s" % (name, usage)
        else:
            reply += name
        reply += "\n"
    conn.reply(reply)


def _unixctl_version(conn, unused_argv, unused_aux):
    assert isinstance(conn, UnixctlConnection)
    version = "%s (Open vSwitch) %s %s" % (ovs.util.PROGRAM_NAME,
                                           ovs.version.VERSION,
                                           ovs.version.BUILDNR)
    conn.reply(version)


def command_register(name, usage, min_args, max_args, callback, aux):
    """ Registers a command with the given 'name' to be exposed by the
    UnixctlServer. 'usage' describes the arguments to the command; it is used
    only for presentation to the user in "help" output.

    'callback' is called when the command is received.  It is passed a
    UnixctlConnection object, the list of arguments as unicode strings, and
    'aux'.  Normally 'callback' should reply by calling
    UnixctlConnection.reply() or UnixctlConnection.reply_error() before it
    returns, but if the command cannot be handled immediately, then it can
    defer the reply until later.  A given connection can only process a single
    request at a time, so a reply must be made eventually to avoid blocking
    that connection."""

    assert isinstance(name, strtypes)
    assert isinstance(usage, strtypes)
    assert isinstance(min_args, int)
    assert isinstance(max_args, int)
    assert isinstance(callback, types.FunctionType)

    if name not in commands:
        commands[name] = _UnixctlCommand(usage, min_args, max_args, callback,
                                         aux)


def socket_name_from_target(target):
    assert isinstance(target, strtypes)

    if target.startswith("/"):
        return 0, target

    pidfile_name = "%s/%s.pid" % (ovs.dirs.RUNDIR, target)
    pid = ovs.daemon.read_pidfile(pidfile_name)
    if pid < 0:
        return -pid, "cannot read pidfile \"%s\"" % pidfile_name

    return 0, "%s/%s.%d.ctl" % (ovs.dirs.RUNDIR, target, pid)


class UnixctlConnection(object):
    def __init__(self, rpc):
        assert isinstance(rpc, ovs.jsonrpc.Connection)
        self._rpc = rpc
        self._request_id = None

    def run(self):
        self._rpc.run()
        error = self._rpc.get_status()
        if error or self._rpc.get_backlog():
            return error

        for _ in range(10):
            if error or self._request_id:
                break

            error, msg = self._rpc.recv()
            if msg:
                if msg.type == Message.T_REQUEST:
                    self._process_command(msg)
                else:
                    # XXX: rate-limit
                    vlog.warn("%s: received unexpected %s message"
                              % (self._rpc.name,
                                 Message.type_to_string(msg.type)))
                    error = errno.EINVAL

            if not error:
                error = self._rpc.get_status()

        return error

    def reply(self, body):
        self._reply_impl(True, body)

    def reply_error(self, body):
        self._reply_impl(False, body)

    # Called only by unixctl classes.
    def _close(self):
        self._rpc.close()
        self._request_id = None

    def _wait(self, poller):
        self._rpc.wait(poller)
        if not self._rpc.get_backlog():
            self._rpc.recv_wait(poller)

    def _reply_impl(self, success, body):
        assert isinstance(success, bool)
        assert body is None or isinstance(body, strtypes)

        assert self._request_id is not None

        if body is None:
            body = ""

        if body and not body.endswith("\n"):
            body += "\n"

        if success:
            reply = Message.create_reply(body, self._request_id)
        else:
            reply = Message.create_error(body, self._request_id)

        self._rpc.send(reply)
        self._request_id = None

    def _process_command(self, request):
        assert isinstance(request, ovs.jsonrpc.Message)
        assert request.type == ovs.jsonrpc.Message.T_REQUEST

        self._request_id = request.id

        error = None
        params = request.params
        method = request.method
        command = commands.get(method)
        if command is None:
            error = '"%s" is not a valid command' % method
        elif len(params) < command.min_args:
            error = '"%s" command requires at least %d arguments' \
                    % (method, command.min_args)
        elif len(params) > command.max_args:
            error = '"%s" command takes at most %d arguments' \
                    % (method, command.max_args)
        else:
            for param in params:
                if not isinstance(param, strtypes):
                    error = '"%s" command has non-string argument' % method
                    break

            if error is None:
                unicode_params = [unicode(p) for p in params]
                command.callback(self, unicode_params, command.aux)

        if error:
            self.reply_error(error)


class UnixctlServer(object):
    def __init__(self, listener):
        assert isinstance(listener, ovs.stream.PassiveStream)
        self._listener = listener
        self._conns = []

    def run(self):
        for _ in range(10):
            error, stream = self._listener.accept()
            if not error:
                rpc = ovs.jsonrpc.Connection(stream)
                self._conns.append(UnixctlConnection(rpc))
            elif error == errno.EAGAIN:
                break
            else:
                # XXX: rate-limit
                vlog.warn("%s: accept failed: %s" % (self._listener.name,
                                                     os.strerror(error)))

        for conn in copy.copy(self._conns):
            error = conn.run()
            if error and error != errno.EAGAIN:
                conn._close()
                self._conns.remove(conn)

    def wait(self, poller):
        self._listener.wait(poller)
        for conn in self._conns:
            conn._wait(poller)

    def close(self):
        for conn in self._conns:
            conn._close()
        self._conns = None

        self._listener.close()
        self._listener = None

    @staticmethod
    def create(path):
        assert path is None or isinstance(path, strtypes)

        if path is not None:
            path = "punix:%s" % ovs.util.abs_file_name(ovs.dirs.RUNDIR, path)
        else:
            path = "punix:%s/%s.%d.ctl" % (ovs.dirs.RUNDIR,
                                           ovs.util.PROGRAM_NAME, os.getpid())

        error, listener = ovs.stream.PassiveStream.open(path)
        if error:
            ovs.util.ovs_error(error, "could not initialize control socket %s"
                               % path)
            return error, None

        command_register("help", "", 0, 0, _unixctl_help, None)
        command_register("version", "", 0, 0, _unixctl_version, None)

        return 0, UnixctlServer(listener)


class UnixctlClient(object):
    def __init__(self, conn):
        assert isinstance(conn, ovs.jsonrpc.Connection)
        self._conn = conn

    def transact(self, command, argv):
        assert isinstance(command, strtypes)
        assert isinstance(argv, list)
        for arg in argv:
            assert isinstance(arg, strtypes)

        request = Message.create_request(command, argv)
        error, reply = self._conn.transact_block(request)

        if error:
            vlog.warn("error communicating with %s: %s"
                      % (self._conn.name, os.strerror(error)))
            return error, None, None

        if reply.error is not None:
            return 0, str(reply.error), None
        else:
            assert reply.result is not None
            return 0, None, str(reply.result)

    def close(self):
        self._conn.close()
        self.conn = None

    @staticmethod
    def create(path):
        assert isinstance(path, str)

        unix = "unix:%s" % ovs.util.abs_file_name(ovs.dirs.RUNDIR, path)
        error, stream = ovs.stream.Stream.open_block(
            ovs.stream.Stream.open(unix))

        if error:
            vlog.warn("failed to connect to %s" % path)
            return error, None

        return 0, UnixctlClient(ovs.jsonrpc.Connection(stream))