# Copyright (c) 2012 Nicira, Inc.
#
# 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, version):
    assert isinstance(conn, UnixctlConnection)
    version = "%s (Open vSwitch) %s" % (ovs.util.PROGRAM_NAME, version)
    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, version=None):
        """Creates a new UnixctlServer which listens on a unixctl socket
        created at 'path'.  If 'path' is None, the default path is chosen.
        'version' contains the version of the server as reported by the unixctl
        version command.  If None, ovs.version.VERSION is used."""

        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())

        if version is None:
            version = ovs.version.VERSION

        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, version)

        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))