# vi: ts=4 expandtab syntax=python
#
#    Copyright (C) 2009-2010 Canonical Ltd.
#    Copyright (C) 2012 Hewlett-Packard Development Company, L.P.
#
#    Author: Scott Moser <scott.moser@canonical.com>
#    Author: Juerg Haefliger <juerg.haefliger@hp.com>
#
#    This program is free software: you can redistribute it and/or modify
#    it under the terms of the GNU General Public License version 3, as
#    published by the Free Software Foundation.
#
#    This program is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#    GNU General Public License for more details.
#
#    You should have received a copy of the GNU General Public License
#    along with this program.  If not, see <http://www.gnu.org/licenses/>.
"""
rsyslog module allows configuration of syslog logging via rsyslog
Configuration is done under the cloud-config top level 'rsyslog'.

Under 'rsyslog' you can define:
  - configs:  [default=[]]
    this is a list.  entries in it are a string or a dictionary.
    each entry has 2 parts:
       * content
       * filename
    if the entry is a string, then it is assigned to 'content'.
    for each entry, content is written to the provided filename.
    if filename is not provided, its default is read from 'config_filename'

    Content here can be any valid rsyslog configuration.  No format
    specific format is enforced.

    For simply logging to an existing remote syslog server, via udp:
      configs: ["*.* @192.168.1.1"]

  - remotes: [default={}]
    This is a dictionary of name / value pairs.
    In comparison to 'config's, it is more focused in that it only supports
    remote syslog configuration.  It is not rsyslog specific, and could
    convert to other syslog implementations.

    Each entry in remotes is a 'name' and a 'value'.
     * name: an string identifying the entry.  good practice would indicate
       using a consistent and identifiable string for the producer.
       For example, the MAAS service could use 'maas' as the key.
     * value consists of the following parts:
       * optional filter for log messages
         default if not present: *.*
       * optional leading '@' or '@@' (indicates udp or tcp respectively).
         default if not present (udp): @
         This is rsyslog format for that. if not present, is '@'.
       * ipv4 or ipv6 or hostname
         ipv6 addresses must be in [::1] format. (@[fd00::1]:514)
       * optional port
         port defaults to 514

  - config_filename: [default=20-cloud-config.conf]
    this is the file name to use if none is provided in a config entry.

  - config_dir: [default=/etc/rsyslog.d]
    this directory is used for filenames that are not absolute paths.

  - service_reload_command: [default="auto"]
    this command is executed if files have been written and thus the syslog
    daemon needs to be told.

Note, since cloud-init 0.5 a legacy version of rsyslog config has been
present and is still supported. See below for the mappings between old
value and new value:
   old value           -> new value
   'rsyslog'           -> rsyslog/configs
   'rsyslog_filename'  -> rsyslog/config_filename
   'rsyslog_dir'       -> rsyslog/config_dir

the legacy config does not support 'service_reload_command'.

Example config:
  #cloud-config
  rsyslog:
    configs:
      - "*.* @@192.158.1.1"
      - content: "*.*   @@192.0.2.1:10514"
        filename: 01-example.conf
      - content: |
        *.*   @@syslogd.example.com
    remotes:
      maas: "192.168.1.1"
      juju: "10.0.4.1"
    config_dir: config_dir
    config_filename: config_filename
    service_reload_command: [your, syslog, restart, command]

Example Legacy config:
  #cloud-config
  rsyslog:
    - "*.* @@192.158.1.1"
  rsyslog_dir: /etc/rsyslog-config.d/
  rsyslog_filename: 99-local.conf
"""

import os
import re
import six

from cloudinit import log as logging
from cloudinit import util

DEF_FILENAME = "20-cloud-config.conf"
DEF_DIR = "/etc/rsyslog.d"
DEF_RELOAD = "auto"
DEF_REMOTES = {}

KEYNAME_CONFIGS = 'configs'
KEYNAME_FILENAME = 'config_filename'
KEYNAME_DIR = 'config_dir'
KEYNAME_RELOAD = 'service_reload_command'
KEYNAME_LEGACY_FILENAME = 'rsyslog_filename'
KEYNAME_LEGACY_DIR = 'rsyslog_dir'
KEYNAME_REMOTES = 'remotes'

LOG = logging.getLogger(__name__)

COMMENT_RE = re.compile(r'[ ]*[#]+[ ]*')
HOST_PORT_RE = re.compile(
    r'^(?P<proto>[@]{0,2})'
    '(([[](?P<bracket_addr>[^\]]*)[\]])|(?P<addr>[^:]*))'
    '([:](?P<port>[0-9]+))?$')


def reload_syslog(command=DEF_RELOAD, systemd=False):
    service = 'rsyslog'
    if command == DEF_RELOAD:
        if systemd:
            cmd = ['systemctl', 'reload-or-try-restart', service]
        else:
            cmd = ['service', service, 'restart']
    else:
        cmd = command
    util.subp(cmd, capture=True)


def load_config(cfg):
    # return an updated config with entries of the correct type
    # support converting the old top level format into new format
    mycfg = cfg.get('rsyslog', {})

    if isinstance(cfg.get('rsyslog'), list):
        mycfg = {KEYNAME_CONFIGS: cfg.get('rsyslog')}
        if KEYNAME_LEGACY_FILENAME in cfg:
            mycfg[KEYNAME_FILENAME] = cfg[KEYNAME_LEGACY_FILENAME]
        if KEYNAME_LEGACY_DIR in cfg:
            mycfg[KEYNAME_DIR] = cfg[KEYNAME_LEGACY_DIR]

    fillup = (
        (KEYNAME_CONFIGS, [], list),
        (KEYNAME_DIR, DEF_DIR, six.string_types),
        (KEYNAME_FILENAME, DEF_FILENAME, six.string_types),
        (KEYNAME_RELOAD, DEF_RELOAD, six.string_types + (list,)),
        (KEYNAME_REMOTES, DEF_REMOTES, dict))

    for key, default, vtypes in fillup:
        if key not in mycfg or not isinstance(mycfg[key], vtypes):
            mycfg[key] = default

    return mycfg


def apply_rsyslog_changes(configs, def_fname, cfg_dir):
    # apply the changes in 'configs' to the paths in def_fname and cfg_dir
    # return a list of the files changed
    files = []
    for cur_pos, ent in enumerate(configs):
        if isinstance(ent, dict):
            if "content" not in ent:
                LOG.warn("No 'content' entry in config entry %s", cur_pos + 1)
                continue
            content = ent['content']
            filename = ent.get("filename", def_fname)
        else:
            content = ent
            filename = def_fname

        filename = filename.strip()
        if not filename:
            LOG.warn("Entry %s has an empty filename", cur_pos + 1)
            continue

        filename = os.path.join(cfg_dir, filename)

        # Truncate filename first time you see it
        omode = "ab"
        if filename not in files:
            omode = "wb"
            files.append(filename)

        try:
            endl = ""
            if not content.endswith("\n"):
                endl = "\n"
            util.write_file(filename, content + endl, omode=omode)
        except Exception:
            util.logexc(LOG, "Failed to write to %s", filename)

    return files


def parse_remotes_line(line, name=None):
    try:
        data, comment = COMMENT_RE.split(line)
        comment = comment.strip()
    except ValueError:
        data, comment = (line, None)

    toks = data.strip().split()
    match = None
    if len(toks) == 1:
        host_port = data
    elif len(toks) == 2:
        match, host_port = toks
    else:
        raise ValueError("line had multiple spaces: %s" % data)

    toks = HOST_PORT_RE.match(host_port)

    if not toks:
        raise ValueError("Invalid host specification '%s'" % host_port)

    proto = toks.group('proto')
    addr = toks.group('addr') or toks.group('bracket_addr')
    port = toks.group('port')

    if addr.startswith("[") and not addr.endswith("]"):
        raise ValueError("host spec had invalid brackets: %s" % addr)

    if comment and not name:
        name = comment

    t = SyslogRemotesLine(name=name, match=match, proto=proto,
                          addr=addr, port=port)
    t.validate()
    return t


class SyslogRemotesLine(object):
    def __init__(self, name=None, match=None, proto=None, addr=None,
                 port=None):
        if not match:
            match = "*.*"
        self.name = name
        self.match = match
        if not proto:
            proto = "udp"
        if proto == "@":
            proto = "udp"
        elif proto == "@@":
            proto = "tcp"
        self.proto = proto

        self.addr = addr
        if port:
            self.port = int(port)
        else:
            self.port = None

    def validate(self):
        if self.port:
            try:
                int(self.port)
            except ValueError:
                raise ValueError("port '%s' is not an integer" % self.port)

        if not self.addr:
            raise ValueError("address is required")

    def __repr__(self):
        return "[name=%s match=%s proto=%s address=%s port=%s]" % (
            self.name, self.match, self.proto, self.addr, self.port
        )

    def __str__(self):
        buf = self.match + " "
        if self.proto == "udp":
            buf += "@"
        elif self.proto == "tcp":
            buf += "@@"

        if ":" in self.addr:
            buf += "[" + self.addr + "]"
        else:
            buf += self.addr

        if self.port:
            buf += ":%s" % self.port

        if self.name:
            buf += " # %s" % self.name
        return buf


def remotes_to_rsyslog_cfg(remotes, header=None, footer=None):
    if not remotes:
        return None
    lines = []
    if header is not None:
        lines.append(header)
    for name, line in remotes.items():
        if not line:
            continue
        try:
            lines.append(str(parse_remotes_line(line, name=name)))
        except ValueError as e:
            LOG.warn("failed loading remote %s: %s [%s]", name, line, e)
    if footer is not None:
        lines.append(footer)
    return '\n'.join(lines) + "\n"


def handle(name, cfg, cloud, log, _args):
    if 'rsyslog' not in cfg:
        log.debug(("Skipping module named %s,"
                   " no 'rsyslog' key in configuration"), name)
        return

    mycfg = load_config(cfg)
    configs = mycfg[KEYNAME_CONFIGS]

    if mycfg[KEYNAME_REMOTES]:
        configs.append(
            remotes_to_rsyslog_cfg(
                mycfg[KEYNAME_REMOTES],
                header="# begin remotes",
                footer="# end remotes",
            ))

    if not mycfg['configs']:
        log.debug("Empty config rsyslog['configs'], nothing to do")
        return

    changes = apply_rsyslog_changes(
        configs=mycfg[KEYNAME_CONFIGS],
        def_fname=mycfg[KEYNAME_FILENAME],
        cfg_dir=mycfg[KEYNAME_DIR])

    if not changes:
        log.debug("restart of syslog not necessary, no changes made")
        return

    try:
        restarted = reload_syslog(
            command=mycfg[KEYNAME_RELOAD],
            systemd=cloud.distro.uses_systemd()),
    except util.ProcessExecutionError as e:
        restarted = False
        log.warn("Failed to reload syslog", e)

    if restarted:
        # This only needs to run if we *actually* restarted
        # syslog above.
        cloud.cycle_logging()
        # This should now use rsyslog if
        # the logging was setup to use it...
        log.debug("%s configured %s files", name, changes)
