# This file is part of fedmsg.
# Copyright (C) 2012 - 2014 Red Hat, Inc.
#
# fedmsg is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
#
# fedmsg 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
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with fedmsg; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
#
# Authors:  Ralph Bean <rbean@redhat.com>
#
""" :mod:`fedmsg.config` handles loading, processing and validation of
all configuration.

The configuration values used at runtime are determined by checking in
the following order

    - Built-in defaults
    - Config file (/etc/fedmsg.d/*.py)
    - Config file (./fedmsg.d/*.py)
    - Command line arguments

For example, if a config value does not appear in either the config file or on
the command line, then the built-in default is used.  If a value appears in
both the config file and as a command line argument, then the command line
value is used.

You can print the runtime configuration to the terminal by using the
``fedmsg-config`` command implemented by
:func:`fedmsg.commands.config.config`.
"""

import argparse
import copy
import os
import sys
import textwrap
import warnings

from kitchen.iterutils import iterate
from fedmsg.encoding import pretty_dumps


VALID_ENVIRONMENTS = ['dev', 'stg', 'prod']
bare_format = "[%(asctime)s][%(name)10s %(levelname)7s] %(message)s"

defaults = dict(
    topic_prefix="org.fedoraproject",
    environment="dev",
    io_threads=1,
    post_init_sleep=0.5,
    timeout=2,
    print_config=False,
    high_water_mark=0,  # zero means no limit
    zmq_linger=1000,    # Wait one second before timing out on fedmsg-relay
    active=False,       # generally only true for fedmsg-logger
    persistent_store=None,  # an object.  See the fedmsg.replay module.
    logging=dict(
        version=1,
        formatters=dict(
            bare={
                "datefmt": "%Y-%m-%d %H:%M:%S",
                "format": bare_format
            },
        ),
        handlers=dict(
            console={
                "class": "logging.StreamHandler",
                "formatter": "bare",
                "level": "INFO",
                "stream": "ext://sys.stdout",
            }
        ),
        loggers=dict(
            fedmsg={
                "level": "INFO",
                "propagate": False,
                "handlers": ["console"],
            },
            moksha={
                "level": "INFO",
                "propagate": False,
                "handlers": ["console"],
            },
        ),
    ),
)

__cache = {}


def load_config(extra_args=None,
                doc=None,
                filenames=None,
                invalidate_cache=False,
                fedmsg_command=False,
                disable_defaults=False):
    """ Setup a runtime config dict by integrating the following sources
    (ordered by precedence):

      - defaults (unless disable_defaults = True)
      - config file
      - command line arguments

    If the ``fedmsg_command`` argument is False, no command line arguments are
    checked.

    """
    global __cache

    if invalidate_cache:
        __cache = {}

    if __cache:
        return __cache

    # Coerce defaults if arguments are not supplied.
    extra_args = extra_args or []
    doc = doc or ""

    if not disable_defaults:
        config = copy.deepcopy(defaults)
    else:
        config = {}

    config.update(_process_config_file(filenames=filenames))

    # This is optional (and defaults to false) so that only 'fedmsg-*' commands
    # are required to provide these arguments.
    # For instance, the moksha-hub command takes a '-v' argument and internally
    # makes calls to fedmsg.  We don't want to impose all of fedmsg's CLI
    # option constraints on programs that use fedmsg, so we make it optional.
    if fedmsg_command:
        config.update(_process_arguments(extra_args, doc, config))

    # If the user specified a config file on the command line, then start over
    # but read in that file instead.
    if not filenames and config.get('config_filename', None):
        return load_config(extra_args, doc,
                           filenames=[config['config_filename']],
                           fedmsg_command=fedmsg_command,
                           disable_defaults=disable_defaults)

    # Just a little debug option.  :)
    if config.get('print_config'):
        print(pretty_dumps(config))
        sys.exit(0)

    if config.get('environment', 'prod') not in VALID_ENVIRONMENTS:
        raise ValueError("%r not one of %r" % (
            config['environment'], VALID_ENVIRONMENTS))

    if not disable_defaults and 'endpoints' not in config:
        raise ValueError("No config value 'endpoints' found.")

    if not isinstance(config.get('endpoints', {}), dict):
        raise ValueError("The 'endpoint' config value must be a dict.")

    if 'endpoints' in config:
        config['endpoints'] = dict([
            (k, list(iterate(v))) for k, v in config['endpoints'].items()
        ])

    if 'srv_endpoints' in config and len(config['srv_endpoints']) > 0:
        from dns.resolver import query, NXDOMAIN, Timeout, NoNameservers
        for e in config['srv_endpoints']:
            urls = []
            try:
                records = query('_fedmsg._tcp.{0}'.format(e), 'SRV')
            except NXDOMAIN:
                warnings.warn("There is no appropriate SRV records " +
                              "for {0}".format(e))
                continue
            except Timeout:
                warnings.warn("The DNS query for the SRV records of" +
                              " {0} timed out.".format(e))
                continue
            except NoNameservers:
                warnings.warn("No name server is available, please " +
                              "check the configuration")
                break

            for rec in records:
                urls.append('tcp://{hostname}:{port}'.format(
                    hostname=rec.target.to_text(),
                    port=rec.port
                ))
            config['endpoints'][e] = list(iterate(urls))

    if 'topic_prefix_re' not in config and 'topic_prefix' in config:
        # Turn "org.fedoraproject" into "org\.fedoraproject\.(dev|stg|prod)"
        config['topic_prefix_re'] = config['topic_prefix'].replace('.', '\.')\
            + '\.(%s)' % '|'.join(VALID_ENVIRONMENTS)

    __cache = config
    return config


def build_parser(declared_args, doc, config=None, prog=None):
    """ Return the global :class:`argparse.ArgumentParser` used by all fedmsg
    commands.

    Extra arguments can be supplied with the `declared_args` argument.
    """

    config = config or copy.deepcopy(defaults)
    prog = prog or sys.argv[0]

    parser = argparse.ArgumentParser(
        description=textwrap.dedent(doc),
        formatter_class=argparse.RawDescriptionHelpFormatter,
        prog=prog,
    )

    parser.add_argument(
        '--io-threads',
        dest='io_threads',
        type=int,
        help="Number of io threads for 0mq to use",
        default=config['io_threads'],
    )
    parser.add_argument(
        '--topic-prefix',
        dest='topic_prefix',
        type=str,
        help="Prefix for the topic of each message sent.",
        default=config['topic_prefix'],
    )
    parser.add_argument(
        '--post-init-sleep',
        dest='post_init_sleep',
        type=float,
        help="Number of seconds to sleep after initializing.",
        default=config['post_init_sleep'],
    )
    parser.add_argument(
        '--config-filename',
        dest='config_filename',
        help="Config file to use.",
        default=None,
    )
    parser.add_argument(
        '--print-config',
        dest='print_config',
        help='Simply print out the configuration and exit.  No action taken.',
        default=False,
        action='store_true',
    )
    parser.add_argument(
        '--timeout',
        dest='timeout',
        help="Timeout in seconds for any blocking zmq operations.",
        type=float,
        default=config['timeout'],
    )
    parser.add_argument(
        '--high-water-mark',
        dest='high_water_mark',
        help="Limit on the number of messages in the queue before blocking.",
        type=int,
        default=config['high_water_mark'],
    )
    parser.add_argument(
        '--linger',
        dest='zmq_linger',
        help="Number of milliseconds to wait before timing out connections.",
        type=int,
        default=config['zmq_linger'],
    )

    for args, kwargs in declared_args:
        # Replace the hard-coded extra_args default with the config file value
        # (if it exists)
        if all([k in kwargs for k in ['dest', 'default']]):
            kwargs['default'] = config.get(
                kwargs['dest'], kwargs['default'])

        # Having slurped smart defaults from the config file, add the CLI arg.
        parser.add_argument(*args, **kwargs)

    return parser


def _process_arguments(declared_args, doc, config):
    parser = build_parser(declared_args, doc, config)
    args = parser.parse_args()
    return dict(args._get_kwargs())


def _gather_configs_in(directory):
    """ Return list of fully qualified python filenames in the given dir """
    try:
        return sorted([
            os.path.join(directory, fname)
            for fname in os.listdir(directory)
            if fname.endswith('.py')
        ])
    except OSError:
        return []


def _recursive_update(d1, d2):
    """ Little helper function that does what d1.update(d2) does,
    but works nice and recursively with dicts of dicts of dicts.

    It's not necessarily very efficient.
    """

    for k in set(d1).intersection(d2):
        if isinstance(d1[k], dict) and isinstance(d2[k], dict):
            d1[k] = _recursive_update(d1[k], d2[k])
        else:
            d1[k] = d2[k]

    for k in set(d2).difference(d1):
        d1[k] = d2[k]

    return d1


def execfile(fname, variables):
    """ This is builtin in python2, but we have to roll our own on py3. """
    with open(fname) as f:
        code = compile(f.read(), fname, 'exec')
        exec(code, variables)


def _process_config_file(filenames=None):

    filenames = filenames or []

    # Validate that these files are really files
    for fname in filenames:
        if not os.path.isfile(fname):
            raise ValueError("%r is not a file." % fname)

    # If nothing specified, look in the default locations
    if not filenames:
        filenames = [
            '/etc/fedmsg-config.py',
            os.path.expanduser('~/.fedmsg-config.py'),
            os.getcwd() + '/fedmsg-config.py',
        ]
        folders = ["/etc/fedmsg.d/", os.path.expanduser('~/.fedmsg.d/'),
                   os.getcwd() + '/fedmsg.d/', ]
        if 'VIRTUAL_ENV' in os.environ:
            folders.append(os.path.join(
                os.environ['VIRTUAL_ENV'], 'etc/fedmsg.d'))

        filenames = sum(map(_gather_configs_in, folders), []) + filenames

    # Each .ini file should really be a python module that
    # builds a config dict.
    config = {}
    for fname in filenames:
        if os.path.isfile(fname):
            variables = {}
            try:
                execfile(fname, variables)
                config = _recursive_update(config, variables['config'])
            except IOError as e:
                warnings.warn(str(e))

    return config
