import os
import sys

from logging import (getLevelName, getLogger,
                     FileHandler, StreamHandler, Formatter)

from optparse import OptionParser
from ConfigParser import ConfigParser, NoSectionError

from landscape import VERSION
from landscape.lib.persist import Persist

from landscape.upgraders import UPGRADE_MANAGERS


def init_logging(configuration, program_name):
    """Given a basic configuration, set up logging."""
    handlers = []
    if not os.path.exists(configuration.log_dir):
        os.makedirs(configuration.log_dir)
    log_filename = os.path.join(configuration.log_dir, program_name+".log")
    handlers.append(FileHandler(log_filename))
    if not configuration.quiet:
        handlers.append(StreamHandler(sys.stdout))
    getLogger().setLevel(getLevelName(configuration.log_level.upper()))
    for handler in handlers:
        getLogger().addHandler(handler)
        format = ("%(asctime)s %(levelname)-8s [%(threadName)-10s] "
                  "%(message)s")
        handler.setFormatter(Formatter(format))


class BaseConfiguration(object):
    """Base class for configuration implementations.

    @cvar required_options: Optionally, a sequence of key names to require when
        reading or writing a configuration.
    @cvar unsaved_options: Optionally, a sequence of key names to never write
        to the configuration file.  This is useful when you want to provide
        command-line options that should never end up in a configuration file.
    @cvar default_config_filenames: A sequence of filenames to check when
        reading or writing a configuration.
    """

    required_options = ()
    unsaved_options = ()
    default_config_filenames = ["/etc/landscape/client.conf"]
    if (os.path.dirname(os.path.abspath(sys.argv[0]))
        == os.path.abspath("scripts")):
        default_config_filenames.insert(0, "landscape-client.conf")
    default_config_filenames = tuple(default_config_filenames)
    config_section = "client"

    def __init__(self):
        """Default configuration.

        Default values for supported options are set as in L{make_parser}.
        """
        self._set_options = {}
        self._command_line_args = []
        self._command_line_options = {}
        self._config_filename = None
        self._config_file_options = {}
        self._parser = self.make_parser()
        self._command_line_defaults = self._parser.defaults.copy()
        # We don't want them mixed with explicitly given options,
        # otherwise we can't define the precedence properly.
        self._parser.defaults.clear()

    def __getattr__(self, name):
        """Find and return the value of the given configuration parameter.

        The following sources will be searched:
          - The attributes that were explicitly set on this object,
          - The parameters specified on the command line,
          - The parameters specified in the configuration file, and
          - The defaults.

        If no values are found and the parameter does exist as a possible
        parameter, C{None} is returned.

        Otherwise C{AttributeError} is raised.
        """
        for options in [self._set_options,
                        self._command_line_options,
                        self._config_file_options,
                        self._command_line_defaults]:
            if name in options:
                value = options[name]
                break
        else:
            if self._parser.has_option("--" + name.replace("_", "-")):
                value = None
            else:
                raise AttributeError(name)
        if isinstance(value, basestring):
            option = self._parser.get_option("--" + name.replace("_", "-"))
            if option is not None:
                value = option.convert_value(None, value)
        return value

    def get(self, name, default=None):
        """Return the value of the C{name} option or C{default}."""
        try:
            return self.__getattr__(name)
        except AttributeError:
            return default

    def __setattr__(self, name, value):
        """Set a configuration parameter.

        If the name begins with C{_}, it will only be set on this object and
        not stored in the configuration file.
        """
        if name.startswith("_"):
            super(BaseConfiguration, self).__setattr__(name, value)
        else:
            self._set_options[name] = value

    def reload(self):
        """Reload options using the configured command line arguments.

        @see: L{load_command_line}
        """
        self.load(self._command_line_args)

    def load(self, args, accept_nonexistent_config=False):
        """
        Load configuration data from command line arguments and a config file.

        @raise: A SystemExit if the arguments are bad.
        """
        self.load_command_line(args)

        # Parse configuration file, if found.
        if self.config:
            if os.path.isfile(self.config):
                self.load_configuration_file(self.config)
            elif not accept_nonexistent_config:
                sys.exit("error: file not found: %s" % self.config)
        else:
            for potential_config_file in self.default_config_filenames:
                if os.access(potential_config_file, os.R_OK):
                    self.load_configuration_file(potential_config_file)
                    break

        self._load_external_options()

        # Check that all needed options were given.
        for option in self.required_options:
            if not getattr(self, option):
                sys.exit("error: must specify --%s "
                         "or the '%s' directive in the config file."
                         % (option.replace('_', '-'), option))

    def _load_external_options(self):
        """Hook for loading options from elsewhere (e.g. for --import)."""

    def load_command_line(self, args):
        """Load configuration data from the given command line."""
        self._command_line_args = args
        values = self._parser.parse_args(args)[0]
        self._command_line_options = vars(values)

    def load_configuration_file(self, filename):
        """Load configuration data from the given file name.

        If any data has already been set on this configuration object,
        then the old data will take precedence.
        """
        self._config_filename = filename
        config_parser = ConfigParser()
        config_parser.read(filename)
        try:
            self._config_file_options = dict(
                config_parser.items(self.config_section))
        except NoSectionError:
            pass

    def write(self):
        """Write back configuration to the configuration file.

        Values which match the default option in the parser won't be saved.

        Options are considered in the following precedence:

          1. Manually set options (C{config.option = value})
          2. Options passed in the command line
          3. Previously existent options in the configuration file

        The filename picked for saving configuration options is the one
        returned by L{get_config_filename}.
        """
        # The filename we'll write to
        filename = self.get_config_filename()

        config_parser = ConfigParser()
        # Make sure we read the old values from the config file so that we
        # don't remove *unrelated* values.
        config_parser.read(filename)
        if not config_parser.has_section(self.config_section):
            config_parser.add_section(self.config_section)
        all_options = self._config_file_options.copy()
        all_options.update(self._command_line_options)
        all_options.update(self._set_options)
        for name, value in all_options.items():
            if (name != "config" and
                name not in self.unsaved_options):
                if value == self._command_line_defaults.get(name):
                    config_parser.remove_option(self.config_section, name)
                else:
                    config_parser.set(self.config_section, name, value)
        config_file = open(filename, "w")
        config_parser.write(config_file)
        config_file.close()

    def make_parser(self):
        """Parser factory for supported options

        @return: An L{OptionParser} preset with options that all
            landscape-related programs accept. These include
              - C{config} (C{None})
        """
        parser = OptionParser(version=VERSION)
        parser.add_option("-c", "--config", metavar="FILE",
                          help="Use config from this file (any command line "
                               "options override settings from the file) "
                               "(default: '/etc/landscape/client.conf').")
        return parser

    def get_config_filename(self):
        """Pick the proper configuration file.

        The picked filename is:
          1. C{self.config}, if defined
          2. The last loaded configuration file, if any
          3. The first filename in C{self.default_config_filenames}
        """
        if self.config:
            return self.config
        if self._config_filename:
            return self._config_filename
        if self.default_config_filenames:
            for potential_config_file in self.default_config_filenames:
                if os.access(potential_config_file, os.R_OK):
                    return potential_config_file
            return self.default_config_filenames[0]
        return None

    def get_command_line_options(self):
        """Get currently loaded command line options.

        @see: L{load_command_line}
        """
        return self._command_line_options


class Configuration(BaseConfiguration):
    """Configuration data for Landscape client.

    This contains all simple data, some of it calculated.
    """

    def make_parser(self):
        """Parser factory for supported options.

        @return: An L{OptionParser} preset for all options
            from L{BaseConfiguration.make_parser} plus:
              - C{data_path} (C{"/var/lib/landscape/client/"})
              - C{quiet} (C{False})
              - C{log_dir} (C{"/var/log/landscape"})
              - C{log_level} (C{"info"})
              - C{ignore_sigint} (C{False})
        """
        parser = super(Configuration, self).make_parser()
        parser.add_option("-d", "--data-path", metavar="PATH",
                          default="/var/lib/landscape/client/",
                          help="The directory to store data files in "
                               "(default: '/var/lib/landscape/client/').")
        parser.add_option("-q", "--quiet", default=False, action="store_true",
                          help="Do not log to the standard output.")
        parser.add_option("-l", "--log-dir", metavar="FILE",
                          help="The directory to write log files to "
                               "(default: '/var/log/landscape').",
                          default="/var/log/landscape")
        parser.add_option("--log-level", default="info",
                          help="One of debug, info, warning, error or "
                               "critical.")
        parser.add_option("--ignore-sigint", action="store_true",
                          default=False, help="Ignore interrupt signals.")
        parser.add_option("--ignore-sigusr1", action="store_true",
                          default=False, help="Ignore SIGUSR1 signal to "
                                              "rotate logs.")

        return parser

    @property
    def sockets_path(self):
        """Return the path to the directory where Unix sockets are created."""
        return os.path.join(self.data_path, "sockets")


def get_versioned_persist(service):
    """Get a L{Persist} database with upgrade rules applied.

    Load a L{Persist} database for the given C{service} and upgrade or
    mark as current, as necessary.
    """
    persist = Persist(filename=service.persist_filename)
    upgrade_manager = UPGRADE_MANAGERS[service.service_name]
    if os.path.exists(service.persist_filename):
        upgrade_manager.apply(persist)
    else:
        upgrade_manager.initialize(persist)
    persist.save(service.persist_filename)
    return persist