import os.path
import sys
from logging import getLogger
from optparse import OptionParser

from configobj import ConfigObj
from configobj import ConfigObjError
from twisted.python.compat import StringType

from landscape.lib import cli


def add_cli_options(parser, filename=None):
    """Add common config-related CLI options to the given arg parser."""
    cfgfilehelp = (
        "Use config from this file (any command line "
        "options override settings from the file)."
    )
    if filename is not None:
        cfgfilehelp += f" (default: {filename!r})"
    parser.add_option(
        "-c",
        "--config",
        metavar="FILE",
        default=filename,
        help=cfgfilehelp,
    )


class ConfigSpecOptionParser(OptionParser):

    _config_spec_definitions = {}

    def __init__(self, unsaved_options=None):
        OptionParser.__init__(self, unsaved_options)

    def add_option(self, *args, **kwargs):
        option = OptionParser.add_option(self, *args, **kwargs)
        print(dir(option))
        print(option.get_opt_string())
        return option


class BaseConfiguration:
    """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.

    Default values for supported options are set as in make_parser.
    """

    version = None

    required_options = ()
    unsaved_options = ()
    default_config_filenames = ()
    default_data_dir = None
    config_section = None

    def __init__(self):
        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, StringType):
            option = self._parser.get_option("--" + name.replace("_", "-"))
            if option is not None:
                value = option.convert_value(None, value)
        return value

    def clone(self):
        """
        Return a new configuration object, with the same settings as this one.
        """
        config = self.__class__()
        config._set_options = self._set_options.copy()
        config._command_line_options = self._command_line_options.copy()
        config._config_filename = self._config_filename
        config._config_file_options = self._config_file_options.copy()
        return config

    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().__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_default_config=False):
        """
        Load configuration data from command line arguments and a config file.

        @param accept_nonexistent_default_config: If True, don't complain if
            default configuration files aren't found

        @raise: A SystemExit if the arguments are bad.

        """
        self.load_command_line(args)

        if self.config:
            config_filenames = [self.config]
            allow_missing = False
        else:
            config_filenames = self.default_config_filenames
            allow_missing = accept_nonexistent_default_config
        # Parse configuration file, if found.
        for config_filename in config_filenames:
            if os.path.isfile(config_filename) and os.access(
                config_filename,
                os.R_OK,
            ):

                self.load_configuration_file(config_filename)
                break

        else:
            if not allow_missing:
                if len(config_filenames) == 1:
                    message = (
                        f"error: config file {config_filenames[0]} "
                        "can't be read"
                    )
                else:
                    message = "error: no config file could be read"
                sys.exit(message)

        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 --{} "
                    "or the '{}' directive in the config file.".format(
                        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_obj = self._get_config_object()
        try:
            self._config_file_options = config_obj[self.config_section]
        except KeyError:
            pass

    def _get_config_object(self, alternative_config=None):
        """Create a L{ConfigObj} consistent with our preferences.

        @param config_source: Optional readable source to read from instead of
            the default configuration file.
        """
        config_source = alternative_config or self.get_config_filename()
        # Setting list_values to False prevents ConfigObj from being "smart"
        # about lists (it now treats them as strings). See bug #1228301 for
        # more context.
        # Setting raise_errors to False causes ConfigObj to batch all parsing
        # errors into one ConfigObjError raised at the end of the parse instead
        # of raising the first one and then exiting.  This also allows us to
        # recover the good config values in the error handler below.
        # Setting write_empty_values to True prevents configObj writes
        # from writing "" as an empty value, which get_plugins interprets as
        # '""' which search for a plugin named "".  See bug #1241821.
        try:
            config_obj = ConfigObj(
                config_source,
                list_values=False,
                raise_errors=False,
                write_empty_values=True,
                encoding=getattr(self, "encoding", None),
            )
        except ConfigObjError as e:
            logger = getLogger()
            logger.warn("ERROR at {}: {}".format(config_source, str(e)))
            # Good configuration values are recovered here
            config_obj = e.config
        return config_obj

    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()

        # Make sure we read the old values from the config file so that we
        # don't remove *unrelated* values.
        config_obj = self._get_config_object()
        if self.config_section not in config_obj:
            config_obj[self.config_section] = {}
        all_options = self._config_file_options.copy()
        all_options.update(self._command_line_options)
        all_options.update(self._set_options)
        section = config_obj[self.config_section]
        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)
                    and name not in self._config_file_options
                    and name not in self._command_line_options
                ):

                    # We don't want to write this value to the config file
                    # as it is default value and as not present in the
                    # config file
                    if name in config_obj[self.config_section]:
                        del config_obj[self.config_section][name]
                else:
                    section[name] = value
        config_obj[self.config_section] = section
        config_obj.filename = filename
        config_obj.write()

    def make_parser(self, cfgfile=None, datadir=None):
        """Parser factory for supported options.

        @return: An OptionParser preset with options that all
            programs commonly accept. These include
              - config
              - data_path
        """
        parser = OptionParser(version=self.version)
        cli.add_cli_options(parser, cfgfile, datadir)
        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


def get_bindir(config=None):
    """Return the directory path where the client binaries are.

    If the config is None, it doesn't have a "bindir" attribute, or its
    value is None, then sys.argv[0] is returned.
    """
    try:
        bindir = config.bindir
    except AttributeError:  # ...also the result if config is None.
        bindir = None
    if bindir is None:
        bindir = os.path.dirname(os.path.abspath(sys.argv[0]))
    return bindir
