"""
Labeltool command line interface

This is based on django's ManagementUtility.
"""

import os
import sys
from optparse import make_option, OptionParser
import sloth


class CommandError(Exception):
    """
    Exception class indicating a problem while executing a management
    command.

    If this exception is raised during the execution of a management
    command, it will be caught and turned into a nicely-printed error
    message to the appropriate output stream (i.e., stderr); as a
    result, raising this exception (with a sensible description of the
    error) is the preferred way to indicate that something has gone
    wrong in the execution of a command.
    """
    pass


class BaseCommand(object):
    """
    The base class from which all management commands ultimately
    derive.

    Use this class if you want access to all of the mechanisms which
    parse the command-line arguments and work out what code to call in
    response; if you don't need to change any of that behavior,
    consider using one of the subclasses defined in this file.

    If you are interested in overriding/customizing various aspects of
    the command-parsing and -execution behavior, the normal flow works
    as follows:

    1. ``sloth-cli` loads the command class
       and calls its ``run_from_argv()`` method.

    2. The ``run_from_argv()`` method calls ``create_parser()`` to get
       an ``OptionParser`` for the arguments, parses them, performs
       any environment changes requested by options like
       ``pythonpath``, and then calls the ``execute()`` method,
       passing the parsed arguments.

    3. The ``execute()`` method attempts to carry out the command by
       calling the ``handle()`` method with the parsed arguments; any
       output produced by ``handle()`` will be printed to standard
       output.

    4. If ``handle()`` raised a ``CommandError``, ``execute()`` will
       instead print an error message to ``stderr``.

    Thus, the ``handle()`` method is typically the starting point for
    subclasses; built-in commands and command types either place
    all of their logic in ``handle()``, or perform some additional
    parsing work in ``handle()`` and then delegate from it to more
    specialized methods as needed.

    Several attributes affect behavior at various steps along the way:

    ``args``
        A string listing the arguments accepted by the command,
        suitable for use in help messages; e.g., a command which takes
        a list of application names might set this to '<appname
        appname ...>'.

    ``help``
        A short description of the command, which will be printed in
        help messages.

    ``option_list``
        This is the list of ``optparse`` options which will be fed
        into the command's ``OptionParser`` for parsing arguments.

    """
    # Metadata about this command.
    option_list = (
        make_option('-v', '--verbosity', action='store', dest='verbosity', default='2',
            type='choice', choices=['0', '1', '2', '3', '4'],
            help='Verbosity level; 0=critical, 1=error, 2=warning, 3=info, 4=debug'),
        make_option('-c', '--config',
            help='The Python path to a configuration file, e.g. "myconfig". If this isn\'t provided, sloth\'s default configuration will be used.'),
        make_option('--pythonpath',
            help='A directory to add to the Python path, e.g. "/home/user/labeling".'),
    )
    help = ''
    args = ''

    # Configuration shortcuts that alter various logic.
    can_import_settings = True

    def __init__(self):
        #self.style = color_style()
        self.labeltool = None

    def usage(self, subcommand):
        """
        Return a brief description of how to use this command, by
        default from the attribute ``self.help``.
        """
        usage = '%%prog %s [options] %s' % (subcommand, self.args)
        if self.help:
            return '%s\n\n%s' % (usage, self.help)
        else:
            return usage

    def get_version(self):
        return sloth.VERSION

    def create_parser(self, prog_name, subcommand):
        """
        Create and return the ``OptionParser`` which will be used to
        parse the arguments to this command.
        """
        return OptionParser(prog=prog_name,
                            usage=self.usage(subcommand),
                            version=self.get_version(),
                            option_list=self.option_list)

    def print_help(self, prog_name, subcommand):
        """
        Print the help message for this command, derived from
        ``self.usage()``.
        """
        parser = self.create_parser(prog_name, subcommand)
        parser.print_help()

    def run_from_argv(self, argv):
        """
        Set up any environment changes requested (e.g. python path
        and sloth configuration), then run this command.
        """
        parser = self.create_parser(argv[0], argv[1])
        options, args = parser.parse_args(argv[2:])
        #handle_default_options(options)
        self.execute(*args, **options.__dict__)

    def execute(self, *args, **options):
        """
        Try to execute this command, performing model validation if
        needed (as controlled by the attribute
        ``self.requires_model_validation``). If the command raises a
        ``CommandError``, intercept it and print it sensibly to
        stderr.
        """
        try:
            self.stdout = options.get('stdout', sys.stdout)
            self.stderr = options.get('stderr', sys.stderr)
            output = self.handle(*args, **options)
            if output:
                self.stdout.write(output)
        except CommandError as e:
            self.stderr.write('Error: %s\n' % e)
            sys.exit(1)

    def handle(self, *args, **options):
        """
        The actual logic of the command. Subclasses must implement
        this method.
        """
        raise NotImplementedError()


class NoArgsCommand(BaseCommand):
    """
    A command which takes no arguments on the command line.

    Rather than implementing ``handle()``, subclasses must implement
    ``handle_noargs()``; ``handle()`` itself is overridden to ensure
    no arguments are passed to the command.

    Attempting to pass arguments will raise ``CommandError``.
    """
    args = ''

    def handle(self, *args, **options):
        if args:
            raise CommandError("Command doesn't accept any arguments")
        return self.handle_noargs(**options)

    def handle_noargs(self, **options):
        """
        Perform this command's actions.

        """
        raise NotImplementedError()


class LaxOptionParser(OptionParser):
    """
    An option parser that doesn't raise any errors on unknown options.

    This is needed because the --settings and --pythonpath options affect
    the commands (and thus the options) that are available to the user.
    """
    def error(self, msg):
        pass

    def print_help(self):
        """Output nothing.

        The lax options are included in the normal option parser, so under
        normal usage, we don't need to print the lax options.
        """
        pass

    def print_lax_help(self):
        """Output the basic options available to every command.

        This just redirects to the default print_help() behaviour.
        """
        OptionParser.print_help(self)

    def _process_args(self, largs, rargs, values):
        """
        Overrides OptionParser._process_args to exclusively handle default
        options and ignore args and other options.

        This overrides the behavior of the super class, which stop parsing
        at the first unrecognized option.
        """
        while rargs:
            arg = rargs[0]
            try:
                if arg[0:2] == "--" and len(arg) > 2:
                    # process a single long option (possibly with value(s))
                    # the superclass code pops the arg off rargs
                    self._process_long_opt(rargs, values)
                elif arg[:1] == "-" and len(arg) > 1:
                    # process a cluster of short options (possibly with
                    # value(s) for the last one only)
                    # the superclass code pops the arg off rargs
                    self._process_short_opts(rargs, values)
                else:
                    # it's either a non-default option or an arg
                    # either way, add it to the args list so we can keep
                    # dealing with options
                    del rargs[0]
                    raise Exception
            except:
                largs.append(arg)
