from alembic import command, util, package_dir
from argparse import ArgumentParser
import ConfigParser
import inspect
import os

class Config(object):
    """Represent an Alembic configuration.

    Within an ``env.py`` script, this is available
    via the :attr:`.EnvironmentContext.config` attribute,
    which in turn is available at ``alembic.context``::
    
        from alembic import context
        
        some_param = context.config.get_main_option("my option")
    
    When invoking Alembic programatically, a new
    :class:`.Config` can be created by passing
    the name of an .ini file to the constructor::
    
        from alembic.config import Config
        alembic_cfg = Config("/path/to/yourapp/alembic.ini")

    With a :class:`.Config` object, you can then
    run Alembic commands programmatically using the directives
    in :mod:`alembic.command`.
    
    The :class:`.Config` object can also be constructed without
    a filename.   Values can be set programmatically, and
    new sections will be created as needed::
    
        from alembic.config import Config
        alembic_cfg = Config()
        alembic_cfg.set_main_option("url", "postgresql://foo/bar")
        alembic_cfg.set_section_option("mysection", "foo", "bar")

    :param file_: name of the .ini file to open.
    :param ini_section: name of the main Alembic section within the 
     .ini file
    :param output_buffer: optional file-like input buffer which
     will be passed to the :class:`.MigrationContext` - used to redirect
     access when using Alembic programmatically.

    """
    def __init__(self, file_=None, ini_section='alembic', output_buffer=None):
        """Construct a new :class:`.Config`
        
        """
        self.config_file_name = file_
        self.config_ini_section = ini_section
        self.output_buffer = output_buffer

    config_file_name = None
    """Filesystem path to the .ini file in use."""

    config_ini_section = None
    """Name of the config file section to read basic configuration
    from.  Defaults to ``alembic``, that is the ``[alembic]`` section
    of the .ini file.  This value is modified using the ``-n/--name``
    option to the Alembic runnier.

    """

    @util.memoized_property
    def file_config(self):
        """Return the underlying :class:`ConfigParser` object.

        Direct access to the .ini file is available here,
        though the :meth:`.Config.get_section` and 
        :meth:`.Config.get_main_option`
        methods provide a possibly simpler interface.

        """

        if self.config_file_name:
            here = os.path.abspath(os.path.dirname(self.config_file_name))
        else:
            here = ""
        file_config = ConfigParser.SafeConfigParser({'here':here})
        if self.config_file_name:
            file_config.read([self.config_file_name])
        else:
            file_config.add_section(self.config_ini_section)
        return file_config

    def get_template_directory(self):
        """Return the directory where Alembic setup templates are found.

        This method is used by the alembic ``init`` and ``list_templates``
        commands.

        """
        return os.path.join(package_dir, 'templates')

    def get_section(self, name):
        """Return all the configuration options from a given .ini file section
        as a dictionary.

        """
        return dict(self.file_config.items(name))

    def set_main_option(self, name, value):
        """Set an option programmatically within the 'main' section.
        
        This overrides whatever was in the .ini file.
        
        """
        self.file_config.set(self.config_ini_section, name, value)

    def remove_main_option(self, name):
        self.file_config.remove_option(self.config_ini_section, name)

    def set_section_option(self, section, name, value):
        """Set an option programmatically within the given section.
        
        The section is created if it doesn't exist already.
        The value here will override whatever was in the .ini
        file.
        
        """
        if not self.file_config.has_section(section):
            self.file_config.add_section(section)
        self.file_config.set(section, name, value)

    def get_section_option(self, section, name, default=None):
        """Return an option from the given section of the .ini file.

        """
        if not self.file_config.has_section(section):
            util.err("No config file %r found, or file has no "
                                "'[%s]' section" % 
                                (self.config_file_name, section))
        if self.file_config.has_option(section, name):
            return self.file_config.get(section, name)
        else:
            return default

    def get_main_option(self, name, default=None):
        """Return an option from the 'main' section of the .ini file.

        This defaults to being a key from the ``[alembic]`` 
        section, unless the ``-n/--name`` flag were used to 
        indicate a different section.

        """
        return self.get_section_option(self.config_ini_section, name, default)


def main(argv=None, **kwargs):
    """The console runner function for Alembic."""

    def add_options(parser, positional, kwargs):
        if 'template' in kwargs:
            parser.add_argument("-t", "--template",
                            default='generic',
                            type=str,
                            help="Setup template for use with 'init'")
        if 'message' in kwargs:
            parser.add_argument("-m", "--message",
                            type=str,
                            help="Message string to use with 'revision'")
        if 'sql' in kwargs:
            parser.add_argument("--sql",
                            action="store_true",
                            help="Don't emit SQL to database - dump to "
                                    "standard output/file instead")
        if 'tag' in kwargs:
            parser.add_argument("--tag",
                            type=str,
                            help="Arbitrary 'tag' name - can be used by "
                            "custom env.py scripts.")
        if 'autogenerate' in kwargs:
            parser.add_argument("--autogenerate",
                            action="store_true",
                            help="Populate revision script with candidate "
                            "migration operations, based on comparison of database to model.")


        # TODO:
        # --dialect - name of dialect when --sql mode is set - *no DB connections
        # should occur, add this to env.py templates as a conditional*
        positional_help = {
            'directory':"location of scripts directory",
            'revision':"revision identifier"
        }
        for arg in positional:
            subparser.add_argument(arg, help=positional_help.get(arg))

    parser = ArgumentParser()
    parser.add_argument("-c", "--config", 
                        type=str, 
                        default="alembic.ini", 
                        help="Alternate config file")
    parser.add_argument("-n", "--name", 
                        type=str, 
                        default="alembic", 
                        help="Name of section in .ini file to use for Alembic config")
    subparsers = parser.add_subparsers()

    for fn in [getattr(command, n) for n in dir(command)]:
        if inspect.isfunction(fn) and \
            fn.__name__[0] != '_' and \
            fn.__module__ == 'alembic.command':

            spec = inspect.getargspec(fn)
            if spec[3]:
                positional = spec[0][1:-len(spec[3])]
                kwarg = spec[0][-len(spec[3]):]
            else:
                positional = spec[0][1:]
                kwarg = []

            subparser =  subparsers.add_parser(
                                fn.__name__, 
                                help=fn.__doc__)
            add_options(subparser, positional, kwarg)
            subparser.set_defaults(cmd=(fn, positional, kwarg))

    options = parser.parse_args(argv)

    fn, positional, kwarg = options.cmd

    cfg = Config(options.config, options.name)
    try:
        fn(cfg, 
                    *[getattr(options, k) for k in positional], 
                    **dict((k, getattr(options, k)) for k in kwarg)
                )
    except util.CommandError, e:
        util.err(str(e))
