import re
import cgi
import sys
import urllib
from sqlalchemy import exceptions

"""Provide the URL object as well as the make_url parsing function."""

class URL(object):
    """Represent the components of a URL used to connect to a database.

    This object is suitable to be passed directly to a ``create_engine()``
    call.  The fields of the URL are parsed from a string by the
    ``module-level make_url()`` function.  the string format of the URL is
    an RFC-1738-style string.

    Attributes on URL include:

    drivername
      The name of the database backend.

    username
      The user name for the connection.

    password
      His password.

    host
      The name of the host.

    port
      The port number.

    database
      The database.

    query
      A dictionary containing key/value pairs representing the URL's query string.
    """

    def __init__(self, drivername, username=None, password=None, host=None, port=None, database=None, query=None):
        self.drivername = drivername
        self.username = username
        self.password = password
        self.host = host
        if port is not None:
            self.port = int(port)
        else:
            self.port = None
        self.database= database
        self.query = query or {}

    def __str__(self):
        s = self.drivername + "://"
        if self.username is not None:
            s += self.username
            if self.password is not None:
                s += ':' + urllib.quote_plus(self.password)
            s += "@"
        if self.host is not None:
            s += self.host
        if self.port is not None:
            s += ':' + str(self.port)
        if self.database is not None:
            s += '/' + self.database
        if len(self.query):
            keys = self.query.keys()
            keys.sort()
            s += '?' + "&".join(["%s=%s" % (k, self.query[k]) for k in keys])
        return s

    def get_module(self):
        """Return the SQLAlchemy database module corresponding to this URL's driver name."""
        try:
            return getattr(__import__('sqlalchemy.databases.%s' % self.drivername).databases, self.drivername)
        except ImportError:
            if sys.exc_info()[2].tb_next is None:
                raise exceptions.ArgumentError('unknown database %r' % self.drivername)
            raise

    def translate_connect_args(self, names):
        """Translate this URL's attributes into a dictionary of connection arguments.

        Given a list of argument names corresponding to the URL
        attributes (`host`, `database`, `username`, `password`,
        `port`), will assemble the attribute values of this URL into
        the dictionary using the given names.
        """

        a = {}
        attribute_names = ['host', 'database', 'username', 'password', 'port']
        for n in names:
            sname = attribute_names.pop(0)
            if n is None:
                continue
            if getattr(self, sname, None):
                a[n] = getattr(self, sname)
        return a

def make_url(name_or_url):
    """Given a string or unicode instance, produce a new URL instance.

    The given string is parsed according to the rfc1738 spec.  If an
    existing URL object is passed, just returns the object.
    """

    if isinstance(name_or_url, basestring):
        return _parse_rfc1738_args(name_or_url)
    else:
        return name_or_url

def _parse_rfc1738_args(name):
    pattern = re.compile(r'''
            (\w+)://
            (?:
                ([^:/]*)
                (?::([^/]*))?
            @)?
            (?:
                ([^/:]*)
                (?::([^/]*))?
            )?
            (?:/(.*))?
            '''
            , re.X)

    m = pattern.match(name)
    if m is not None:
        (name, username, password, host, port, database) = m.group(1, 2, 3, 4, 5, 6)
        if database is not None:
            tokens = database.split(r"?", 2)
            database = tokens[0]
            query = (len(tokens) > 1 and dict( cgi.parse_qsl(tokens[1]) ) or None)
        else:
            query = None
        opts = {'username':username,'password':password,'host':host,'port':port,'database':database, 'query':query}
        if opts['password'] is not None:
            opts['password'] = urllib.unquote_plus(opts['password'])
        return URL(name, **opts)
    else:
        raise exceptions.ArgumentError("Could not parse rfc1738 URL from string '%s'" % name)

def _parse_keyvalue_args(name):
    m = re.match( r'(\w+)://(.*)', name)
    if m is not None:
        (name, args) = m.group(1, 2)
        opts = dict( cgi.parse_qsl( args ) )
        return URL(name, *opts)
    else:
        return None