# -*- coding: utf-8 -*-
#
# File: portato/db/__init__.py
# This file is part of the Portato-Project, a graphical portage-frontend.
#
# Copyright (C) 2006-2010 René 'Necoro' Neumann
# This is free software.  You may redistribute copies of it under the terms of
# the GNU General Public License version 2.
# There is NO WARRANTY, to the extent permitted by law.
#
# Written by René 'Necoro' Neumann <necoro@necoro.net>

from __future__ import absolute_import

from collections import namedtuple

from . import database as db
from .exceptions import UnknownDatabaseTypeError, DatabaseInstantiationError, DatabaseInitError
from ..session import Session, SectionDict
from ..helper import debug, warning, error, info
from ..odict import OrderedDict

DBType = namedtuple("DBType", "name descr module cls alt")

types = [
        ("eixsql",
                DBType(
                    _("eix + SQLite"),
                    _("Similar to SQLite, but now uses the eix database to get the package information.\nThis should be much faster on startup, but requires that your eix database is always up-to-date.\nAdditionally, this is the only database allowing searching in descriptions."),
                    "eix_sql", "EixSQLDatabase",
                    "sql")),
        ("sql",
                DBType(
                    _("SQLite"),
                    _("Uses an SQLite-database to store package information.\nMay take longer to generate at the first time, but has advantages if portato is re-started with an unchanged portage tree. Additionally it allows to use fast SQL expressions for fetching the data."),
                    "sql", "SQLDatabase",
                    "dict")),
        ("dict",
                DBType(
                    _("Hashmap"),
                    _("Uses an in-memory hashmap to store package information.\nHas been used since at least version 0.3.3, but all information has to be regenerated on each startup."),
                    "hash", "HashDatabase",
                    None))
        ]

types = OrderedDict(types)

class Database(db.Database):
    DEFAULT = "dict"

    def __new__ (cls, type = None):
        try:
            if not '_the_instance' in cls.__dict__:
                dbcls = cls._generate(type)
                cls._the_instance = dbcls(cls._get_session())
            elif type is not None:
                raise DatabaseInstantiationError("Database instantiation called with 'type' argument multiple times.")
        except (ImportError, DatabaseInitError) as e:
            db = types[cls.DB_TYPE]
            error(_("Cannot load %s."), db.cls)
            error(_("Error: %s"), e)

            if db.alt is not None:
                return cls.__new__(cls, db.alt)
            else:
                error(_("No alternative database given. Aborting."))
                raise DatabaseInstantiationError("Cannot load database.")

        return cls._the_instance
    
    @classmethod
    def _generate(cls, type):
        if type is None:
            warning("No database type specified! Falling back to default.")
            type = cls.DEFAULT

        try:
            db = types[type]
        except KeyError:
            error(_("Unknown database type: %s"), type)
            raise UnknownDatabaseTypeError, type
        
        cls.DB_TYPE = type
        info(_("Using database type '%s'"), db.cls)

        mod = __import__(db.module, globals(), locals(), [db.cls])
        return getattr(mod, db.cls)

    @classmethod
    def _get_session(cls):
        return SectionDict(Session("db.cfg", name = "DB"), cls.DB_TYPE)