# DatabaseStorage for django.
# 2009 (c) GameKeeper Gambling Ltd, Ivanov E.
import StringIO
import urlparse

from django.conf import settings
from django.core.files import File
from django.core.files.storage import Storage
from django.core.exceptions import ImproperlyConfigured

try:
    import pyodbc
except ImportError:
    raise ImproperlyConfigured("Could not load pyodbc dependency.\
    \nSee http://code.google.com/p/pyodbc/")

REQUIRED_FIELDS = ('db_table', 'fname_column', 'blob_column', 'size_column', 'base_url')

class DatabaseStorage(Storage):
    """
    Class DatabaseStorage provides storing files in the database. 
    """

    def __init__(self, option=settings.DB_FILES):
        """Constructor. 
        
        Constructs object using dictionary either specified in contucotr or
in settings.DB_FILES. 
        
        @param option dictionary with 'db_table', 'fname_column',
'blob_column', 'size_column', 'base_url'  keys. 
        
        option['db_table']
            Table to work with.
        option['fname_column']
            Column in the 'db_table' containing filenames (filenames can
contain pathes). Values should be the same as where FileField keeps
filenames. 
            It is used to map filename to blob_column. In sql it's simply
used in where clause. 
        option['blob_column']
            Blob column (for example 'image' type), created manually in the
'db_table', used to store image.
        option['size_column']
            Column to store file size. Used for optimization of size()
method (another way is to open file and get size)
        option['base_url']
            Url prefix used with filenames. Should be mapped to the view,
that returns an image as result. 
        """

        if not option or not all([field in option for field in REQUIRED_FIELDS]):
            raise ValueError("You didn't specify required options")

        self.db_table = option['db_table']
        self.fname_column = option['fname_column']
        self.blob_column = option['blob_column']
        self.size_column = option['size_column']
        self.base_url = option['base_url']

        #get database settings
        self.DATABASE_ODBC_DRIVER = settings.DATABASE_ODBC_DRIVER
        self.DATABASE_NAME = settings.DATABASE_NAME
        self.DATABASE_USER = settings.DATABASE_USER
        self.DATABASE_PASSWORD = settings.DATABASE_PASSWORD
        self.DATABASE_HOST = settings.DATABASE_HOST
        
        self.connection = pyodbc.connect('DRIVER=%s;SERVER=%s;DATABASE=%s;UID=%s;PWD=%s'%(self.DATABASE_ODBC_DRIVER,self.DATABASE_HOST,self.DATABASE_NAME,
                                                                                          self.DATABASE_USER, self.DATABASE_PASSWORD) )
        self.cursor = self.connection.cursor()

    def _open(self, name, mode='rb'):
        """Open a file from database. 
        
        @param name filename or relative path to file based on base_url. path should contain only "/", but not "\". Apache sends pathes with "/".
        If there is no such file in the db, returs None
        """
        
        assert mode == 'rb', "You've tried to open binary file without specifying binary mode! You specified: %s"%mode

        row = self.cursor.execute("SELECT %s from %s where %s = '%s'"%(self.blob_column,self.db_table,self.fname_column,name) ).fetchone()
        if row is None:
            return None
        inMemFile = StringIO.StringIO(row[0])
        inMemFile.name = name
        inMemFile.mode = mode
        
        retFile = File(inMemFile)
        return retFile

    def _save(self, name, content):
        """Save 'content' as file named 'name'.
        
        @note '\' in path will be converted to '/'. 
        """
        
        name = name.replace('\\', '/')
        binary = pyodbc.Binary(content.read())
        size = len(binary)
        
        #todo: check result and do something (exception?) if failed.
        if self.exists(name):
            self.cursor.execute("UPDATE %s SET %s = ?, %s = ? WHERE %s = '%s'"%(self.db_table,self.blob_column,self.size_column,self.fname_column,name), 
                                 (binary, size)  )
        else:
            self.cursor.execute("INSERT INTO %s VALUES(?, ?, ?)"%(self.db_table), (name, binary, size)  )
        self.connection.commit()
        return name

    def exists(self, name):
        row = self.cursor.execute("SELECT %s from %s where %s = '%s'"%(self.fname_column,self.db_table,self.fname_column,name)).fetchone()
        return row is not None
    
    def get_available_name(self, name):
        return name

    def delete(self, name):
        if self.exists(name):
            self.cursor.execute("DELETE FROM %s WHERE %s = '%s'"%(self.db_table,self.fname_column,name))
            self.connection.commit()

    def url(self, name):
        if self.base_url is None:
            raise ValueError("This file is not accessible via a URL.")
        return urlparse.urljoin(self.base_url, name).replace('\\', '/')
    
    def size(self, name):
        row = self.cursor.execute("SELECT %s from %s where %s = '%s'"%(self.size_column,self.db_table,self.fname_column,name)).fetchone()
        if row is None:
            return 0
        else:
            return int(row[0])