##
## jambtables.py
## Login : <uli@pu.smp.net>
## Started on  Tue Jun 22 06:31:42 2010 Uli Fouquet
## $Id$
## 
## Copyright (C) 2010 Uli Fouquet
## This program is free software; you can redistribute it and/or modify
## it under the terms of the GNU General Public License as published by
## the Free Software Foundation; either version 2 of the License, or
## (at your option) any later version.
## 
## This program is distributed in the hope that it will be useful,
## but WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
## GNU General Public License for more details.
## 
## You should have received a copy of the GNU General Public License
## along with this program; if not, write to the Free Software
## Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
##
"""WAeUP SIRP support for JAMB tables.

JAMB tables are datasets delivered by JAMB.
"""
import csv
import os
import shutil
import tempfile
import grok

from datetime import datetime
from BTrees.OOBTree import OOBTree
from BTrees.Length import Length

from waeup.sirp.jambtables.interfaces import IJAMBDataTable

#: The header fields required for a valid JAMB table CSV file.
JAMB_DATA_HEADERS = [
    'firstname', 'lastname', 'middlenames', 'screening_type',
    'screening_venue', 'reg_no', 'sex', 'course1', 'jamb_state',
    'screening_date', 'jamb_lga', 'fst_sit_fname', 'date_of_birth']

def filter_data(datadict):
    """Filter items whose key contains 'ignore'

    The function will remove all fields whose name start with
    ``ignore``. All data will be convertetd to unicode except
    ``data_of_birth``, which is turned into a `dateteime` object.
    """
    keys = datadict.keys()
    for key in keys:
        if not 'ignore' in key:
            continue
        del datadict[key]
    for name in JAMB_DATA_HEADERS:
        datadict[name] = unicode(datadict[name])
    datadict['date_of_birth'] = datetime.strptime(
        datadict['date_of_birth'],
        '%d/%m/%Y'
        ).date()
    
    return datadict


class JAMBDataTable(grok.Model):
    """A data table that contains JAMB data.

    JAMB data tables are plain but fast as they store nearly no data
    inside the ZODB. All data is held on-disk in CSV tables.

    As a consequence these tables are read-only.
    """
    #: Implement :class:`IJAMBDataTable`
    grok.implements(IJAMBDataTable)

    #: The datetime when data was imported.
    import_datetime = None

    #: The username of the person that initiated the last import.
    importer_username = None
    
    def __init__(self):
        super(JAMBDataTable, self).__init__()
        self._datafile_path = None
        self._data_len = 0
        self._temporary = False
        return

    def __del__(self):
        self.clear()

    def __iter__(self):
        reader = None
        if self._datafile_path is not None:
            reader = csv.DictReader(open(self._datafile_path, 'rb'))
        if reader is None:
            raise StopIteration
        for line in reader:
            data_dict = filter_data(line)
            yield data_dict

    def keys(self):
        """Get iterator over all registration numbers stored in table.
        """
        for item in self:
            yield item['reg_no']

    def items(self):
        """Get tuples of registration number and datasets for each entry in
           data table.
        """
        for item in self:
            yield (item['reg_no'], item)
            
    def clear(self):
        """Remove all existing entries.

        Unsets also the :attr:`import_datetime` and
        :attr:`importer_username` attributes.
        """
        self.import_datetime = None
        self.importer_username = None
        if self._datafile_path is None:
            return
        if self._temporary:
            if not os.path.exists(self._datafile_path):
                return
            shutil.rmtree(os.path.dirname(self._datafile_path))
        self._datafile_path = None
            
    def importFromCSV(self, filepath, username=None):
        """Importing data from a CSV file means to copy the source to a safe
           location.

           If the username is set, it will be stored as well in
           :attr:`importer_username`.
        """
        self.clear()
        self.import_datetime = datetime.now()
        self.importer_username = None
        if username is not None:
            self.importer_username = unicode(username)
        self._copyDataFile(filepath)

    def _copyDataFile(self, path):
        """Copy file in path to the JAMBData storage.

        See :meth:`_getJAMBTableStorage`.
        """
        storage = self._getJAMBTableStorage()
        self._datafile_path = os.path.join(
            storage, os.path.basename(path)
            )
        shutil.copy2(path, self._datafile_path)
        return

    def _getJAMBTableStorage(self):
        """Get a path to store copies of datatables.

        We normally store data in a ``jambdata`` subdir of datacenter,
        but if none exists, we create a temporary dir and set
        `temporary` to ``True``.

        Any not existent directory is created.

        Note, that temporary dirs will be deleted when the
        JAMBDataTable object is destroyed.

        Returns absolute path to the JAMB data storage.
        """
        site = grok.getSite()
        if site is None:
            jambtable_storage = tempfile.mkdtemp()
            self._temporary = True
        else:
            datacenter = site['datacenter']
            jambtable_storage = os.path.join(datacenter.storage, 'jambdata')
        if not os.path.isdir(jambtable_storage):
            os.mkdir(jambtable_storage)
        return os.path.abspath(jambtable_storage)