# coding: utf-8

# copyright 2015-2016 LOGILAB S.A. (Paris, FRANCE), all rights reserved.

# contact http://www.logilab.fr/ -- mailto:contact@logilab.fr

#

# This file is part of CubicWeb.

#

# CubicWeb is free software: you can redistribute it and/or modify it under the

# terms of the GNU Lesser General Public License as published by the Free

# Software Foundation, either version 2.1 of the License, or (at your option)

# any later version.

#

# CubicWeb 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 Lesser General Public License for more

# details.

#

# You should have received a copy of the GNU Lesser General Public License along

# with CubicWeb.  If not, see <http://www.gnu.org/licenses/>.

import logging

from copy import copy

from collections import defaultdict

from itertools import chain

from base64 import b64encode

from six.moves import range

from yams.constraints import SizeConstraint

from cubicweb.dataimport import stores, pgstore

class MassiveObjectStore(stores.RQLObjectStore):

    """Store for massive import of data, with delayed insertion of meta data.

    WARNINGS:

    - This store may only be used with PostgreSQL for now, as it relies

      on the COPY FROM method, and on specific PostgreSQL tables to get all

      the indexes.

    - This store can only insert relations that are not inlined (i.e.,

      which do *not* have inlined=True in their definition in the schema),

      unless they are specified as entity attributes.

    It should be used as follows:

       store = MassiveObjectStore(cnx)

       eid_p = store.prepare_insert_entity('Person',

                                           cwuri='http://dbpedia.org/toto',

                                           name='Toto')

       eid_loc = store.prepare_insert_entity('Location',

                                             cwuri='http://geonames.org/11111',

                                             name='Somewhere')

       store.prepare_insert_relation(eid_p, 'lives_in', eid_loc)

       store.flush()

       ...

       store.commit()

       store.finish()

    Full-text indexation is not handled, you'll have to reindex the proper entity types by yourself

    if desired.

    """

    def __init__(self, cnx,

                 on_commit_callback=None, on_rollback_callback=None,

                 slave_mode=False,

                 eids_seq_range=10000,

                 metagen=None):

        """ Create a MassiveObject store, with the following attributes:

        - cnx: CubicWeb cnx

        - eids_seq_range: size of eid range reserved by the store for each batch

        """

        super(MassiveObjectStore, self).__init__(cnx)

        self.on_commit_callback = on_commit_callback

        self.on_rollback_callback = on_rollback_callback

        self.slave_mode = slave_mode

        self.eids_seq_range = eids_seq_range

        if metagen is None:

            metagen = stores.MetadataGenerator(cnx)

        self.metagen = metagen

        self.logger = logging.getLogger('dataimport.massive_store')

        self.sql = cnx.system_sql

        self.schema = self._cnx.vreg.schema

        self.default_values = get_default_values(self.schema)

        self.get_next_eid = lambda g=self._get_eid_gen(): next(g)

        self._dbh = PGHelper(cnx)

        cnx.read_security = False

        cnx.write_security = False

        self._data_entities = defaultdict(list)

        self._data_relations = defaultdict(list)

        self._initialized = set()

        self._constraints_dropped = self.slave_mode

    def _get_eid_gen(self):

        """ Function getting the next eid. This is done by preselecting

        a given number of eids from the 'entities_id_seq', and then

        storing them"""

        while True:

            last_eid = self._cnx.repo.system_source.create_eid(self._cnx, self.eids_seq_range)

            for eid in range(last_eid - self.eids_seq_range + 1, last_eid + 1):

                yield eid

    # SQL utilities #########################################################

        if not self._constraints_dropped:

            self._constraints_dropped = True

        for tablename in ('created_by_relation', 'owned_by_relation',

            self._dbh.drop_indexes(tablename)

    def restart_eid_sequence(self, start_eid):

        self.sql(self._cnx.repo.system_source.dbhelper.sql_restart_numrange(

            'entities_id_seq', initial_value=start_eid))

        self._cnx.commit()

    # store api ################################################################

    def prepare_insert_entity(self, etype, **kwargs):

        """Given an entity type, attributes and inlined relations, returns the inserted entity's

        eid.

        """

        if not self.slave_mode and etype not in self._initialized:

            self._initialized.add(etype)

            self.sql('CREATE TABLE IF NOT EXISTS cwmassive_initialized'

                     '(retype text, type varchar(128))')

            self.sql("INSERT INTO cwmassive_initialized VALUES (%(e)s, 'etype')", {'e': etype})

        attrs = self.metagen.base_etype_attrs(etype)

        data = copy(attrs)  # base_etype_attrs is @cached, a copy is necessary

        data.update(kwargs)

        if 'eid' not in data:

            # If eid is not given and the eids sequence is set, use the value from the sequence

            eid = self.get_next_eid()

            data['eid'] = eid

        # XXX default values could be set once for all in base entity

        default_values = self.default_values[etype]

        missing_keys = set(default_values) - set(data)

        data.update((key, default_values[key]) for key in missing_keys)

        self.metagen.init_entity_attrs(etype, data['eid'], data)

        self._data_entities[etype].append(data)

        return data['eid']

    def prepare_insert_relation(self, eid_from, rtype, eid_to, **kwargs):

        """Insert into the database a  relation ``rtype`` between entities with eids ``eid_from``

        and ``eid_to``.

        Relation must not be inlined.

        """

        if not self.slave_mode and rtype not in self._initialized:

            assert not self._cnx.vreg.schema.rschema(rtype).inlined

            self._initialized.add(rtype)

            self.sql('CREATE TABLE IF NOT EXISTS cwmassive_initialized'

                     '(retype text, type varchar(128))')

            self.sql("INSERT INTO cwmassive_initialized VALUES (%(e)s, 'rtype')", {'e': rtype})

        self._data_relations[rtype].append({'eid_from': eid_from, 'eid_to': eid_to})

    def flush(self):

        """Flush the data"""

        self.flush_entities()

        self.flush_relations()

    def commit(self):

        """Commit the database transaction."""

        self.on_commit()

        super(MassiveObjectStore, self).commit()

    def finish(self):

        """Remove temporary tables and columns."""

        if self.slave_mode:

            raise RuntimeError('Store cleanup is not allowed in slave mode')

        self.logger.info("Start cleaning")

        # Get all the initialized etypes/rtypes

        if self._dbh.table_exists('cwmassive_initialized'):

            cu = self.sql('SELECT retype, type FROM cwmassive_initialized')

            for retype, _type in cu.fetchall():

                self.logger.info('Cleanup for %s' % retype)

                if _type == 'rtype':

                    # Cleanup relations tables

                    self._cleanup_relations(retype)

                self.sql('DELETE FROM cwmassive_initialized WHERE retype = %(e)s',

                         {'e': retype})

        self._dbh.restore_indexes_and_constraints()

        # Delete the meta data table

        self.sql('DROP TABLE IF EXISTS cwmassive_initialized')

        self.commit()

    # FLUSH #################################################################

    def on_commit(self):

        if self.on_commit_callback:

            self.on_commit_callback()

    def on_rollback(self, exc, etype, data):

        if self.on_rollback_callback:

            self.on_rollback_callback(exc, etype, data)

            self._cnx.rollback()

        else:

            raise exc

    def flush_relations(self):

        """Flush the relations data."""

        for rtype, data in self._data_relations.items():

            if not data:

                # There is no data for these etype for this flush round.

                continue

            buf = pgstore._create_copyfrom_buffer(data, ('eid_from', 'eid_to'))

            if not buf:

                # The buffer is empty. This is probably due to error in _create_copyfrom_buffer

                raise ValueError

            cursor = self._cnx.cnxset.cu

            # Push into the tmp table

            cursor.copy_from(buf, '%s_relation_tmp' % rtype.lower(),

                             null='NULL', columns=('eid_from', 'eid_to'))

            # Clear data cache

            self._data_relations[rtype] = []

    def flush_entities(self):

        """Flush the entities data."""

        for etype, data in self._data_entities.items():

            if not data:

                # There is no data for these etype for this flush round.

                continue

            # XXX It may be interresting to directly infer the columns' names from the schema

            # XXX For now, the _create_copyfrom_buffer does a "row[column]"

            # which can lead to a key error.

            # Thus we should create dictionary with all the keys.

            columns = set()

            for d in data:

                columns.update(d)

            _data = []

            _base_data = dict.fromkeys(columns)

            for d in data:

                _d = _base_data.copy()

                _d.update(d)

                _data.append(_d)

            buf = pgstore._create_copyfrom_buffer(_data, columns)

            if not buf:

                # The buffer is empty. This is probably due to error in _create_copyfrom_buffer

                raise ValueError('Error in buffer creation for etype %s' % etype)

            columns = ['cw_%s' % attr for attr in columns]

            cursor = self._cnx.cnxset.cu

            try:

                cursor.copy_from(buf, 'cw_%s' % etype.lower(), null='NULL', columns=columns)

            except Exception as exc:

                self.on_rollback(exc, etype, data)

            # Clear data cache

            self._data_entities[etype] = []

            if not self.slave_mode:

                self._insert_etype_metadata(etype)

    def _cleanup_relations(self, rtype):

        """ Cleanup rtype table """

        # Push into relation table while removing duplicate

        self.sql('INSERT INTO %(r)s_relation (eid_from, eid_to) SELECT DISTINCT '

                 'T.eid_from, T.eid_to FROM %(r)s_relation_tmp AS T '

                 'WHERE NOT EXISTS (SELECT 1 FROM %(r)s_relation AS TT WHERE '

                 'TT.eid_from=T.eid_from AND TT.eid_to=T.eid_to);' % {'r': rtype})

        # Drop temporary relation table

        self.sql('DROP TABLE %(r)s_relation_tmp' % {'r': rtype.lower()})

    def _insert_etype_metadata(self, etype):

        """Massive insertion of meta data for a given etype, based on SQL statements.

        """

        # insert standard metadata relations

        for rtype, eid in self.metagen.base_etype_rels(etype).items():

            self._insert_meta_relation(etype, eid, '%s_relation' % rtype)

        # insert cw_source, is and is_instance_of relations (normally handled by the system source)

        self._insert_meta_relation(etype, self.metagen.source.eid, 'cw_source_relation')

        eschema = self.schema[etype]

        self._insert_meta_relation(etype, eschema.eid, 'is_relation')

        for parent_eschema in chain(eschema.ancestors(), [eschema]):

            self._insert_meta_relation(etype, parent_eschema.eid, 'is_instance_of_relation')

        # finally insert records into the entities table

        self.sql("INSERT INTO entities (eid, type) "

                 "SELECT cw_eid, '%s' FROM cw_%s "

                 "WHERE NOT EXISTS (SELECT 1 FROM entities WHERE eid=cw_eid)"

                 % (etype, etype.lower()))

    def _insert_meta_relation(self, etype, eid_to, rtype):

        self.sql("INSERT INTO %s (eid_from, eid_to) SELECT cw_eid, %s FROM cw_%s "

                 "WHERE NOT EXISTS (SELECT 1 FROM entities WHERE eid=cw_eid)"

                 % (rtype, eid_to, etype.lower()))

def get_size_constraints(schema):

    """analyzes yams ``schema`` and returns the list of size constraints.

    The returned value is a dictionary mapping entity types to a

    sub-dictionnaries mapping attribute names -> max size.

    """

    size_constraints = {}

    # iterates on all entity types

    for eschema in schema.entities():

        # for each entity type, iterates on attribute definitions

        size_constraints[eschema.type] = eschema_constraints = {}

        for rschema, aschema in eschema.attribute_definitions():

            # for each attribute, if a size constraint is found,

            # append it to the size constraint list

            maxsize = None

            rdef = rschema.rdef(eschema, aschema)

            for constraint in rdef.constraints:

                if isinstance(constraint, SizeConstraint):

                    maxsize = constraint.max

                    eschema_constraints[rschema.type] = maxsize

    return size_constraints

def get_default_values(schema):

    """analyzes yams ``schema`` and returns the list of default values.

    The returned value is a dictionary mapping entity types to a

    sub-dictionnaries mapping attribute names -> default values.

    """

    default_values = {}

    # iterates on all entity types

    for eschema in schema.entities():

        # for each entity type, iterates on attribute definitions

        default_values[eschema.type] = eschema_constraints = {}

        for rschema, _ in eschema.attribute_definitions():

            # for each attribute, if a size constraint is found,

            # append it to the size constraint list

            if eschema.default(rschema.type) is not None:

                eschema_constraints[rschema.type] = eschema.default(rschema.type)

    return default_values

class PGHelper(object):

    """This class provides some helper methods to manipulate a postgres database metadata (index and

    constraints).

    """

    def __init__(self, cnx):

        self.sql = cnx.system_sql

        # Deals with pg schema, see #3216686

        pg_schema = cnx.repo.config.system_source_config.get('db-namespace') or 'public'

        self.pg_schema = pg_schema

    def drop_indexes(self, tablename):

        """Drop indexes and constraints, storing them in a table for later restore."""

        # Create a table to save the constraints, it allows reloading even after crash

        self.sql('CREATE TABLE IF NOT EXISTS cwmassive_constraints(sql TEXT, insert_order SERIAL)')

        indexes = self.table_indexes(tablename)

        for name, query in indexes.items():

            self.sql('INSERT INTO cwmassive_constraints(sql) VALUES (%(sql)s)', {'sql': query})

            self.sql('DROP INDEX %s' % name)

    def drop_constraints(self, tablename):

        self.sql('CREATE TABLE IF NOT EXISTS cwmassive_constraints(sql TEXT, insert_order SERIAL)')

        constraints = self.table_constraints(tablename)

        for name, query in constraints.items():

            self.sql('INSERT INTO cwmassive_constraints(sql) VALUES (%(sql)s)', {'sql': query})

            self.sql('ALTER TABLE %s DROP CONSTRAINT %s' % (tablename, name))

    def restore_indexes_and_constraints(self):

        """Restore indexes and constraints."""

        if not self.table_exists('cwmassive_constraints'):

            return

        cu = self.sql('SELECT sql, insert_order FROM cwmassive_constraints '

                      'ORDER BY insert_order DESC')