# 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.schema import PURE_VIRTUAL_RTYPES

from cubicweb.server.schema2sql import rschema_has_table

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.,

    It should be used as follows:

       store = MassiveObjectStore(cnx)

       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()

        if not self.slave_mode:

            # drop constraint and metadata table, they will be recreated when self.finish() is

            # called

            self._drop_all_constraints()

            self._drop_metatables_constraints()

    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 #########################################################

    def _drop_all_constraints(self):

        etypes_tables = ('cw_%s' % eschema.type.lower() for eschema in self.schema.entities()

                         if not eschema.final)

        rtypes_tables = ('%s_relation' % rschema.type.lower() for rschema in self.schema.relations()

                         if rschema_has_table(rschema, skip_relations=PURE_VIRTUAL_RTYPES))

        for tablename in chain(etypes_tables, rtypes_tables, ('entities',)):

            self._dbh.drop_constraints(tablename)

    def _drop_metatables_constraints(self):

        """ Drop all the constraints for the meta data"""

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

                          'is_instance_of_relation', 'is_relation',

                          'entities'):

            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._dbh.drop_indexes('cw_%s' % etype.lower())

            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})

            self.sql('ALTER TABLE cw_%s ADD COLUMN extid VARCHAR(256)' % etype.lower())

        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)

        extid = self.metagen.entity_extid(etype, data['eid'], data)

        if extid is not None:

            extid = b64encode(extid).decode('ascii')

        data['extid'] = extid

        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._dbh.drop_indexes('%s_relation' % rtype.lower())

            self.sql('CREATE TABLE %s_relation_tmp (eid_from integer, eid_to integer)'

                     % rtype.lower())

            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 == 'etype':

                    self.sql('ALTER TABLE cw_%s DROP COLUMN extid' % retype)

                elif _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

        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):

        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 if attr != 'extid' else 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, asource, extid) "

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

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

                 % (etype, self.metagen.source.uri, 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})