import re

import pkg_resources
import yaml
from django.apps import apps
from django.apps.config import AppConfig
from django.core.exceptions import ObjectDoesNotExist
from django.db import connections, models
from django.db.models import CharField, TextField
from django.db.models.base import ModelBase
from model_mommy import mommy

from comissoes.models import Composicao, Participacao
from parlamentares.models import Parlamentar
from sessao.models import SessaoPlenaria

# BASE ######################################################################

#  apps to be migrated, in app dependency order (very important)
appconfs = [apps.get_app_config(n) for n in [
    'parlamentares',
    'comissoes',
    'materia',
    'norma',
    'sessao',
    'lexml',
    'protocoloadm', ]]

stubs_list = []

name_sets = [set(m.__name__ for m in ac.get_models()) for ac in appconfs]

# apps do not overlap
for s1 in name_sets:
    for s2 in name_sets:
        if s1 is not s2:
            assert not s1.intersection(s2)

# apps include all legacy models
legacy_app = apps.get_app_config('legacy')
legacy_model_names = set(m.__name__ for m in legacy_app.get_models())

model_dict = {m.__name__: m for ac in appconfs for m in ac.get_models()}


# RENAMES ###################################################################

MODEL_RENAME_PATTERN = re.compile('(.+) \((.+)\)')


def get_renames():
    field_renames = {}
    model_renames = {}
    for app in appconfs:
        app_rename_data = yaml.load(
            pkg_resources.resource_string(app.module.__name__, 'legacy.yaml'))
        for model_name, renames in app_rename_data.items():
            match = MODEL_RENAME_PATTERN.match(model_name)
            if match:
                model_name, old_name = match.groups()
            else:
                old_name = None
            model = getattr(app.models_module, model_name)
            if old_name:
                model_renames[model] = old_name
            field_renames[model] = renames

    # collect renames from parent classes
    for model, renames in field_renames.items():
        if any(parent in field_renames for parent in model.__mro__[1:]):
            renames = {}
            for parent in reversed(model.__mro__):
                if parent in field_renames:
                    renames.update(field_renames[parent])
            field_renames[model] = renames

    # remove abstract classes
    field_renames = {m: r for m, r in field_renames.items()
                     if not m._meta.abstract}

    return field_renames, model_renames


# MIGRATION #################################################################

def info(msg):
    print('INFO: ' + msg)


def warn(msg):
    print('CUIDADO! ' + msg)


def get_fk_related(field, value, label=None):
    fields_dict = {}

    if value is None and field.null is False:
        value = 0
    if value is not None:
        try:
            value = field.related_model.objects.get(id=value)
        except ObjectDoesNotExist:
            msg = 'FK [%s] não encontrada para valor %s ' \
                '(em %s %s)' % (
                    field.name, value,
                    field.model.__name__, label or '---')
            if value == 0:
                # se FK == 0, criamos um stub e colocamos o valor '????????
                # para qualquer CharField ou TextField que possa haver
                if not field.null:
                    all_fields = field.related_model._meta.get_fields()
                    fields_dict = {f.name: '????????????'[:f.max_length]
                                   for f in all_fields
                                   if isinstance(f, (CharField, TextField)) and
                                   not f.choices and not f.blank}
                    value = mommy.make(field.related_model,
                                       **fields_dict)
                    warn(msg + ' => STUB criada para campos não nuláveis!')
                else:
                    value = None
                    warn(msg + ' => usando None para valores iguais a zero!')
            else:
                value = make_stub(field.related_model, value)
                stubs_list.append((value.id, field))
                warn(msg + ' => STUB criada!')
        else:
            assert value
    return value


def get_field(model, fieldname):
    return model._meta.get_field(fieldname)


def exec_sql(sql, db='default'):
    cursor = connections[db].cursor()
    cursor.execute(sql)
    return cursor


def iter_sql_records(sql, db):
    class Record:
        pass
    cursor = exec_sql(sql, db)
    fieldnames = [name[0] for name in cursor.description]
    for row in cursor.fetchall():
        record = Record()
        record.__dict__.update(zip(fieldnames, row))
        yield record


def save_with_id(new, id):
    sequence_name = '%s_id_seq' % type(new)._meta.db_table
    cursor = exec_sql('SELECT last_value from %s;' % sequence_name)
    (last_value,) = cursor.fetchone()
    if last_value == 1 or id != last_value + 1:
        # we explicitly set the next id if last_value == 1
        # because last_value == 1 for a table containing either 0 or 1 records
        # (we would have trouble for id == 2 and a missing id == 1)
        exec_sql('ALTER SEQUENCE %s RESTART WITH %s;' % (sequence_name, id))
    new.save()
    assert new.id == id, 'New id is different from provided!'


def make_stub(model, id):
    new = mommy.prepare(model)
    save_with_id(new, id)
    return new


class DataMigrator:

    def __init__(self):
        self.field_renames, self.model_renames = get_renames()

    def populate_renamed_fields(self, new, old):
        renames = self.field_renames[type(new)]

        for field in new._meta.fields:
            old_field_name = renames.get(field.name)
            field_type = field.get_internal_type()
            if old_field_name:
                old_value = getattr(old, old_field_name)
                if isinstance(field, models.ForeignKey):
                    old_type = type(old)  # not necessarily a model
                    if hasattr(old_type, '_meta') and \
                            old_type._meta.pk.name != 'id':
                        label = old.pk
                    else:
                        label = '-- WITHOUT PK --'
                    value = get_fk_related(field, old_value, label)
                else:
                    value = getattr(old, old_field_name)
                if field_type == 'CharField' or field_type == 'TextField':
                    if value is None:
                        warn(
                            "Field %s (%s) from model %s"
                            " => settig empty string '' for %s value" %
                            (field.name, field_type, field.model.__name__,
                             value))
                        value = ''
                setattr(new, field.name, value)

    def migrate(self, obj=appconfs):
        # warning: model/app migration order is of utmost importance

        self.to_delete = []
        info('Starting %s migration...' % obj)
        self._do_migrate(obj)
        # exclude logically deleted in legacy base
        info('Deleting models with ind_excluido...')
        for obj in self.to_delete:
            obj.delete()
        info('Deleting unnecessary stubs...')
        self.delete_stubs()

    def _do_migrate(self, obj):
        if isinstance(obj, AppConfig):
            models_to_migrate = (model for model in obj.models.values()
                                 if model in self.field_renames)
            self._do_migrate(models_to_migrate)
        elif isinstance(obj, ModelBase):
            self.migrate_model(obj)
        elif hasattr(obj, '__iter__'):
            for item in obj:
                self._do_migrate(item)
        else:
            raise TypeError(
                'Parameter must be a Model, AppConfig or a sequence of them')

    def migrate_model(self, model):
        print('Migrating %s...' % model.__name__)

        legacy_model_name = self.model_renames.get(model, model.__name__)
        legacy_model = legacy_app.get_model(legacy_model_name)
        legacy_pk_name = legacy_model._meta.pk.name

        # Clear all model entries
        # They may have been created in a previous migration attempt
        model.objects.all().delete()

        # setup migration strategy for tables with or without a pk
        if legacy_pk_name == 'id':
            # There is no pk in the legacy table
            def save(new, old):
                new.save()

            old_records = iter_sql_records(
                'select * from ' + legacy_model._meta.db_table, 'legacy')
        else:
            def save(new, old):
                save_with_id(new, getattr(old, legacy_pk_name))

            old_records = legacy_model.objects.all().order_by(legacy_pk_name)

        adjust = MIGRATION_ADJUSTMENTS.get(model)

        # convert old records to new ones
        for old in old_records:
            new = model()
            self.populate_renamed_fields(new, old)
            if adjust:
                adjust(new, old)
            save(new, old)
            if getattr(old, 'ind_excluido', False):
                self.to_delete.append(new)

    def delete_stubs(self):
        for line in stubs_list:
            stub, field = line
            # Filter all objects in model and delete from related model
            # if quantity is equal to zero
            if field.model.objects.filter(**{field.name: stub}).exists():
                field.related_model.objects.get(**{'id': stub}).delete()


def migrate(obj=appconfs):
    dm = DataMigrator()
    dm.migrate(obj)


# MIGRATION_ADJUSTMENTS #####################################################

def adjust_participacao(new_participacao, old):
    composicao = Composicao()
    composicao.comissao, composicao.periodo = [
        get_fk_related(Composicao._meta.get_field(name), value)
        for name, value in (('comissao', old.cod_comissao),
                            ('periodo', old.cod_periodo_comp))]
    # check if there is already an "equal" one in the db
    already_created = Composicao.objects.filter(
        comissao=composicao.comissao, periodo=composicao.periodo)
    if already_created:
        assert len(already_created) == 1  # we must never have made 2 copies
        [composicao] = already_created
    else:
        composicao.save()
    new_participacao.composicao = composicao


def adjust_parlamentar(new_parlamentar, old):
    value = new_parlamentar.unidade_deliberativa
    # Field is defined as not null in legacy db,
    # but data includes null values
    #  => transform None to False
    if value is None:
        warn('null converted to False')
        new_parlamentar.unidade_deliberativa = False


def adjust_sessaoplenaria(new, old):
    assert not old.tip_expediente


MIGRATION_ADJUSTMENTS = {
    Participacao: adjust_participacao,
    Parlamentar: adjust_parlamentar,
    SessaoPlenaria: adjust_sessaoplenaria,
}

# CHECKS ####################################################################


def get_ind_excluido(obj):
    legacy_model = legacy_app.get_model(type(obj).__name__)
    return getattr(legacy_model.objects.get(
        **{legacy_model._meta.pk.name: obj.id}), 'ind_excluido', False)


def check_app_no_ind_excluido(app):
    for model in app.models.values():
        assert not any(get_ind_excluido(obj) for obj in model.objects.all())
    print('OK!')