# Copyright (C) 2018-2020 by BDE ENS Paris-Saclay
# SPDX-License-Identifier: GPL-3.0-or-later

import json
import time
from collections import defaultdict

from django.apps import apps
from django.core.management.base import BaseCommand
from django.db import transaction
from polymorphic.models import PolymorphicModel


def timed(method):
    """"
    A simple decorator to measure time elapsed in class function (hence the args[0])
    """

    def _timed(*args, **kw):
        ts = time.time()
        result = method(*args, **kw)
        te = time.time()
        args[0].print_success(f"\n    {method.__name__} executed ({te-ts:.2f}s)")
        return result

    return _timed


class ImportCommand(BaseCommand):
    """
    Generic command for import of NK15 database
    """

    def __init__(self, *args, **kwargs):
        super().__init__(args, kwargs)
        self.MAP_IDBDE = dict()

    def print_success(self, to_print):
        return self.stdout.write(self.style.SUCCESS(to_print))

    def print_error(self, to_print):
        return self.stdout.write(self.style.ERROR(to_print))

    def update_line(self, n, total, content):
        n = str(n)
        total = str(total)
        n.rjust(len(total))
        print(f"\r ({n}/{total}) {content:16.16}", end="")

    def create_parser(self, prog_name, subcommand, **kwargs):
        parser = super().create_parser(prog_name, subcommand, **kwargs)
        parser.add_argument('--nk15db', action='store', default='nk15', help='NK15 database name')
        parser.add_argument('--nk15user', action='store', default='nk15_user', help='NK15 database owner')
        parser.add_argument('-s', '--save', default='map.json', action='store', help="save mapping of idbde")
        parser.add_argument('-m', '--map', default='map.json', action='store', help="import mapping of idbde")
        parser.add_argument('-c', '--chunk', type=int, default=100, help="chunk size for bulk_create")
        return parser

    def save_map(self, filename):
        with open(filename, 'w') as fp:
            json.dump(self.MAP_IDBDE, fp, sort_keys=True, indent=2)

    def load_map(self, filename):
        with open(filename, 'r') as fp:
            self.MAP_IDBDE = json.load(fp, object_hook=lambda d: {int(k): int(v) for k, v in d.items()})


class BulkCreateManager(object):
    """
    This helper class keeps track of ORM objects to be created for multiple
    model classes, and automatically creates those objects with `bulk_create`
    when the number of objects accumulated for a given model class exceeds
    `chunk_size`.
    Upon completion of the loop that's `add()`ing objects, the developer must
    call `done()` to ensure the final set of objects is created for all models.
    """

    def __init__(self, chunk_size=100):
        self._create_queues = defaultdict(list)
        self.chunk_size = chunk_size

    def _commit(self, model_class):
        model_key = model_class._meta.label
        # check for mutli-table inheritance it happens
        # if model_class is a grand-child of PolymorphicModel
        if model_class.__base__.__base__ is PolymorphicModel:
            self._commit(model_class.__base__)
            with transaction.atomic():
                for obj in self._create_queues[model_key]:
                    obj.save_base(raw=True)
        else:
            model_class.objects.bulk_create(self._create_queues[model_key])
        self._create_queues[model_key] = []

    def add(self, *args):
        """
        Add an object to the queue to be created, and call bulk_create if we
        have enough objs.
        """
        for obj in args:
            model_class = type(obj)
            model_key = model_class._meta.label
            self._create_queues[model_key].append(obj)
            if len(self._create_queues[model_key]) >= self.chunk_size:
                self._commit(model_class)

    def done(self):
        """
        Always call this upon completion to make sure the final partial chunk
        is saved.
        """
        for model_name, objs in self._create_queues.items():
            if len(objs) > 0:
                self._commit(apps.get_model(model_name))