from datetime import datetime, timedelta
from typing import Optional

import pytz

from delphi_api.const import ENABLE_FAKE_DATA
from delphi_api.errors import Codes, InvalidInputError
from delphi_api.utils import DateUtils, Models
from delphi_api.v3.constants import (
    DUMMY_POPULARITY,
    DUMMY_POPULARITY_CHANGE,
)
from delphi_api.v3.data_models.schemas.generics import PopularitySchema
from delphi_api.v3.view_models.artist import ArtistsViewModel
from delphi_api.v3.view_models.fake_utils import FakeUtils
from delphi_api.v3.view_models.params import Params
from delphi_api.v3.view_models.query_builder import QueryBuilder


class PopularityViewModel:

    @staticmethod
    def _get_fake_popularity(params: Params) -> dict:
        return FakeUtils.get_fake_temporal_data(params, 'spotify_popularity',
                                                count=DUMMY_POPULARITY,
                                                change_amount=DUMMY_POPULARITY_CHANGE,
                                                count_max=100)

    @classmethod
    def get_many(cls, params: dict):
        params = Params(**params)
        if ENABLE_FAKE_DATA:
            result = cls._get_fake_popularity(params)
        else:
            result = cls.get_popularity_data(params)
        result = QueryBuilder.sort_results(result, params)
        result = QueryBuilder.limit_offset_results(result, params)
        return PopularitySchema(many=True).dump(result)

    @classmethod
    def get_popularity_data(cls, params: Params):
        base_key = 'artist_id'
        followers = ArtistsViewModel.get_followers_data(params)
        items = PopularitySchema(many=True).dump(followers)
        grouped_data = Models.aggregate_generic(items, base_key, group_by=params.group_by)
        return Models.flatten_generic(grouped_data)

    @classmethod
    def get_latest_artist_popularity(cls, artist_id: str) -> Optional[int]:
        """Get the most recent artist followers data and return the popularity value"""
        offset = 7
        today = datetime.now(tz=pytz.utc)
        start = today - timedelta(days=offset)
        params = Params(
            artist_id=artist_id,
            start_date=DateUtils.as_str(start),
            end_date=DateUtils.as_str(today)
        )
        followers = ArtistsViewModel.get_followers_data(params)
        if followers and len(followers):
            return followers[-1].get('spotify_popularity')
        return None

    @staticmethod
    def validate_params(params: Params):
        """Check the parameters provided by the client are compatible before continuing"""
        err = False
        id_field = 'artist_id'
        if not params.artist_id:
            err = ('Missing at least one identifiying parameter from set: '
                   f'[{id_field}]')
        if err:
            raise InvalidInputError({
                'code': Codes.invalid_input.value,
                'description': err,
            })