import { TimeFrame } from '@energyweb/utils-general';
import { Injectable } from '@nestjs/common';
import * as Moment from 'moment';
import { extendMoment } from 'moment-range';

import { CreateDemandDTO } from './create-demand.dto';

const moment = extendMoment(Moment);

@Injectable()
export class DemandTimePeriodService<TProduct> {
    public generateValidityDates(createDemand: CreateDemandDTO<TProduct>) {
        let { start, end } = createDemand;

        start = new Date(start);
        end = new Date(end);

        const range = moment.range(start, end);

        const { diff, step } = this.timeFrameToTimeDiff(createDemand.periodTimeFrame);
        const validFrom = Array.from(range.by(diff, { step, excludeEnd: true })).map((v) =>
            v.toDate()
        );

        return validFrom.map((v, i) => ({
            validFrom: v,
            generationFrom: v,
            generationTo: validFrom[i + 1] || end
        }));
    }

    private timeFrameToTimeDiff(timeFrame: TimeFrame): {
        diff: Moment.unitOfTime.Diff;
        step?: number;
    } {
        switch (timeFrame) {
            case TimeFrame.Yearly:
                return { diff: 'year' };
            case TimeFrame.Monthly:
                return { diff: 'month' };
            case TimeFrame.Weekly:
                return { diff: 'week' };
            case TimeFrame.Daily:
                return { diff: 'day' };
            case TimeFrame.Hourly:
                return { diff: 'hour' };
            case TimeFrame.HalfHourly:
                return { diff: 'minute', step: 30 };
            default:
                throw new Error('Unknown timeframe');
        }
    }
}