import { Injectable, Logger } from "@nestjs/common";
import { PrismaService } from "../../../prisma/prisma.service";
import { getYearStart, roundToQuarterHour } from "src/common/utils/date-utils";

@Injectable()
export class SickLeaveService {
    constructor(private readonly prisma: PrismaService) {}

    private readonly logger = new Logger(SickLeaveService.name);

    async calculateSickLeavePay(employeeId: number, referenceDate: Date, daysRequested: number, modifier: number): Promise<number> {
        //sets the year to jan 1st to dec 31st
        const periodStart = getYearStart(referenceDate);
        const periodEnd   = referenceDate;

        //fetches all shifts of a selected employee
        const shifts = await this.prisma.shifts.findMany({
            where: {
                timesheet: { employee_id: employeeId },
                date: { gte: periodStart, lte: periodEnd},
            },
            select: { date: true },
        });

        //count the amount of worked days
        const workedDates = new Set(
            shifts.map(shift => shift.date.toISOString().slice(0,10))
        );
        const daysWorked = workedDates.size;
        this.logger.debug(`Sick leave: days worked= ${daysWorked} in ${periodStart.toDateString()} -> ${periodEnd.toDateString()}`);

        //less than 30 worked days returns 0
        if (daysWorked < 30) {
            return 0;
        }

        //default 3 days allowed after 30 worked days
        let acquiredDays = 3;

        //identify the date of the 30th worked day
        const orderedDates = Array.from(workedDates).sort();
        const thresholdDate = new Date(orderedDates[29]); // index 29 is the 30th day

        //calculate each completed month, starting the 1st of the next month
        const firstBonusDate = new Date(thresholdDate.getFullYear(), thresholdDate.getMonth() +1, 1);
        let months = (periodEnd.getFullYear() - firstBonusDate.getFullYear()) * 12 +
                     (periodEnd.getMonth() - firstBonusDate.getMonth()) + 1;
        if(months < 0) months = 0;
        acquiredDays += months;

        //cap of 10 days
        if (acquiredDays > 10) acquiredDays = 10;

        this.logger.debug(`Sick leave: threshold Date = ${thresholdDate.toDateString()}, bonusMonths = ${months}, acquired Days = ${acquiredDays}`);

        const payableDays = Math.min(acquiredDays, daysRequested);
        const rawHours = payableDays * 8 * modifier;
        const rounded = roundToQuarterHour(rawHours)
        this.logger.debug(`Sick leave pay: days= ${payableDays}, modifier= ${modifier}, hours= ${rounded}`);
        return rounded;
    }
}