sc4/lib/core/simulator-date.js

A command line utility for automating SimCity 4 modding tasks & modifying savegames

// # simulator-date.ts
import { getJulianFromUnix, getUnixFromJulian } from 'sc4/utils';
// Epoch is 2000-01-01T12:00:00Z, which is 946728000000 as unix timestamp, and 
// 245154 as julian date.
const epochUnix = 946728000000;
const epochJulian = 245154;
// # SimulatorDate
// This class helps us work with dates in the game. JavaScript's builtin date is 
// not flexible enough for this, and temporal isn't ready for production yet, so 
// we implement the logic ourselves. We will inspired ourselves on temporal 
// though, meaning that evrything is functional. Nothing is modified by 
// reference! Also note that we don't need any hour logic.
export default class SimulatorDate {
    year = 2000;
    month = 1;
    day = 1;
    unix = epochUnix;
    julian = epochJulian;
    static fromJulian(julian) {
        let unix = getUnixFromJulian(julian);
        return new SimulatorDate({ unix, julian });
    }
    static fromUnix(timestamp) {
        let julian = getJulianFromUnix(timestamp);
        return new SimulatorDate({ julian, unix: timestamp });
    }
    static fromYearMonthDay(year, month, day) {
        let unix = getDate(year, month, day).getTime();
        let julian = getJulianFromUnix(unix);
        return new SimulatorDate({ unix, julian, year, month, day });
    }
    // ## epoch()
    static epoch() {
        return new SimulatorDate({
            year: 2000,
            month: 1,
            day: 1,
            unix: epochUnix,
            julian: epochJulian,
        });
    }
    // ## constructor()
    // The constructor is not meant to be used publicly, use the static `.from` 
    // methods instead!
    constructor(opts) {
        let { unix, julian, year, month, day } = opts;
        this.unix = unix;
        this.julian = julian;
        if (year === undefined || month === undefined || day === undefined) {
            ({ year, month, day } = getYmd(new Date(this.unix)));
        }
        this.year = year;
        this.month = month;
        this.day = day;
    }
    // ## toJulian()
    toJulian() {
        return this.julian;
    }
    // ## with(opts)
    with(opts) {
        let { year = this.year, month = this.month, day = this.day, } = opts;
        return SimulatorDate.fromYearMonthDay(year, month, day);
    }
    // # add(opts)
    add(opts) {
        let date = new SimulatorDate({ ...this });
        let { years, months, days } = opts;
        if (years !== undefined) {
            date = date.with({ year: date.year + years });
        }
        if (months !== undefined) {
            let next = date.month + months;
            let deltaYears = Math.trunc(next / 12);
            let month = (next % 12) || 12;
            date = date.with({ year: date.year + deltaYears, month });
        }
        if (days !== undefined) {
            date = SimulatorDate.fromJulian(date.julian + days);
        }
        return date;
    }
    [Symbol.for('nodejs.util.inspect.custom')](_level, util) {
        let { year } = this;
        let month = String(this.month).padStart(2, '0');
        let day = String(this.day).padStart(2, '0');
        return util.stylize(`${year}-${month}-${day}`, 'date');
    }
    [Symbol.toPrimitive]() {
        return this.unix;
    }
}
// # getYmd(date)
// Extracts the year, date and month from a JS date.
function getYmd(date) {
    let year = date.getUTCFullYear();
    let month = date.getUTCMonth() + 1;
    let day = date.getUTCDate();
    return { year, month, day };
}
// # getDate()
// Helper function for easily returning a standard js date, given year, month 
// and day.
function getDate(year, month, day) {
    let date = emptyDate();
    date.setUTCFullYear(year);
    // JS dates count from 0.
    date.setUTCMonth(month - 1);
    date.setUTCDate(day);
    return date;
}
function emptyDate() {
    return new Date(epochUnix);
}