export class DateBuilder {
	// constructors
	constructor(date = new Date()) {
		if (!(date instanceof Date)) {
			throw new Error("Invalid date object.");
		}
		this.date = new Date(date.getTime()); // Create a copy to avoid mutating the original date
	}

	// methods
	addYears(years) {
		this.date.setFullYear(this.date.getFullYear() + years);
		return this;
	}

	addMonths(months) {
		this.date.setMonth(this.date.getMonth() + months);
		return this;
	}

	addDays(days) {
		this.date.setDate(this.date.getDate() + days);
		return this;
	}

	addHours(hours) {
		this.date.setHours(this.date.getHours() + hours);
		return this;
	}

	addMinutes(minutes) {
		this.date.setMinutes(this.date.getMinutes() + minutes);
		return this;
	}

	addSeconds(seconds) {
		this.date.setSeconds(this.date.getSeconds() + seconds);
		return this;
	}

	addMillis(millis) {
		this.date.setTime(this.date.getTime() + millis);
		return this;
	}

	withDate(year, month, day) {
		this.date.setFullYear(year, month - 1, day); // month is 0-based
		return this;
	}

	withTime(hour, minute = 0, second = 0, millisecond = 0) {
		this.date.setHours(hour, minute, second, millisecond);
		return this;
	}

	atStartOfDay() {
		this.date.setHours(0, 0, 0, 0);
		return this;
	}

	atEndOfDay() {
		this.date.setHours(23, 59, 59, 999);
		return this;
	}

	build() {
		return new Date(this.date.getTime()); // Return a copy to avoid external mutation
	}
}