RotatingFileTransport.ts

import type { Blueprint, Schemas } from '@boost/common/optimal';
import type { Rotation } from '../types';
import { FileTransport, type FileTransportOptions } from './FileTransport';

const DAYS_IN_WEEK = 7;

export interface RotatingFileTransportOptions extends FileTransportOptions {
	/** Period in which to rotate files. Will append a timestamp to the rotated log file. */
	rotation: Rotation;
}

export class RotatingFileTransport extends FileTransport<RotatingFileTransportOptions> {
	protected lastTimestamp: string = this.formatTimestamp(Date.now());

	override blueprint(schemas: Schemas): Blueprint<RotatingFileTransportOptions> {
		const { string } = schemas;

		return {
			...super.blueprint(schemas),
			rotation: string().oneOf(['hourly', 'daily', 'weekly', 'monthly']),
		};
	}

	/**
	 * Format a `Date` object into a format used within the log file name.
	 */
	formatTimestamp(ms: number): string {
		const { rotation } = this.options;
		const date = new Date(ms);
		let timestamp = `${date.getFullYear()}${String(date.getMonth() + 1).padStart(2, '0')}`;

		if (rotation === 'monthly') {
			return timestamp;
		}

		// Special case, calculate the week manually and return,
		// but do not append so other rotations inherit!
		if (rotation === 'weekly') {
			const firstDay = new Date(date.getFullYear(), date.getMonth(), 1).getDay();
			const offsetDate = date.getDate() + firstDay - 1;

			timestamp += `.W${Math.floor(offsetDate / DAYS_IN_WEEK) + 1}`;

			return timestamp;
		}

		timestamp += String(date.getDate()).padStart(2, '0');

		if (rotation === 'daily') {
			return timestamp;
		}

		timestamp += `.${String(date.getHours()).padStart(2, '0')}`;

		return timestamp;
	}

	/**
	 * @inheritDoc
	 */
	protected override checkIfNeedsRotation() {
		if (
			this.lastSize > this.options.maxSize ||
			this.formatTimestamp(Date.now()) !== this.lastTimestamp
		) {
			this.closeStreamAndRotateFile();
		}
	}

	/**
	 * @inheritDoc
	 */
	protected override getRotatedFileName(): string {
		const name = this.path.name(true);
		const ext = this.path.ext(true);

		return `${name}-${this.lastTimestamp}.${ext}`;
	}

	/**
	 * @inheritDoc
	 */
	protected override rotateFile() {
		super.rotateFile();

		// Update timestamp to the new format
		this.lastTimestamp = this.formatTimestamp(Date.now());
	}
}