@hugoalh/http-header-retry-after/mod.js

A module to handle the HTTP header `Retry-After` according to the specification RFC 9110.

const regexpDateRFC7231 = /^[A-Z][a-z][a-z], \d\d [A-Z][a-z][a-z] \d\d\d\d \d\d:\d\d:\d\d GMT$/;
const regexpDecimalInteger = /^\d+$/;
/**
 * Handle the HTTP header `Retry-After` according to the specification RFC 9110.
 */
export class HTTPHeaderRetryAfter {
    get [Symbol.toStringTag]() {
        return "HTTPHeaderRetryAfter";
    }
    #timestamp;
    /**
     * Initialize.
     * @param {number | string | Date | Headers | Response} input Input.
     */
    constructor(input) {
        if (typeof input === "number") {
            if (!(input >= 0 && input <= Number.MAX_SAFE_INTEGER)) {
                throw new RangeError(`Parameter \`input\` is not a number which is positive and safe!`);
            }
            this.#timestamp = new Date(Date.now() + input * 1000);
        }
        else if (input instanceof Date) {
            this.#timestamp = new Date(input);
        }
        else {
            let inputFmt;
            if (input instanceof Response) {
                inputFmt = input.headers.get("Retry-After") ?? "0";
            }
            else if (input instanceof Headers) {
                inputFmt = input.get("Retry-After") ?? "0";
            }
            else {
                inputFmt = input;
            }
            if (regexpDateRFC7231.test(inputFmt)) {
                this.#timestamp = new Date(inputFmt);
            }
            else if (regexpDecimalInteger.test(inputFmt)) {
                this.#timestamp = new Date(Date.now() + Number(inputFmt) * 1000);
            }
            else {
                throw new SyntaxError(`\`${inputFmt}\` is not a valid HTTP header \`Retry-After\` value!`);
            }
        }
    }
    /**
     * Get `Date`.
     * @returns {Date}
     */
    getDate() {
        return new Date(this.#timestamp);
    }
    /**
     * Get remain time in milliseconds.
     * @returns {number}
     */
    getRemainTimeMilliseconds() {
        return Math.max(0, this.#timestamp.valueOf() - Date.now());
    }
    /**
     * Get remain time in seconds.
     * @returns {number}
     */
    getRemainTimeSeconds() {
        return (this.getRemainTimeMilliseconds() / 1000);
    }
    /**
     * Stringify.
     * @returns {string}
     */
    stringify() {
        return this.toString();
    }
    /**
     * Convert to string.
     * @returns {string}
     */
    toString() {
        return this.#timestamp.toUTCString();
    }
    /**
     * Initialize in safe way.
     * @param {number | string | Date | Headers | Response} input Input.
     * @returns {HTTPHeaderRetryAfter | null}
     */
    static parseSafe(input) {
        try {
            return new this(input);
        }
        catch {
            return null;
        }
    }
}
export default HTTPHeaderRetryAfter;