got/dist/source/core/parse-link-header.js

Human-friendly and powerful HTTP request library for Node.js

const splitHeaderValue = (value, separator) => {
    const values = [];
    let current = '';
    let inQuotes = false;
    let inReference = false;
    let isEscaped = false;
    for (const character of value) {
        if (inQuotes) {
            if (isEscaped) {
                isEscaped = false;
            }
            else if (character === '\\') {
                isEscaped = true;
            }
            else if (character === '"') {
                inQuotes = false;
            }
        }
        else if (character === '"') {
            inQuotes = true;
        }
        else if (character === '<' || character === '>') {
            inReference = character === '<';
        }
        else if (!inReference && character === separator) {
            // Link headers use both quoted strings and <URI-reference> values, so raw
            // splitting on `,` / `;` would break valid values containing those characters.
            values.push(current);
            current = '';
            continue;
        }
        current += character;
    }
    if (inQuotes) {
        throw new Error(`Failed to parse Link header: ${value}`);
    }
    values.push(current);
    return values;
};
export default function parseLinkHeader(link) {
    const parsed = [];
    for (const item of splitHeaderValue(link, ',')) {
        // HTTP list recipients ignore empty members (RFC 9110, section 5.6.1.2).
        if (item.trim() === '') {
            continue;
        }
        // https://tools.ietf.org/html/rfc5988#section-5
        const [rawUriReference, ...rawLinkParameters] = splitHeaderValue(item, ';');
        const trimmedUriReference = rawUriReference.trim();
        // eslint-disable-next-line @typescript-eslint/prefer-string-starts-ends-with
        if (trimmedUriReference[0] !== '<' || trimmedUriReference.at(-1) !== '>') {
            throw new Error(`Invalid format of the Link header reference: ${trimmedUriReference}`);
        }
        // Optional whitespace is allowed inside the angle brackets (RFC 8288, section 3).
        const reference = trimmedUriReference.slice(1, -1).trim();
        if (reference.includes('<') || reference.includes('>')) {
            throw new Error(`Invalid format of the Link header reference: ${trimmedUriReference}`);
        }
        // Parameter names can match `Object.prototype` properties, so use a null-prototype object.
        const parameters = Object.create(null);
        for (const rawParameter of rawLinkParameters) {
            const trimmedRawParameter = rawParameter.trim();
            const center = trimmedRawParameter.indexOf('=');
            // The parameter value is optional. See https://www.rfc-editor.org/rfc/rfc8288#section-3
            const name = center === -1 ? trimmedRawParameter : trimmedRawParameter.slice(0, center).trim();
            if (name === '') {
                throw new Error(`Failed to parse Link header: ${link}`);
            }
            const value = center === -1 ? '' : trimmedRawParameter.slice(center + 1).trim();
            const normalizedName = name.toLowerCase();
            if (!Object.hasOwn(parameters, normalizedName)) {
                parameters[normalizedName] = value;
            }
        }
        parsed.push({
            reference,
            parameters,
        });
    }
    return parsed;
}