@nestjs/platform-express/adapters/utils/get-media-type-version.util.js

Nest - modern, fast, powerful node.js web framework (@platform-express)

/**
 * Splits a header value at separators outside quoted strings in linear time.
 * Backslash-escaped characters inside quoted strings are treated as literals.
 */
const splitOutsideQuotes = (value, separator) => {
    const parts = [];
    let start = 0;
    let isQuoted = false;
    const len = value.length;
    for (let index = 0; index < len; index++) {
        const character = value[index];
        if (isQuoted && character === '\\') {
            // A quoted-pair consumes the next character, including an escaped quote.
            index++;
        }
        else if (character === '"') {
            isQuoted = !isQuoted;
        }
        else if (character === separator && !isQuoted) {
            parts.push(value.slice(start, index));
            start = index + 1;
        }
    }
    parts.push(value.slice(start));
    return parts;
};
/**
 * Returns the version carried by an `Accept` header for media type versioning,
 * e.g. `2` for `application/json;v=2` with the `v=` key.
 *
 * The version parameter may follow other parameters and may belong to any
 * media range of a list (`text/html, application/json;v=2`); the first match
 * wins. Returns `undefined` when no parameter starts with the key.
 *
 * Quoted parameter values are unescaped, and separators inside them are ignored.
 * An unterminated quoted string runs to the end of the header value, so a
 * version that follows its opening quote is not read.
 *
 * Duplicated in each platform package so that a platform package never
 * depends on a newer `@nestjs/core` than the one installed.
 */
export function getMediaTypeVersion(acceptHeader, key) {
    const mediaRanges = []
        .concat(acceptHeader ?? [])
        .flatMap(value => splitOutsideQuotes(value, ','));
    for (const mediaRange of mediaRanges) {
        const [, ...parameters] = splitOutsideQuotes(mediaRange, ';');
        for (const parameter of parameters) {
            const trimmedParameter = parameter.trim();
            if (trimmedParameter.startsWith(key)) {
                const version = trimmedParameter.slice(key.length);
                if (version.startsWith('"') && version.endsWith('"')) {
                    return version.slice(1, -1).replace(/\\([\s\S])/g, '$1');
                }
                return version;
            }
        }
    }
    return undefined;
}