@curveball/kernel/dist/conditional.js

Curveball is a framework writting in Typescript for Node.js

/**
 * This method will check the following request headers:
 *
 * 1. If-Match
 * 2. If-None-Match
 * 3. If-Modified-Since
 * 4. If-Unmodified-Since
 *
 * To check these headers,v alues for lastModified and etag should be passed.
 *
 * The result of this function will return a suggested HTTP status. It will
 * return
 * * '200' if all the preconditions passed.
 * * '304' is a 'Not Modified' status should be returned, and
 * * '412' if a 'Precondition failed' error should be returned.
 */
export function conditionalCheck(request, lastModified, etag) {
    validateETag(etag);
    if (request.headers.has('If-Match')) {
        return ifMatchCheck(request.headers.get('If-Match'), etag);
    }
    if (request.headers.has('If-None-Match')) {
        return ifNoneMatchCheck(request.method, request.headers.get('If-None-Match'), etag);
    }
    if (request.headers.has('If-Modified-Since')) {
        return ifModifiedSinceCheck(request.method, request.headers.get('If-Modified-Since'), lastModified);
    }
    if (request.headers.has('If-Unmodified-Since')) {
        return ifUnmodifiedSinceCheck(request.headers.get('If-Unmodified-Since'), lastModified);
    }
    return 200;
}
function ifMatchCheck(header, serverState) {
    if (header === '*') {
        return serverState !== null ? 200 : 412;
    }
    const headerTags = header.split(',').map(foo => foo.trim());
    for (const tag of headerTags) {
        if (tag === serverState)
            return 200;
    }
    return 412;
}
function ifNoneMatchCheck(method, header, serverState) {
    let pass;
    if (header === '*') {
        pass = serverState === null;
    }
    else {
        const headerTags = header.split(',').map(foo => foo.trim());
        pass = true;
        for (const tag of headerTags) {
            if (tag === serverState) {
                pass = false;
            }
        }
    }
    if (!pass) {
        if (method === 'GET' || method === 'HEAD') {
            return 304;
        }
        else {
            return 412;
        }
    }
    return 200;
}
function ifModifiedSinceCheck(method, header, serverState) {
    if (method !== 'GET' && method !== 'HEAD') {
        // Only GET and HEAD are supported, everything else is ignored
        return 200;
    }
    if (serverState === null) {
        return 200;
    }
    const headerDate = new Date(header);
    return (serverState.getTime() > headerDate.getTime()) ? 200 : 304;
}
function ifUnmodifiedSinceCheck(header, serverState) {
    // This is not in any spec, but I believe that we should reject requests
    // if we don't know that the Last-Modified value is.
    if (serverState === null) {
        return 412;
    }
    const headerDate = new Date(header);
    return (serverState.getTime() <= headerDate.getTime()) ? 200 : 412;
}
function validateETag(etag) {
    if (etag === null)
        return;
    if (!/^(W\/)?"[\x21\x23-\x7e]+"$/.test(etag)) {
        throw new Error('Etags must be valid. Did you forget the double-quotes?');
    }
}
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