json-prune-fetch-response.ts

import {
    hit,
    logMessage,
    getFetchData,
    objectToString,
    matchRequestProps,
    jsonPruner,
    getPrunePath,
    forgeResponse,
    type FetchResource,
    isPruningNeeded,
    matchStackTrace,
    toRegExp,
    isValidStrPattern,
    escapeRegExp,
    isEmptyObject,
    getRequestData,
    getRequestProps,
    parseMatchProps,
    isValidParsedData,
    getMatchPropsData,
    getWildcardPropertyInChain,
    shouldAbortInlineOrInjectedScript,
    getNativeRegexpTest,
    backupRegExpValues,
    restoreRegExpValues,
} from '../helpers';
import { type Source } from './scriptlets';

/**
 * @scriptlet json-prune-fetch-response
 *
 * @description
 * Removes specified properties from the JSON response of a fetch call.
 *
 * Related UBO scriptlet:
 * https://github.com/gorhill/uBlock/commit/749cec0f095f659d6c0b90eb89b729e9deb07c87
 *
 * ### Syntax
 *
 * ```text
 * example.org#%#//scriptlet('json-prune-fetch-response'[, propsToRemove[, obligatoryProps[, propsToMatch[, stack]]]])
 * ```
 *
 * - `propsToRemove` — optional, string of space-separated properties to remove
 * - `obligatoryProps` — optional, string of space-separated properties
 *   which must be all present for the pruning to occur
 * - `propsToMatch` — optional, string of space-separated properties to match; possible props:
 *     - string or regular expression for matching the URL passed to fetch call;
 *       empty string, wildcard `*` or invalid regular expression will match all fetch calls
 *     - colon-separated pairs `name:value` where
 *         <!-- markdownlint-disable-next-line line-length -->
 *         - `name` is [`init` option name](https://developer.mozilla.org/en-US/docs/Web/API/WindowOrWorkerGlobalScope/fetch#parameters)
 *         - `value` is string or regular expression for matching the value of the option passed to fetch call;
 *           invalid regular expression will cause any value matching
 * - `stack` — optional, string or regular expression that must match the current function call stack trace;
 *   if regular expression is invalid it will be skipped
 *
 * > Note please that you can use wildcard `*` for chain property name,
 * > e.g. `ad.*.src` instead of `ad.0.src ad.1.src ad.2.src`.
 *
 * > Usage with with only propsToMatch argument will log fetch calls to browser console.
 * > It may be useful for debugging but it is not allowed for prod versions of filter lists.
 *
 * > Scriptlet does nothing if response body can't be converted to JSON.
 *
 * ### Examples
 *
 * 1. Removes property `example` from the JSON response of any fetch call
 *
 *     ```adblock
 *     example.org#%#//scriptlet('json-prune-fetch-response', 'example')
 *     ```
 *
 *     For instance, if the JSON response of a fetch call is:
 *
 *     ```js
 *     {one: 1, example: true}
 *     ```
 *
 *     then the response will be modified to:
 *
 *     ```js
 *     {one: 1}
 *     ```
 *
 * 2. A property in a list of properties can be a chain of properties
 *
 *     ```adblock
 *     example.org#%#//scriptlet('json-prune-fetch-response', 'a.b', 'ads.url.first')
 *     ```
 *
 * 3. Removes property `content.ad` from the JSON response of a fetch call if URL contains `content.json`
 *
 *     ```adblock
 *     example.org#%#//scriptlet('json-prune-fetch-response', 'content.ad', '', 'content.json')
 *     ```
 *
 * 4. Removes property `content.ad` from the JSON response of a fetch call if its error stack trace contains `test.js`
 *
 *     ```adblock
 *     example.org#%#//scriptlet('json-prune-fetch-response', 'content.ad', '', '', 'test.js')
 *     ```
 *
 * 5. A property in a list of properties can be a chain of properties with wildcard in it
 *
 *     ```adblock
 *     example.org#%#//scriptlet('json-prune-fetch-response', 'content.*.media.src', 'content.*.media.ad')
 *     ```
 *
 * 6. Log all JSON responses of a fetch call
 *
 *     ```adblock
 *     example.org#%#//scriptlet('json-prune-fetch-response')
 *     ```
 *
 * @added v1.10.25.
 */
export function jsonPruneFetchResponse(
    source: Source,
    propsToRemove: string,
    obligatoryProps: string,
    propsToMatch = '',
    stack = '',
) {
    // do nothing if browser does not support fetch or Proxy (e.g. Internet Explorer)
    // https://developer.mozilla.org/en-US/docs/Web/API/WindowOrWorkerGlobalScope/fetch
    // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy
    if (typeof fetch === 'undefined'
        || typeof Proxy === 'undefined'
        || typeof Response === 'undefined') {
        return;
    }

    const prunePaths = getPrunePath(propsToRemove);
    const requiredPaths = getPrunePath(obligatoryProps);

    const nativeStringify = window.JSON.stringify;
    const nativeRequestClone = window.Request.prototype.clone;
    const nativeResponseClone = window.Response.prototype.clone;
    const nativeFetch = window.fetch;

    const fetchHandlerWrapper = async (
        target: typeof fetch,
        thisArg: any,
        args: [FetchResource, RequestInit],
    ): Promise<Response> => {
        const fetchData = getFetchData(args, nativeRequestClone);

        if (!matchRequestProps(source, propsToMatch, fetchData)) {
            return Reflect.apply(target, thisArg, args);
        }

        let originalResponse;
        let clonedResponse;
        try {
            // eslint-disable-next-line prefer-spread
            originalResponse = await nativeFetch.apply(null, args);
            clonedResponse = nativeResponseClone.call(originalResponse);
        } catch {
            logMessage(source, `Could not make an original fetch request: ${fetchData.url}`);
            return Reflect.apply(target, thisArg, args);
        }

        let json;
        try {
            json = await originalResponse.json();
        } catch (e) {
            const message = `Response body can't be converted to json: ${objectToString(fetchData)}`;
            logMessage(source, message);
            return clonedResponse;
        }

        const modifiedJson = jsonPruner(source, json, prunePaths, requiredPaths, stack, {
            nativeStringify,
            nativeRequestClone,
            nativeResponseClone,
            nativeFetch,
        });

        const forgedResponse = forgeResponse(
            originalResponse,
            nativeStringify(modifiedJson),
        );
        hit(source);

        return forgedResponse;
    };

    const fetchHandler = {
        apply: fetchHandlerWrapper,
    };

    window.fetch = new Proxy(window.fetch, fetchHandler);
}

export const jsonPruneFetchResponseNames = [
    'json-prune-fetch-response',
    // aliases are needed for matching the related scriptlet converted into our syntax
    'json-prune-fetch-response.js',
    'ubo-json-prune-fetch-response.js',
    'ubo-json-prune-fetch-response',
];

// eslint-disable-next-line prefer-destructuring
jsonPruneFetchResponse.primaryName = jsonPruneFetchResponseNames[0];

jsonPruneFetchResponse.injections = [
    hit,
    logMessage,
    getFetchData,
    objectToString,
    matchRequestProps,
    jsonPruner,
    getPrunePath,
    forgeResponse,
    isPruningNeeded,
    matchStackTrace,
    toRegExp,
    isValidStrPattern,
    escapeRegExp,
    isEmptyObject,
    getRequestData,
    getRequestProps,
    parseMatchProps,
    isValidParsedData,
    getMatchPropsData,
    getWildcardPropertyInChain,
    shouldAbortInlineOrInjectedScript,
    getNativeRegexpTest,
    backupRegExpValues,
    restoreRegExpValues,
];