@appsemble/node-utils/resourceEtag.js

NodeJS utilities used by Appsemble internally.

import { createHash } from 'node:crypto';
import sortKeys from 'sort-keys';
import { AppsembleError } from './AppsembleError.js';
import { throwKoaError } from './koa.js';
// Server-managed metadata keys that are echoed in resource responses but are not
// part of the resource's identity for ETag purposes. Stripped only at the top
// level; nested user data may legitimately contain keys with the same names.
const ignoredEtagFields = new Set(['$author', '$editor', '$etag', '$group', '$seed', '$ephemeral']);
function canonicalize(value) {
    if (value instanceof Date) {
        return value.toJSON();
    }
    if (Array.isArray(value)) {
        return value.map(canonicalize);
    }
    if (value && typeof value === 'object') {
        return sortKeys(Object.fromEntries(Object.entries(value).map(([key, entry]) => [
            key,
            canonicalize(entry),
        ])), { deep: true });
    }
    return value;
}
export function createResourceEtag(resource) {
    const stripped = {};
    for (const [key, value] of Object.entries(resource)) {
        if (!ignoredEtagFields.has(key)) {
            stripped[key] = value;
        }
    }
    const canonicalResource = JSON.stringify(canonicalize(stripped));
    const hash = createHash('sha256').update(canonicalResource, 'utf8').digest('base64url');
    return `"${hash}"`;
}
export function addResourceEtag(resource) {
    return {
        ...resource,
        $etag: createResourceEtag(resource),
    };
}
// RFC 7232 §3.1: If-Match uses the strong-comparison function, so weak
// validators (prefixed with `W/`) must not match. Tokens are split with a
// quoted-string-aware parser instead of a naive `,` split.
function parseIfMatchValue(ifMatch) {
    if (ifMatch === '*') {
        return ['*'];
    }
    const tokens = [];
    let i = 0;
    while (i < ifMatch.length) {
        while (i < ifMatch.length &&
            (ifMatch[i] === ' ' || ifMatch[i] === ',' || ifMatch[i] === '\t')) {
            i += 1;
        }
        if (i >= ifMatch.length) {
            break;
        }
        // Skip any leading weak prefix; strong comparison rejects it.
        let weak = false;
        if (ifMatch[i] === 'W' && ifMatch[i + 1] === '/') {
            weak = true;
            i += 2;
        }
        if (ifMatch[i] !== '"') {
            // Malformed token; skip until next comma.
            while (i < ifMatch.length && ifMatch[i] !== ',') {
                i += 1;
            }
            continue;
        }
        const start = i;
        i += 1;
        while (i < ifMatch.length && ifMatch[i] !== '"') {
            i += 1;
        }
        if (i >= ifMatch.length) {
            break;
        }
        i += 1;
        if (!weak) {
            tokens.push(ifMatch.slice(start, i));
        }
    }
    return tokens;
}
export function matchesResourceIfMatch(ifMatch, currentEtag) {
    if (!ifMatch) {
        return true;
    }
    const values = new Set((Array.isArray(ifMatch) ? ifMatch : [ifMatch]).flatMap(parseIfMatchValue));
    return values.has('*') || values.has(currentEtag);
}
export function setResourceEtagHeader(ctx, resource) {
    if (!resource) {
        return;
    }
    const etag = typeof resource.$etag === 'string' ? resource.$etag : createResourceEtag(resource);
    ctx.set('ETag', etag);
}
export class ResourcePreconditionFailedError extends AppsembleError {
    constructor(resourceType, resourceId) {
        super('This resource has changed since it was loaded. Fetch the latest version and try again.');
        this.error = 'Precondition Failed';
        this.statusCode = 412;
        this.name = 'ResourcePreconditionFailedError';
        this.data = {
            code: 'RESOURCE_PRECONDITION_FAILED',
            resourceId,
            resourceType,
        };
    }
}
export function throwResourcePreconditionFailedKoaError(ctx, resourceType, resourceId) {
    const error = new ResourcePreconditionFailedError(resourceType, resourceId);
    throwKoaError(ctx, error.statusCode, error.message, error.data);
}
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