78 lines
2.9 KiB
Plaintext
78 lines
2.9 KiB
Plaintext
import { generateDigest } from "./digest.js";
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//#region src/middleware/etag/index.ts
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/**
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* Default headers to pass through on 304 responses. From the spec:
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* > The response must not contain a body and must include the headers that
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* > would have been sent in an equivalent 200 OK response: Cache-Control,
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* > Content-Location, Date, ETag, Expires, and Vary.
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*/
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const RETAINED_304_HEADERS = [
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"cache-control",
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"content-location",
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"date",
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"etag",
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"expires",
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"vary"
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];
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const stripWeak = (tag) => tag.replace(/^W\//, "");
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function etagMatches(etag, ifNoneMatch) {
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return ifNoneMatch != null && ifNoneMatch.split(",").some((t) => stripWeak(t.trim()) === stripWeak(etag));
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}
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function initializeGenerator(generator) {
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if (!generator) {
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if (crypto && crypto.subtle) generator = (body) => crypto.subtle.digest({ name: "SHA-1" }, body);
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}
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return generator;
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}
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/**
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* ETag Middleware for Hono.
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*
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* @see {@link https://hono.dev/docs/middleware/builtin/etag}
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*
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* @param {ETagOptions} [options] - The options for the ETag middleware.
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* @param {boolean} [options.weak=false] - Define using or not using a weak validation. If true is set, then `W/` is added to the prefix of the value.
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* @param {string[]} [options.retainedHeaders=RETAINED_304_HEADERS] - The headers that you want to retain in the 304 Response.
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* @param {function(Uint8Array): ArrayBuffer | Promise<ArrayBuffer>} [options.generateDigest] -
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* A custom digest generation function. By default, it uses 'SHA-1'
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* This function is called with the response body as a `Uint8Array` and should return a hash as an `ArrayBuffer` or a Promise of one.
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* @returns {MiddlewareHandler} The middleware handler function.
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*
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* @example
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* ```ts
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* const app = new Hono()
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*
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* app.use('/etag/*', etag())
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* app.get('/etag/abc', (c) => {
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* return c.text('Hono is hot')
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* })
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* ```
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*/
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const etag = (options) => {
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const retainedHeaders = new Set((options?.retainedHeaders ?? RETAINED_304_HEADERS).map((header) => header.toLowerCase()));
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const weak = options?.weak ?? false;
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const generator = initializeGenerator(options?.generateDigest);
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return async function etag(c, next) {
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const ifNoneMatch = c.req.header("If-None-Match") ?? null;
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await next();
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if (!(c.req.method === "GET" || c.req.method === "HEAD" || c.req.method === "QUERY") || !c.res.ok) return;
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const res = c.res;
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let etag = res.headers.get("ETag");
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if (!etag) {
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if (!generator) return;
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const hash = await generateDigest(res.clone().body, generator);
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if (hash === null) return;
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etag = weak ? `W/"${hash}"` : `"${hash}"`;
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}
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if (ifNoneMatch === "*" || etagMatches(etag, ifNoneMatch)) {
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c.res = new Response(null, {
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status: 304,
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statusText: "Not Modified",
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headers: { ETag: etag }
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});
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for (const key of Array.from(c.res.headers.keys())) if (!retainedHeaders.has(key.toLowerCase())) c.res.headers.delete(key);
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} else c.res.headers.set("ETag", etag);
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};
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};
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//#endregion
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export { RETAINED_304_HEADERS, etag };
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