84 lines
2.8 KiB
TypeScript
84 lines
2.8 KiB
TypeScript
/**
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* Serves the built frontend, as its static files and, for every client-side
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* route, `index.html` with its placeholders filled. main.ts installs it after
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* the routers.
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*
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* @module
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*/
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import { Context, Next, send } from "@oak/oak";
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import { loadIndexHtml } from "./index-html.ts";
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async function serveIndexHtml(
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context: Context<Record<string, object>>,
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root: string,
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) {
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const html = await loadIndexHtml(root);
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context.response.type = "text/html";
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// It names the hashed chunks of the current build, so it is always
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// revalidated.
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context.response.headers.set("Cache-Control", "no-cache");
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context.response.body = html;
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}
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/**
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* Prefixes the build output whose URL changes whenever its content does, which
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* are Vite's hashed chunks and the emoji data under its package version (see
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* vite.config.ts).
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*/
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const IMMUTABLE_PREFIXES = ["/assets/", "/emojibase/"];
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const ONE_YEAR_MS = 365 * 24 * 60 * 60 * 1000;
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/**
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* Returns the middleware that serves a static file from the first of
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* `staticPaths` that has it, and `index.html` of the first for any other path.
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* Hashed build output is cached for a year, and a missing chunk is a 404.
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* main.ts passes dist/ then public/.
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*/
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export function routeStaticFilesFrom(
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staticPaths: string[],
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): (context: Context<Record<string, object>>, next: Next) => Promise<void> {
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// It is the last middleware and always answers, so it never calls `next`.
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return async (context: Context<Record<string, object>>, _next: Next) => {
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const pathname = context.request.url.pathname;
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if (pathname === "/" || pathname === "/index.html") {
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await serveIndexHtml(context, staticPaths[0]);
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return;
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}
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const immutable = IMMUTABLE_PREFIXES.some((prefix) =>
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pathname.startsWith(prefix)
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);
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// A request without Accept-Encoding technically accepts any coding (RFC
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// 9110), but in practice it's curl or a bot that can't decode brotli.
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const compress = context.request.headers.has("accept-encoding");
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for (const path of staticPaths) {
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try {
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// send() picks a prebuilt .br or .gz sibling when the browser accepts
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// it.
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await send(context, pathname, {
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root: path,
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brotli: compress,
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gzip: compress,
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...(immutable && { maxage: ONE_YEAR_MS, immutable: true }),
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});
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context.response.headers.append("Vary", "Accept-Encoding");
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return;
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} catch {
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continue;
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}
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}
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// A chunk from an older build (an open tab after a deploy) must fail as a
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// 404, not load index.html as a script; the app reloads on that failure.
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if (immutable) {
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context.response.status = 404;
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return;
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}
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// Any other path is a client-side route, opened directly or reloaded.
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await serveIndexHtml(context, staticPaths[0]);
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};
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}
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