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render.tsx
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render.tsx
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/** @jsx h */
import { renderToString } from "preact-render-to-string";
import { ComponentChildren, ComponentType, h, options } from "preact";
import {
AppModule,
ErrorPage,
Island,
RenderFunction,
Route,
UnknownPage,
} from "./types.ts";
import { HEAD_CONTEXT } from "../runtime/head.ts";
import { CSP_CONTEXT, nonce, NONE, UNSAFE_INLINE } from "../runtime/csp.ts";
import { ContentSecurityPolicy } from "../runtime/csp.ts";
import { bundleAssetUrl } from "./constants.ts";
import { assetHashingHook } from "../runtime/utils.ts";
export interface RenderOptions<Data> {
route: Route<Data> | UnknownPage | ErrorPage;
islands: Island[];
app: AppModule;
imports: string[];
preloads: string[];
url: URL;
params: Record<string, string | string[]>;
renderFn: RenderFunction;
data?: Data;
error?: unknown;
lang?: string;
}
export type InnerRenderFunction = () => string;
export class RenderContext {
#id: string;
#state: Map<string, unknown> = new Map();
#styles: string[] = [];
#url: URL;
#route: string;
#lang: string;
constructor(id: string, url: URL, route: string, lang: string) {
this.#id = id;
this.#url = url;
this.#route = route;
this.#lang = lang;
}
/** A unique ID for this logical JIT render. */
get id(): string {
return this.#id;
}
/**
* State that is persisted between multiple renders with the same render
* context. This is useful because one logical JIT render could have multiple
* preact render passes due to suspense.
*/
get state(): Map<string, unknown> {
return this.#state;
}
/**
* All of the CSS style rules that should be inlined into the document.
* Adding to this list across multiple renders is supported (even across
* suspense!). The CSS rules will always be inserted on the client in the
* order specified here.
*/
get styles(): string[] {
return this.#styles;
}
/** The URL of the page being rendered. */
get url(): URL {
return this.#url;
}
/** The route matcher (e.g. /blog/:id) that the request matched for this page
* to be rendered. */
get route(): string {
return this.#route;
}
/** The language of the page being rendered. Defaults to "en". */
get lang(): string {
return this.#lang;
}
set lang(lang: string) {
this.#lang = lang;
}
}
function defaultCsp() {
return {
directives: { defaultSrc: [NONE], styleSrc: [UNSAFE_INLINE] },
reportOnly: false,
};
}
/**
* This function renders out a page. Rendering is asynchronous, and streaming.
* Rendering happens in multiple steps, because of the need to handle suspense.
*
* 1. The page's vnode tree is constructed.
* 2. The page's vnode tree is passed to the renderer.
* - If the rendering throws a promise, the promise is awaited before
* continuing. This allows the renderer to handle async hooks.
* - Once the rendering throws no more promises, the initial render is
* complete and a body string is returned.
* - During rendering, every time a `<Suspense>` is rendered, it, and it's
* attached children are recorded for later rendering.
* 3. Once the inital render is complete, the body string is fitted into the
* HTML wrapper template.
* 4. The full inital render in the template is yielded to be sent to the
* client.
* 5. Now the suspended vnodes are rendered. These are individually rendered
* like described in step 2 above. Once each node is done rendering, it
* wrapped in some boilderplate HTML, and suffixed with some JS, and then
* sent to the client. On the client the HTML will be slotted into the DOM
* at the location of the original `<Suspense>` node.
*/
export async function render<Data>(
opts: RenderOptions<Data>,
): Promise<[string, ContentSecurityPolicy | undefined]> {
const props: Record<string, unknown> = {
params: opts.params,
url: opts.url,
route: opts.route.pattern,
data: opts.data,
};
if (opts.error) {
props.error = opts.error;
}
const csp: ContentSecurityPolicy | undefined = opts.route.csp
? defaultCsp()
: undefined;
const headComponents: ComponentChildren[] = [];
const vnode = h(CSP_CONTEXT.Provider, {
value: csp,
children: h(HEAD_CONTEXT.Provider, {
value: headComponents,
children: h(opts.app.default, {
Component() {
return h(opts.route.component! as ComponentType<unknown>, props);
},
}),
}),
});
const ctx = new RenderContext(
crypto.randomUUID(),
opts.url,
opts.route.pattern,
opts.lang ?? "en",
);
if (csp) {
// Clear the csp
const newCsp = defaultCsp();
csp.directives = newCsp.directives;
csp.reportOnly = newCsp.reportOnly;
}
// Clear the head components
headComponents.splice(0, headComponents.length);
// Setup the interesting VNode types
ISLANDS.splice(0, ISLANDS.length, ...opts.islands);
// Clear the encountered vnodes
ENCOUNTERED_ISLANDS.clear();
// Clear the island props
ISLAND_PROPS = [];
let bodyHtml: string | null = null;
function render() {
bodyHtml = renderToString(vnode);
return bodyHtml;
}
await opts.renderFn(ctx, render as InnerRenderFunction);
if (bodyHtml === null) {
throw new Error("The `render` function was not called by the renderer.");
}
const imports = opts.imports.map((url) => {
const randomNonce = crypto.randomUUID().replace(/-/g, "");
if (csp) {
csp.directives.scriptSrc = [
...csp.directives.scriptSrc ?? [],
nonce(randomNonce),
];
}
return [url, randomNonce] as const;
});
if (ENCOUNTERED_ISLANDS.size > 0) {
// Load the main.js script
{
const randomNonce = crypto.randomUUID().replace(/-/g, "");
if (csp) {
csp.directives.scriptSrc = [
...csp.directives.scriptSrc ?? [],
nonce(randomNonce),
];
}
const url = bundleAssetUrl("/main.js");
imports.push([url, randomNonce] as const);
}
// Prepare the inline script that loads and revives the islands
let islandImports = "";
let islandRegistry = "";
for (const island of ENCOUNTERED_ISLANDS) {
const randomNonce = crypto.randomUUID().replace(/-/g, "");
if (csp) {
csp.directives.scriptSrc = [
...csp.directives.scriptSrc ?? [],
nonce(randomNonce),
];
}
const url = bundleAssetUrl(`/island-${island.id}.js`);
imports.push([url, randomNonce] as const);
islandImports += `\nimport ${island.name} from "${url}";`;
islandRegistry += `\n ${island.id}: ${island.name},`;
}
const initCode = `import { revive } from "${
bundleAssetUrl("/main.js")
}";${islandImports}\nrevive({${islandRegistry}\n});`;
// Append the inline script to the body
const randomNonce = crypto.randomUUID().replace(/-/g, "");
if (csp) {
csp.directives.scriptSrc = [
...csp.directives.scriptSrc ?? [],
nonce(randomNonce),
];
}
(bodyHtml as string) +=
`<script id="__FRSH_ISLAND_PROPS" type="application/json">${
JSON.stringify(ISLAND_PROPS)
}</script><script type="module" nonce="${randomNonce}">${initCode}</script>`;
}
const html = template({
bodyHtml,
headComponents,
imports,
preloads: opts.preloads,
styles: ctx.styles,
lang: ctx.lang,
});
return [html, csp];
}
export interface TemplateOptions {
bodyHtml: string;
headComponents: ComponentChildren[];
imports: (readonly [string, string])[];
styles: string[];
preloads: string[];
lang: string;
}
export function template(opts: TemplateOptions): string {
const page = (
<html lang={opts.lang}>
<head>
<meta charSet="UTF-8" />
<meta http-equiv="X-UA-Compatible" content="IE=edge" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
{opts.preloads.map((src) => <link rel="modulepreload" href={src} />)}
{opts.imports.map(([src, nonce]) => (
<script src={src} nonce={nonce} type="module"></script>
))}
<style
id="__FRSH_STYLE"
dangerouslySetInnerHTML={{ __html: opts.styles.join("\n") }}
/>
{opts.headComponents}
</head>
<body dangerouslySetInnerHTML={{ __html: opts.bodyHtml }} />
</html>
);
return "<!DOCTYPE html>" + renderToString(page);
}
// Set up a preact option hook to track when vnode with custom functions are
// created.
const ISLANDS: Island[] = [];
const ENCOUNTERED_ISLANDS: Set<Island> = new Set([]);
let ISLAND_PROPS: unknown[] = [];
const originalHook = options.vnode;
let ignoreNext = false;
options.vnode = (vnode) => {
assetHashingHook(vnode);
const originalType = vnode.type as ComponentType<unknown>;
if (typeof vnode.type === "function") {
const island = ISLANDS.find((island) => island.component === originalType);
if (island) {
if (ignoreNext) {
ignoreNext = false;
return;
}
ENCOUNTERED_ISLANDS.add(island);
vnode.type = (props) => {
ignoreNext = true;
const child = h(originalType, props);
ISLAND_PROPS.push(props);
return h(
`!--frsh-${island.id}:${ISLAND_PROPS.length - 1}--`,
null,
child,
);
};
}
}
if (originalHook) originalHook(vnode);
};