sitegen/framework/lib/assets.ts

// Static and dynamic assets are built alongside the server binary.
// This module implements decoding and serving of the asset blobs,
// but also implements patching of dynamic assets. The `Manifest`
// is generated by `incremental.ts`
const debug = console.scoped("assets");
const root = import.meta.dirname;
let current: Loaded | null = null;

// TODO: rename all these types
type DynamicId = string;
export type { Key };
export type Manifest =
  & {
    [K in Key]: StaticAsset | DynamicAsset;
  }
  & {
    [string: string]: StaticAsset | DynamicAsset;
  };
export interface StaticAsset extends AssetBase {
  type: 0;
}
interface AssetBase {
  headers: Record<string, string> & { etag: string };
  raw: BufferView;
  gzip: BufferView;
  zstd: BufferView;
}
export interface DynamicAsset {
  type: 1;
  id: DynamicId;
}
interface Loaded {
  map: Manifest;
  static: Buffer;
  dynamic: Map<DynamicId, DynamicEntry>;
}
export interface DynamicEntry extends AssetBase {
  buffer: Buffer;
}
type CacheMode = "auto" | "long-term" | "temporary" | "no-cache";

export async function reload() {
  const map = await fs.readJson<Manifest>(path.join(root, "asset.json"));
  const statics = await fs.readFile(path.join(root, "asset.blob"));
  const dynamic = new Map(
    await Promise.all(
      Object.entries(map)
        .filter((entry): entry is [string, DynamicAsset] => entry[1].type === 1)
        .map(async ([k, v]) =>
          [
            v.id,
            await fs.readFile(path.join(root, "dynamic", v.id))
              .then(loadRegenerative),
          ] as const
        ),
    ),
  );
  return (current = { map, static: statics, dynamic });
}

export async function middleware(c: Context, next: Next) {
  if (!current) current = await reload();
  const asset = current.map[c.req.path];
  if (asset) return assetInner(c, c.req.path, asset, 200);
  return next();
}

export async function notFound(c: Context) {
  if (!current) current = await reload();
  let pathname = c.req.path;
  do {
    const asset = current.map[pathname + "/404"];
    if (asset) return assetInner(c, pathname + "/404", asset, 404);
    pathname = pathname.slice(0, pathname.lastIndexOf("/"));
  } while (pathname);
  const asset = current.map["/404"];
  if (asset) return assetInner(c, "/404", asset, 404);
  return c.text("the 'Not Found' page was not found", 404);
}

export async function serveAsset(
  c: Context,
  id: Key,
  status: StatusCode = 200,
  cache: CacheMode = 'auto',
) {
  return assetInner(
    c,
    id,
    (current ?? (await reload())).map[id],
    status,
    cache,
  );
}

/** @deprecated */
export function hasAsset(id: string) {
  return UNWRAP(current).map[id] !== undefined;
}

export function etagMatches(etag: string, ifNoneMatch: string) {
  return ifNoneMatch === etag || ifNoneMatch.split(/,\s*/).indexOf(etag) > -1;
}

function assetInner(
  c: Context,
  key: string,
  asset: Manifest[Key],
  status: StatusCode,
  cache: CacheMode = "auto",
) {
  ASSERT(current);
  if (asset.type === 0) {
    return respondWithBufferAndViews(
      c,
      key,
      current.static,
      asset,
      status,
      cache,
    );
  } else {
    const entry = UNWRAP(current.dynamic.get(asset.id));
    return respondWithBufferAndViews(
      c,
      key,
      entry.buffer,
      entry,
      status,
      cache,
    );
  }
}

function respondWithBufferAndViews(
  c: Context,
  key: string,
  buffer: Buffer,
  asset: AssetBase,
  status: StatusCode,
  cache: CacheMode,
) {
  const ifNoneMatch = c.req.header("If-None-Match");
  if (ifNoneMatch) {
    const etag = asset.headers.etag;
    if (etagMatches(etag, ifNoneMatch)) {
      return (c.res = new Response(null, {
        status: 304,
        statusText: "Not Modified",
        headers: {
          ETag: etag,
        },
      }));
    }
  }
  const acceptEncoding = c.req.header("Accept-Encoding") ?? "";
  let body;
  let headers = asset.headers;
  if (acceptEncoding.includes("zstd")) {
    body = buffer.subarray(...asset.zstd);
    headers = {
      ...asset.headers,
      "Content-Encoding": "zstd",
    };
  } else if (acceptEncoding.includes("gzip")) {
    body = buffer.subarray(...asset.gzip);
    headers = {
      ...asset.headers,
      "Content-Encoding": "gzip",
    };
  } else {
    body = buffer.subarray(...asset.raw);
  }
  debug(
    `${key} encoding=${headers["Content-Encoding"] ?? "raw"} status=${status}`,
  );
  if (!Object.keys(headers).some((x) => x.toLowerCase() === "cache-control")) {
    if (cache === "auto") {
      if (status < 200 || status >= 300) {
        cache = 'no-cache';
      } else if (headers['content-type']?.includes('text/html')) {
        cache = 'temporary';
      } else {
        cache = 'long-term';
      }
    }
    if (cache === "no-cache") {
      headers["Cache-Control"] = "no-store";
    } else if (cache === "long-term") {
      headers["Cache-Control"] =
        "public, max-age=7200, stale-while-revalidate=7200, immutable";
    } else if (cache === "temporary") {
      headers["Cache-Control"] =
        "public, max-age=7200, stale-while-revalidate=7200";
    }
  }
  return (c.res = new Response(body, { headers, status }));
}

export function packDynamicBuffer(
  raw: Buffer,
  gzip: Buffer,
  zstd: Buffer,
  headers: Record<string, string>,
) {
  const headersBuffer = Buffer.from(
    Object.entries(headers)
      .map((entry) => entry.join(":"))
      .join("\n"),
    "utf-8",
  );
  const header = new Uint32Array(3);
  header[0] = headersBuffer.byteLength + header.byteLength;
  header[1] = header[0] + raw.byteLength;
  header[2] = header[1] + gzip.byteLength;
  return Buffer.concat([
    Buffer.from(header.buffer),
    headersBuffer,
    raw,
    gzip,
    zstd,
  ]);
}

function loadRegenerative(buffer: Buffer): DynamicEntry {
  const headersEnd = buffer.readUInt32LE(0);
  const headers = Object.fromEntries(
    buffer
      .subarray(3 * 4, headersEnd)
      .toString("utf-8")
      .split("\n")
      .map((line) => {
        const i = line.indexOf(":");
        return [line.slice(0, i), line.slice(i + 1)];
      }),
  );
  const raw = buffer.readUInt32LE(4);
  const gzip = buffer.readUInt32LE(8);
  const hasEtag = (v: object): v is typeof v & { etag: string } =>
    "etag" in v && typeof v.etag === "string";
  ASSERT(hasEtag(headers));
  return {
    headers,
    buffer,
    raw: [headersEnd, raw],
    gzip: [raw, gzip],
    zstd: [gzip, buffer.byteLength],
  };
}

const gzip = util.promisify(zlib.gzip);
const zstdCompress = util.promisify(zlib.zstdCompress);

export async function overwriteDynamic(
  key: Key,
  value: string | Buffer,
  headers: Record<string, string>,
) {
  if (!current) current = await reload();
  const asset = UNWRAP(current.map[key]);
  ASSERT(asset.type === 1);
  UNWRAP(current.dynamic.has(asset.id));
  const buffer = Buffer.from(value);
  const etag = JSON.stringify(
    crypto.createHash("sha1").update(buffer).digest("hex"),
  );
  const [gzipBuffer, zstdBuffer] = await Promise.all([
    gzip(buffer),
    zstdCompress(buffer),
  ]);
  const packed = packDynamicBuffer(buffer, gzipBuffer, zstdBuffer, {
    ...headers,
    etag,
  });
  current.dynamic.set(asset.id, loadRegenerative(packed));
  await fs.writeFile(path.join(root, "dynamic", asset.id), packed);
}

process.on("message", (msg: any) => {
  if (msg?.type === "clover.assets.reload") reload();
});

import * as fs from "#sitegen/fs";
import type { Context, Next } from "hono";
import type { StatusCode } from "hono/utils/http-status";
import type { BufferView } from "../incremental.ts";
import { Buffer } from "node:buffer";
import * as path from "node:path";
import type { AssetKey as Key } from "../../.clover/ts/asset.d.ts";
import * as crypto from "node:crypto";
import * as zlib from "node:zlib";
import * as util from "node:util";
import * as console from "@paperclover/console";