blog/lib/hash.ts

import { Transform } from "node:stream";
import { createHash } from "node:crypto";
import File from "vinyl";
import { globSync } from "glob";
import { readFileSync } from "node:fs";
import { PRODUCTION } from "./environment.js";

export function readAssetManifest(): { [entry: string]: string } {
    return Object.assign(
        {},
        ...globSync("dist/_assets/*.manifest").map((path) =>
            JSON.parse(readFileSync(path).toString()),
        ),
    );
}

function fileHash(buffer: Buffer) {
    const hash = createHash("sha256");
    hash.update(buffer.toString());
    return hash.digest("hex");
}

export default function (manifestName: string) {
    const mappings: { [path: string]: string } = {};

    return new Transform({
        readableObjectMode: true,
        writableObjectMode: true,
        transform(chunk: File, _, callback) {
            const hash = PRODUCTION ? fileHash(chunk.contents as Buffer) : "00000000";
            const newName = `${chunk.basename.substring(0, chunk.basename.length - chunk.extname.length)}.${hash.substring(0, 8)}${chunk.extname}`;

            mappings[chunk.basename] = newName;
            chunk.basename = newName;

            callback(null, chunk);
        },
        final(callback) {
            const mappingFile = new File({
                path: manifestName,
                contents: Buffer.from(JSON.stringify(mappings)),
            });
            this.push(mappingFile);

            callback(null);
        },
    });
}