blog/lib/hash.ts

import { createHash } from "node:crypto";
import File from "vinyl";
import { PRODUCTION } from "./environment.js";
import { Observable } from "rxjs";

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

const hashPath =
    (mappings: Map<string, string>) =>
    (file: File): File => {
        const hash = PRODUCTION ? fileHash(file.contents as Buffer) : "00000000";
        const newName = [
            file.basename.substring(0, file.basename.length - file.extname.length),
            hash.substring(0, 8),
            file.extname.substring(1),
        ].join(".");

        mappings.set(file.basename, newName);
        file.basename = newName;

        return file;
    };

export default function (manifestName: string) {
    return (observable: Observable<File>): Observable<File> =>
        new Observable((subscriber) => {
            const mappings = new Map<string, string>();
            const hash = hashPath(mappings);

            observable.subscribe({
                next(file) {
                    subscriber.next(hash(file));
                },
                error(e) {
                    subscriber.error(e);
                },
                complete() {
                    const mappingFile = new File({
                        path: manifestName,
                        contents: Buffer.from(JSON.stringify(Object.fromEntries(mappings))),
                    });

                    subscriber.next(mappingFile);
                    subscriber.complete();
                },
            });
        });
}