blog/lib/hash.ts

import { createHash } from "node:crypto";
import { PRODUCTION } from "./environment.ts";
import { Observable } from "rxjs";
import { Buffer } from "node:buffer";
import { VFile } from "vfile";

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

const hashPath = (mappings: Map<string, string>) => (file: VFile): VFile => {
    const hash = PRODUCTION ? fileHash(file.value) : "00000000";
    const newName = [
        file.stem!,
        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<VFile>): Observable<VFile> =>
        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 VFile({
                        path: manifestName,
                        value: JSON.stringify(Object.fromEntries(mappings)),
                    });

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