blog/lib/tasks/fonts.ts

import File from "vinyl";
import tmp from "tmp";
import { execFile } from "node:child_process";
import { readFileSync, unlinkSync } from "node:fs";
import hashPaths from "../hash.js";
import { dest, fromGlob } from "../rx-utils.js";
import { mergeMap } from "rxjs";

const FONT_PRESETS = {
    mono: { ranges: ["20-7F", "2205", "2E22-2E25", "2713", "2717"] },
    text: { ranges: ["20-7F", "A0-FF", "2000-206F", "20AC"] },
};

function compileFont(font: File): Promise<File> {
    const [, variant, weight] = /([A-Z][a-z]+)-(\w+)\.ttf$/.exec(font.basename);
    const tmpOutput = tmp.fileSync({ discardDescriptor: true });
    const unicodes = FONT_PRESETS[variant.toLowerCase()].ranges;

    return new Promise((resolve) => {
        execFile("pyftsubset", [
            font.path,
            `--unicodes=${unicodes.join(",")}`,
            `--output-file=${tmpOutput.name}`,
            "--flavor=woff2",
        ]).once("exit", () => {
            font.path = `iosevka-adaedra-${variant.toLowerCase()}-${weight.toLowerCase()}.woff2`;
            font.contents = readFileSync(tmpOutput.name);
            font.base = null;

            unlinkSync(tmpOutput.name);
            resolve(font);
        });
    });
}

export const fonts = () =>
    fromGlob("vendor/*.ttf")
        .pipe(mergeMap(compileFont), hashPaths("fonts.manifest"))
        .forEach(dest("dist/_assets"));