#!/usr/bin/env node

const { basename, dirname, format, relative, resolve } = require("path");
const { readdir, stat, readFile, writeFile, mkdir } = require("fs").promises;

const dedent = require("dedent");

const ENC = "utf-8";

const INLINE_REGEX = /(.*)\s*\/\/\s*inline\s*$/gimu;
const DEFER_REGEX = /(.*)\s*\/\/\s*link\s*$/gimu;
const INLINE_BLOCK_REGEX =
	/\/\/\s*>*\s*<{3,}\s*inline([\s\S]*?)\/\/\s*>{3,}.*/gimu;
const DEFER_BLOCK_REGEX =
	/\/\/\s*>*\s*<{3,}\s*link([\s\S]*?)\/\/\s*>{3,}.*/gimu;

function genHeader(filename) {
	return dedent`
    // THIS FILE IS AUTOGENERATED, DO NOT MODIFY!
    //
    // To change the contents of this file,
    // edit \`${filename}\`
    // and run \`npm run build:css\`.
    //
    // During development you can run \`npm run watch:css\`
    // to continuosly rebuild this file.
  `;
}

// <https://stackoverflow.com/a/45130990/870615>
async function getFiles(dir) {
	const subdirs = await readdir(dir);
	const files = await Promise.all(
		subdirs.map(async (subdir) => {
			const res = resolve(dir, subdir);
			return (await stat(res)).isDirectory() ? getFiles(res) : res;
		}),
	);
	return files.reduce((a, f) => a.concat(f), []);
}

(async function main() {
	try {
		const files =
			process.argv.length > 2 ? [process.argv[2]] : await getFiles("_sass");
		await Promise.all(
			files
				.filter((f) => f.endsWith(".pre.scss"))
				.map(async (file) => {
					const content = await readFile(file, ENC);
					const name = basename(file, ".pre.scss");
					const filename = format({ name, ext: ".scss" });
					const dir = dirname(file);

					const inline = content
						.replace(INLINE_REGEX, "$1")
						.replace(INLINE_BLOCK_REGEX, "$1")
						.replace(DEFER_REGEX, "// $1")
						.replace(DEFER_BLOCK_REGEX, "");

					const defer = content
						.replace(DEFER_REGEX, "$1")
						.replace(DEFER_BLOCK_REGEX, "$1")
						.replace(INLINE_REGEX, "// $1")
						.replace(INLINE_BLOCK_REGEX, "");

					const path = relative(resolve(), dirname(file));
					const header = genHeader([path, basename(file)].join("/"));

					await Promise.all([
						mkdir(resolve(dir, "__inline__"), { recursive: true }),
						mkdir(resolve(dir, "__link__"), { recursive: true }),
					]);
					return Promise.all([
						writeFile(
							resolve(dir, "__inline__", filename),
							header + "\n\n" + inline,
							ENC,
						),
						writeFile(
							resolve(dir, "__link__", filename),
							header + "\n\n" + defer,
							ENC,
						),
					]);
				}),
		);
		process.exit(0);
	} catch (e) {
		console.error(e); // eslint-disable-line
		process.exit(1);
	}
})();