const fs = require("fs");
const JSON5 = require("json5");

const exampleFile = process.argv[2];
const targetFile = process.argv[3];

if (!exampleFile || !targetFile) {
	process.exit(1);
}

function deepMerge(target, source) {
	const result = { ...target };
	for (const key of Object.keys(source)) {
		if (
			source[key] !== null &&
			typeof source[key] === "object" &&
			!Array.isArray(source[key])
		) {
			result[key] = deepMerge(target[key] || {}, source[key]);
		} else {
			if (!(key in result)) {
				result[key] = source[key];
			}
		}
	}
	return result;
}

let example;
try {
	const content = fs.readFileSync(exampleFile, "utf-8");
	example = JSON5.parse(content);
} catch {
	process.exit(1);
}

let current = {};
try {
	if (fs.existsSync(targetFile)) {
		const content = fs.readFileSync(targetFile, "utf-8");
		current = JSON5.parse(content);
	}
} catch {
	current = {};
}

const merged = deepMerge(current, example);

const isJson5 = targetFile.endsWith(".json5");
const output = isJson5
	? JSON5.stringify(merged, null, 4)
	: JSON.stringify(merged, null, 4);
fs.writeFileSync(targetFile, output + "\n");