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');