#!/usr/bin/env node
const fs = require('fs');
const path = require('path');
const json5 = require('json5');

const [srcFile, destFile] = process.argv.slice(2);

if (!srcFile || !destFile) {
    console.error('Usage: merge-config.js <source.example> <dest.json>');
    process.exit(1);
}

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

const srcContent = fs.readFileSync(srcFile, 'utf8');
let srcData;
try {
    srcData = json5.parse(srcContent);
} catch (e) {
    console.error(`--> [SKIP] Could not parse ${srcFile}: ${e.message}`);
    process.exit(0);
}

if (typeof srcData !== 'object' || Array.isArray(srcData)) {
    console.error(`--> [SKIP] ${srcFile} is not a JSON object, copying directly`);
    fs.copyFileSync(srcFile, destFile);
    process.exit(0);
}

let destData = {};
let existingKeys = [];
if (fs.existsSync(destFile)) {
    try {
        const destContent = fs.readFileSync(destFile, 'utf8');
        destData = json5.parse(destContent);
        existingKeys = Object.keys(destData);
    } catch (e) {
        console.error(`--> Warning: could not parse ${destFile}, overwriting from example`);
    }
}

const fullMerged = deepMerge(destData, srcData);

const ordered = {};
for (const key of Object.keys(srcData)) {
    ordered[key] = fullMerged[key];
}
for (const key of Object.keys(destData)) {
    if (!(key in srcData)) {
        ordered[key] = destData[key];
    }
}

const newKeys = Object.keys(ordered).filter(k => !existingKeys.includes(k));
if (newKeys.length > 0) {
    console.log(`--> Added ${newKeys.length} new key(s) to ${path.basename(destFile)}`);
}

fs.writeFileSync(destFile, JSON.stringify(ordered, null, 4) + '\n');
console.log(`--> [OK] ${path.basename(destFile)} is up to date`);