const {Worker, isMainThread, parentPort, workerData} = require("worker_threads");
const readCht = require("./cht");
const { readFile, access } = require("fs/promises");
const ncpu = require("os").availableParallelism();

const trimcheat = (dat, info, order) => {
    let parts = [], start = 0, done = false;
    while (!done) {
        let pos = dat.indexOf("[GameInfo]", start);
        if (pos > 0) {
            pos = dat.indexOf("[", pos + "[GameInfo]".length);
            if (pos > 0) {
                parts.push(dat.slice(start, pos));
                start = pos;
            }
            else {
                parts.push(dat.slice(start, dat.length));
                done = true;
            }
        }
        else {
            parts.push(dat.slice(start, dat.length));
            done = true;
        }
    }
    return parts.map(tr => readCht(tr, info, order));
}

const loadcheat = async (order, serial, title, file) => {
    if( false == await access(file).catch( e => false ) ) {
        return Promise.resolve();
    }

    try {
        const chtfile = await readFile(file);
        const cheats = chtfile.toString("utf-8");
        let cheat = null;
        if (cheats.indexOf("[GameInfo]") != cheats.lastIndexOf("[GameInfo]"))
            cheat = trimcheat(cheats, { serial }, order);
        else cheat = [readCht(cheats, { serial }, order)];
        return { serial, cheat }
    }
    catch (e) {
        console.log("bad cheat: %s[order=%d]\n%s", title, order, e.stack)
        return { serial }
    };
}

if( isMainThread ) {
    module.exports = ncpu > 3 ? function(list) {
        const nPerThread = Math.ceil(list.length / ncpu);
        const results = new Array(ncpu);
        let n = 0;
        return new Promise( ok => {
            const workers = new Array(ncpu).fill(0).map( (_,i) => {
                const sublist = list.slice(i * nPerThread, (i+1) * nPerThread);
                const worker = new Worker(__filename, { workerData: sublist });
                worker.once("message", msg => {
                    results[i] = msg;
                    worker.unref();
                    if( ++n == ncpu ) ok(results.flat());
                });
            } );
        });
    } : list => Promise.all( list.map( game => {
        const [order, serial, title] = game;
        const file = `./gba/${order}.u8`;
        return loadcheat(order, serial, title ?? order, file);
    } ) );
}
else {
    const list = workerData;
    Promise.all( list.map( game => {
        const [order, serial, title] = game;
        const file = `./gba/${order}.u8`;
        return loadcheat(order, serial, title ?? order, file);
    } ) ).then( res => parentPort.postMessage(res) );
}