const crypto = require('crypto');

function checkDifficulty(hashBuffer, difficultyBits) {
    let bits = difficultyBits;
    let i = 0;
    while (bits > 0) {
        const byte = hashBuffer[i];
        if (bits >= 8) {
            if (byte !== 0) return false;
            bits -= 8;
        } else {
            const mask = 0xFF << (8 - bits);
            if ((byte & mask) !== 0) return false;
            bits = 0;
        }
        i++;
    }
    return true;
}

function main() {
    if (process.argv.length !== 4) {
        console.error(`Usage: node ${process.argv[1]} <challenge_string> <difficulty_bits>`);
        process.exit(1);
    }

    const challenge = process.argv[2];
    const difficultyBits = parseInt(process.argv[3], 10);

    if (isNaN(difficultyBits) || difficultyBits <= 0 || difficultyBits > 256) {
        console.error('Difficulty bits must be a number between 1 and 256');
        process.exit(1);
    }

    let counter = 0;

    while (true) {
        const input = challenge + counter;
        const hash = crypto.createHash('sha256').update(input).digest();

        if (checkDifficulty(hash, difficultyBits)) {
            console.log('===================');
            console.log(`Found nonce: ${counter}`);
            console.log('===================');
            console.log(`Hash: ${hash.toString('hex')}`);
            break;
        }

        if ((counter & 0xFFFFF) === 0) {
            console.log(`Attempts: ${counter}`);
        }

        counter++;
    }
}

main();