const axios = require('axios');
const crypto = require('crypto');
const { lookup } = require('mime-types');

async function megadl(megaUrl) {
    try {
        const match = megaUrl.match(/mega\.nz\/(?:#!|file\/)([a-zA-Z0-9_-]+)[!#]([a-zA-Z0-9_-]+)/);
        if (!match) throw new Error('Invalid MEGA URL format.');
        const [, fileId, key] = match;
        
        const { data } = await axios.post('https://g.api.mega.co.nz/cs', [{
            a: 'g', g: 1, ssl: 2, v: 2, p: fileId
        }], { headers: { 'Content-Type': 'application/json' } });
        
        const fileInfo = data[0];
        if (!fileInfo || !fileInfo.at) throw new Error('File not found.');
        
        const keyBuffer = Buffer.from((key.replace(/-/g, '+').replace(/_/g, '/') + '='.repeat((4 - (key.length % 4)) % 4)), 'base64');
        
        const paddedKey = Buffer.concat([keyBuffer, Buffer.alloc((4 - (keyBuffer.length % 4)) % 4)]);
        let keyArray = Array.from({ length: paddedKey.length / 4 }, (_, i) => paddedKey.readUInt32BE(i * 4));
        if (keyArray.length === 8) keyArray = [keyArray[0] ^ keyArray[4], keyArray[1] ^ keyArray[5], keyArray[2] ^ keyArray[6], keyArray[3] ^ keyArray[7]];
        
        const keyBuf = Buffer.alloc(keyArray.length * 4);
        keyArray.forEach((val, i) => keyBuf.writeUInt32BE(val >>> 0, i * 4));
        
        const encAttr = Buffer.from((fileInfo.at.replace(/-/g, '+').replace(/_/g, '/') + '='.repeat((4 - (fileInfo.at.length % 4)) % 4)), 'base64');
        const decipher = crypto.createDecipheriv('aes-128-cbc', keyBuf, Buffer.alloc(16, 0));
        decipher.setAutoPadding(false);
        const decrypted = Buffer.concat([decipher.update(encAttr), decipher.final()]);
        
        const trimmed = decrypted.toString('utf8').replace(/\0+$/, '');
        const attributes = trimmed.startsWith('MEGA{') ? JSON.parse(trimmed.substring(4)) : { n: 'Unknown' };
        const ext = attributes.n?.split('.').pop() || null;
        
        return {
            fileId,
            fileName: attributes.n || 'Unknown',
            fileSize: fileInfo.s === 0 ? '0 Bytes' : `${(fileInfo.s / Math.pow(1024, Math.floor(Math.log(fileInfo.s) / Math.log(1024)))).toFixed(2)} ${['Bytes', 'KB', 'MB', 'GB', 'TB'][Math.floor(Math.log(fileInfo.s) / Math.log(1024))]}`,
            mimeType: lookup(ext?.toLowerCase()) || null,
            downloadUrl: fileInfo.g
        };
    } catch (error) {
        throw new Error(error.message);
    }
};

// Usage:
megadl('https://mega.nz/file/EntxADbJ#UCXeVEZbEo0ci9xKBFJzgMPol39MfFecwoB-TXfp1yc').then(console.log);