const fs = require('fs');
const crypto = require('crypto');

function jwt_secret() {
  let file = fs.readFileSync( '../data/jwt_secret.txt', 'utf8' );
  if( file.endsWith( '\n' ) ) {
    file = file.slice( 0, -1 );
  }

  return file;
}

function write( content, filename ) {
  const chatJson = content;

  const salt = crypto.randomBytes( 16 );
  const key = crypto.pbkdf2Sync( jwt_secret(), salt, 100000, 32, 'sha512' );
  const iv = crypto.randomBytes( 12 );

  const cipher = crypto.createCipheriv( 'aes-256-gcm', key, iv );
  let encrypted = cipher.update( chatJson, 'utf8', 'hex' );
  encrypted += cipher.final( 'hex' );
  const authTag = cipher.getAuthTag().toString( 'hex' );

  let fullStr = salt.toString( 'hex' ) + iv.toString( 'hex' ) + authTag + encrypted;

  fs.writeFileSync( filename, fullStr );
}

function read( filename ) {
  let contents = '';
  try {
    contents = fs.readFileSync( filename, 'utf8' );
  } catch( e ) {
    console.log( '0' );
    return;
  }
  const salt = Buffer.from( contents.slice( 0, 32 ), 'hex' );
  const iv = Buffer.from( contents.slice( 32, 56 ), 'hex' );
  const authTag = Buffer.from( contents.slice( 56, 88 ), 'hex' );
  const data = contents.slice( 88 );

  const key = crypto.pbkdf2Sync( jwt_secret(), salt, 100000, 32, 'sha512' );
  const decipher = crypto.createDecipheriv( 'aes-256-gcm', key, iv );
  decipher.setAuthTag( authTag );

  let decrypted = decipher.update( data, 'hex', 'utf8' );
  decrypted += decipher.final( 'utf8' );

  return decrypted;
}

function main() {
  const args = process.argv.slice(2);
  const operation = args[0];

  switch( operation ) {
    case 'read': {
      try {
        const data = read( args[1] );
        console.log( JSON.parse( JSON.stringify( data ) ) );
      } catch( e ) {
        console.log( "0" );
        console.log( e.message );
      }
      break;
    }
    case 'write': {
      try {
        const data = args[2];
        write( data, args[1] );
        console.log( "1" );
      } catch( e ) {
        console.log( "0" );
        console.log( e.message );
      }
      break;
    }
  }
}

main();