Description

In this stage, add the ability to read and write the original and cipher data into files.

Objectives

The program must parse two additional arguments -in and -out to specify the full name of a file to read the data and write the result. Arguments -mode, -key, and -data must work as before.

Your program should read data from -data or from a file specified in the -in argument. That's the reason why you can't have both -data and -in arguments simultaneously.

1. If there is no -mode, the program should work in the enc mode;
2. If there is no -key, the program should consider that key is 0;
3. If there is no -data and no -in the program should assume that the data is an empty string;
4. If there is no -out argument, the program must print data to the standard output;
5. If there are both -data and -in arguments, your program should prefer -data over -in.

If there is something strange (an input file does not exist, or an argument doesn't have a value), the program should not fail. Instead, it must display a clear message about the problem and stop successfully. The message should contain the word Error.

Examples

Example 1: reading and writing to files; the arguments are: -mode enc -in road_to_treasure.txt -out protected.txt -key 5

The program must get data from road_to_treasure.txt, encrypt the data with key 5, create a file called protected.txt, and write ciphertext to it.

Example 2: encryption; the arguments are -mode enc -key 5 -data "Welcome to hyperskill!"

\jqhtrj%yt%m~ujwxpnqq&

Example 3: decryption; the arguments are -key 5 -data "\jqhtrj%yt%m~ujwxpnqq&" -mode dec

Welcome to hyperskill!