The project MUST be compiled by the following command in the project's root directory: $ go build -o creditcard .

Validate

The validate feature checks if a credit card number is valid using Luhn's Algorithm.

Requirements:

• The number must be at least 13 digits long.
• If valid, print OK to stdout and exit with status 0.
• If invalid, print INCORRECT to stderr and exit with status 1.
• Support passing multiple entries.
• Support --stdin flag to pass number from stdin.

Generate

The generate feature creates possible credit card numbers by replacing asterisks (*) with digits.

Requirements:

• Replace up to 4 asterisks (*) with digits. If more - it's an error. Asterisks should be at the end of the given credit card number.
• Print the generated numbers to stdout.
• Numbers must be printed in ascending order.
• Exit with status 1 if there is any error.
• Support --pick flag to randomly pick a single entry.

Information

The information feature provides details about the card based on data in brands.txt and issuers.txt.

Requirements:

• Output the card number, validity, brand, and issuer.
• Support --stdin flag to pass number from stdin.
• Support passing multiple entries.

Issue

The issue feature generates a random valid credit card number for a specified brand and issuer.

Requirements:

• Pick a random number for the specified brand and issuer.
• Exit with status 1 if there is any error.

Example:
$ ./creditcard issue --brands=brands.txt --issuers=issuers.txt --brand=VISA --issuer="Kaspi Gold"
4400430180300003