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RS School NodeJS course

You can generate a new repository with the same directory structure and files as an existing repository using GitHub article: Creating a repository from a template.

N.B. This structure is recommended for the implementation tasks starting from the second. The first task is not related to subsequent ones.

Task 1. Caesar cipher CLI tool

Implement CLI tool that will encode and decode a text by Caesar cipher.

CLI tool should accept 4 options (short alias and full name):

  1. -s, --shift: a shift
  2. -i, --input: an input file
  3. -o, --output: an output file
  4. -a, --action: an action encode/decode

Details:

  1. For command-line arguments could be used one of
  1. Action (encode/decode) and the shift are required, if one of them missed - an error should be shown, the process should exit with non-zero status code.
  2. If the input file is missed - use stdin as an input source.
  3. If the output file is missed - use stdout as an output destination.
  4. If the input and/or output file is given but doesn't exist or you can't read it (e.g. because of permissions or it is a directory) - human-friendly error should be printed in stderr.
  5. If passed params are fine the output (file or stdout) should contain encoded/decoded content of input (file or stdin).
  6. For encoding/decoding use only the English alphabet, all other characters should be kept untouched.

Hints: As suggested solution to make streams code more robust, and memory effective, consider to use pipeline method. Structure can be the following:

pipeline(
  input_stream, // input file stream or stdin stream
  transform_stream, // standard Transform stream or https://github.com/rvagg/through2
  output_stream // output file stream or stdout stream
)
.then(success and error callbacks)

Usage example:

$ node my_caesar_cli -a encode -s 7 -i "./input.txt" -o "./output.txt"
$ node my_caesar_cli --action encode --shift 7 --input plain.txt --output encoded.txt
$ node my_caesar_cli --action decode --shift 7 --input decoded.txt --output plain.txt

input.txt This is secret. Message about "_" symbol!

output.txt Aopz pz zljyla. Tlzzhnl hivba "_" zftivs!