Simple Cipher

[rabestro]

Port exercise from Bash track:
https://exercism.org/tracks/bash/exercises/simple-cipher

Something like:

#!/usr/bin/env gawk -f
# These variables are initialized on the command line (using '-v'):
# - command
# - key
@load "ordchr"

BEGIN {
    FS = ""
    OFS = ""
}

{
    for (i = 1; i <= NF; i++)
        @command(i)
    print
}

function encode(i) {
    $i = chr((ord($i) - ord("a") + keyShift()) % 26 + ord("a"))
}
function decode(i) {
    $i = chr((ord($i) - ord("a") - keyShift()) % 26 + ord("a"))
}
function keyShift() {
    KeyIndex %= length(key)
    KeyIndex++
    return ord(substr(key, KeyIndex, 1)) - ord("a")
}

Need to generate a key to pass the test:

@test  "Can generate a random key" {
    #[[ $BATS_RUN_SKIPPED == "true" ]] || skip
    run bash simple_cipher.sh key
    assert_success
    key=$output
    assert [ "${#key}" -ge 100 ]     # at least 100 chars
    [[ "$key" =~ ^[[:lower:]]+$ ]]   # only lowercase letters
}

[rabestro]

Proposed solution:

# These variables are initialized on the command line (using '-v'):
# - type
# - key
@load "ordchr"

BEGIN {
    OFS = FS = ""
    AlphabetSize = ord("z") - ord("a") + 1
    if (!key) randomKey()
}
{
    for (i = 1; i <= NF; i++)
        @type(i)
    print
}

function encode(i) {
    $i = chr((ord($i) - ord("a") + keyShift()) % AlphabetSize + ord("a"))
}
function decode(i) {
    $i = chr((ord($i) - ord("a") - keyShift()) % AlphabetSize + ord("a"))
}
function keyShift() {
    KeyIndex %= length(key)
    KeyIndex++
    return ord(substr(key, KeyIndex, 1)) - ord("a")
}
function randomKey(   i) {
    for (i = 1; i <= 100; i++)
        $i = randomLetter()
    print
    exit
}
function randomLetter() {
    return chr(ord("a") + int(rand() * AlphabetSize))
}