#!/usr/bin/env bash

set -euo pipefail

firstDigits() {
    sed 's|^[^0-9]*\([0-9]\).*|\1|'
}

lastDigits() {
    sed 's|^.*\([0-9]\)[^0-9]*$|\1|'
}

sumTensDigits() {
    echo $(("$(xargs -I '{}' echo '{} * 10 +') 0"))
}

sumOnesDigits() {
    echo $(("$(xargs -I '{}' echo '{} +') 0"))
}

detectDigits() {
    sed '
         s|zero|0|g;

         s|twone|2|g;
         s|one|1|g;

         s|eightwo|8|g;
         s|two|2|g;

         s|eighthree|8|g;
         s|three|3|g;

         s|four|4|g;
         s|five|5|g;
         s|six|6|g;
         s|seven|7|g;

         s|nineight|9|g;
         s|eight|8|g;

         s|nine|9|g
         '
}

detectReverseDigits() {
    sed '
         s|enorez|1|g
         s|orez|0|g;

         s|thgieno|8|g;
         s|eno|1|g;

         s|owt|2|g;

         s|thgieerht|8|g;
         s|eerht|3|g;

         s|ruof|4|g;

         s|thgievif|8|g;
         s|evif|5|g;

         s|xis|6|g;

         s|enineves|9|g
         s|neves|7|g;

         s|thgie|8|g;

         s|enin|9|g
         '
}

part1 () {
    local input tensSum onesSum
    input=$(cat)
    tensSum=$(<<< "$input" firstDigits | sumTensDigits)
    onesSum=$(<<< "$input" lastDigits | sumOnesDigits)
    echo $(("$tensSum + $onesSum"))
}

part2 () {
    local input tensSum onesSum
    input=$(cat)
    tensSum=$(<<< "$input" detectDigits | firstDigits | sumTensDigits)
    onesSum=$(<<< "$input" rev | detectReverseDigits | firstDigits | sumOnesDigits)
    echo $(("$tensSum + $onesSum"))
}

main () {
    local input part1Answer part2Answer
    input=$(cat)

    part1Answer=$(part1 <<< "$input")
    echo "Part 1 Answer: $part1Answer"

    part2Answer=$(part2 <<< "$input")
    echo "Part 2 Answer: $part2Answer"
}

main