#!/bin/bash

# Find valid calls of mul(), do(), and don't()
function_calls=$(cat input.txt | grep -e 'mul([[:digit:]]\+,[[:digit:]]\+)' -e 'do()' -e "don't()" -o)

mul () {
    # Takes a string of number1,number2 and multiplies them.
    local multiplicand=$(echo $1 | cut -d , -f 1)
    local multiplier=$(echo $1 | cut -d , -f 2)
    echo $((multiplicand * multiplier))

}

total=0
doing=1

# Loop over the function calls and execute them. Need -0 to ignore single quotes.
for call in $(  echo $function_calls | xargs -0 ); do

    if [ $call == 'do()' ]; then
        doing=1
    elif [ $call == "don't()" ]; then
        doing=0
    elif [ $doing -eq 0 ]; then
        continue
    else
        args=$(echo $call | sed 's/mul(//g' | sed 's/)//g')
        product=$(mul $args)
        total=$((total + product))
    fi

done

echo $total