#!/usr/bin/env bash

FILE=input
ITERATIONS=75

# Get max num size by squaring the largest number
MAX_NUM_SIZE=0
while read -r NUM
do
  if [[ ${#NUM} -gt $MAX_NUM_SIZE ]]
  then
    MAX_NUM_SIZE=${#NUM}
  fi
done <<< "$( < input tr " " "\n" )"
(( MAX_NUM_SIZE*=2 ))

# Just pre-compute a large number of digits
{
# Rule 1
printf "0 1 \n"

# Rule 2 : If even number of digits, split half half
for (( i=10 ; i<100; i+=1 ))
do
  DIGIT_COUNT=${#i}
  HALF=$(( DIGIT_COUNT / 2 ))
  printf "%s %s %s \n" "$i" "$(( 10#${i:0:$HALF} ))" "$(( 10#${i:$HALF} ))"
done
for (( i=1000 ; i<10000; i+=1 ))
do
  DIGIT_COUNT=${#i}
  HALF=$(( DIGIT_COUNT / 2 ))
  printf "%s %s %s \n" "$i" "$(( 10#${i:0:$HALF} ))" "$(( 10#${i:$HALF} ))"
done
for (( i=100000 ; i<1000000; i+=1 ))
do
  DIGIT_COUNT=${#i}
  HALF=$(( DIGIT_COUNT / 2 ))
  printf "%s %s %s \n" "$i" "$(( 10#${i:0:$HALF} ))" "$(( 10#${i:$HALF} ))"
done

# Rule 3
for (( i=1; i<10; i+=1 ))
do
  printf "%s %s \n" "$i" "$(( i * 2024 ))"
done 
for (( i=100; i<1000; i+=1 ))
do
  printf "%s %s \n" "$i" "$(( i * 2024 ))"
done 
for (( i=10000; i<100000; i+=1 ))
do
  printf "%s %s \n" "$i" "$(( i * 2024 ))"
done 
} | sort -n > kv-cache
printf "Cache built. KV size: %s \n" "$( wc -l kv-cache )" 

# Load cache file
declare -A KV_CACHE
while read -r LINE
do
  KV_CACHE[${LINE%% *}]="${LINE#* }"
done < kv-cache

NUM=0
get_num () {

  NUM=$1

  # Rule 1 : Convert 0 to 1
  if [[ $NUM -eq 0 ]]
  then
    printf "1 \n"
    return
  fi

  # Rule 2 : If even number of digits, split half half
  DIGIT_COUNT=${#NUM}
  if [[ $(( DIGIT_COUNT % 2 )) -eq 0 ]]
  then
    HALF=$(( DIGIT_COUNT / 2 ))
    printf "%s %s " "$(( 10#${NUM:0:$HALF} ))" "$(( 10#${NUM:$HALF} ))"
    return
  fi

  # Rule 3 : Multiply by 2024
  printf "%s \n" "$(( NUM * 2024 ))"
  return
}

# Start the loop
tr " " "\n" < "$FILE" > temp-input
for (( i=0; i<75; i++ ))
do
  printf "%s Position %s\n" "$( date )" "$i"
  while read -r NUM
  do
    if [[ -v ${KV_CACHE[$NUM]} ]]
    then
      printf "%s \n" "${KV_CACHE[$NUM]}"
    else
      get_num "$NUM"
    fi
  done < temp-input |
  tr " " "\n" |
  grep -Eo '[0-9]*' | 
  sponge temp-input
done
printf "Final count: %s\n" "$(wc -l < temp-input)"