#!/usr/bin/env bash

declare -A KV_CACHE
read -r -a ROCK_LIST <<< "$( cat input )"
DUMP_KV_CACHE=0
BLINK_NUM=75
# KV Cache provides n depth search, 
# but must always be fully divisible by BLINK_NUM
DEPTH=5 
if [[ $(( BLINK_NUM % DEPTH )) -gt 0 ]] ;then printf "BLINK_NUM DEPTH mismatch.\n" && exit ; fi

ROCK_RETURN=()
ROCK_NUM=0
blink_rock () {

  #printf "Blinking rock : %s\n" "$ROCK_NUM" >&2

  # Remove leading zeroes
  #ROCK_NUM=$(( 10#$ROCK_NUM ))
  # Rule 1 : Convert 0 to 1
  if [[ $ROCK_NUM -eq 0 ]]
  then
    ROCK_RETURN=( 1 )
    return
  fi

  # Rule 2 : If even number of digits, split half half
  DIGIT_COUNT=${#ROCK_NUM}
  if [[ $(( DIGIT_COUNT % 2 )) -eq 0 ]] && [[ $DIGIT_COUNT -gt 0 ]]
  then
    HALF=$(( DIGIT_COUNT / 2 ))
    read -r -a ROCK_RETURN <<< "$( printf "%s %s " "$(( 10#${ROCK_NUM:0:$HALF} ))" "$(( 10#${ROCK_NUM:$HALF} ))" )"
    return    
  fi

  # Rule 3 : Multiply by 2024
  ROCK_RETURN=( $(( ROCK_NUM * 2024 )) )
  return
}

ROCKS_TO_BLINK=()
BLINKED_ROCKS=()
# Updates the global array
blink_rocks () {
  
  BLINKED_ROCKS=()
  for ROCK in "${ROCKS_TO_BLINK[@]}"
  do
    ROCK_NUM=$ROCK
    blink_rock
    BLINKED_ROCKS+=( "${ROCK_RETURN[@]}" )
  done
  #printf "BLINKED_ROCKS: " >&2
  #printf "%s " "${BLINKED_ROCKS[@]}" >&2
  #printf "\n" >&2
}

#FINAL_LIST=()
# Keeps track of 
read -r -a FINAL_LIST <<< "$( printf "%s " "${ROCK_LIST[@]}" )"
POSITION=0
while [[ $POSITION -lt $BLINK_NUM ]]
do
  printf "%s Working on position %s\n" "$( date )" "$POSITION"
  INTER_LIST_1=()
  # Essentially move $DEPTH steps at a time
  for ROCK in "${FINAL_LIST[@]}"
  do
    # Check if this is already cached
    if [[ -v KV_CACHE["$ROCK"] ]]
    then
      # Retrieve cached entry
      read -r -a X <<< "${KV_CACHE[$ROCK]}"
      INTER_LIST_1+=( "${X[@]}" )
      #printf "Cache hit. Key: %s, Value: " "$ROCK"
      #printf "%s " "${KV_CACHE[$ROCK]}"
      #printf "\n"
    else
      # Build cache entry
      ROCKS_TO_BLINK=( "$ROCK" )
      for (( i=0; i<DEPTH; i++ ))
      do
        blink_rocks
        read -r -a ROCKS_TO_BLINK <<< "$( printf "%s " "${BLINKED_ROCKS[@]}" )"
      done
      KV_CACHE[$ROCK]=$( printf "%s " "${BLINKED_ROCKS[@]}" )
      INTER_LIST_1+=( "${BLINKED_ROCKS[@]}" )
    fi
  done

  read -r -a FINAL_LIST <<< "$( printf "%s " "${INTER_LIST_1[@]}" )"

  # All rocks are calculated $DEPTH ahead
  (( POSITION+=DEPTH ))
done
#FINAL_LIST+=( "${BLINKED_ROCKS[@]}" )

# Dump KV cache for debugging
if [[ $DUMP_KV_CACHE -eq 0 ]]
then
  printf "Number of keys in KV cache: %s\n" "${#KV_CACHE[@]}"
  printf "Dumping KV CACHE\n"
  for KEY in "${!KV_CACHE[@]}"
  do
    printf "Key: %s, Value: %s\n" "$KEY" "${KV_CACHE[$KEY]}"
  done | sort
fi
#printf "%s " "${FINAL_LIST[@]}"
#printf "\n"
printf "%s\n" "${#FINAL_LIST[@]}"