#!/usr/bin/env bash

set -o errexit
set -o nounset
set -o pipefail
if [[ "${TRACE-0}" == "1" ]]; then
  set -o xtrace
fi

cd "$(dirname "$0")"

INPUT_FILE="$1"

get_seeds ()
{
  echo -n "$(grep seeds "${INPUT_FILE}" | cut -d ' ' -f 2-)"
}

gen_map ()
{
  # Generates files for given index of map in input file.
  local paragraph map_name map_content
  paragraph=$(($1+1)) # number of paragraph in input file
  map_name=$(awk -v RS= "{if(NR == ${paragraph}) print}" "${INPUT_FILE}" | head -n 1 | cut -d ' ' -f 1)
  map_content=$(awk -v RS= "{if(NR == ${paragraph}) print}" "${INPUT_FILE}"| tail -n +2)
  echo "${map_content}" > "${map_name}.map"
  maps+=("${map_name}.map")
}

map_seed ()
{
  # Usage: map_seed MAP_FILE SEED_NUMBER
  # Prints the mapping of the seed number in the give map.
  local map seed dest_start source_start length diff
  map="$1"
  seed="$2"
  while read -r line; do
    dest_start=$(cut -d ' ' -f 1 <<< "${line}")
    source_start=$(cut -d ' ' -f 2 <<< "${line}")
    length=$(cut -d ' ' -f 3 <<< "${line}")
    if [[ ${seed} -ge ${source_start} && ${seed} -le $((source_start+length-1)) ]]; then
      diff=$((seed-source_start))
      echo -n $((dest_start+diff))
      return
    fi
  done < "${map}"
  echo -n "${seed}" # no mapping
}

main ()
{
  IFS=" " read -r -a seeds <<< "$(get_seeds)"
  declare -a maps=()
  declare -a destinations=()
  local map_count destination lowest
  map_count=$(awk -v RS= 'END {print NR}' "${INPUT_FILE}")
  map_count=$((map_count-1)) # one of the paragraphs in the file is seeds
  for ((i=1; i<=map_count; i++)); do
    gen_map "${i}"
  done
  for seed in "${seeds[@]}"; do
    destination=''
    for map in "${maps[@]}"; do
      if [[ -z ${destination} ]]; then
        destination=$(map_seed "${map}" "${seed}")
      else
        destination=$(map_seed "${map}" "${destination}")
      fi
    done
    destinations+=("${destination}")
  done
  lowest="${destinations[0]}"
  for dest in "${destinations[@]}"; do
    if [[ ${dest} -lt ${lowest} ]]; then
      lowest="${dest}"
    fi
  done
  echo "${lowest}"
  rm -f ./*.map
}

main