#! /bin/bash

#set -x

FILE_IN="${1}"

safe_count=0

function debug_echo() {
  echo "$@" 1>&2
}

function check_is_safe() {
  local is_up_down="${1}"
  local first_val="${2}"
  local second_val="${3}"

  local fun_is_safe=1

  prev_diff=$((first_val - second_val))
  debug_echo "diff ${prev_diff}"


  if [[ "${prev_diff}" -gt 0 ]]; then
    debug_echo "going up"
    if [[ "${is_up_down}" -le 0 ]]; then
      debug_echo "wrong direction"
      fun_is_safe=0
    fi
  else
    debug_echo "going down"
    if [[ "${is_up_down}" -ge 0 ]]; then
      debug_echo "wrong direction"
      fun_is_safe=0
    fi
  fi

  if [[ "${prev_diff#-}" -le 0 ]] || [[ "${prev_diff#-}" -ge 4 ]]; then
    debug_echo "outside range"
    fun_is_safe=0
  fi

  if [[ "${fun_is_safe}" -ne 0 ]]; then
    debug_echo "safe"
  else
    debug_echo "unsafe"
  fi

  echo "${fun_is_safe}"
}

while read -r l; do
  echo "reading new line [$l]"

  IFS=" "
  read -ra line_split <<< "${l}"
  unset IFS

  # start with the first val
  prev_val="${line_split[0]}"

  is_safe=2

  # if positive, going up, if negative, going down!
  is_up_down="$((line_split[1] - line_split[0]))"

  safety_trigger=1

  if [[ "${is_up_down}" -ge 0 ]]; then
    echo "Initially going up"
  else
    echo "Initially going down"
  fi

  for idx in "${!line_split[@]}"; do
    [[ "${idx}" -eq 0 ]] && continue
    echo "index $idx"
    v="${line_split[${idx}]}"
    echo "checking [${v}] against previous [${prev_val}]"
    test_is_safe=$(check_is_safe "${is_up_down}" "${v}" "${prev_val}")

    debug_echo "safe val ${test_is_safe}"

    if [[ "${test_is_safe}" -eq 0 ]]; then
      # normally we fail this set
      is_safe=$((is_safe - 1))
    fi

    if [[ "${test_is_safe}" -eq 0 ]] && [[ "${safety_trigger}" -eq 1 ]]; then
      # but we let 1 happen if the trigger hasnt... triggered
      safety_trigger=0
      if [[ "${idx}" -eq 1 ]]; then
        # we may have to re-calculate is_up_down!
        is_up_down="$((line_split[2] - line_split[0]))"
        echo "allowing flip up/down"
      fi
      echo "-------------------"
      echo "allowing 1 failure!"
      echo "-------------------"
    else
      # we skip the re-assign once to 'skip' a number
      prev_val=$v
    fi
  done

  if [[ "${is_safe}" -gt 0 ]]; then
    safe_count=$((safe_count + 1))
  fi
done <"$FILE_IN"

echo "final safe count ${safe_count}"