more fail

day/02/demo_2_input.txt

@@ -2,3 +2,9 @@
 1 2 3 99
 1 3 2 3
 9 8 9 10
+9 10 11 11
+9 10 10 11
+9 8 2 7
+9 8 7 1
+9 4 10 11
+9 4 10 11 10

day/02/demo_input_1.txt

@@ -0,0 +1 @@
+7 6 4 2 1

day/02/demo_input_2.txt

@@ -0,0 +1 @@
+1 2 7 8 9

day/02/demo_input_3.txt

@@ -0,0 +1 @@
+9 7 6 2 1

day/02/demo_input_4.txt

@@ -0,0 +1 @@
+1 3 2 4 5

day/02/demo_input_5.txt

@@ -0,0 +1 @@
+8 6 4 4 1

day/02/demo_input_6.txt

@@ -0,0 +1 @@
+1 3 6 7 9

day/02/part2.sh

@@ -0,0 +1,111 @@
+#! /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}"