#!/usr/bin/env bash

FUNCNEST=99999
MAP_FILE=input-map
DIRECTIONS_FILE=input-movements
MAP_WIDTH=$(( ( $( head -1 "$MAP_FILE" | wc -c ) -1 ) * 2 ))

# Move the robot
move_robot() {
  MAP_ARRAY[ROBOT_POSITION]=.
  ROBOT_POSITION=$NEXT_POSITION
  MAP_ARRAY[ROBOT_POSITION]=@
}

# Function to move box in n direction
vertical_move_box () {
  local BOX_COORDINATE=$1
  local BOX_MOVE_DIRECTION=$2

  # Normalise coordinates
  if [[ ${MAP_ARRAY[$BOX_COORDINATE]} == "[" ]]
  then
    local L_SIDE=$BOX_COORDINATE
    local R_SIDE=$(( BOX_COORDINATE +1 ))
  elif [[ ${MAP_ARRAY[$BOX_COORDINATE]} == "]" ]]
  then
    local L_SIDE=$(( BOX_COORDINATE -1 ))
    local R_SIDE=$BOX_COORDINATE
  fi
  local L_SIDE_MOVE_COORDINATE=$(( L_SIDE + BOX_MOVE_DIRECTION ))
  local R_SIDE_MOVE_COORDINATE=$(( R_SIDE + BOX_MOVE_DIRECTION ))

  # Recurse if there are more boxes
  if [[ ${MAP_ARRAY[L_SIDE_MOVE_COORDINATE]} == "[" ]] || \
     [[ ${MAP_ARRAY[L_SIDE_MOVE_COORDINATE]} == "]" ]]
  then
    vertical_move_box "$L_SIDE_MOVE_COORDINATE" "$BOX_MOVE_DIRECTION"
  fi
  if [[ ${MAP_ARRAY[R_SIDE_MOVE_COORDINATE]} == "[" ]] || \
     [[ ${MAP_ARRAY[R_SIDE_MOVE_COORDINATE]} == "]" ]]
  then
    vertical_move_box "$R_SIDE_MOVE_COORDINATE" "$BOX_MOVE_DIRECTION"
  fi

  MAP_ARRAY[L_SIDE_MOVE_COORDINATE]="["
  MAP_ARRAY[R_SIDE_MOVE_COORDINATE]="]"
  MAP_ARRAY[L_SIDE]="."
  MAP_ARRAY[R_SIDE]="."
}


# Function to check if box can be moved in n direction
vertical_check_move_box () {
  local BOX_COORDINATE=$1
  local BOX_MOVE_DIRECTION=$2

  # Normalise coordinates
  if [[ ${MAP_ARRAY[$BOX_COORDINATE]} == "[" ]]
  then
    local L_SIDE=$BOX_COORDINATE
    local R_SIDE=$(( BOX_COORDINATE +1 ))
  elif [[ ${MAP_ARRAY[$BOX_COORDINATE]} == "]" ]]
  then
    L_SIDE=$(( BOX_COORDINATE -1 ))
    R_SIDE=$BOX_COORDINATE
  fi

  # Check if boxes are movable
  local L_SIDE_MOVE_COORDINATE=$(( L_SIDE + BOX_MOVE_DIRECTION ))
  local R_SIDE_MOVE_COORDINATE=$(( R_SIDE + BOX_MOVE_DIRECTION ))
  if [[ ${MAP_ARRAY[$L_SIDE_MOVE_COORDINATE]} == '.' ]] && \
     [[ ${MAP_ARRAY[$R_SIDE_MOVE_COORDINATE]} == '.' ]] # Can move
  then
    return 0
  elif [[ ${MAP_ARRAY[$L_SIDE_MOVE_COORDINATE]} == '#' ]] || \
       [[ ${MAP_ARRAY[$R_SIDE_MOVE_COORDINATE]} == '#' ]] # Blocked by wall
  then
    return 1
  fi

  # Recurse if there are more boxes
  if [[ ${MAP_ARRAY[L_SIDE_MOVE_COORDINATE]} == "[" ]] || \
     [[ ${MAP_ARRAY[L_SIDE_MOVE_COORDINATE]} == "]" ]]
  then
    vertical_check_move_box "$L_SIDE_MOVE_COORDINATE" "$BOX_MOVE_DIRECTION"
    if [[ $? -eq 1 ]]
    then
      return 1
    fi
  fi
  if [[ ${MAP_ARRAY[R_SIDE_MOVE_COORDINATE]} == "[" ]] || \
     [[ ${MAP_ARRAY[R_SIDE_MOVE_COORDINATE]} == "]" ]]
  then
    vertical_check_move_box "$R_SIDE_MOVE_COORDINATE" "$BOX_MOVE_DIRECTION"
    if [[ $? -eq 1 ]]
    then
      return 1
    fi
  fi
}

horizontal_move_box () {

  local BOX_COOR=$1
  local BOX_MOVE_DIRECTION=$2

  local NEXT_SPOT=$(( BOX_COOR + BOX_MOVE_DIRECTION * 2 ))
  if [[ ${MAP_ARRAY[$NEXT_SPOT]} == "#" ]]
  then
    return 1 # Failed to move box
  elif [[ ${MAP_ARRAY[$NEXT_SPOT]} == "[" ]] || \
       [[ ${MAP_ARRAY[$NEXT_SPOT]} == "]" ]]
  then
    horizontal_move_box "$NEXT_SPOT" "$BOX_MOVE_DIRECTION"
    if [[ $? -eq 1 ]] ; then return 1 ; fi
  elif [[ ${MAP_ARRAY[$NEXT_SPOT]} != "." ]]
  then
    return 1
  fi

  # Move the box
  if [[ $NEXT_SPOT -lt $(( BOX_COOR + BOX_MOVE_DIRECTION )) ]]
  then
    MAP_ARRAY[NEXT_SPOT]="["
    MAP_ARRAY[BOX_COOR + BOX_MOVE_DIRECTION]="]"
  else
    MAP_ARRAY[BOX_COOR + BOX_MOVE_DIRECTION]="["
    MAP_ARRAY[NEXT_SPOT]="]"
  fi
  MAP_ARRAY[BOX_COOR]="."
}

# Load map
read -r -a MAP_ARRAY <<< "$( 
  < "$MAP_FILE" paste -s -d "" | 
  sed -E '
    s/#/##/g; 
    s/\./../g; 
    s/@/@./g; 
    s/O/[]/g; 
    s/(.)(.)/\1 \2 /g' 
)"
MAP_LEN=${#MAP_ARRAY[@]}

print_map () {
  printf "%s " "${MAP_ARRAY[@]}" | 
    fold -w $(( MAP_WIDTH * 2 ))
  printf "\n"
}

# Get robot position
for (( i=0; i<MAP_LEN; i++ ))
do
  if [[ ${MAP_ARRAY[$i]} == "@" ]]
  then
    ROBOT_POSITION=$i
    break
  fi
done
printf "Robot position : %s\n" "$ROBOT_POSITION"

# Hardcode direction values
UP=$(( - MAP_WIDTH ))
DOWN=$MAP_WIDTH
LEFT=-1
RIGHT=1

# Iterate through directions
MOVES=0
print_map
while read -r DIRECTION
do

  # Interpret directions
  if [[ $DIRECTION == "^" ]]
  then
    DIRECTION_VALUE=$UP
  elif [[ $DIRECTION == "v" ]]
  then
    DIRECTION_VALUE=$DOWN
  elif [[ $DIRECTION == "<" ]]
  then
    DIRECTION_VALUE=$LEFT
  elif [[ $DIRECTION == ">" ]]
  then
    DIRECTION_VALUE=$RIGHT
  fi

  NEXT_POSITION=$(( ROBOT_POSITION + DIRECTION_VALUE ))

  # Box in front
  if [[ ${MAP_ARRAY[$NEXT_POSITION]} == "[" ]] || \
     [[ ${MAP_ARRAY[$NEXT_POSITION]} == "]" ]]
  then
    #printf "Hit box.\n"
    if [[ $DIRECTION_VALUE -eq $LEFT ]] || \
       [[ $DIRECTION_VALUE -eq $RIGHT ]]
    then
      #printf "Left right box movement.\n"
      if horizontal_move_box "$NEXT_POSITION" "$DIRECTION_VALUE"
      then
        move_robot
      fi
    elif [[ $DIRECTION_VALUE -eq $UP ]] || \
         [[ $DIRECTION_VALUE -eq $DOWN ]]
    then
      #printf "Up down box movement.\n"
      if vertical_check_move_box "$NEXT_POSITION" "$DIRECTION_VALUE"
      then
        vertical_move_box "$NEXT_POSITION" "$DIRECTION_VALUE"
        move_robot
      fi
    fi

  # Wall in front, do nothing
  elif [[ ${MAP_ARRAY[$NEXT_POSITION]} == "#" ]]
  then
    #printf "Next: %s Skipping\n" "${MAP_ARRAY[$NEXT_POSITION]}"
    :
  # Empty space, move forward
  elif [[ ${MAP_ARRAY[$NEXT_POSITION]} == "." ]]
  then
    #printf "Next: %s Move robot forward\n" "${MAP_ARRAY[$NEXT_POSITION]}"
    move_robot
  fi
  (( MOVES++ ))

  #print_map
done <<< "$( < "$DIRECTIONS_FILE" paste -s -d "" | sed -E 's/(.)(.)/\1 \2 /g' | tr ' ' '\n' )"
printf "Moves: %s\n" "$MOVES"

print_map

# Calculate GPS values for boxes
SUM=0
BOX_COUNT=0
for (( i=0; i<MAP_LEN; i++ ))
do
  if [[ ${MAP_ARRAY[i]} == "[" ]]
  then
    (( BOX_COUNT++ ))
    X=$(( i % MAP_WIDTH ))
    Y=$(( i / MAP_WIDTH * 100 ))
    GPS=$(( X + Y ))
    #printf "Box %s X: %s Y: %s GPS: %s\n" "$i" "$X" "$Y" "$GPS"
    (( SUM+=GPS ))
  fi
done
printf "Sum: %s\n" "$SUM"
printf "Box count: %s\n" "$BOX_COUNT"