#!/usr/bin/env bash

declare -a __GRID__PERPENDICULAR_DIRECTIONS=(
  '1 0'
  '0 1'
  '0 -1'
  '-1 0'
)

grid.coord_to_index() {
  local width="$1" x="$2" y="$3"
  printf '%d' "$((y * width + x))"
}

grid.index_to_coord() {
  local width="$1" index="$2"
  printf '%d %d\n' "$((index % width))" "$((index / width))"
}

grid.text_to_grid() {
  local -n __grid_text_to_grid_grid="$1"
  local text="$2" width=0 height=0 c=0

  __grid_text_to_grid_grid=()

  while read -r line; do
    ((height++))
    [[ "$width" ]] && width="${#line}"
    while IFS= read -rd '' -n 1 char; do
      [[ "$char" == $'\n' ]] && continue
      __grid_text_to_grid_grid+=(["$c"]="$char")
      ((c++))
    done <<<"$line"
  done <<<"$text"

  __grid_text_to_grid_grid+=([width]="$width")
  __grid_text_to_grid_grid+=([height]="$height")
}

grid.perpendicular_neighbors() {
  local -n __grid_perpendicular_neighbors_grid="$1"
  local x="$2" y="$3"
  
  for dir in "${__GRID__PERPENDICULAR_DIRECTIONS[@]}"; do
    local dx dy nx ny
    read -r dx dy <<<"$dir"
    nx="$(( x + dx ))"
    ny="$(( y + dy ))"
    (( nx >= 0 && nx < __grid_perpendicular_neighbors_grid[width] && ny >= 0 && ny < __grid_perpendicular_neighbors_grid[height] )) || continue
    printf '%d %d\n'  "$nx" "$ny"
  done
}

grid.get() {
  local -n __grid_get_grid="$1"
  local x="$2" y="$3" width="${__grid_get_grid[width]}"

  (( x >= 0 && x < __grid_get_grid[width] && y >= 0 && y < __grid_get_grid[height] )) || {
    echo "($x,$y) is out of bounds for grid of size (${__grid_get_grid[width]},${__grid_get_grid[height]})" >&2
    return 1
  }

  printf '%s\n' "${__grid_get_grid["$((y * width + x))"]}"
}

grid.set() {
  local -n __grid_set_grid="$1"
  local x="$2" y="$3" value="$4" width="${__grid_set_grid[width]}"

  (( x >= 0 && x < __grid_set_grid[width] && y >= 0 && y < __grid_set_grid[height] )) || {
    echo "($x,$y) is out of bounds for grid of size (${__grid_set_grid[width]},${__grid_set_grid[height]})" >&2
    return 1
  }
  __grid_set_grid["$((y * width + x))"]="$value"
}