shweeper

#!/bin/sh -e
# XXX This script is very slow as a result of making many calls to awk.
# Could the whole script be converted to awk?

help() {
	cat - >&2 <<EOF
shweeper [gridsize]

Commands are taken over standard input. To reveal a square, type the
number of the row followed by the letter of the column or vice versa
(no spaces). For example:

a1
1a

To mark a square as a mine, either prepend or append an exclamation
mark to your command. For example:

a1!
1a!
!a1
!1a

Squares do not need to be marked as mines in order to win.

The default gridsize is 9 and the maximum is 26.

The program will exit with a status of 0 for a win or 2 for a loss.
EOF
}

getcell() {
	awk -v x="$1" -v y="$2" 'NR == y { print $x }' <<-EOF
		$3
	EOF
}

setcell() {
	awk -v x="$1" -v y="$2" -v c="$3" '
		NR == y { $x = c }
		{ print $0 }' <<-EOF
		$4
	EOF
}

# using -a instead of && actually saves seconds(!) in update_grid
in_bounds() {
	[ "$1" -gt 0 -a "$1" -le "$gridsize" \
		-a "$2" -gt 0 -a "$2" -le "$gridsize" ]
}

# XXX very hot spot
update_grid() {
	in_bounds "$1" "$2" || return 0

	known_cell=$(getcell "$1" "$2" "$known_grid")
	case "$known_cell" in .)
		hidden_cell=$(getcell "$1" "$2" "$hidden_grid")
		known_grid=$(setcell "$1" "$2" "$hidden_cell" "$known_grid")

		case "$hidden_cell" in
			X) gameover=1 ;;
			0)
				update_grid "$(($1-1))" "$(($2-1))"
				update_grid "$(($1-1))" "$(($2  ))"
				update_grid "$(($1-1))" "$(($2+1))"
				update_grid "$(($1+1))" "$(($2-1))"
				update_grid "$(($1+1))" "$(($2  ))"
				update_grid "$(($1+1))" "$(($2+1))"
				update_grid "$(($1  ))" "$(($2+1))"
				update_grid "$(($1  ))" "$(($2-1))"
				;;
		esac
		;;
	esac
}

case "$1" in
	-h|--help) help; exit 0 ;;
	[0-9]|[0-9][0-9]) gridsize="$1" ;;
	'') gridsize=9 ;;
	*) help; exit 1 ;;
esac

# generate blank grid
known_grid=$(
	y=0
	while [ "$y" -lt "$gridsize" ]; do
		x=0
		while [ "$x" -lt "$gridsize" ]; do
			printf '. '
			x=$((x+1))
		done
		printf '\n'
		y=$((y+1))
	done
)

hidden_grid=$(awk -v gs="$gridsize" '
		BEGIN {
			srand()
			SUBSEP = ","

			# place mines
			for (y = 1; y <= gs; y++)
				for (x = 1; x <= gs; x++)
					grid[x,y] = rand() < 0.1234567
		}

		END {
			# build up numbers around the mines, mark mines with an X
			for (y = 1; y <= gs; y++)
				for (x = 1; x <= gs; x++)
					finalgrid[x,y] = grid[x,y] == 1 ? "X" : grid[x-1,y-1]+grid[x,y-1]+grid[x+1,y-1]+grid[x-1,y]+grid[x+1,y]+grid[x-1,y+1]+grid[x,y+1]+grid[x+1,y+1]

			# print result
			for (y = 1; y <= gs; y++) {
				for (x = 1; x <= gs; x++)
					printf("%s ", finalgrid[x,y])
				printf "\n"
			}
		}
	' /dev/null
)

bombs=$(tr -d ' 0-8\n' | wc -c) <<-EOF
	$hidden_grid
EOF

alphabet_multiline=$(printf '%s\n' A B C D E F G H I \
	J K L M N O P Q R S T U V W X Y Z | head -n "$gridsize")
alphabet=$(tr -d '\n') <<-EOF
	$alphabet_multiline
EOF

unset -v gameover
while :; do
	unknown_cells=$(tr -d ' 0-8\n' | wc -c) <<-EOF
		$known_grid
	EOF

	echo "   $alphabet"
	awk '{ gsub(" ", "", $0); printf("%02d|%s|%02d\n", NR, $0, NR) }' <<-EOF
		$known_grid
	EOF
	echo "   $alphabet"

	if [ "$unknown_cells" -eq "$bombs" ]; then
		echo 'You win!' >&2; exit 0;
	elif [ "$gameover" ]; then
		echo 'You lose!' >&2; exit 2;
	fi

	read -r coords
	case "$coords" in
		!*) mark=1; coords=${coords#!} ;;
		*!) mark=1; coords=${coords%!} ;;
		*) unset -v mark ;;
	esac

	case "$coords" in
		[A-Za-z]*) x=${coords%%[0-9]*}; y=${coords##*[A-Za-z]} ;;
		[0-9]*) x=${coords##*[0-9]}; y=${coords%%[A-Za-z]*} ;;
		*) continue ;; # retry in case of invalid input
	esac

	x=$(awk -v x="$x" '$0 == toupper(x) { print NR }') <<-EOF
		$alphabet_multiline
	EOF

	in_bounds "$x" "$y" || continue

	if [ "$mark" ]; then
		case "$(getcell "$x" "$y" "$known_grid")" in
			.) known_grid=$(setcell "$x" "$y" '!' "$known_grid") ;;
			!) known_grid=$(setcell "$x" "$y" '.' "$known_grid") ;;
		esac
	else
		update_grid "$x" "$y"
	fi
done