zdiffwalk

#!/usr/bin/env bash

zdiffwalk_usage() {
	cat <<EOusage | mdformat

**NAME**
	${0##*/} - walk through zfs snapshots, showing diffs

**SYNOPSIS**
	${0##*/} [**-t**] _dataset_

**DESCRIPTION**
	Walks through a dataset's zfs snapshots, listing the file
	differences between each pair

	Options:
	**-t**	include timestamp of changed files

	Once running, you can nagivate using:
	**j**	next pair
	**k**	previous pair
	**l**	display a list of snapshots
	**g**	go to a specific point in the list
	**z**	zoom
	**r**	refresh snapshot list
	**q**	quit

EOusage
}

zdiffwalk_briefusage() {
	cat <<EObrief | mdformat
**j** = next, **k** = previous, **l** = list snapshots, **g** = go snap,
**z** = zoom, **r** = refresh list, **q** = quit
EObrief
}

mdformat() {
	local md so us mr me
	if [ -t 1 ]; then
		md=$(tput md)	# bold
		so=$(tput so)	# standout (inverse?)
		us=$(tput us)	# underline
		mr=$(tput mr)	# reverse
		me=$(tput me)	# exit attributes
	fi
	sed -E \
		-e "s/\*\*([^*]+)\*\*/$md\1$me/g" \
		-e "s/\*([^*]+)\*/$us\1$me/g" \
		-e "s/_([^_]+)_/$us\1$me/g" \
		-e "s/^#+ *(.+)/$so\1$me/g" \
		-e "s/#([^#]+)#/$mr\1$me/g"
}

zdiffwalk_vars() {
	local -g zdiffwalk_snaps=()
	local -g Verbose
	# Defaults
	if [ -t 0 ]; then
		Verbose=true
	else
		Verbose=false
	fi
	showtime=false
}

zdiffwalk() {
	zdiffwalk_vars

	local i opt
	local lhs=0

	# Options
	while getopts vqt opt; do
		case "$opt" in
			v)	Verbose=true ;;
			q)	Verbose=false ;;
			t)	showtime=true ;;
			*)	zdiffwalk_usage; exit 1 ;;
		esac
	done
	shift $((OPTIND - 1))

	[[ $# -eq 0 ]] && { zdiffwalk_usage; exit 65; }

	if ! zfs list -Ho name "$1" >/dev/null; then
		exit 65
	elif ! zfs list -t snapshot -rHo name | grep -q "^$1@"; then
		echo "cannot diff '$1': dataset has no snapshots" >&2
		exit 65
	fi

	mapfile -t zdiffwalk_snaps < <(zfs list -t snapshot -rHo name -d 1 "$1")

	if [ ${#zdiffwalk_snaps[@]} -eq 1 ]; then
		if $showtime; then
			zfs diff -t "${zdiffwalk_snaps[$lhs]}" | sed 's/^\([0-9]*\).[0-9]*/\1/' |
			while read -r d t line; do printf "%s\t%s\t%s\n" "$(date -r "$d" '+[%Y-%m-%d %T]')" "$t" "$line"; done
		else
			zfs diff "${zdiffwalk_snaps[0]}"
		fi
		exit $?
	fi

	$Verbose && echo "Browsing ${#zdiffwalk_snaps[@]} snapshots..."
	for ((i=0;i<${#zdiffwalk_snaps[@]};i++)); do
		printf "(%d) %s\n" "$i" "${zdiffwalk_snaps[$i]}"
	done

	while :; do
		echo ">> ($lhs) zfs diff \"${zdiffwalk_snaps[$lhs]}\" \"${zdiffwalk_snaps[$((lhs+1))]}\""
		if $showtime; then
			zfs diff -t "${zdiffwalk_snaps[$lhs]}" "${zdiffwalk_snaps[$((lhs+1))]}" | sed 's/^\([0-9]*\).[0-9]*/\1/' |
			while read -r d t line; do printf "%s\t%s\t%s\n" "$(date -r "$d" '+[%Y-%m-%d %T]')" "$t" "$line"; done
		else
			zfs diff "${zdiffwalk_snaps[$lhs]}" "${zdiffwalk_snaps[$((lhs+1))]}"
		fi
		choice=""
		while :; do
			read -s -n 1 -p "(j/k/g/l/z/r/?/q)? " choice
			echo "$choice"
			case "$choice" in
				q) break 2 ;;
				j) ((lhs++)) ;;
				k) ((lhs--)) ;;
				z)
				 	zfs diff "${zdiffwalk_snaps[$lhs]}" "${zdiffwalk_snaps[$((lhs+1))]}" | nl
				 	;;
				g)
					read -p "Jump to (0-$((${#zdiffwalk_snaps[@]} - 1))): " go
					if [[ "$go" =~ ^[0-9]+$ ]] && [ "$go" -lt ${#zdiffwalk_snaps[@]} ]; then
						lhs=$go
					fi
					;;
				l)
					for ((i=0;i<${#zdiffwalk_snaps[@]};i++)); do
					 	printf "(%d) %s\n" "$i" "${zdiffwalk_snaps[$i]}"
					done
					;&
				r) mapfile -t zdiffwalk_snaps < <(zfs list -t snapshot -rHo name -d 1 "$1") ;;
				\?) zdiffwalk_briefusage ;;
				*) continue ;;
			esac
			break
		done
		case "$lhs" in
			-1) lhs=0 ;;
			${#zdiffwalk_snaps[@]}) break ;;
		esac
	done
}

# only execute if we're called directly
case "$-" in
	*i*) : ;;
	*) zdiffwalk "$@" ;;
esac