# fm-mass-rename
# rename files programmatically or systematically with the help of
# $EDITOR

# ls isn't safe, but if filenames contain newlines we have bigger
# problems
originals=$(mktemp)
ls > "$originals"

modified=$(mktemp)
cat > "$modified" <<EOF
# generated by fm-mass-rename
# edit the filenames using your text editor -- make sure that
# the number of files remain the same
#
# of course, if you have files with newlines in their names or
# files with hashes in front stuff will break, so be careful
#
# to abort, just delete some lines and save and quit
#
# good luck!
EOF
cat < "$originals" >> "$modified"

${EDITOR:-nvim} "$modified"

# remove comments from $modified
sed -i /^#/d "$modified"

# check if both are the same length -- if not, something's wrong
original_len=$(wc -l $originals | cut -d' ' -f1)
modified_len=$(wc -l $modified | cut -d' ' -f1)

if [ "$original_len" -ne "$modified_len" ]; then
	cat <<EOF
It seems that you've omitted or deleted some lines -- this is
unsafe and so I'm stopping. Make sure you don't delete any lines
and try again.
EOF
exit 1
fi

combined=$(paste "$originals" "$modified" -d'|')

paste "$originals" "$modified" -d'|' | while read input; do
	orig="${input%%|*}"
	dest="${input#*|}"
	[ "$orig" = "$dest" ] && continue
	if [ -f "$dest" ]; then
		printf "clobber destination file '%s' with contents of '%s'? (y/n)\n" "$dest" "$orig"

		read result
		if [ x"$result" = "xy" ]; then
			printf "clobbering '%s'\n" "$dest"
			mv "$orig" "$dest"
			continue
		else
			printf "skipping copying '%s' to '%s'\n" "$orig" "$dest"
		fi
	fi

	printf "moving '%s' to '%s'\n" "$orig" "$dest"
	mv "$orig" "$dest"
done