added an example script for keymaps based on the nvim-surround plugin

examples/surround_plugin.sh

@@ -1,4 +1,5 @@
 _get_surround_target() {
+	# get the delimiters to surround our selection with
 	read_key -v _s_ch
 	case "$_s_ch" in
 	  \(|\)) _sl='('; _sr=')' ;;
@@ -10,6 +11,8 @@ _get_surround_target() {
 
 }
 _read_obj() {
+	# use the 'read_key' builtin to have our keymap function take user input
+	# keep reading keys until we have something that looks like a text object
 	_obj=""
 	while read_key -v key; do
 	  if [[ "${#_obj}" -ge 3 ]]; then return 1; fi
@@ -42,6 +45,7 @@ _read_obj() {
 
 }
 _scan_left() {
+	# search to the left for a pattern in a string
 	local needle="$1"
 	local haystack="$2"
 	local i=$((${#haystack} - 1))
@@ -60,6 +64,7 @@ _scan_left() {
 
 }
 _scan_right() {
+	# search to the right for a pattern in a string
 	local needle="$1"
 	local haystack="$2"
 	local i=0
@@ -78,13 +83,21 @@ _scan_right() {
 
 }
 _surround_1() {
+	# here we get our text object and our delimiters
 	local _obj
 	_read_obj
 	_get_surround_target
+
+	# the $_KEYS variable can be used to send a sequence of keys
+	# back to the editor. here, we prefix the text object with 'v'
+	# to make the line editor enter visual mode and select the text object.
 	_KEYS="v$_obj"
 
 }
 _surround_2() {
+	# this is called after _surround_1. the editor received our visual
+	# selection command, so now we can operate on the range it has selected.
+	# $_ANCHOR and $_CURSOR can be used to find both sides of the selection
 	local start
 	local end
 	if [ "$_ANCHOR" -lt "$_CURSOR" ]; then
@@ -98,43 +111,68 @@ _surround_2() {
 
 	delta=$((end - start))
 
+	# use parameter expansion to slice up the buffer into 3 parts
 	left="${_BUFFER:0:$start}"
 	mid="${_BUFFER:$start:$delta}"
 	right="${_BUFFER:$end}"
+
+	# slide our delimiters inbetween those parts
 	_BUFFER="$left$_sl$mid$_sr$right"
 	_CURSOR=$start
 
 }
 _surround_del() {
+	# this one is pretty weird
+
+	# get our delimiters
 	_get_surround_target
+
+	# slice the buffer in half at the cursor
 	local left_buf="${_BUFFER:0:$_CURSOR}"
 	local right_buf="${_BUFFER:$left}"
 	local left=""
 	local right=""
+
+	# scan left to see if we find our left delimiter
 	_scan_left $_sl "$left_buf"
 
 	if [ "$?" -ne 0 ]; then
+		# we didnt find $_sl to the left of the cursor
+		# so let's look for it to the right of the cursor
 	  _scan_right $_sl "$right_buf"
 
-	  [ "$?" -ne 0 ] && return 1
+	  [ "$?" -ne 0 ] && return 1 # did not find it
+
+		# we found the left delimiter to the right of the cursor.
+		# _scan_right set the value of $right so lets take that and put it in $left
 	  left=$right
 	fi
 
+	# this is the start of the middle part of the buffer
 	mid_start=$((left + 1))
 	right=""
 	left_buf="${_BUFFER:0:$left}"
-	right_buf="${_BUFFER:$mid_start}"
+	right_buf="${_BUFFER:$mid_start}" # from mid_start to end of buffer
-	_scan_right $_sr "$right_buf"
+	_scan_right $_sr "$right_buf" # scan right
 
 	[ "$?" -ne 0 ] && return 1
 
-	mid_end=$((mid_start + right))
+	# right now contains the distance we traveled to hit our right delimiter
-	right_start=$((mid_end + 1))
+	mid_end=$((mid_start + right)) # use that to calculate the end of the middle
+	right_start=$((mid_end + 1)) # and get the start of the last part
+
+	# and now we just slice it like we did in _surround_2
 	new_left_buf="${_BUFFER:0:$left}"
 	new_mid_buf="${_BUFFER:$mid_start:$right}"
 	new_right_buf="${_BUFFER:$right_start}"
 
-
+	# put them back together. the end result is a buffer without those pesky delimiters
 	_BUFFER="$new_left_buf$new_mid_buf$new_right_buf"
 
 }
+
+# map our functions to some keys
+# our savvy readers will notice that these are the same
+# default keybinds set by kylechui's 'nvim-surround' plugin
+keymap -n 'ds' '<CMD>!_surround_del<CR>'
+keymap -n 'ys' '<CMD>!_surround_1<CR><CMD>!_surround_2<CR>' # chain these two together