Adjust addOrEditKeyValPair to optionally take two or three arguments (adjust test to suit)

Add a removeKey function with test

update webpage.sh to reference functions in utils.sh (this can likely be abstracted/refactored further)

Signed-off-by: Adam Warner <me@adamwarner.co.uk>

advanced/Scripts/utils.sh

@@ -15,7 +15,10 @@
 #  - New functions must have a test added for them in test/test_any_utils.py
 
 #######################
-# Takes three arguments key, value, and file.
+# Takes either
+#   - Three arguments: key, value, and file.
+#   - Two arguments: key, and file
+#
 # Checks the target file for the existence of the key
 #   - If it exists, it changes the value
 #   - If it does not exist, it adds the value
@@ -25,13 +28,46 @@
 #######################
 addOrEditKeyValPair() {
   local key="${1}"
-  local value="${2}"
-  local file="${3}"
-  if grep -q "^${key}=" "${file}"; then
-    sed -i "/^${key}=/c\\${key}=${value}" "${file}"
-  else
-    echo "${key}=${value}" >> "${file}"
+  local value
+  local file
+  
+  # If two arguments have been passed, then the second one is the file - there is no value
+  if [ $# -lt 3 ]; then    
+    file="${2}"
+  else    
+    value="${2}"
+    file="${3}"
   fi
+
+  if [[ "${value}" != "" ]]; then
+    # value has a value, so it is a key pair
+    if grep -q "^${key}=" "${file}"; then
+      # Key already exists in file, modify the value
+      sed -i "/^${key}=/c\\${key}=${value}" "${file}"
+    else
+      # Key does not already exist, add it and it's value
+      echo "${key}=${value}" >> "${file}"
+    fi
+  else
+    # value has no value, so it is just a key. Add it if it does not already exist
+    if ! grep -q "^${key}" "${file}"; then
+      # Key does not exist, add it.
+      echo "${key}" >> "${file}"
+    fi
+  fi
+}
+
+#######################
+# Takes two arguments key, and file.
+# Deletes a key from target file
+#
+# Example usage:
+# removeKey "PIHOLE_DNS_1" "/etc/pihole/setupVars.conf"
+#######################
+removeKey() {
+  local key="${1}"
+  local file="${2}"
+  sed -i "/^${key}/d" "${file}"
 }
 
 #######################