Change FTLcheckUpdate logic

- execute `curl` in a separate step
- use api.github.com and `jq` to retrieve tag_name
- check if current FTL version is less than latest
- show error message if return is empty (curl failed)

Signed-off-by: RD WebDesign <github@rdwebdesign.com.br>

automated install/basic-install.sh

@@ -2442,15 +2442,23 @@ FTLcheckUpdate() {
         if [[ ${ftlLoc} ]]; then
             local FTLversion
             FTLversion=$(/usr/bin/pihole-FTL tag)
-            local FTLlatesttag
 
-            if ! FTLlatesttag=$(curl -sI https://github.com/pi-hole/FTL/releases/latest | grep --color=never -i Location: | awk -F / '{print $NF}' | tr -d '[:cntrl:]'); then
+            local FTLlatesttag
+            FTLlatesttag=$(curl -s https://api.github.com/repos/pi-hole/FTL/releases/latest | jq -sRr 'fromjson? | .tag_name | values')
+
+            if [ -z "${FTLlatesttag}" ]; then
                 # There was an issue while retrieving the latest version
                 printf "  %b Failed to retrieve latest FTL release metadata" "${CROSS}"
                 return 3
             fi
 
-            if [[ "${FTLversion}" != "${FTLlatesttag}" ]]; then
+            # Convert version strings into numbers for comparison
+            local convertedFTLversion convertedFTLlatesttag
+            convertedFTLversion="$(VersionConverter "${FTLversion}")"
+            convertedFTLlatesttag="$(VersionConverter "${FTLlatesttag}")"
+
+            if [[ "${convertedFTLversion}" -lt "${convertedFTLlatesttag}" ]]; then
+                # FTL is out of date
                 return 0
             else
                 printf "  %b Latest FTL Binary already installed (%s). Confirming Checksum...\\n" "${INFO}" "${FTLlatesttag}"
@@ -2502,6 +2510,12 @@ copy_to_install_log() {
     chmod 644 "${installLogLoc}"
 }
 
+# converts a given version string e.g. v3.7.1 to 3007001000 to allow for easier comparison of multi digit version numbers
+# credits https://apple.stackexchange.com/a/123408
+VersionConverter() {
+  echo "$@" | tr -d '[:alpha:]' | awk -F. '{ printf("%d%03d%03d%03d\n", $1,$2,$3,$4); }';
+}
+
 main() {
     ######## FIRST CHECK ########
     # Must be root to install