Improved error handling, dependency checks, and code readability (#136)

* Improved error handling, dependency checks, and code readability

* error handling

build_deb.sh

@@ -2,39 +2,41 @@
 
 set -e
 
+# Function to display error message and exit
+error_exit() {
+    echo "Error: $1" >&2
+    exit 1
+}
+
 # Sanitize package signing options
 COUNT=0
 for sign_param in DEB_SIGN_KEY DEB_SIGN_KEY_ID DEB_SIGN_KEY_PATH; do
     if [[ -n "${!sign_param}" ]]; then ((COUNT+=1)); fi
 done
 if (( COUNT > 1 )); then
-    echo "Error: At most one of DEB_SIGN_KEY or DEB_SIGN_KEY_ID or DEB_SIGN_KEY_PATH vars must be defined " >&2
-    exit 1
+    error_exit "At most one of DEB_SIGN_KEY or DEB_SIGN_KEY_ID or DEB_SIGN_KEY_PATH vars must be defined"
 fi
 
 # Import GPG signing private key if it is provided
 if [[ -n "${DEB_SIGN_KEY_ID}" ]]; then
     # Check if gpg knows about this key id
     if [[ $(gpg --list-keys ${DEB_SIGN_KEY_ID} 2>&1) =~ "No public key" ]]; then
-        echo "Error: No public key ${DEB_SIGN_KEY_ID}" >&2
-        exit 1
+        error_exit "No public key ${DEB_SIGN_KEY_ID}"
     else
         SIGN_ARGS="-k${DEB_SIGN_KEY_ID}"
     fi
 elif [[ -n "${DEB_SIGN_KEY}" ]]; then
-    echo "${DEB_SIGN_KEY}" | gpg --import
+    echo "${DEB_SIGN_KEY}" | gpg --import || error_exit "Unable to import signing key from var DEB_SIGN_KEY"
     KEY_ID=$(gpg --list-keys --with-colon | awk -F: '/^fpr/ {print $10;exit}')
     if [[ -z ${KEY_ID} ]]; then
-        echo "Error: Unable to import signing key from var DEB_SIGN_KEY" >&2
-        exit 1
+        error_exit "Unable to import signing key from var DEB_SIGN_KEY"
     fi
     SIGN_ARGS="-k${KEY_ID}"
 elif [[ -n "${DEB_SIGN_KEY_PATH}" ]]; then
-    gpg --import --with-colons "${DEB_SIGN_KEY_PATH}"
+    gpg --import --with-colons "${DEB_SIGN_KEY_PATH}" || error_exit "Unable to import signing key from path: ${DEB_SIGN_KEY_PATH}"
     KEY_ID=$(gpg --list-keys --with-colon | awk -F: '/^fpr/ {print $10;exit}')
     if [[ -z ${KEY_ID} ]]; then
-        echo "Error: Unable to import signing key from path: ${DEB_SIGN_KEY_PATH}" >&2
-        exit 1
+        error_exit "Unable to import signing key from path: ${DEB_SIGN_KEY_PATH}"
     fi
     SIGN_ARGS="-k${KEY_ID}"
 else