refactor: harden diagnostics and consolidate runtime code

iso/builder/lib/bootloader.sh

@@ -85,6 +85,14 @@ render_bootloader_template() {
     initrd_placeholder="$7"
     initrd="$8"
 
+    for required_placeholder in \
+        "@VERSION@" \
+        "$kernel_placeholder" \
+        "@APPEND_LIVE@" \
+        "$initrd_placeholder"; do
+        require_template_placeholder "$template" "$required_placeholder" || return 1
+    done
+
     BEE_RENDER_VERSION="$version" \
     BEE_RENDER_KERNEL_PLACEHOLDER="$kernel_placeholder" \
     BEE_RENDER_KERNEL="$kernel" \

iso/builder/lib/iso-validation.sh

@@ -359,9 +359,12 @@ validate_live_cmdline_params() {
             bad = 1
         }
 
-        $1 == command && has("boot=live") {
+        $1 == command {
             live_entries++
 
+            if (!has("boot=live")) {
+                reject("missing boot=live")
+            }
             if (!has("udev.children_max=1")) {
                 reject("missing udev.children_max=1")
             }
@@ -432,7 +435,7 @@ validate_iso_live_boot_entries() {
         exit 1
     }
 
-    if grep -q '@APPEND_LIVE@\|@KERNEL_LIVE@\|@INITRD_LIVE@' "$grub_cfg" "$isolinux_cfg"; then
+    if grep -Eq '@[A-Z][A-Z_]*@' "$grub_cfg" "$isolinux_cfg"; then
         echo "ERROR: unresolved live-build placeholders remain in ISO bootloader config" >&2
         rm -f "$grub_cfg" "$isolinux_cfg"
         exit 1

iso/builder/lib/template.sh

@@ -0,0 +1,55 @@
+require_template_placeholder() {
+    file="$1"
+    placeholder="$2"
+    if [ -z "$placeholder" ]; then
+        echo "ERROR: template placeholder must not be empty" >&2
+        return 1
+    fi
+    if ! BEE_TEMPLATE_PLACEHOLDER="$placeholder" awk '
+        index($0, ENVIRON["BEE_TEMPLATE_PLACEHOLDER"]) { found=1 }
+        END { exit found ? 0 : 1 }
+    ' "$file"; then
+        echo "ERROR: required placeholder $placeholder is missing from $file" >&2
+        return 1
+    fi
+}
+
+replace_literal_in_file() {
+    file="$1"
+    placeholder="$2"
+    replacement="$3"
+    require_template_placeholder "$file" "$placeholder" || return 1
+    tmp="$(mktemp "${TMPDIR:-/tmp}/bee-template.XXXXXX")"
+
+    if BEE_TEMPLATE_PLACEHOLDER="$placeholder" \
+       BEE_TEMPLATE_REPLACEMENT="$replacement" \
+       awk '
+        function replace_literal(text, needle, value, at) {
+            while ((at = index(text, needle)) != 0) {
+                text = substr(text, 1, at - 1) value substr(text, at + length(needle))
+            }
+            return text
+        }
+        {
+            print replace_literal($0,
+                ENVIRON["BEE_TEMPLATE_PLACEHOLDER"],
+                ENVIRON["BEE_TEMPLATE_REPLACEMENT"])
+        }
+    ' "$file" > "$tmp" && cat "$tmp" > "$file"; then
+        status=0
+    else
+        status=$?
+    fi
+    rm -f "$tmp"
+    return "$status"
+}
+
+validate_project_version() {
+    version="$1"
+    case "$version" in
+        ""|[!A-Za-z0-9]*|*[!A-Za-z0-9]|*[!A-Za-z0-9.-]*)
+            return 1
+            ;;
+    esac
+    return 0
+}