extract_live_grub_entry() {
    cfg="$1"
    live_linux="$(awk '/^[[:space:]]*linux[[:space:]]+\/live\// { print; exit }' "$cfg")"
    live_initrd="$(awk '/^[[:space:]]*initrd[[:space:]]+\/live\// { print; exit }' "$cfg")"
    [ -n "$live_linux" ] || return 1
    [ -n "$live_initrd" ] || return 1

    grub_kernel="$(printf '%s\n' "$live_linux" | awk '{print $2}')"
    grub_append="$(printf '%s\n' "$live_linux" | cut -d' ' -f3-)"
    grub_initrd="$(printf '%s\n' "$live_initrd" | awk '{print $2}')"
    [ -n "$grub_kernel" ] || return 1
    [ -n "$grub_append" ] || return 1
    [ -n "$grub_initrd" ] || return 1
    return 0
}

load_live_build_boot_config() {
    lb_dir="$1"
    binary_cfg="$lb_dir/config/binary"
    chroot_cfg="$lb_dir/config/chroot"
    [ -f "$binary_cfg" ] || return 1
    [ -f "$chroot_cfg" ] || return 1

    # These files are generated by live-build. Its configuration code derives
    # LB_LINUX_FLAVOURS by removing an optional :architecture suffix from each
    # LB_LINUX_FLAVOURS_WITH_ARCH item; the default flavour is the first item.
    unset LB_BOOTAPPEND_LIVE LB_LINUX_FLAVOURS_WITH_ARCH
    # shellcheck disable=SC1090
    . "$binary_cfg"
    # shellcheck disable=SC1090
    . "$chroot_cfg"

    [ -n "${LB_BOOTAPPEND_LIVE:-}" ] || return 1
    [ -n "${LB_LINUX_FLAVOURS_WITH_ARCH:-}" ] || return 1
    live_build_append="$LB_BOOTAPPEND_LIVE"
    live_build_flavour="$(printf '%s\n' "$LB_LINUX_FLAVOURS_WITH_ARCH" | awk '{ split($1, item, ":"); print item[1] }')"
    [ -n "$live_build_flavour" ] || return 1
    return 0
}

extract_live_isolinux_entry() {
    cfg="$1"
    isolinux_linux="$(awk '/^[[:space:]]*linux[[:space:]]+\/live\// { print; exit }' "$cfg")"
    isolinux_initrd="$(awk '/^[[:space:]]*initrd[[:space:]]+\/live\// { print; exit }' "$cfg")"
    isolinux_append="$(awk '/^[[:space:]]*append[[:space:]]+/ { sub(/^[[:space:]]*append[[:space:]]+/, ""); print; exit }' "$cfg")"
    [ -n "$isolinux_linux" ] || return 1
    [ -n "$isolinux_initrd" ] || return 1
    [ -n "$isolinux_append" ] || return 1

    isolinux_kernel="$(printf '%s\n' "$isolinux_linux" | awk '{print $2}')"
    isolinux_initrd_path="$(printf '%s\n' "$isolinux_initrd" | awk '{print $2}')"
    [ -n "$isolinux_kernel" ] || return 1
    [ -n "$isolinux_initrd_path" ] || return 1
    return 0
}

write_canonical_grub_cfg() {
    cfg="$1"
    kernel="$2"
    append_live="$3"
    initrd="$4"
    version_label="${PROJECT_VERSION_EFFECTIVE}"

    template="${BUILDER_DIR}/config/bootloaders/grub-efi/grub.cfg"
    tmp_cfg="${cfg}.new"
    render_bootloader_template "$template" "$tmp_cfg" \
        "$version_label" "@KERNEL_LIVE@" "$kernel" "$append_live" "@INITRD_LIVE@" "$initrd"
    mv "$tmp_cfg" "$cfg"
}

write_canonical_isolinux_cfg() {
    cfg="$1"
    kernel="$2"
    initrd="$3"
    append_live="$4"
    flavour="$5"
    version_label="${PROJECT_VERSION_EFFECTIVE}"

    template="${BUILDER_DIR}/config/bootloaders/isolinux/live.cfg.in"
    tmp_cfg="${cfg}.new"
    render_bootloader_template "$template" "$tmp_cfg" \
        "$version_label" "@LINUX@" "$kernel" "$append_live" "@INITRD@" "$initrd" "$flavour"
    mv "$tmp_cfg" "$cfg"
}

# Render literal placeholders without sed replacement-string semantics. Values
# containing '&', backslashes, or the sed delimiter must be copied unchanged.
render_bootloader_template() {
    template="$1"
    output="$2"
    version="$3"
    kernel_placeholder="$4"
    kernel="$5"
    append_live="$6"
    initrd_placeholder="$7"
    initrd="$8"
    flavour="${9:-}"

    for required_placeholder in \
        "@VERSION@" \
        "$kernel_placeholder" \
        "@APPEND_LIVE@" \
        "$initrd_placeholder"; do
        require_template_placeholder "$template" "$required_placeholder" || return 1
    done
    if grep -Fq '@FLAVOUR@' "$template" && [ -z "$flavour" ]; then
        echo "ERROR: template $template requires a non-empty @FLAVOUR@ value" >&2
        return 1
    fi

    BEE_RENDER_VERSION="$version" \
    BEE_RENDER_KERNEL_PLACEHOLDER="$kernel_placeholder" \
    BEE_RENDER_KERNEL="$kernel" \
    BEE_RENDER_APPEND="$append_live" \
    BEE_RENDER_INITRD_PLACEHOLDER="$initrd_placeholder" \
    BEE_RENDER_INITRD="$initrd" \
    BEE_RENDER_FLAVOUR="$flavour" \
    awk '
        function replace_literal(text, needle, replacement, at) {
            while ((at = index(text, needle)) != 0) {
                text = substr(text, 1, at - 1) replacement substr(text, at + length(needle))
            }
            return text
        }
        {
            version = ENVIRON["BEE_RENDER_VERSION"]
            kernel_placeholder = ENVIRON["BEE_RENDER_KERNEL_PLACEHOLDER"]
            kernel = ENVIRON["BEE_RENDER_KERNEL"]
            append_live = ENVIRON["BEE_RENDER_APPEND"]
            initrd_placeholder = ENVIRON["BEE_RENDER_INITRD_PLACEHOLDER"]
            initrd = ENVIRON["BEE_RENDER_INITRD"]
            flavour = ENVIRON["BEE_RENDER_FLAVOUR"]
            line = replace_literal($0, "@VERSION@", version)
            line = replace_literal(line, kernel_placeholder, kernel)
            line = replace_literal(line, "@APPEND_LIVE@", append_live)
            line = replace_literal(line, initrd_placeholder, initrd)
            line = replace_literal(line, "@FLAVOUR@", flavour)
            print line
        }
    ' "$template" > "$output"
}

enforce_live_build_bootloader_assets() {
    lb_dir="$1"
    grub_cfg="$lb_dir/binary/boot/grub/grub.cfg"
    grub_dir="$lb_dir/binary/boot/grub"
    isolinux_cfg="$lb_dir/binary/isolinux/live.cfg"

    if ! load_live_build_boot_config "$lb_dir"; then
        echo "bootloader sync: WARNING: could not load live boot settings from $lb_dir/config" >&2
        live_build_append=""
        live_build_flavour=""
    fi

    if [ -f "$grub_cfg" ]; then
        if extract_live_grub_entry "$grub_cfg"; then
            cp "${BUILDER_DIR}/config/bootloaders/grub-efi/config.cfg" "$grub_dir/config.cfg"
            write_canonical_grub_cfg "$grub_cfg" "$grub_kernel" "${live_build_append:-$grub_append}" "$grub_initrd"
            echo "bootloader sync: rewrote binary/boot/grub/grub.cfg with canonical EASY-BEE menu"
        else
            echo "bootloader sync: WARNING: could not extract live entry from $grub_cfg" >&2
        fi
    fi

    if [ -f "$isolinux_cfg" ]; then
        if extract_live_isolinux_entry "$isolinux_cfg"; then
            if [ -n "$live_build_flavour" ]; then
                write_canonical_isolinux_cfg "$isolinux_cfg" "$isolinux_kernel" "$isolinux_initrd_path" "${live_build_append:-$isolinux_append}" "$live_build_flavour"
                echo "bootloader sync: rewrote binary/isolinux/live.cfg with canonical EASY-BEE menu"
            else
                echo "bootloader sync: WARNING: could not determine live-build kernel flavour" >&2
            fi
        else
            echo "bootloader sync: WARNING: could not extract live entry from $isolinux_cfg" >&2
        fi
    fi
}