Implement opt-in countdown feature and add to image recipe

stack/lab/Dockerfile

@@ -47,6 +47,11 @@ RUN jupyter nbextension enable --py --sys-prefix appmode && \
 # Swap appmode icon for AiiDAlab gears icon, shown during app load
 COPY --chown=${NB_UID}:${NB_GID} gears.svg ${CONDA_DIR}/share/jupyter/nbextensions/appmode/gears.svg
 
+# Set up opt-in countdown feature
+ARG PYTHON_MINOR_VERSION
+ENV PYTHON_MINOR_VERSION=${PYTHON_MINOR_VERSION}
+COPY --chown=${NB_UID}:${NB_GID} countdown/ ${CONDA_DIR}/lib/python${PYTHON_MINOR_VERSION}/site-packages/notebook/static/custom/
+
 # Copy start-up scripts for AiiDAlab.
 COPY before-notebook.d/* /usr/local/bin/before-notebook.d/
 
@@ -99,5 +104,4 @@ ENV NOTEBOOK_ARGS=\
 "--TerminalManager.cull_interval=300"
 
 # Set up the logo of notebook interface
-ARG PYTHON_MINOR_VERSION
 COPY --chown=${NB_UID}:${NB_GID} aiidalab-wide-logo.png ${CONDA_DIR}/lib/python${PYTHON_MINOR_VERSION}/site-packages/notebook/static/base/images/logo.png

stack/lab/before-notebook.d/70_prepare_countdown_config.sh

@@ -0,0 +1,22 @@
+#!/bin/bash
+set -e
+
+CUSTOM_DIR="${CONDA_DIR}/lib/python${PYTHON_MINOR_VERSION}/site-packages/notebook/static/custom"
+
+if [ "$LIFETIME" ]; then
+    EPHEMERAL=true
+
+    # Convert LIFETIME from HH:MM:SS to seconds
+    IFS=: read -r H M S <<<"$LIFETIME"
+    LIFETIME_SEC=$((10#$H * 3600 + 10#$M * 60 + 10#$S))
+
+    # Calculate expiry timestamp in UTC
+    EXPIRY=$(date -u -d "+${LIFETIME_SEC} seconds" +"%Y-%m-%dT%H:%M:%SZ")
+    export EXPIRY
+else
+    EPHEMERAL=false
+fi
+
+export EPHEMERAL
+envsubst <"${CUSTOM_DIR}/config.json.template" >"$CUSTOM_DIR/config.json"
+rm "${CUSTOM_DIR}/config.json.template"

stack/lab/countdown/config.json.template

@@ -0,0 +1,4 @@
+{
+  "ephemeral": ${EPHEMERAL},
+  "expiry": "${EXPIRY}"
+}

stack/lab/countdown/custom.css

@@ -0,0 +1,33 @@
+#culling-countdown {
+  position: sticky;
+  top: 0;
+  left: 0;
+  width: 100%;
+  background-color: #0078d4;
+  color: white;
+  text-align: center;
+  padding: 8px;
+  font-size: 18px;
+  font-weight: bold;
+  z-index: 9999;
+}
+
+#shutdown-warning,
+#save-info {
+  display: none;
+}
+
+#shutdown-warning {
+  font-size: 20px;
+}
+
+#save-info {
+  font-size: 16px;
+  text-align: center;
+  font-weight: normal;
+  font-size: 18px;
+}
+
+#culling-timer {
+  margin-left: 5px;
+}

stack/lab/countdown/custom.js

@@ -0,0 +1,103 @@
+require(["base/js/namespace", "base/js/events"], (Jupyter, events) => {
+  const parseLifetimeToMs = (str) => {
+    const parts = str.split(":").map(Number);
+    if (parts.length !== 3 || parts.some(isNaN)) {
+      return null;
+    }
+    const [h, m, s] = parts;
+    return ((h * 60 + m) * 60 + s) * 1000;
+  };
+
+  const insertCountdown = (remainingMs) => {
+    if (document.getElementById("culling-countdown")) {
+      return;
+    }
+
+    const banner = document.createElement("div");
+    banner.id = "culling-countdown";
+
+    const shutdownWarning = document.createElement("div");
+    shutdownWarning.id = "shutdown-warning";
+    shutdownWarning.innerHTML = "⚠️ Shutdown imminent! ⚠️";
+    banner.appendChild(shutdownWarning);
+
+    const countdown = document.createElement("div");
+    countdown.id = "countdown";
+    countdown.innerHTML = `Session time remaining: `;
+    const timer = document.createElement("span");
+    timer.id = "culling-timer";
+    timer.innerHTML = "Calculating...";
+    countdown.appendChild(timer);
+    banner.appendChild(countdown);
+
+    const saveInfo = document.createElement("div");
+    saveInfo.id = "save-info";
+    saveInfo.innerHTML = `
+      Consider saving your work using the <b>File Manager</b> or the <b>Terminal</b>
+    `;
+    banner.appendChild(saveInfo);
+
+    const endTime = new Date(Date.now() + remainingMs);
+
+    const formatTime = (seconds) => {
+      const hrs = `${Math.floor(seconds / 3600)}`.padStart(2, "0");
+      const mins = `${Math.floor((seconds % 3600) / 60)}`.padStart(2, "0");
+      const secs = `${Math.floor(seconds % 60)}`.padStart(2, "0");
+      return `${hrs}:${mins}:${secs}`;
+    };
+
+    const updateTimer = () => {
+      const now = new Date();
+      const timeLeft = (endTime - now) / 1000;
+      if (timeLeft < 0) {
+        clearInterval(interval);
+        return;
+      }
+      if (timeLeft < 1800) {
+        banner.style.backgroundColor = "#DAA801";
+        saveInfo.style.display = "block";
+      }
+      if (timeLeft < 300) {
+        banner.style.backgroundColor = "red";
+        shutdownWarning.style.display = "block";
+        shutdownWarning.innerHTML = "⚠️ Shutdown imminent ⚠️";
+      }
+      timer.innerHTML = formatTime(timeLeft);
+    };
+
+    updateTimer();
+    const interval = setInterval(updateTimer, 1000);
+
+    const container = document.getElementById("header");
+    if (container) {
+      container.parentNode.insertBefore(banner, container);
+    }
+  };
+
+  loadCountdown = async () => {
+    try {
+      const response = await fetch("/static/custom/config.json");
+      const config = await response.json();
+
+      // Opt-in point for deployments
+      if (!config.ephemeral) {
+        return;
+      }
+
+      if (!config.expiry) {
+        console.warn("Missing `expiry` in config file");
+        return;
+      }
+
+      const expiry = new Date(config.expiry).getTime();
+      const remaining = expiry - Date.now();
+
+      insertCountdown(Math.max(0, remaining));
+    } catch (err) {
+      console.error("Countdown init failed:", err);
+    }
+  };
+
+  events.on("app_initialized.NotebookApp", loadCountdown);
+  loadCountdown();
+});