feat+fix: changed the primary data source for the data analysis and added the relative card in the dashboard page.

api/src/storage/influx.js

@@ -118,6 +118,51 @@ async function exportSessionCSV(sensor, session, since, until = null) {
     return header + '\n' + csvRows.join('\n') + '\n';
 }
 
+/**
+ * Utility interna: esegue una Flux query e restituisce le righe come array di oggetti.
+ */
+function runFlux(fluxQuery) {
+    const rows = [];
+    return new Promise((resolve, reject) => {
+        querying.queryRows(fluxQuery, {
+            next(row, tableMeta) { rows.push(tableMeta.toObject(row)); },
+            error: reject,
+            complete() { resolve(rows); },
+        });
+    });
+}
+
+/**
+ * Elenca tutte le sessioni presenti in InfluxDB, con primo e ultimo timestamp.
+ * Sorgente di verità: tag sensor + session sul measurement "logs".
+ * @param {string} [lookback='-5y'] - range di ricerca (es. '-365d', '-5y')
+ * @returns {Promise<Array<{session, sensor, startTime, endTime}>>}
+ */
+async function listInfluxSessions(lookback = '-5y') {
+    const base = `
+        from(bucket: "${sessionBucket}")
+            |> range(start: ${lookback})
+            |> filter(fn: (r) => r._measurement == "logs")
+            |> group(columns: ["sensor", "session"])
+            |> keep(columns: ["_time", "sensor", "session"])
+    `;
+    const [firstRows, lastRows] = await Promise.all([
+        runFlux(base + '|> first()'),
+        runFlux(base + '|> last()'),
+    ]);
+
+    const map = {};
+    firstRows.forEach(r => {
+        if (!r.session) return;
+        map[r.session] = { session: r.session, sensor: r.sensor, startTime: r._time };
+    });
+    lastRows.forEach(r => {
+        if (map[r.session]) map[r.session].endTime = r._time;
+    });
+
+    return Object.values(map).sort((a, b) => new Date(b.startTime) - new Date(a.startTime));
+}
+
 async function checkInflux() {
     try {
         const result = await querying.collectRows(
@@ -139,6 +184,7 @@ module.exports = {
     write: append,
     writeBatch,
     query,
+    listInfluxSessions,
     querySessionHistory,
     exportSessionCSV,
     checkInflux