bug fixes for measurement container lagged retrieval-> unit conversion and sample output

src/measurements/MeasurementContainer.js

@@ -169,6 +169,50 @@ class MeasurementContainer {
       return this;
   }
 
+    /**
+   * Check whether a measurement series exists.
+   *
+   * You can rely on the current chain (type/variant/position already set via
+   * type().variant().position()), or pass them explicitly via the options.
+   *
+   * @param {object} options
+   * @param {string} [options.type]      Override the current type
+   * @param {string} [options.variant]   Override the current variant
+   * @param {string} [options.position]  Override the current position
+   * @param {boolean} [options.requireValues=false]
+   *        When true, the series must contain at least one stored value.
+   *
+   * @returns {boolean}
+   */
+  exists({ type, variant, position, requireValues = false } = {}) {
+    const typeKey = type ?? this._currentType;
+    if (!typeKey) return false;
+
+    const variantKey = variant ?? this._currentVariant;
+    if (!variantKey) return false;
+
+    const positionKey = position ?? this._currentPosition;
+
+    const typeBucket = this.measurements[typeKey];
+    if (!typeBucket) return false;
+
+    const variantBucket = typeBucket[variantKey];
+    if (!variantBucket) return false;
+
+    if (!positionKey) {
+      // No specific position requested – just check the variant bucket.
+      return requireValues
+        ? Object.values(variantBucket).some(m => m?.values?.length > 0)
+        : Object.keys(variantBucket).length > 0;
+    }
+
+    const measurement = variantBucket[positionKey];
+    if (!measurement) return false;
+
+    return requireValues ? measurement.values?.length > 0 : true;
+  }
+
+
 
   unit(unitName) {
     if (!this._ensureChainIsValid()) return this;
@@ -252,8 +296,9 @@ class MeasurementContainer {
     const measurement = this.get();
     if (!measurement) return null;
     
-    const value = measurement.getLaggedSample(lag);
-    if (value === null) return null;
+    let sample = measurement.getLaggedSample(lag);
+    if (sample === null) return null;
+    const value = sample.value;
 
     // Return as-is if no unit conversion requested
     if (!requestedUnit) {
@@ -263,12 +308,17 @@ class MeasurementContainer {
     // Convert if needed
     if (measurement.unit && requestedUnit !== measurement.unit) {
       try {
-        return convertModule(value).from(measurement.unit).to(requestedUnit);
+        const convertedValue = convertModule(value).from(measurement.unit).to(requestedUnit);
+        //replace old value in sample and return obj
+        sample.value = convertedValue ;
+        sample.unit = requestedUnit;
+        return sample;
+
       } catch (error) {
         if (this.logger) {
           this.logger.error(`Unit conversion failed: ${error.message}`);
         }
-        return value; // Return original value if conversion fails
+        return sample; // Return original value if conversion fails
       }
     }
 

src/measurements/examples.js

@@ -175,6 +175,25 @@ const downstreamData = basicContainer
   .position('downstream')
   .get();
 
+  //check wether a serie exists
+const hasSeries = measurements
+  .type("flow")
+  .variant("measured")
+  .exists();                // true if any position exists
+
+const hasUpstreamValues = measurements
+  .type("flow")
+  .variant("measured")
+  .exists({ position: "upstream", requireValues: true });
+
+// Passing everything explicitly
+const hasPercent = measurements.exists({
+  type: "volume",
+  variant: "percent",
+  position: "atEquipment",
+});
+
+
 console.log(`Downstream: ${downstreamVal} ${downstreamData.unit} at ${downstreamData.distance}m\n`);
 
 // ====================================