fix(api): implement dynamic downsampling for telemetry history ranges

Author: tevfik

internal/api/data/handlers.go

@@ -254,6 +254,14 @@ func (h *Handler) GetData(c *gin.Context) {
 		if dur := parseDuration(rangeStr); dur > 0 {
 			end = time.Now()
 			start = end.Add(-dur)
+
+			// Calculate dynamic interval for downsampling if not explicitly requested
+			if c.Query("int") == "" && limit > 0 {
+				interval = dur / time.Duration(limit)
+				if interval < 10*time.Second {
+					interval = 10 * time.Second
+				}
+			}
 		}
 	}
 
@@ -272,7 +280,12 @@ func (h *Handler) GetData(c *gin.Context) {
 		interval = parseDuration(intStr)
 	}
 
-	points, err := h.Store.GetDataHistoryWithRange(deviceID, start, end, limit)
+	dbLimit := limit
+	if interval > 0 {
+		dbLimit = 100000 // Fetch a large number of raw points for aggregation
+	}
+
+	points, err := h.Store.GetDataHistoryWithRange(deviceID, start, end, dbLimit)
 	if err != nil {
 		c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
 		return