From a1a595135c6cec1426f7444fdf41816eae585ca8 Mon Sep 17 00:00:00 2001
From: Marcus Young <m.a.young@soton.ac.uk>
Date: Tue, 2 Feb 2021 14:54:20 +0000
Subject: [PATCH] Check that evaluation of surface generates results before
 processing.

---
 R/otp_evaluate_surface.R | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/R/otp_evaluate_surface.R b/R/otp_evaluate_surface.R
index d605b66..c503ff6 100644
--- a/R/otp_evaluate_surface.R
+++ b/R/otp_evaluate_surface.R
@@ -150,6 +150,17 @@ otp_evaluate_surface <-
       error.id <- "OK"
     }
     
+    # Check that there are some results
+    if (length(asjson$data[[1]]$sums) == 0) {
+      response <-
+        list(
+          "errorId" = 1001,
+          "errorMessage" = "No results - are the pointset destinations within the area covered by the surface?",
+          "query" = url
+        )
+      return (response)
+    }
+    
     response <- list()
     response["errorId"] <- error.id
     response["surfaceId"] <- as.integer(surfaceId)