change sort function by jsonata realisation and remove test overrides

Author: sergeevik

src/main/java/com/dashjoin/jsonata/Functions.java

@@ -1950,38 +1950,59 @@ public static List sort(List arr, Object comparator) {
             return arr;
         }
 
-        List result = new ArrayList<>(arr);
 
         if (comparator != null) {
-            Comparator comp = new Comparator() {
-
-                @Override
-                public int compare(Object o1, Object o2) {
-                    try {
-                        Boolean swap = toBoolean(funcApply(comparator, Arrays.asList(o1, o2)));
-                        if (swap == null)
-                          return 0;
-                        if (swap)
-                          return 1;
-                        else
-                          return -1;
-                    } catch (Throwable e) {
-                        // TODO Auto-generated catch block
-                        //e.printStackTrace();
-                        throw new RuntimeException(e);
-                    }
-                }
-                
-            };
-            if (comparator instanceof Comparator)
-              result.sort((Comparator)comparator);
-            else
-              result.sort((Comparator)comp);
-        } else {
-            result.sort(null);
+            if (comparator instanceof Comparator) {
+                List sorted = new ArrayList<>(arr);
+                sorted.sort((Comparator) comparator);
+                return sorted;
+            }
+
+            Object[] sorted  = arr.toArray();
+            Object[] buffer = new Object[sorted.length];
+            mergeSort(sorted, buffer, 0, sorted.length - 1, comparator);
+            List result = new ArrayList<>(sorted.length);
+            Collections.addAll(result, sorted);
+            return result;
         }
 
-        return result;
+        List sorted = new ArrayList<>(arr);
+        sorted.sort(null);
+        return sorted;
+    }
+
+    private static void mergeSort(Object[] sorted, Object[] buffer, int lo, int hi, Object jsonataComparator) {
+        if (lo >= hi) {
+            return;
+        }
+        int mid = (lo + hi) / 2;
+        mergeSort(sorted, buffer, lo, mid, jsonataComparator);
+        mergeSort(sorted, buffer, mid + 1, hi, jsonataComparator);
+        merge(sorted, buffer, lo, mid, hi, jsonataComparator);
+    }
+
+    private static void merge(Object[] sorted, Object[] buffer, int lo, int mid, int hi, Object jsonataComparator) {
+        int i = lo, j = mid + 1, k = lo;
+
+        while (i <= mid && j <= hi) {
+            boolean swap;
+            try {
+                Boolean sw = toBoolean(funcApply(jsonataComparator, Arrays.asList(sorted[i], sorted[j])));
+                swap = Boolean.TRUE.equals(sw);
+            } catch (Throwable e) {
+                throw new RuntimeException(e);
+            }
+
+            if (swap) {
+                buffer[k++] = sorted[j++];
+            } else {
+                buffer[k++] = sorted[i++];
+            }
+        }
+        while (i <= mid) buffer[k++] = sorted[i++];
+        while (j <= hi) buffer[k++] = sorted[j++];
+
+        System.arraycopy(buffer, lo, sorted, lo, hi - lo + 1);
     }
 
     /**

test/test-overrides.json

@@ -130,16 +130,6 @@
             "alternateResult": "1e+20",
             "reason": "toString precision should be 15, handled differently by Java Bigdecimal(..., new MathContext(15)"
         },
-        { 
-            "name": "function-sort/case009.json",
-            "alternateResult": ["0406634348", "040657863", "0406654608", "0406654603"],
-            "reason": "the sort expression is evaluated correctly - however the sort algorithm seems to behave slightly different for equality - jsonata expects the native order to be preserved"
-        },
-        { 
-            "name": "function-sort/case010.json",
-            "alternateResult": ["0406634348", "0406654608", "040657863", "0406654603"],
-            "reason": "same as above, works if the condition is changed to >="
-        },
         { 
             "name": "function-applications/case008.json",
             "ignoreError": true,