Remake cut feature to be simpler to use and avoid bugs, fixes #35

src/replace-words.js

@@ -230,7 +230,7 @@ function replaceExceptions(options) {
 
 /* Replaces cut statements with cuts */
 function replaceCuts() {
-  const searchTerm = /cut\/([^\/]+)\/(-?[\d]+)\/(?:(-?[\d]+)\/)?/i;
+  const searchTerm = /cut\/([^\/]+)\/(off|only) (first|last) ([1-9][0-9]*)\//i;
   walk(document.body, searchTerm, null, cutMethod);
 }
 
@@ -379,31 +379,27 @@ function cutMethod(node, searchTerm, unused) {
   const match = node.nodeValue.match(searchTerm);
   if (match == null) { return; }
   const target = match[1];
-  let start = Number(match[2]);
-  let end = Number(match[3]);
+  const length = target.length
+  const isOnly = match[2] == "only";
+  const isFirst = match[3] == "first";
+  const index = Number(match[4]);
 
-  if (isNaN(end)) {
-    if (start < 0) { // Cut off from the right side
-      end = target.length + start;
+  let start, end;
+  if (isOnly) {
+    if (isFirst) { // only first n
       start = 0;
-    } else { // Cut off from the left side
-      end = target.length;
+      end = Math.min(index, length - 1);
+    } else { // only last n
+      start = Math.max(length - index, 1);
+      end = length;
     }
   } else {
-    const isNegStart = (start < 0) || ((start == 0) && (end < 0));
-    if (isNegStart) { // Starting from the right, move by end
-      const mod = start;
-      start = target.length + mod;
-      end = target.length + mod + end;
-    } else { // Starting from the left, move by end
-      end = start + end;
-    }
-
-    // Start should always be less than end
-    if (start > end) {
-      const greater = start;
-      start = end;
-      end = greater;
+    if (isFirst) { // off first n
+      start = Math.min(index, length - 1);;
+      end = length;
+    } else { // off last n
+      start = 0;
+      end = Math.max(length - index, 1);
     }
   }