Add typo-resistency to filter graceful

src/util/filter.ts

@@ -81,21 +81,47 @@
     // permutations of the pattern to find a better match. The
     // permutations only swap neighbouring characters, e.g
     // `cnoso` becomes `conso`, `cnsoo`, `cnoos`.
-    const tries = Math.min(7, pattern.length - 1)
-    for (let movingPatternPos = patternPos + 1; movingPatternPos < tries; movingPatternPos++) {
-      const newPattern = nextTypoPermutation(pattern, movingPatternPos)
+    //
+    // For the last 2 permutations try to remove the last characters,
+    // maybe the last few letters are typos. For example,
+    // `conson` could be a typo for `console`
+    const maxTriesPermutation = Math.min(7, pattern.length - 1);
+    const maxTries = maxTriesPermutation + pattern.length;
+
+    // Loop for existing permutations
+    for (let i = 1; i <= maxTriesPermutation; i++) {
+      const newPattern = nextTypoPermutation(pattern, patternPos + i);
+      checkAndUpdateTopCandidate(newPattern, 3);
+    }
+
+    const lastChar = pattern.charAt(pattern.length - 1);
+
+    if ((/[a-zA-Z0-9]/.test(lastChar))) {
+      // Loop for removing characters at all positions
+      for (let i = 0; i < pattern.length; i++) {
+        const newPattern = pattern.slice(0, i) + pattern.slice(i + 1);
+        checkAndUpdateTopCandidate(newPattern, 4);
+      }
+
+      // Loop for removing last characters
+      for (let i = 1; i < 3; i++) {
+        const newPattern = pattern.slice(0, pattern.length - i);
+        checkAndUpdateTopCandidate(newPattern, i+4);
+      }
+    }
+
+    function checkAndUpdateTopCandidate(newPattern: string, penalty: number) {
       if (newPattern) {
-        const candidate = fuzzyScore(newPattern, newPattern.toLowerCase(), patternPos, word, lowWord, wordPos, options)
+        const candidate = fuzzyScore(newPattern, newPattern.toLowerCase(), patternPos, word, lowWord, wordPos, options);
         if (candidate) {
-          candidate[0] -= 3 // permutation penalty
+          candidate[0] -= penalty; // permutation penalty
           if (!top || candidate[0] > top[0]) {
-            top = candidate
+            top = candidate;
           }
         }
       }
     }
   }
-
   return top
 }