1 files changed, 76 insertions, 0 deletions
diff --git a/toolkit/modules/NLP.jsm b/toolkit/modules/NLP.jsm
new file mode 100644
index 000000000..f596ad9da
--- /dev/null
+++ b/toolkit/modules/NLP.jsm
@@ -0,0 +1,76 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+this.EXPORTED_SYMBOLS = ["NLP"];
+
+/**
+ * NLP, which stands for Natural Language Processing, is a module that provides
+ * an entry point to various methods to interface with human language.
+ *
+ * At least, that's the goal. Eventually. Right now, the find toolbar only really
+ * needs the Levenshtein distance algorithm.
+ */
+this.NLP = {
+  /**
+   * Calculate the Levenshtein distance between two words.
+   * The implementation of this method was heavily inspired by
+   * http://locutus.io/php/strings/levenshtein/index.html
+   * License: MIT.
+   *
+   * @param  {String} word1   Word to compare against
+   * @param  {String} word2   Word that may be different
+   * @param  {Number} costIns The cost to insert a character
+   * @param  {Number} costRep The cost to replace a character
+   * @param  {Number} costDel The cost to delete a character
+   * @return {Number}
+   */
+  levenshtein(word1 = "", word2 = "", costIns = 1, costRep = 1, costDel = 1) {
+    if (word1 === word2)
+      return 0;
+
+    let l1 = word1.length;
+    let l2 = word2.length;
+    if (!l1)
+      return l2 * costIns;
+    if (!l2)
+      return l1 * costDel;
+
+    let p1 = new Array(l2 + 1)
+    let p2 = new Array(l2 + 1)
+
+    let i1, i2, c0, c1, c2, tmp;
+
+    for (i2 = 0; i2 <= l2; i2++)
+      p1[i2] = i2 * costIns;
+
+    for (i1 = 0; i1 < l1; i1++) {
+      p2[0] = p1[0] + costDel;
+
+      for (i2 = 0; i2 < l2; i2++) {
+        c0 = p1[i2] + ((word1[i1] === word2[i2]) ? 0 : costRep);
+        c1 = p1[i2 + 1] + costDel;
+
+        if (c1 < c0)
+          c0 = c1;
+
+        c2 = p2[i2] + costIns;
+
+        if (c2 < c0)
+          c0 = c2;
+
+        p2[i2 + 1] = c0;
+      }
+
+      tmp = p1;
+      p1 = p2;
+      p2 = tmp;
+    }
+
+    c0 = p1[l2];
+
+    return c0;
+  }
+};