feat: Added obfuscate.

flake.nix

@@ -17,6 +17,8 @@
         buildInputs = with pkgs; [
           nodejs
           yarn
+
+          nodePackages.typescript-language-server
         ];
       };
 

package.json

@@ -22,6 +22,6 @@
     "typedoc": "^0.24.7",
     "typedoc-plugin-markdown": "^3.15.3",
     "typescript": "^5.0.4",
-    "vitest": "^0.31.1"
+    "vitest": "^2.0.3"
   }
 }

src/obfuscate.spec.ts

@@ -0,0 +1,16 @@
+import { describe, expect, test } from "vitest";
+
+import { obfuscate } from "./obfuscate";
+
+describe('obfuscate', function() {
+  test.each([
+    ['brower.spencer@gmail.com', [/^.{3}/, '@', '.com'], ['co'], 'bro•••••••••••@•••••.••m'],
+    ['brower.spencer@gmail.com', [/^.{3}/, '@', '.com'], [], 'bro•••••••••••@•••••.com']
+  ])('%# works', function (str, allow, deny, want) {
+    const got = obfuscate(str, allow, deny);
+
+    expect(want.length).toEqual(str.length)
+    
+    expect(got).toBe(want);
+  });  
+});

src/obfuscate.ts

@@ -0,0 +1,56 @@
+export type Patterns = Array<string | RegExp>;
+
+/**
+ * Replaces all but the first `length` characters of a string with `•`.
+ *
+ * @param {string} string The string to obfuscate.
+ * @param {string[]} whitelistPatterns
+ * @return {string} The obfuscated string.
+ */
+export function obfuscate(
+  string: string,
+  whitelistPatterns: Patterns = [],
+  blacklistPatterns: Patterns = []
+): string {
+  return [
+    whitelist(whitelistPatterns),
+    blacklist(blacklistPatterns)
+  ].reduce(
+    (str, fn) => fn(str),
+    string
+  );
+}
+
+function mergePatterns(patterns: Patterns): string {
+  return patterns
+    .map((pattern) =>
+      typeof pattern === "string" ? escapeRegExp(pattern) : pattern.source
+    )
+    .join("|");
+}
+
+function whitelist(patterns: Patterns) {
+  const whitelistPattern = RegExp(mergePatterns(patterns), "dgm");
+
+  return (string: string) =>
+    Array.from(string.matchAll(whitelistPattern))
+      .map((result) => [result[0], result.indices[0][0]])
+      .reduce(
+        (carry, [word, index]) => carry.padEnd(index, "\u2022") + word,
+        ""
+      );
+}
+
+function blacklist(patterns: Patterns) {
+  const blacklistPattern = new RegExp(mergePatterns(patterns), "dgm");
+  //return string => Array.from(string.matchAll(blacklistPattern)).filter(x => x[0].length)
+  return (string: string) =>
+    string.replaceAll(blacklistPattern, (match: string) => {
+     return "".padEnd(match.length, "\u2022");
+    });
+}
+
+function escapeRegExp(string: string): string {
+  return string.replace(/[.*+?^${}()|[/\]\\]/g, "\\$&");
+}
+