impr(input): extract visual equivalence check to a util function

!nuf

also adds greek characters
closes monkeytypegame#7036

Author: Miodec

frontend/__tests__/utils/strings.spec.ts

@@ -465,4 +465,44 @@ describe("string utils", () => {
       });
     });
   });
+
+  describe("areCharactersVisuallyEqual", () => {
+    it("should return true for identical characters", () => {
+      expect(Strings.areCharactersVisuallyEqual("a", "a")).toBe(true);
+      expect(Strings.areCharactersVisuallyEqual("!", "!")).toBe(true);
+    });
+
+    it("should return false for different characters", () => {
+      expect(Strings.areCharactersVisuallyEqual("a", "b")).toBe(false);
+      expect(Strings.areCharactersVisuallyEqual("!", "?")).toBe(false);
+    });
+
+    it("should return true for equivalent apostrophe variants", () => {
+      expect(Strings.areCharactersVisuallyEqual("'", "'")).toBe(true);
+      expect(Strings.areCharactersVisuallyEqual("'", "'")).toBe(true);
+      expect(Strings.areCharactersVisuallyEqual("'", "ʼ")).toBe(true);
+    });
+
+    it("should return true for equivalent quote variants", () => {
+      expect(Strings.areCharactersVisuallyEqual('"', '"')).toBe(true);
+      expect(Strings.areCharactersVisuallyEqual('"', '"')).toBe(true);
+      expect(Strings.areCharactersVisuallyEqual('"', "„")).toBe(true);
+    });
+
+    it("should return true for equivalent dash variants", () => {
+      expect(Strings.areCharactersVisuallyEqual("-", "–")).toBe(true);
+      expect(Strings.areCharactersVisuallyEqual("-", "—")).toBe(true);
+      expect(Strings.areCharactersVisuallyEqual("–", "—")).toBe(true);
+    });
+
+    it("should return true for equivalent comma variants", () => {
+      expect(Strings.areCharactersVisuallyEqual(",", "‚")).toBe(true);
+    });
+
+    it("should return false for characters from different equivalence groups", () => {
+      expect(Strings.areCharactersVisuallyEqual("'", '"')).toBe(false);
+      expect(Strings.areCharactersVisuallyEqual("-", "'")).toBe(false);
+      expect(Strings.areCharactersVisuallyEqual(",", '"')).toBe(false);
+    });
+  });
 });

frontend/src/ts/controllers/input-controller.ts

@@ -44,6 +44,7 @@ import {
 import { tryCatchSync } from "@monkeytype/util/trycatch";
 import { canQuickRestart } from "../utils/quick-restart";
 import * as PageTransition from "../states/page-transition";
+import { areCharactersVisuallyEqual } from "../utils/strings";
 
 let dontInsertSpace = false;
 let correctShiftUsed = true;
@@ -405,37 +406,8 @@ function isCharCorrect(char: string, charIndex: number): boolean {
     }
   }
 
-  if (
-    (char === "’" ||
-      char === "‘" ||
-      char === "'" ||
-      char === "ʼ" ||
-      char === "׳" ||
-      char === "ʻ") &&
-    (originalChar === "’" ||
-      originalChar === "‘" ||
-      originalChar === "'" ||
-      originalChar === "ʼ" ||
-      originalChar === "׳" ||
-      originalChar === "ʻ")
-  ) {
-    return true;
-  }
-
-  if (
-    (char === `"` || char === "”" || char === "“" || char === "„") &&
-    (originalChar === `"` ||
-      originalChar === "”" ||
-      originalChar === "“" ||
-      originalChar === "„")
-  ) {
-    return true;
-  }
-
-  if (
-    (char === "–" || char === "—" || char === "-") &&
-    (originalChar === "-" || originalChar === "–" || originalChar === "—")
-  ) {
+  const visuallyEqual = areCharactersVisuallyEqual(char, originalChar);
+  if (visuallyEqual) {
     return true;
   }
 

frontend/src/ts/utils/strings.ts

@@ -261,6 +261,41 @@ export function isWordRightToLeft(
   return reverseDirection ? !result : result;
 }
 
+export const CHAR_EQUIVALENCE_MAPS = [
+  new Map(
+    ["’", "‘", "'", "ʼ", "׳", "ʻ", "᾽", "᾽"].map((char, index) => [char, index])
+  ),
+  new Map([`"`, "”", "“", "„"].map((char, index) => [char, index])),
+  new Map(["–", "—", "-", "‐"].map((char, index) => [char, index])),
+  new Map([",", "‚"].map((char, index) => [char, index])),
+];
+
+/**
+ * Checks if two characters are visually/typographically equivalent for typing purposes.
+ * This allows users to type different variants of the same character and still be considered correct.
+ * @param char1 The first character to compare
+ * @param char2 The second character to compare
+ * @returns true if the characters are equivalent, false otherwise
+ */
+export function areCharactersVisuallyEqual(
+  char1: string,
+  char2: string
+): boolean {
+  // If characters are exactly the same, they're equivalent
+  if (char1 === char2) {
+    return true;
+  }
+
+  // Check each equivalence map
+  for (const map of CHAR_EQUIVALENCE_MAPS) {
+    if (map.has(char1) && map.has(char2)) {
+      return true;
+    }
+  }
+
+  return false;
+}
+
 // Export testing utilities for unit tests
 export const __testing = {
   hasRTLCharacters,