Add dynamic text replacement. Closes #223.

frontend/src/utils/textReplace.ts

@@ -0,0 +1,142 @@
+const ENABLED_KEY = 'remoteterm-text-replace-enabled';
+const MAP_KEY = 'remoteterm-text-replace-map';
+
+const DEFAULT_MAP: Record<string, string> = {
+  А: 'A',
+  В: 'B',
+  Е: 'E',
+  Ё: 'E',
+  З: '3',
+  К: 'K',
+  М: 'M',
+  Н: 'H',
+  О: 'O',
+  Р: 'P',
+  С: 'C',
+  Т: 'T',
+  Х: 'X',
+  Ь: 'b',
+  а: 'a',
+  е: 'e',
+  ё: 'e',
+  о: 'o',
+  р: 'p',
+  с: 'c',
+  у: 'y',
+  х: 'x',
+};
+
+export const DEFAULT_MAP_JSON = JSON.stringify(DEFAULT_MAP, null, 2);
+
+export function getTextReplaceEnabled(): boolean {
+  try {
+    return localStorage.getItem(ENABLED_KEY) === 'true';
+  } catch {
+    return false;
+  }
+}
+
+export function setTextReplaceEnabled(enabled: boolean): void {
+  try {
+    if (enabled) {
+      localStorage.setItem(ENABLED_KEY, 'true');
+    } else {
+      localStorage.removeItem(ENABLED_KEY);
+    }
+  } catch {
+    // localStorage may be unavailable
+  }
+}
+
+export function getTextReplaceMapJson(): string {
+  try {
+    const raw = localStorage.getItem(MAP_KEY);
+    if (raw !== null) return raw;
+  } catch {
+    // fall through
+  }
+  return DEFAULT_MAP_JSON;
+}
+
+/** Persist the map JSON only if it's valid. Returns null on success or an error string. */
+export function setTextReplaceMapJson(json: string): string | null {
+  try {
+    const parsed = JSON.parse(json);
+    if (typeof parsed !== 'object' || parsed === null || Array.isArray(parsed))
+      return 'Must be a JSON object.';
+    const rawEntries = Object.entries(parsed);
+    for (const [k, v] of rawEntries) {
+      if (typeof k !== 'string' || typeof v !== 'string')
+        return 'All keys and values must be strings.';
+    }
+    const entries = rawEntries as [string, string][];
+    // Check for re-expansion: no key may appear as a substring of any replacement value.
+    for (const [needle] of entries) {
+      if (needle.length === 0) continue;
+      for (const [, replacement] of entries) {
+        if (replacement.includes(needle)) {
+          return `Key "${needle}" appears inside replacement "${replacement}" and would re-expand on every keystroke.`;
+        }
+      }
+    }
+    localStorage.setItem(MAP_KEY, json);
+    return null;
+  } catch {
+    return 'Invalid JSON.';
+  }
+}
+
+/** Build a sorted-by-length-desc array of [needle, replacement] for efficient matching. */
+function buildReplacements(json: string): [string, string][] {
+  try {
+    const parsed = JSON.parse(json) as Record<string, string>;
+    return Object.entries(parsed)
+      .filter(([k]) => k.length > 0)
+      .sort((a, b) => b[0].length - a[0].length);
+  } catch {
+    return [];
+  }
+}
+
+/**
+ * Apply text replacements and compute the adjusted cursor position.
+ * Returns null if nothing changed.
+ */
+export function applyTextReplacements(
+  text: string,
+  cursorPos: number,
+  mapJson: string
+): { text: string; cursor: number } | null {
+  const replacements = buildReplacements(mapJson);
+  if (replacements.length === 0) return null;
+
+  let result = '';
+  let newCursor = cursorPos;
+  let i = 0;
+
+  while (i < text.length) {
+    let matched = false;
+    for (const [needle, replacement] of replacements) {
+      if (text.startsWith(needle, i)) {
+        result += replacement;
+        // Adjust cursor if this match is before or spans the cursor
+        if (i + needle.length <= cursorPos) {
+          newCursor += replacement.length - needle.length;
+        } else if (i < cursorPos) {
+          // Cursor is inside this match — place it after the replacement
+          newCursor = result.length;
+        }
+        i += needle.length;
+        matched = true;
+        break;
+      }
+    }
+    if (!matched) {
+      result += text[i];
+      i++;
+    }
+  }
+
+  if (result === text) return null;
+  return { text: result, cursor: newCursor };
+}