feat: vendor permission system source

pi-permission-system/src/expand-home.ts

@@ -0,0 +1,42 @@
+import { homedir } from "node:os";
+import { join } from "node:path";
+
+/**
+ * The spellings of the home directory this package resolves, in every pattern
+ * and path literal.
+ *
+ * `$HOME` and `${HOME}` are the two spellings of the same shell variable and
+ * must stay interchangeable: a rule keyed on one form has to match a path
+ * written in the other, and the bash path projection classifies a token by the
+ * shape it has *after* this expansion (#694).
+ */
+const HOME_PREFIXES = ["~", "$HOME", "${HOME}"] as const;
+
+/**
+ * Expand a home-directory prefix in a pattern or path value to the OS home
+ * directory.
+ *
+ * A prefix is recognized only when it stands alone or is followed by a path
+ * separator, so a longer name (`~username`, `$HOMEDIR`, `${HOMEDIR}`) and a
+ * braced parameter expansion carrying an operator (`${HOME:-/tmp}`,
+ * `${HOME%/*}`) are both left untouched.
+ *
+ * Supported forms, for each prefix in {@link HOME_PREFIXES}:
+ * - `<prefix>`       → `homedir()`
+ * - `<prefix>/path`  → `homedir()/path`
+ * - `<prefix>\path`  → `homedir()\path` (Windows)
+ *
+ * All other patterns are returned unchanged.
+ */
+export function expandHomePath(pattern: string): string {
+  for (const prefix of HOME_PREFIXES) {
+    if (pattern === prefix) return homedir();
+    if (!pattern.startsWith(prefix)) continue;
+
+    const rest = pattern.slice(prefix.length);
+    if (rest.startsWith("/") || rest.startsWith("\\")) {
+      return join(homedir(), rest.slice(1));
+    }
+  }
+  return pattern;
+}