feat: improve auth setup flows

src/infra/env-file.ts

@@ -0,0 +1,55 @@
+import fs from "node:fs";
+import path from "node:path";
+
+import { resolveConfigDir } from "../utils.js";
+
+function escapeRegExp(value: string): string {
+  return value.replace(/[.*+?^${}()|[\]\\]/g, "\\$&");
+}
+
+export function upsertSharedEnvVar(params: {
+  key: string;
+  value: string;
+  env?: NodeJS.ProcessEnv;
+}): { path: string; updated: boolean; created: boolean } {
+  const env = params.env ?? process.env;
+  const dir = resolveConfigDir(env);
+  const filepath = path.join(dir, ".env");
+  const key = params.key.trim();
+  const value = params.value;
+
+  let raw = "";
+  if (fs.existsSync(filepath)) {
+    raw = fs.readFileSync(filepath, "utf8");
+  }
+
+  const lines = raw.length ? raw.split(/\r?\n/) : [];
+  const matcher = new RegExp(`^(\\s*(?:export\\s+)?)${escapeRegExp(key)}\\s*=`);
+  let updated = false;
+  let replaced = false;
+
+  const nextLines = lines.map((line) => {
+    const match = line.match(matcher);
+    if (!match) return line;
+    replaced = true;
+    const prefix = match[1] ?? "";
+    const next = `${prefix}${key}=${value}`;
+    if (next !== line) updated = true;
+    return next;
+  });
+
+  if (!replaced) {
+    nextLines.push(`${key}=${value}`);
+    updated = true;
+  }
+
+  if (!fs.existsSync(dir)) {
+    fs.mkdirSync(dir, { recursive: true, mode: 0o700 });
+  }
+
+  const output = `${nextLines.join("\n")}\n`;
+  fs.writeFileSync(filepath, output, "utf8");
+  fs.chmodSync(filepath, 0o600);
+
+  return { path: filepath, updated, created: !raw };
+}