feat(auth): add UserStore with bcryptjs password hashing

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/data/users.test.ts

@@ -0,0 +1,56 @@
+import { describe, it, expect, beforeEach, afterEach } from "vitest";
+import { createDatabase, type BotDatabase } from "./database.js";
+import { createUserStore, UsernameTakenError, type UserStore } from "./users.js";
+
+describe("UserStore", () => {
+  let botDb: BotDatabase;
+  let users: UserStore;
+
+  beforeEach(() => {
+    botDb = createDatabase(":memory:");
+    users = createUserStore(botDb.db);
+  });
+
+  afterEach(() => {
+    botDb.close();
+  });
+
+  it("countUsers is 0 on a fresh db", () => {
+    expect(users.countUsers()).toBe(0);
+  });
+
+  it("createUser stores the user and bumps countUsers", async () => {
+    const u = await users.createUser("alice", "pw-hunter2");
+    expect(u.id).toMatch(/^[0-9a-f-]{36}$/);
+    expect(u.username).toBe("alice");
+    expect(users.countUsers()).toBe(1);
+  });
+
+  it("findByUsername is case-insensitive and returns null for missing", async () => {
+    await users.createUser("Alice", "pw");
+    expect(users.findByUsername("ALICE")).not.toBeNull();
+    expect(users.findByUsername("alice")).not.toBeNull();
+    expect(users.findByUsername("bob")).toBeNull();
+  });
+
+  it("createUser rejects duplicate usernames (case-insensitive)", async () => {
+    await users.createUser("Alice", "pw");
+    await expect(users.createUser("alice", "pw2")).rejects.toBeInstanceOf(UsernameTakenError);
+  });
+
+  it("verifyPassword accepts correct password and rejects wrong one", async () => {
+    await users.createUser("alice", "correct-horse-battery-staple");
+    const row = users.findByUsername("alice");
+    expect(row).not.toBeNull();
+    expect(await users.verifyPassword("correct-horse-battery-staple", row!.passwordHash)).toBe(true);
+    expect(await users.verifyPassword("wrong", row!.passwordHash)).toBe(false);
+  });
+
+  it("changePassword updates the hash so the old password no longer verifies", async () => {
+    const u = await users.createUser("alice", "old");
+    await users.changePassword(u.id, "new");
+    const row = users.findByUsername("alice");
+    expect(await users.verifyPassword("old", row!.passwordHash)).toBe(false);
+    expect(await users.verifyPassword("new", row!.passwordHash)).toBe(true);
+  });
+});

src/data/users.ts

@@ -0,0 +1,84 @@
+import { randomUUID } from "node:crypto";
+import type Database from "better-sqlite3";
+import bcrypt from "bcryptjs";
+
+const BCRYPT_ROUNDS = 12;
+
+export interface UserRow {
+  id: string;
+  username: string;
+  passwordHash: string;
+  createdAt: number;
+  updatedAt: number;
+}
+
+export interface UserStore {
+  countUsers(): number;
+  createUser(username: string, password: string): Promise<UserRow>;
+  findByUsername(username: string): UserRow | null;
+  findById(id: string): UserRow | null;
+  verifyPassword(plain: string, hash: string): Promise<boolean>;
+  changePassword(userId: string, newPassword: string): Promise<void>;
+}
+
+export class UsernameTakenError extends Error {
+  constructor(username: string) {
+    super(`username taken: ${username}`);
+    this.name = "UsernameTakenError";
+  }
+}
+
+export function createUserStore(db: Database.Database): UserStore {
+  const countStmt = db.prepare("SELECT COUNT(*) AS n FROM users");
+  const insertStmt = db.prepare(
+    "INSERT INTO users (id, username, passwordHash, createdAt, updatedAt) VALUES (?, ?, ?, ?, ?)"
+  );
+  const findByUsernameStmt = db.prepare(
+    "SELECT id, username, passwordHash, createdAt, updatedAt FROM users WHERE username = ? COLLATE NOCASE"
+  );
+  const findByIdStmt = db.prepare(
+    "SELECT id, username, passwordHash, createdAt, updatedAt FROM users WHERE id = ?"
+  );
+  const updatePasswordStmt = db.prepare(
+    "UPDATE users SET passwordHash = ?, updatedAt = ? WHERE id = ?"
+  );
+
+  return {
+    countUsers() {
+      return (countStmt.get() as { n: number }).n;
+    },
+
+    async createUser(username, password) {
+      const hash = await bcrypt.hash(password, BCRYPT_ROUNDS);
+      const id = randomUUID();
+      const now = Date.now();
+      try {
+        insertStmt.run(id, username, hash, now, now);
+      } catch (err) {
+        const msg = (err as Error).message;
+        if (msg.includes("UNIQUE") && msg.includes("users.username")) {
+          throw new UsernameTakenError(username);
+        }
+        throw err;
+      }
+      return { id, username, passwordHash: hash, createdAt: now, updatedAt: now };
+    },
+
+    findByUsername(username) {
+      return (findByUsernameStmt.get(username) as UserRow | undefined) ?? null;
+    },
+
+    findById(id) {
+      return (findByIdStmt.get(id) as UserRow | undefined) ?? null;
+    },
+
+    verifyPassword(plain, hash) {
+      return bcrypt.compare(plain, hash);
+    },
+
+    async changePassword(userId, newPassword) {
+      const hash = await bcrypt.hash(newPassword, BCRYPT_ROUNDS);
+      updatePasswordStmt.run(hash, Date.now(), userId);
+    },
+  };
+}