const Database = require('better-sqlite3');
const path = require('path');
const fs = require('fs');

const DB_PATH = process.env.DB_PATH || path.join(__dirname, 'bills.db');
const SCHEMA_PATH = path.join(__dirname, 'schema.sql');
const DEFAULT_CATEGORIES = [
  'Housing',
  'Utilities',
  'Credit Cards',
  'Loans',
  'Insurance',
  'Subscriptions',
  'Phone & Internet',
  'Transportation',
  'Medical',
  'Other',
];

// ── SQL Whitelist Mappings ────────────────────────────────────────────────────
// Security FIX (2026-05-08): Whitelist all allowed column names to prevent SQL injection
// in migrations that use dynamic ALTER TABLE statements.

const COLUMN_WHITELIST = new Set([
  // users table columns
  'active', 'is_default_admin', 'notification_email', 'notifications_enabled',
  'notify_3d', 'notify_1d', 'notify_due', 'notify_overdue',
  'display_name', 'last_password_change_at', 'auth_provider', 'external_subject',
  'email', 'last_login_at',
  // payments table columns
  'deleted_at',
  // monthly_starting_amounts table columns
  'other_amount',
  // bills table columns
  'history_visibility', 'interest_rate', 'user_id',
  // sessions table columns
  'created_at',
]);

// Security validation function for column names
function isValidColumnName(col) {
  if (!col || typeof col !== 'string') return false;
  // Must be in whitelist AND match valid SQL identifier pattern
  return COLUMN_WHITELIST.has(col) && /^[a-z0-9_]+$/i.test(col);
}

// Security validation function for SQL definition fragments
function isValidSqlDefinition(def) {
  if (!def || typeof def !== 'string') return false;
  // Allow standard column definitions but reject any user input
  // This is safe because all definitions are hardcoded here
  return /^[\w\s\(\)\',!@#$%^&*+=\[\]<>\-.]+$/i.test(def);
}

fs.mkdirSync(path.dirname(DB_PATH), { recursive: true });

let db = null;
let initializing = false;

function assertWritableDbPath() {
  const dir = path.dirname(DB_PATH);
  const probe = path.join(dir, `.write-test-${process.pid}-${Date.now()}`);

  try {
    fs.mkdirSync(dir, { recursive: true });
    fs.writeFileSync(probe, 'ok');
    fs.unlinkSync(probe);

    if (fs.existsSync(DB_PATH)) {
      fs.accessSync(DB_PATH, fs.constants.R_OK | fs.constants.W_OK);
    }
  } catch (err) {
    const message = [
      `Database path is not writable: ${DB_PATH}`,
      `Ensure the DB directory is writable by the app user. In Docker, rebuild the image and recreate the container so the entrypoint can chown /data.`,
      `Original error: ${err.message}`,
    ].join('\n');
    const wrapped = new Error(message);
    wrapped.code = err.code;
    throw wrapped;
  } finally {
    try {
      if (fs.existsSync(probe)) fs.unlinkSync(probe);
    } catch {}
  }
}

function sleep(ms) {
  Atomics.wait(new Int32Array(new SharedArrayBuffer(4)), 0, 0, ms);
}

function getDb() {
  // already ready
  if (db) return db;

  // wait if another init is happening
  while (initializing) {
    sleep(50);
  }

  // check again after wait
  if (db) return db;

  initializing = true;

  try {
    console.log('Opening DB at:', DB_PATH);
    assertWritableDbPath();

    db = new Database(DB_PATH, {
      timeout: 5000
    });

    db.pragma('busy_timeout = 5000');

    try {
      db.pragma('journal_mode = WAL');
    } catch (e) {
      console.warn('WAL failed:', e.message);
    }

    db.pragma('foreign_keys = ON');

    initSchema();
    seedDefaults();

    console.log('DB initialized successfully');

    return db;
  } catch (err) {
    console.error('DB init failed:', err);
    throw err;
  } finally {
    initializing = false;
  }
}

function initSchema() {
  const schema = fs.readFileSync(SCHEMA_PATH, 'utf8');
  db.exec(schema);
  
  // Create schema_migrations table for tracking applied migrations
  db.exec(`
    CREATE TABLE IF NOT EXISTS schema_migrations (
      id INTEGER PRIMARY KEY AUTOINCREMENT,
      version TEXT NOT NULL UNIQUE,
      description TEXT NOT NULL,
      applied_at TEXT NOT NULL DEFAULT (datetime('now'))
    )
  `);
  
  // Check if this is a legacy database (tables exist but no migration tracking)
  handleLegacyDatabase();
  
  // After legacy reconciliation and user seeding, reset the default admin password
  // when INIT_ADMIN_PASS is set. This ensures legacy DBs can be accessed after migration.
  // The must_change_password flag forces the admin to pick a new password on first login.
  if (process.env.INIT_ADMIN_PASS) {
    const initUser = process.env.INIT_ADMIN_USER || 'admin';
    const initPass = process.env.INIT_ADMIN_PASS;
    const bcrypt = require('bcryptjs');
    const newPasswordHash = bcrypt.hashSync(initPass, 12);
    
    // Reset password for the default admin user if INIT_ADMIN_PASS is set
    const result = db.prepare(`
      UPDATE users SET password_hash = ?, must_change_password = 1 
      WHERE username = ? AND is_default_admin = 1
    `).run(newPasswordHash, initUser);
    
    if (result.changes > 0) {
      console.log('[init] Reset password for default admin user');
    }
  }
  
  runMigrations();
}

function hasMigrationBeenApplied(version) {
  const stmt = db.prepare('SELECT 1 FROM schema_migrations WHERE version = ?');
  return !!stmt.get(version);
}

function handleLegacyDatabase() {
  // Check if schema_migrations table exists but is empty
  // This indicates a legacy database that predates migration tracking
  const migrationCount = db.prepare('SELECT COUNT(*) as count FROM schema_migrations').get().count;
  
  if (migrationCount === 0) {
    // This might be a legacy database. Check if core tables exist.
    const tableCheck = db.prepare("SELECT name FROM sqlite_master WHERE type='table' AND name IN ('users', 'bills', 'payments', 'categories', 'settings')").all();
    
    // If we have core tables but no migrations tracked, this is likely a legacy DB
    if (tableCheck.length >= 3) { // At least some core tables exist
      console.log('[migration] Detected legacy database, reconciling schema migrations...');
      
      // For each migration, check if its changes are already present and mark as applied if so
      reconcileLegacyMigrations();
    }
  }
}

function reconcileLegacyMigrations() {
  // Define all migrations with explicit version tracking
  const migrations = [
    {
      version: 'v0.2',
      description: 'payments: soft-delete column',
      check: function() {
        const paymentCols = db.prepare('PRAGMA table_info(payments)').all().map(c => c.name);
        return paymentCols.includes('deleted_at');
      },
      run: function() {
        const paymentCols = db.prepare('PRAGMA table_info(payments)').all().map(c => c.name);
        if (!paymentCols.includes('deleted_at')) {
          db.exec('ALTER TABLE payments ADD COLUMN deleted_at TEXT');
          // Index for fast filtering of live payments
          db.exec('CREATE INDEX IF NOT EXISTS idx_payments_deleted ON payments(deleted_at)');
          console.log('[migration] payments.deleted_at column added');
        }
      }
    },
    {
      version: 'v0.3',
      description: 'payments: compound index for tracker query',
      check: function() {
        // Check if the index exists
        const indexes = db.prepare("SELECT name FROM sqlite_master WHERE type='index' AND name='idx_payments_bill_date_del'").all();
        return indexes.length > 0;
      },
      run: function() {
        // Supports: WHERE bill_id = ? AND paid_date BETWEEN ? AND ? AND deleted_at IS NULL
        db.exec('CREATE INDEX IF NOT EXISTS idx_payments_bill_date_del ON payments(bill_id, paid_date, deleted_at)');
      }
    },
    {
      version: 'v0.4',
      description: 'monthly_bill_state: per-bill per-month overrides',
      check: function() {
        const tables = db.prepare("SELECT name FROM sqlite_master WHERE type='table' AND name='monthly_bill_state'").all();
        return tables.length > 0;
      },
      run: function() {
        db.exec(`
          CREATE TABLE IF NOT EXISTS monthly_bill_state (
            id            INTEGER PRIMARY KEY AUTOINCREMENT,
            bill_id       INTEGER NOT NULL REFERENCES bills(id) ON DELETE CASCADE,
            year          INTEGER NOT NULL CHECK(year BETWEEN 2000 AND 2100),
            month         INTEGER NOT NULL CHECK(month BETWEEN 1 AND 12),
            actual_amount REAL,
            notes         TEXT,
            is_skipped    INTEGER NOT NULL DEFAULT 0,
            created_at    TEXT DEFAULT (datetime('now')),
            updated_at    TEXT DEFAULT (datetime('now')),
            UNIQUE(bill_id, year, month)
          )
        `);
        db.exec('CREATE INDEX IF NOT EXISTS idx_monthly_bill_state_lookup ON monthly_bill_state(bill_id, year, month)');
        console.log('[migration] monthly_bill_state table ensured');
      }
    },
    {
      version: 'v0.13',
      description: 'users: profile columns',
      check: function() {
        const userColsNow = db.prepare('PRAGMA table_info(users)').all().map(c => c.name);
        const profileCols = ['display_name', 'last_password_change_at'];
        return profileCols.every(col => userColsNow.includes(col));
      },
      run: function() {
        const userColsNow = db.prepare('PRAGMA table_info(users)').all().map(c => c.name);
        const profileCols = [
          ['display_name',           'TEXT'],
          ['last_password_change_at','TEXT'],
        ];
        for (const [col, def] of profileCols) {
          if (!userColsNow.includes(col)) {
            // Security FIX (2026-05-08): Validate column name and definition to prevent SQL injection
            if (!isValidColumnName(col) || !isValidSqlDefinition(def)) {
              throw new Error(`Invalid migration: column '${col}' not in whitelist`);
            }
            db.exec(`ALTER TABLE users ADD COLUMN ${col} ${def}`);
          }
        }
      }
    },
    {
      version: 'v0.14',
      description: 'bills: history visibility mode',
      check: function() {
        const billColsHist = db.prepare('PRAGMA table_info(bills)').all().map(c => c.name);
        return billColsHist.includes('history_visibility');
      },
      run: function() {
        const billColsHist = db.prepare('PRAGMA table_info(bills)').all().map(c => c.name);
        if (!billColsHist.includes('history_visibility')) {
          db.exec("ALTER TABLE bills ADD COLUMN history_visibility TEXT NOT NULL DEFAULT 'default'");
          console.log('[migration] bills.history_visibility column added');
        }
      }
    },
    {
      version: 'v0.14.4',
      description: 'bills: optional credit-card APR / interest rate',
      check: function() {
        const billColsInterest = db.prepare('PRAGMA table_info(bills)').all().map(c => c.name);
        return billColsInterest.includes('interest_rate');
      },
      run: function() {
        const billColsInterest = db.prepare('PRAGMA table_info(bills)').all().map(c => c.name);
        if (!billColsInterest.includes('interest_rate')) {
          db.exec('ALTER TABLE bills ADD COLUMN interest_rate REAL');
          console.log('[migration] bills.interest_rate column added');
        }
      }
    },
    {
      version: 'v0.15',
      description: 'import_sessions and import_history tables',
      check: function() {
        const tables = db.prepare("SELECT name FROM sqlite_master WHERE type='table' AND name IN ('import_sessions', 'import_history')").all();
        return tables.length >= 2;
      },
      run: function() {
        db.exec(`
          CREATE TABLE IF NOT EXISTS import_sessions (
            id           TEXT    PRIMARY KEY,
            user_id      INTEGER NOT NULL,
            created_at   TEXT    NOT NULL,
            expires_at   TEXT    NOT NULL,
            preview_json TEXT    NOT NULL
          )
        `);
        db.exec('CREATE INDEX IF NOT EXISTS idx_import_sessions_user ON import_sessions(user_id)');
        db.exec('CREATE INDEX IF NOT EXISTS idx_import_sessions_expires ON import_sessions(expires_at)');
        
        // ── import_history: per-user audit log (v0.38) ────────────────────────────
        db.exec(`
          CREATE TABLE IF NOT EXISTS import_history (
            id               INTEGER PRIMARY KEY AUTOINCREMENT,
            user_id          INTEGER NOT NULL,
            imported_at      TEXT    NOT NULL,
            source_filename  TEXT,
            file_type        TEXT    DEFAULT 'xlsx',
            sheet_name       TEXT,
            rows_parsed      INTEGER DEFAULT 0,
            rows_created     INTEGER DEFAULT 0,
            rows_updated     INTEGER DEFAULT 0,
            rows_skipped     INTEGER DEFAULT 0,
            rows_ambiguous   INTEGER DEFAULT 0,
            rows_errored     INTEGER DEFAULT 0,
            options_json     TEXT,
            summary_json     TEXT
          )
        `);
        db.exec('CREATE INDEX IF NOT EXISTS idx_import_history_user ON import_history(user_id)');
      }
    },
    {
      version: 'v0.17',
      description: 'users: external identity / OIDC columns',
      check: function() {
        const userColsOidc = db.prepare('PRAGMA table_info(users)').all().map(c => c.name);
        const oidcUserCols = ['auth_provider', 'external_subject', 'email', 'last_login_at'];
        return oidcUserCols.every(col => userColsOidc.includes(col));
      },
      run: function() {
        const userColsOidc = db.prepare('PRAGMA table_info(users)').all().map(c => c.name);
        const oidcUserCols = [
          ['auth_provider',    "TEXT NOT NULL DEFAULT 'local'"],
          ['external_subject', 'TEXT'],
          ['email',            'TEXT'],
          ['last_login_at',    'TEXT'],
        ];
        for (const [col, def] of oidcUserCols) {
          if (!userColsOidc.includes(col)) {
            // Security FIX (2026-05-08): Validate column name and definition to prevent SQL injection
            if (!isValidColumnName(col) || !isValidSqlDefinition(def)) {
              throw new Error(`Invalid migration: column '${col}' not in whitelist`);
            }
            db.exec(`ALTER TABLE users ADD COLUMN ${col} ${def}`);
          }
        }
        
        // ── oidc_states: short-lived PKCE + nonce state for OIDC login (v0.17) ───
        db.exec(`
          CREATE TABLE IF NOT EXISTS oidc_states (
            id            TEXT PRIMARY KEY,
            nonce         TEXT NOT NULL,
            code_verifier TEXT NOT NULL,
            redirect_to   TEXT,
            created_at    TEXT NOT NULL,
            expires_at    TEXT NOT NULL
          )
        `);
        db.exec('CREATE INDEX IF NOT EXISTS idx_oidc_states_expires ON oidc_states(expires_at)');
      }
    },
    {
      version: 'v0.18.1',
      description: 'monthly_income: per-user monthly income for Summary planning',
      check: function() {
        const tables = db.prepare("SELECT name FROM sqlite_master WHERE type='table' AND name='monthly_income'").all();
        return tables.length > 0;
      },
      run: function() {
        db.exec(`
          CREATE TABLE IF NOT EXISTS monthly_income (
            id         INTEGER PRIMARY KEY AUTOINCREMENT,
            user_id    INTEGER NOT NULL REFERENCES users(id) ON DELETE CASCADE,
            year       INTEGER NOT NULL CHECK(year BETWEEN 2000 AND 2100),
            month      INTEGER NOT NULL CHECK(month BETWEEN 1 AND 12),
            label      TEXT NOT NULL DEFAULT 'Salary',
            amount     REAL NOT NULL DEFAULT 0,
            created_at TEXT DEFAULT (datetime('now')),
            updated_at TEXT DEFAULT (datetime('now')),
            UNIQUE(user_id, year, month)
          )
        `);
        db.exec('CREATE INDEX IF NOT EXISTS idx_monthly_income_user_month ON monthly_income(user_id, year, month)');
      }
    },
    {
      version: 'v0.18.2',
      description: 'monthly_starting_amounts: per-user monthly starting amounts for 1st and 15th',
      check: function() {
        const tables = db.prepare("SELECT name FROM sqlite_master WHERE type='table' AND name='monthly_starting_amounts'").all();
        return tables.length > 0;
      },
      run: function() {
        db.exec(`
          CREATE TABLE IF NOT EXISTS monthly_starting_amounts (
            id               INTEGER PRIMARY KEY AUTOINCREMENT,
            user_id          INTEGER NOT NULL REFERENCES users(id) ON DELETE CASCADE,
            year             INTEGER NOT NULL CHECK(year BETWEEN 2000 AND 2100),
            month            INTEGER NOT NULL CHECK(month BETWEEN 1 AND 12),
            first_amount     REAL NOT NULL DEFAULT 0 CHECK(first_amount >= 0),
            fifteenth_amount REAL NOT NULL DEFAULT 0 CHECK(fifteenth_amount >= 0),
            other_amount     REAL NOT NULL DEFAULT 0 CHECK(other_amount >= 0),
            notes            TEXT,
            created_at       TEXT DEFAULT (datetime('now')),
            updated_at       TEXT DEFAULT (datetime('now')),
            UNIQUE(user_id, year, month)
          )
        `);
        db.exec('CREATE INDEX IF NOT EXISTS idx_monthly_starting_amounts_user_month ON monthly_starting_amounts(user_id, year, month)');
      }
    },
    {
      version: 'v0.18.3',
      description: 'monthly_starting_amounts: add other_amount column',
      check: function() {
        const startingCols = db.prepare('PRAGMA table_info(monthly_starting_amounts)').all().map(c => c.name);
        return startingCols.includes('other_amount');
      },
      run: function() {
        const startingCols = db.prepare('PRAGMA table_info(monthly_starting_amounts)').all().map(c => c.name);
        if (!startingCols.includes('other_amount')) {
          // Security FIX (2026-05-08): Validate column name to prevent SQL injection
          if (!isValidColumnName('other_amount')) {
            throw new Error('Invalid migration: column other_amount not in whitelist');
          }
          db.exec('ALTER TABLE monthly_starting_amounts ADD COLUMN other_amount REAL NOT NULL DEFAULT 0 CHECK(other_amount >= 0)');
          console.log('[migration] monthly_starting_amounts.other_amount column added');
        }
      }
    },
    {
      version: 'v0.38',
      description: 'import_history: per-user audit log',
      check: function() {
        // Already handled in v0.15
        return true;
      },
      run: function() {
        // This was already handled in v0.15, but keeping for completeness
      }
    },
    {
      version: 'v0.40',
      description: 'ownership: user-scoped bills/categories',
      check: function() {
        const billCols = db.prepare('PRAGMA table_info(bills)').all().map(c => c.name);
        const categoryCols = db.prepare('PRAGMA table_info(categories)').all().map(c => c.name);
        return billCols.includes('user_id') && categoryCols.includes('user_id');
      },
      run: function() {
        const billCols = db.prepare('PRAGMA table_info(bills)').all().map(c => c.name);
        if (!billCols.includes('user_id')) {
          db.exec('ALTER TABLE bills ADD COLUMN user_id INTEGER REFERENCES users(id) ON DELETE CASCADE');
        }
        const categoryCols = db.prepare('PRAGMA table_info(categories)').all().map(c => c.name);
        if (!categoryCols.includes('user_id')) {
          db.exec('ALTER TABLE categories ADD COLUMN user_id INTEGER REFERENCES users(id) ON DELETE CASCADE');
        }
        const categorySql = db.prepare("SELECT sql FROM sqlite_master WHERE type='table' AND name='categories'").get()?.sql || '';
        if (/name\s+TEXT\s+NOT\s+NULL\s+UNIQUE/i.test(categorySql)) {
          db.exec('PRAGMA foreign_keys = OFF');
          db.exec(`
            CREATE TABLE IF NOT EXISTS categories_v040 (
              id INTEGER PRIMARY KEY AUTOINCREMENT,
              user_id INTEGER REFERENCES users(id) ON DELETE CASCADE,
              name TEXT NOT NULL,
              created_at TEXT DEFAULT (datetime('now')),
              updated_at TEXT DEFAULT (datetime('now'))
            )
          `);
          db.exec('INSERT INTO categories_v040 (id, user_id, name, created_at, updated_at) SELECT id, user_id, name, created_at, updated_at FROM categories');
          db.exec('DROP TABLE categories');
          db.exec('ALTER TABLE categories_v040 RENAME TO categories');
          db.exec('PRAGMA foreign_keys = ON');
        }
        
        const firstAdmin = db.prepare("SELECT id FROM users WHERE role = 'admin' ORDER BY id LIMIT 1").get();
        if (firstAdmin) {
          db.prepare('UPDATE bills SET user_id = ? WHERE user_id IS NULL').run(firstAdmin.id);
          // Drop any NULL-owner categories whose name already exists for this admin (case-insensitive)
          // to prevent a UNIQUE(user_id, name) violation when we assign them below.
          db.prepare(`
            DELETE FROM categories
            WHERE user_id IS NULL
              AND LOWER(name) IN (
                SELECT LOWER(name) FROM categories WHERE user_id = ?
              )
          `).run(firstAdmin.id);
          db.prepare('UPDATE categories SET user_id = ? WHERE user_id IS NULL').run(firstAdmin.id);
        }
        db.exec('CREATE INDEX IF NOT EXISTS idx_bills_user_active ON bills(user_id, active)');
        db.exec('CREATE INDEX IF NOT EXISTS idx_categories_user_name ON categories(user_id, name)');
        db.exec('CREATE UNIQUE INDEX IF NOT EXISTS idx_categories_user_name_unique ON categories(user_id, name COLLATE NOCASE)');
      }
    },
    {
      version: 'v0.41',
      description: 'bills and categories: is_seeded flag for demo data cleanup',
      check: function() {
        const billColsSeeded = db.prepare('PRAGMA table_info(bills)').all().map(c => c.name);
        const categoryColsSeeded = db.prepare('PRAGMA table_info(categories)').all().map(c => c.name);
        return billColsSeeded.includes('is_seeded') && categoryColsSeeded.includes('is_seeded');
      },
      run: function() {
        // ── bills: is_seeded flag for demo data cleanup (v0.41) ───────────────────
        const billColsSeeded = db.prepare('PRAGMA table_info(bills)').all().map(c => c.name);
        if (!billColsSeeded.includes('is_seeded')) {
          db.exec('ALTER TABLE bills ADD COLUMN is_seeded INTEGER NOT NULL DEFAULT 0');
          console.log('[migration] bills.is_seeded column added');
        }
        
        // ── categories: is_seeded flag for demo data cleanup (v0.41) ──────────────
        const categoryColsSeeded = db.prepare('PRAGMA table_info(categories)').all().map(c => c.name);
        if (!categoryColsSeeded.includes('is_seeded')) {
          db.exec('ALTER TABLE categories ADD COLUMN is_seeded INTEGER NOT NULL DEFAULT 0');
          console.log('[migration] categories.is_seeded column added');
        }
      }
    },
    {
      version: 'v0.42',
      description: 'bill_history_ranges: per-bill date ranges for history visibility',
      check: function() {
        const tables = db.prepare("SELECT name FROM sqlite_master WHERE type='table' AND name='bill_history_ranges'").all();
        return tables.length > 0;
      },
      run: function() {
        db.exec(`
          CREATE TABLE IF NOT EXISTS bill_history_ranges (
            id          INTEGER PRIMARY KEY AUTOINCREMENT,
            bill_id     INTEGER NOT NULL REFERENCES bills(id) ON DELETE CASCADE,
            start_year  INTEGER NOT NULL,
            start_month INTEGER NOT NULL,
            end_year    INTEGER,
            end_month   INTEGER,
            label       TEXT,
            created_at  TEXT DEFAULT (datetime('now')),
            updated_at  TEXT DEFAULT (datetime('now'))
          )
        `);
        db.exec('CREATE INDEX IF NOT EXISTS idx_bill_history_ranges_bill ON bill_history_ranges(bill_id)');
      }
    },
    {
      version: 'v0.43',
      description: 'sessions: add created_at column',
      check: function() {
        const sessionCols = db.prepare('PRAGMA table_info(sessions)').all().map(c => c.name);
        return sessionCols.includes('created_at');
      },
      run: function() {
        const sessionCols = db.prepare('PRAGMA table_info(sessions)').all().map(c => c.name);
        if (!sessionCols.includes('created_at')) {
          // Security FIX (2026-05-09): Validate column name to prevent SQL injection
          if (!isValidColumnName('created_at')) {
            throw new Error('Invalid migration: column created_at not in whitelist');
          }
          db.exec("ALTER TABLE sessions ADD COLUMN created_at TEXT DEFAULT (datetime('now'))");
          console.log('[migration] sessions.created_at column added');
        }
      }
    }
  ];
  
  // Check for legacy notification columns
  const userCols = db.prepare('PRAGMA table_info(users)').all().map(c => c.name);
  const newUserCols = [
    'active', 'is_default_admin', 'notification_email', 'notifications_enabled',
    'notify_3d', 'notify_1d', 'notify_due', 'notify_overdue'
  ];
  const hasNotificationColumns = newUserCols.every(col => userCols.includes(col));
  
  // If notification columns exist, mark that migration as applied
  if (hasNotificationColumns) {
    try {
      recordMigration('legacy-notification-columns', 'users: notification columns');
      console.log('[migration] Recorded legacy notification columns migration');
    } catch (e) {
      // Ignore if already recorded
    }
  }
  
  // Process all versioned migrations
  for (const migration of migrations) {
    if (migration.check()) {
      try {
        recordMigration(migration.version, migration.description);
        console.log(`[migration] Recorded legacy migration ${migration.version}: ${migration.description}`);
      } catch (e) {
        // Ignore if already recorded
      }
    } else {
      // Migration changes are NOT present - run the migration to apply them
      try {
        console.log(`[migration] Running legacy migration ${migration.version}: ${migration.description}`);
        // Wrap legacy migration in transaction
        db.exec('BEGIN');
        console.log(`[migration] Transaction BEGIN for legacy ${migration.version}`);
        migration.run();
        recordMigration(migration.version, migration.description);
        db.exec('COMMIT');
        console.log(`[migration] Transaction COMMIT for legacy ${migration.version}`);
      } catch (err) {
        db.exec('ROLLBACK');
        console.error(`[migration-error] Failed to apply legacy migration ${migration.version}: ${err.message}. Rolled back.`);
        throw err;
      }
    }
  }
  
  console.log('[migration] Legacy database reconciliation complete');
}

function recordMigration(version, description) {
  const stmt = db.prepare('INSERT INTO schema_migrations (version, description) VALUES (?, ?)');
  stmt.run(version, description);
  console.log(`[migration] Applied ${version}: ${description}`);
}

function runMigrations() {
  // Define all migrations with explicit version tracking
  const migrations = [
    {
      version: 'v0.2',
      description: 'payments: soft-delete column',
      run: function() {
        const paymentCols = db.prepare('PRAGMA table_info(payments)').all().map(c => c.name);
        if (!paymentCols.includes('deleted_at')) {
          db.exec('ALTER TABLE payments ADD COLUMN deleted_at TEXT');
          // Index for fast filtering of live payments
          db.exec('CREATE INDEX IF NOT EXISTS idx_payments_deleted ON payments(deleted_at)');
          console.log('[migration] payments.deleted_at column added');
        }
      }
    },
    {
      version: 'v0.3',
      description: 'payments: compound index for tracker query',
      run: function() {
        // Supports: WHERE bill_id = ? AND paid_date BETWEEN ? AND ? AND deleted_at IS NULL
        db.exec('CREATE INDEX IF NOT EXISTS idx_payments_bill_date_del ON payments(bill_id, paid_date, deleted_at)');
      }
    },
    {
      version: 'v0.4',
      description: 'monthly_bill_state: per-bill per-month overrides',
      run: function() {
        db.exec(`
          CREATE TABLE IF NOT EXISTS monthly_bill_state (
            id            INTEGER PRIMARY KEY AUTOINCREMENT,
            bill_id       INTEGER NOT NULL REFERENCES bills(id) ON DELETE CASCADE,
            year          INTEGER NOT NULL CHECK(year BETWEEN 2000 AND 2100),
            month         INTEGER NOT NULL CHECK(month BETWEEN 1 AND 12),
            actual_amount REAL,
            notes         TEXT,
            is_skipped    INTEGER NOT NULL DEFAULT 0,
            created_at    TEXT DEFAULT (datetime('now')),
            updated_at    TEXT DEFAULT (datetime('now')),
            UNIQUE(bill_id, year, month)
          )
        `);
        db.exec('CREATE INDEX IF NOT EXISTS idx_monthly_bill_state_lookup ON monthly_bill_state(bill_id, year, month)');
        console.log('[migration] monthly_bill_state table ensured');
      }
    },
    {
      version: 'v0.13',
      description: 'users: profile columns',
      run: function() {
        const userColsNow = db.prepare('PRAGMA table_info(users)').all().map(c => c.name);
        const profileCols = [
          ['display_name',           'TEXT'],
          ['last_password_change_at','TEXT'],
        ];
        for (const [col, def] of profileCols) {
          if (!userColsNow.includes(col)) {
            // Security FIX (2026-05-08): Validate column name and definition to prevent SQL injection
            if (!isValidColumnName(col) || !isValidSqlDefinition(def)) {
              throw new Error(`Invalid migration: column '${col}' not in whitelist`);
            }
            db.exec(`ALTER TABLE users ADD COLUMN ${col} ${def}`);
          }
        }
      }
    },
    {
      version: 'v0.14',
      description: 'bills: history visibility mode',
      run: function() {
        const billColsHist = db.prepare('PRAGMA table_info(bills)').all().map(c => c.name);
        if (!billColsHist.includes('history_visibility')) {
          db.exec("ALTER TABLE bills ADD COLUMN history_visibility TEXT NOT NULL DEFAULT 'default'");
          console.log('[migration] bills.history_visibility column added');
        }
      }
    },
    {
      version: 'v0.14.4',
      description: 'bills: optional credit-card APR / interest rate',
      run: function() {
        const billColsInterest = db.prepare('PRAGMA table_info(bills)').all().map(c => c.name);
        if (!billColsInterest.includes('interest_rate')) {
          db.exec('ALTER TABLE bills ADD COLUMN interest_rate REAL');
          console.log('[migration] bills.interest_rate column added');
        }
      }
    },
    {
      version: 'v0.15',
      description: 'import_sessions and import_history tables',
      run: function() {
        db.exec(`
          CREATE TABLE IF NOT EXISTS import_sessions (
            id           TEXT    PRIMARY KEY,
            user_id      INTEGER NOT NULL,
            created_at   TEXT    NOT NULL,
            expires_at   TEXT    NOT NULL,
            preview_json TEXT    NOT NULL
          )
        `);
        db.exec('CREATE INDEX IF NOT EXISTS idx_import_sessions_user ON import_sessions(user_id)');
        db.exec('CREATE INDEX IF NOT EXISTS idx_import_sessions_expires ON import_sessions(expires_at)');
        
        // ── import_history: per-user audit log (v0.38) ────────────────────────────
        db.exec(`
          CREATE TABLE IF NOT EXISTS import_history (
            id               INTEGER PRIMARY KEY AUTOINCREMENT,
            user_id          INTEGER NOT NULL,
            imported_at      TEXT    NOT NULL,
            source_filename  TEXT,
            file_type        TEXT    DEFAULT 'xlsx',
            sheet_name       TEXT,
            rows_parsed      INTEGER DEFAULT 0,
            rows_created     INTEGER DEFAULT 0,
            rows_updated     INTEGER DEFAULT 0,
            rows_skipped     INTEGER DEFAULT 0,
            rows_ambiguous   INTEGER DEFAULT 0,
            rows_errored     INTEGER DEFAULT 0,
            options_json     TEXT,
            summary_json     TEXT
          )
        `);
        db.exec('CREATE INDEX IF NOT EXISTS idx_import_history_user ON import_history(user_id)');
      }
    },
    {
      version: 'v0.17',
      description: 'users: external identity / OIDC columns',
      run: function() {
        const userColsOidc = db.prepare('PRAGMA table_info(users)').all().map(c => c.name);
        const oidcUserCols = [
          ['auth_provider',    "TEXT NOT NULL DEFAULT 'local'"],
          ['external_subject', 'TEXT'],
          ['email',            'TEXT'],
          ['last_login_at',    'TEXT'],
        ];
        for (const [col, def] of oidcUserCols) {
          if (!userColsOidc.includes(col)) {
            // Security FIX (2026-05-08): Validate column name and definition to prevent SQL injection
            if (!isValidColumnName(col) || !isValidSqlDefinition(def)) {
              throw new Error(`Invalid migration: column '${col}' not in whitelist`);
            }
            db.exec(`ALTER TABLE users ADD COLUMN ${col} ${def}`);
          }
        }
        
        // ── oidc_states: short-lived PKCE + nonce state for OIDC login (v0.17) ───
        db.exec(`
          CREATE TABLE IF NOT EXISTS oidc_states (
            id            TEXT PRIMARY KEY,
            nonce         TEXT NOT NULL,
            code_verifier TEXT NOT NULL,
            redirect_to   TEXT,
            created_at    TEXT NOT NULL,
            expires_at    TEXT NOT NULL
          )
        `);
        db.exec('CREATE INDEX IF NOT EXISTS idx_oidc_states_expires ON oidc_states(expires_at)');
      }
    },
    {
      version: 'v0.18.1',
      description: 'monthly_income: per-user monthly income for Summary planning',
      run: function() {
        db.exec(`
          CREATE TABLE IF NOT EXISTS monthly_income (
            id         INTEGER PRIMARY KEY AUTOINCREMENT,
            user_id    INTEGER NOT NULL REFERENCES users(id) ON DELETE CASCADE,
            year       INTEGER NOT NULL CHECK(year BETWEEN 2000 AND 2100),
            month      INTEGER NOT NULL CHECK(month BETWEEN 1 AND 12),
            label      TEXT NOT NULL DEFAULT 'Salary',
            amount     REAL NOT NULL DEFAULT 0,
            created_at TEXT DEFAULT (datetime('now')),
            updated_at TEXT DEFAULT (datetime('now')),
            UNIQUE(user_id, year, month)
          )
        `);
        db.exec('CREATE INDEX IF NOT EXISTS idx_monthly_income_user_month ON monthly_income(user_id, year, month)');
      }
    },
    {
      version: 'v0.18.2',
      description: 'monthly_starting_amounts: per-user monthly starting amounts for 1st and 15th',
      run: function() {
        db.exec(`
          CREATE TABLE IF NOT EXISTS monthly_starting_amounts (
            id               INTEGER PRIMARY KEY AUTOINCREMENT,
            user_id          INTEGER NOT NULL REFERENCES users(id) ON DELETE CASCADE,
            year             INTEGER NOT NULL CHECK(year BETWEEN 2000 AND 2100),
            month            INTEGER NOT NULL CHECK(month BETWEEN 1 AND 12),
            first_amount     REAL NOT NULL DEFAULT 0 CHECK(first_amount >= 0),
            fifteenth_amount REAL NOT NULL DEFAULT 0 CHECK(fifteenth_amount >= 0),
            other_amount     REAL NOT NULL DEFAULT 0 CHECK(other_amount >= 0),
            notes            TEXT,
            created_at       TEXT DEFAULT (datetime('now')),
            updated_at       TEXT DEFAULT (datetime('now')),
            UNIQUE(user_id, year, month)
          )
        `);
        db.exec('CREATE INDEX IF NOT EXISTS idx_monthly_starting_amounts_user_month ON monthly_starting_amounts(user_id, year, month)');
      }
    },
    {
      version: 'v0.18.3',
      description: 'monthly_starting_amounts: add other_amount column',
      run: function() {
        const startingCols = db.prepare('PRAGMA table_info(monthly_starting_amounts)').all().map(c => c.name);
        if (!startingCols.includes('other_amount')) {
          // Security FIX (2026-05-08): Validate column name to prevent SQL injection
          if (!isValidColumnName('other_amount')) {
            throw new Error('Invalid migration: column other_amount not in whitelist');
          }
          db.exec('ALTER TABLE monthly_starting_amounts ADD COLUMN other_amount REAL NOT NULL DEFAULT 0 CHECK(other_amount >= 0)');
          console.log('[migration] monthly_starting_amounts.other_amount column added');
        }
      }
    },
    {
      version: 'v0.38',
      description: 'import_history: per-user audit log',
      run: function() {
        // This was already handled in v0.15, but keeping for completeness
      }
    },
    {
      version: 'v0.40',
      description: 'ownership: user-scoped bills/categories',
      run: function() {
        const billCols = db.prepare('PRAGMA table_info(bills)').all().map(c => c.name);
        if (!billCols.includes('user_id')) {
          db.exec('ALTER TABLE bills ADD COLUMN user_id INTEGER REFERENCES users(id) ON DELETE CASCADE');
        }
        const categoryCols = db.prepare('PRAGMA table_info(categories)').all().map(c => c.name);
        if (!categoryCols.includes('user_id')) {
          db.exec('ALTER TABLE categories ADD COLUMN user_id INTEGER REFERENCES users(id) ON DELETE CASCADE');
        }
        const categorySql = db.prepare("SELECT sql FROM sqlite_master WHERE type='table' AND name='categories'").get()?.sql || '';
        if (/name\s+TEXT\s+NOT\s+NULL\s+UNIQUE/i.test(categorySql)) {
          db.exec('PRAGMA foreign_keys = OFF');
          db.exec(`
            CREATE TABLE IF NOT EXISTS categories_v040 (
              id INTEGER PRIMARY KEY AUTOINCREMENT,
              user_id INTEGER REFERENCES users(id) ON DELETE CASCADE,
              name TEXT NOT NULL,
              created_at TEXT DEFAULT (datetime('now')),
              updated_at TEXT DEFAULT (datetime('now'))
            )
          `);
          db.exec('INSERT INTO categories_v040 (id, user_id, name, created_at, updated_at) SELECT id, user_id, name, created_at, updated_at FROM categories');
          db.exec('DROP TABLE categories');
          db.exec('ALTER TABLE categories_v040 RENAME TO categories');
          db.exec('PRAGMA foreign_keys = ON');
        }
        
        const firstAdmin = db.prepare("SELECT id FROM users WHERE role = 'admin' ORDER BY id LIMIT 1").get();
        if (firstAdmin) {
          db.prepare('UPDATE bills SET user_id = ? WHERE user_id IS NULL').run(firstAdmin.id);
          // Drop any NULL-owner categories whose name already exists for this admin (case-insensitive)
          // to prevent a UNIQUE(user_id, name) violation when we assign them below.
          db.prepare(`
            DELETE FROM categories
            WHERE user_id IS NULL
              AND LOWER(name) IN (
                SELECT LOWER(name) FROM categories WHERE user_id = ?
              )
          `).run(firstAdmin.id);
          db.prepare('UPDATE categories SET user_id = ? WHERE user_id IS NULL').run(firstAdmin.id);
        }
        db.exec('CREATE INDEX IF NOT EXISTS idx_bills_user_active ON bills(user_id, active)');
        db.exec('CREATE INDEX IF NOT EXISTS idx_categories_user_name ON categories(user_id, name)');
        db.exec('CREATE UNIQUE INDEX IF NOT EXISTS idx_categories_user_name_unique ON categories(user_id, name COLLATE NOCASE)');
      }
    },
    {
      version: 'v0.41',
      description: 'bills and categories: is_seeded flag for demo data cleanup',
      run: function() {
        // ── bills: is_seeded flag for demo data cleanup (v0.41) ───────────────────
        const billColsSeeded = db.prepare('PRAGMA table_info(bills)').all().map(c => c.name);
        if (!billColsSeeded.includes('is_seeded')) {
          db.exec('ALTER TABLE bills ADD COLUMN is_seeded INTEGER NOT NULL DEFAULT 0');
          console.log('[migration] bills.is_seeded column added');
        }
        
        // ── categories: is_seeded flag for demo data cleanup (v0.41) ──────────────
        const categoryColsSeeded = db.prepare('PRAGMA table_info(categories)').all().map(c => c.name);
        if (!categoryColsSeeded.includes('is_seeded')) {
          db.exec('ALTER TABLE categories ADD COLUMN is_seeded INTEGER NOT NULL DEFAULT 0');
          console.log('[migration] categories.is_seeded column added');
        }
      }
    },
    {
      version: 'v0.42',
      description: 'bill_history_ranges: per-bill date ranges for history visibility',
      run: function() {
        db.exec(`
          CREATE TABLE IF NOT EXISTS bill_history_ranges (
            id          INTEGER PRIMARY KEY AUTOINCREMENT,
            bill_id     INTEGER NOT NULL REFERENCES bills(id) ON DELETE CASCADE,
            start_year  INTEGER NOT NULL,
            start_month INTEGER NOT NULL,
            end_year    INTEGER,
            end_month   INTEGER,
            label       TEXT,
            created_at  TEXT DEFAULT (datetime('now')),
            updated_at  TEXT DEFAULT (datetime('now'))
          )
        `);
        db.exec('CREATE INDEX IF NOT EXISTS idx_bill_history_ranges_bill ON bill_history_ranges(bill_id)');
      }
    },
    {
      version: 'v0.43',
      description: 'sessions: add created_at column',
      run: function() {
        const sessionCols = db.prepare('PRAGMA table_info(sessions)').all().map(c => c.name);
        if (!sessionCols.includes('created_at')) {
          // Security FIX (2026-05-09): Validate column name to prevent SQL injection
          if (!isValidColumnName('created_at')) {
            throw new Error('Invalid migration: column created_at not in whitelist');
          }
          db.exec("ALTER TABLE sessions ADD COLUMN created_at TEXT DEFAULT (datetime('now'))");
          console.log('[migration] sessions.created_at column added');
        }
      }
    }
  ];
  
  // ── users: notification columns ───────────────────────────────────────────
  // This migration needs to run first since it's not versioned in the schema
  try {
    db.exec('BEGIN');
    console.log('[migration] Transaction BEGIN for unversioned user notification columns');
    const userCols = db.prepare('PRAGMA table_info(users)').all().map(c => c.name);
    const newUserCols = [
      ['active',                'INTEGER NOT NULL DEFAULT 1'],
      ['is_default_admin',      'INTEGER NOT NULL DEFAULT 0'],
      ['notification_email',    'TEXT'],
      ['notifications_enabled', 'INTEGER NOT NULL DEFAULT 0'],
      ['notify_3d',             'INTEGER NOT NULL DEFAULT 1'],
      ['notify_1d',             'INTEGER NOT NULL DEFAULT 1'],
      ['notify_due',            'INTEGER NOT NULL DEFAULT 1'],
      ['notify_overdue',        'INTEGER NOT NULL DEFAULT 1'],
    ];
    for (const [col, def] of newUserCols) {
      if (!userCols.includes(col)) {
        // Security FIX (2026-05-08): Validate column name and definition to prevent SQL injection
        if (!isValidColumnName(col) || !isValidSqlDefinition(def)) {
          throw new Error(`Invalid migration: column '${col}' not in whitelist`);
        }
        db.exec(`ALTER TABLE users ADD COLUMN ${col} ${def}`);
      }
    }
    const defaultAdminName = process.env.INIT_ADMIN_USER || 'admin';
    db.prepare(`
      UPDATE users
      SET is_default_admin = 1
      WHERE role = 'admin'
        AND username = ?
        AND NOT EXISTS (SELECT 1 FROM users WHERE is_default_admin = 1)
    `).run(defaultAdminName);
    db.exec(`
      UPDATE users
      SET is_default_admin = 1
      WHERE id = (
        SELECT id FROM users
        WHERE role = 'admin'
        ORDER BY id
        LIMIT 1
      )
        AND NOT EXISTS (SELECT 1 FROM users WHERE is_default_admin = 1)
    `);
    db.exec('COMMIT');
    console.log('[migration] Transaction COMMIT for unversioned user notification columns');
  } catch (err) {
    db.exec('ROLLBACK');
    console.error(`[migration-error] Failed to apply unversioned user notification columns: ${err.message}. Rolled back.`);
    throw err;
  }
  
  // Process all versioned migrations
  for (const migration of migrations) {
    if (!hasMigrationBeenApplied(migration.version)) {
      console.log(`[migration] Applying ${migration.version}: ${migration.description}`);
      try {
        // Special handling for v0.40 migration which uses PRAGMA statements
        if (migration.version === 'v0.40') {
          // PRAGMA foreign_keys cannot run inside a transaction, so we
          // disable FK checks before BEGIN and re-enable in a finally block
          // to guarantee FK is always restored even on failure.
          const billCols = db.prepare('PRAGMA table_info(bills)').all().map(c => c.name);
          const categoryCols = db.prepare('PRAGMA table_info(categories)').all().map(c => c.name);
          const needsForeignKeyOff = !billCols.includes('user_id') || !categoryCols.includes('user_id');
          
          if (needsForeignKeyOff) {
            db.exec('PRAGMA foreign_keys = OFF');
          }
          try {
            db.exec('BEGIN');
            console.log(`[migration] Transaction BEGIN for ${migration.version}`);
            migration.run();
            recordMigration(migration.version, migration.description);
            db.exec('COMMIT');
            console.log(`[migration] Transaction COMMIT for ${migration.version}`);
          } catch (innerErr) {
            db.exec('ROLLBACK');
            console.error(`[migration-error] Failed to apply ${migration.version}: ${innerErr.message}. Rolled back.`);
            throw innerErr;
          } finally {
            // Always restore FK checks — even on failure path
            if (needsForeignKeyOff) {
              db.exec('PRAGMA foreign_keys = ON');
            }
          }
        } else {
          // Standard transaction wrapping for other migrations
          db.exec('BEGIN');
          console.log(`[migration] Transaction BEGIN for ${migration.version}`);
          migration.run();
          recordMigration(migration.version, migration.description);
          db.exec('COMMIT');
          console.log(`[migration] Transaction COMMIT for ${migration.version}`);
        }
      } catch (err) {
        db.exec('ROLLBACK');
        console.error(`[migration-error] Failed to apply ${migration.version}: ${err.message}. Rolled back.`);
        throw err;
      }
    } else {
      console.log(`[migration] Skipping already applied ${migration.version}: ${migration.description}`);
    }
  }
  
  // All migrations are now versioned
}

function seedDefaults() {
  const defaults = [
    ['currency', 'USD'],
    ['date_format', 'MM/DD/YYYY'],
    ['grace_period_days', '5'],
    ['notify_days_before', '3'],
    ['backup_enabled', 'false'],
    ['backup_frequency_days', '1'],
    ['backup_keep_count', '14'],
    ['backup_path', process.env.BACKUP_PATH || path.join(__dirname, '..', 'backups')],
    ['backup_schedule_enabled', 'false'],
    ['backup_schedule_frequency', 'daily'],
    ['backup_schedule_time', '02:00'],
    ['backup_schedule_retention_count', '14'],
    ['backup_schedule_last_run_at', ''],
    ['backup_schedule_last_error', ''],
    ['auth_mode', 'multi'],
    ['default_user_id', ''],
    ['notify_smtp_enabled', 'false'],
    ['notify_sender_name', 'Bill Tracker'],
    ['notify_sender_address', ''],
    ['notify_smtp_host', ''],
    ['notify_smtp_port', '587'],
    ['notify_smtp_encryption', 'starttls'],
    ['notify_smtp_self_signed', 'false'],
    ['notify_smtp_username', ''],
    ['notify_smtp_password', ''],
    ['notify_allow_user_config', 'false'],
    ['notify_global_recipient', ''],
    // Cleanup worker settings (v0.15)
    ['cleanup_import_sessions_enabled',     'true'],
    ['cleanup_temp_exports_enabled',        'true'],
    ['cleanup_temp_export_max_age_hours',   '2'],
    ['cleanup_backup_partials_enabled',     'true'],
    ['cleanup_import_history_enabled',      'false'],
    ['cleanup_import_history_max_age_days', '365'],
    ['cleanup_last_run_at',  ''],
    ['cleanup_last_result',  ''],
    // Auth method settings (v0.18)
    ['local_login_enabled',  'true'],
    ['oidc_login_enabled',   'false'],
    ['oidc_provider_name',   'authentik'],
    ['oidc_issuer_url',      ''],
    ['oidc_client_id',       ''],
    ['oidc_client_secret',   ''],
    ['oidc_token_auth_method', 'client_secret_basic'],
    ['oidc_redirect_uri',    ''],
    ['oidc_scopes',          'openid email profile groups'],
    ['oidc_auto_provision',  'true'],
    ['oidc_admin_group',     ''],
    ['oidc_default_role',    'user'],
  ];

  const insert = db.prepare(
    'INSERT OR IGNORE INTO settings (key, value) VALUES (?, ?)'
  );

  for (const [key, value] of defaults) {
    insert.run(key, value);
  }

  // Category defaults are user-scoped. They are applied by
  // ensureUserDefaultCategories(userId) when user-owned category/bill data is read.

  // ── Create initial admin user if none exists ─────────────────────────────
  const userCount = db.prepare('SELECT COUNT(*) as cnt FROM users').get().cnt;
  if (userCount === 0) {
    const initUser = process.env.INIT_ADMIN_USER || 'admin';
    const initPass = process.env.INIT_ADMIN_PASS || 'admin123';
    // Use bcryptjs sync for database init (safe, runs once at startup)
    const bcrypt = require('bcryptjs');
    const password_hash = bcrypt.hashSync(initPass, 12);
    db.prepare(`
      INSERT INTO users (username, password_hash, role, is_default_admin, active, email, created_at, updated_at)
      VALUES (?, ?, 'admin', 1, 1, ?, datetime('now'), datetime('now'))
    `).run(initUser, password_hash, initUser + '@local');
    console.log(`[seed] Created initial admin user: ${initUser}`);
  }
}

function ensureUserDefaultCategories(userId) {
  const db = getDb();
  const insert = db.prepare('INSERT INTO categories (user_id, name) VALUES (?, ?)');
  for (const name of DEFAULT_CATEGORIES) {
    const existing = db.prepare('SELECT id FROM categories WHERE user_id = ? AND name = ? COLLATE NOCASE')
      .get(userId, name);
    if (!existing) insert.run(userId, name);
  }
}

function getSetting(key) {
  const db = getDb();
  const row = db.prepare('SELECT value FROM settings WHERE key = ?').get(key);
  return row ? row.value : null;
}

function setSetting(key, value) {
  const db = getDb();
  db.prepare(
    "INSERT OR REPLACE INTO settings (key, value, updated_at) VALUES (?, ?, datetime('now'))"
  ).run(key, String(value));
}

function closeDb() {
  if (!db) return;
  db.close();
  db = null;
}

function getDbPath() {
  return DB_PATH;
}

/**
 * Cleanup expired sessions from the database
 * @returns {Object} Result object with changes count
 */
function cleanupExpiredSessions() {
  const result = db.prepare("DELETE FROM sessions WHERE expires_at < datetime('now')").run();
  console.log(`[cleanup] Purged ${result.changes} expired sessions`);
  return result;
}

module.exports = { getDb, getSetting, setSetting, closeDb, getDbPath, ensureUserDefaultCategories, cleanupExpiredSessions };