import type { Database } from "bun:sqlite";

function tableExists(sqlite: Database, tableName: string) {
  return Boolean(sqlite.query("SELECT name FROM sqlite_master WHERE type = 'table' AND name = ?").get(tableName));
}

function columnExists(sqlite: Database, tableName: string, columnName: string) {
  if (!tableExists(sqlite, tableName)) {
    return false;
  }

  return sqlite
    .query(`PRAGMA table_info(${tableName})`)
    .all() 
    .some((column) => typeof column === "object" && column !== null && "name" in column && column.name === columnName);
}

function resetLegacySchema(sqlite: Database) {
  sqlite.exec(`
    PRAGMA foreign_keys = OFF;
    DROP TABLE IF EXISTS sessions;
    DROP TABLE IF EXISTS audit_events;
    DROP TABLE IF EXISTS refunds;
    DROP TABLE IF EXISTS order_items;
    DROP TABLE IF EXISTS orders;
    DROP TABLE IF EXISTS inventory;
    DROP TABLE IF EXISTS products;
    DROP TABLE IF EXISTS addresses;
    DROP TABLE IF EXISTS users;
    DROP TABLE IF EXISTS customers;
    DROP TABLE IF EXISTS employees;
    PRAGMA foreign_keys = ON;
  `);
}

function needsLegacyReset(sqlite: Database) {
  return tableExists(sqlite, "customers") || tableExists(sqlite, "employees") || columnExists(sqlite, "audit_events", "employee_id");
}

export function initializeDatabase(sqlite: Database) {
  if (needsLegacyReset(sqlite)) {
    resetLegacySchema(sqlite);
  }

  sqlite.exec(`
    PRAGMA foreign_keys = ON;

    CREATE TABLE IF NOT EXISTS users (
      id TEXT PRIMARY KEY,
      username TEXT NOT NULL UNIQUE,
      name TEXT NOT NULL,
      email TEXT NOT NULL UNIQUE,
      role TEXT NOT NULL,
      created_at TEXT NOT NULL
    );

    CREATE TABLE IF NOT EXISTS sessions (
      id TEXT PRIMARY KEY,
      user_id TEXT NOT NULL REFERENCES users(id),
      created_at TEXT NOT NULL,
      expires_at TEXT NOT NULL
    );

    CREATE TABLE IF NOT EXISTS addresses (
      id TEXT PRIMARY KEY,
      full_name TEXT NOT NULL,
      line_1 TEXT NOT NULL,
      line_2 TEXT,
      city TEXT NOT NULL,
      state TEXT NOT NULL,
      postal_code TEXT NOT NULL,
      country TEXT NOT NULL
    );

    CREATE TABLE IF NOT EXISTS products (
      id TEXT PRIMARY KEY,
      sku TEXT NOT NULL UNIQUE,
      name TEXT NOT NULL,
      price_cents INTEGER NOT NULL
    );

    CREATE TABLE IF NOT EXISTS inventory (
      product_id TEXT PRIMARY KEY REFERENCES products(id),
      available_quantity INTEGER NOT NULL
    );

    CREATE TABLE IF NOT EXISTS orders (
      id TEXT PRIMARY KEY,
      order_number TEXT NOT NULL UNIQUE,
      customer_id TEXT NOT NULL REFERENCES users(id),
      shipping_address_id TEXT NOT NULL REFERENCES addresses(id),
      status TEXT NOT NULL,
      notes TEXT,
      created_at TEXT NOT NULL,
      updated_at TEXT NOT NULL
    );

    CREATE TABLE IF NOT EXISTS order_items (
      id TEXT PRIMARY KEY,
      order_id TEXT NOT NULL REFERENCES orders(id),
      product_id TEXT NOT NULL REFERENCES products(id),
      quantity INTEGER NOT NULL,
      unit_price_cents INTEGER NOT NULL
    );

    CREATE TABLE IF NOT EXISTS refunds (
      id TEXT PRIMARY KEY,
      order_id TEXT NOT NULL REFERENCES orders(id),
      amount_cents INTEGER NOT NULL,
      reason TEXT NOT NULL,
      created_at TEXT NOT NULL
    );

    CREATE TABLE IF NOT EXISTS audit_events (
      id TEXT PRIMARY KEY,
      order_id TEXT NOT NULL REFERENCES orders(id),
      actor TEXT NOT NULL,
      type TEXT NOT NULL,
      message TEXT NOT NULL,
      created_at TEXT NOT NULL
    );
  `);

  if (!columnExists(sqlite, "orders", "notes")) {
    sqlite.exec("ALTER TABLE orders ADD COLUMN notes TEXT");
  }
}