# Internationalization

Internationalization in NocoBase is implemented based on [i18next](https://npmjs.com/package/i18next).

## How to register a multilingual package?

```ts
export class MyPlugin extends Plugin {
  load() {
    this.app.i18n.addResources('zh-CN', 'test', {
      Hello: '你好',
      World: '世界',
    });
    this.app.i18n.addResources('en-US', 'test', {
      Hello: 'Hello',
      World: 'World',
    });
  }
}
```

## Two i18n instances

### app.i18n

Global i18n instance, typically used in the CLI.

```ts
app.i18n.t('World') // "世界" or "World"
```

### ctx.i18n

CloneInstance of global i18n with a completely independent context for each request, typically used to respond to multilingual messages based on the client language.

```ts
app.use(async (ctx, next) => {
  ctx.body = `${ctx.i18n.t('Hello')} ${ctx.i18n.t('World')}`;
  await next();
});
```

The client request parameters can be placed in the query string

```bash
GET /?locale=en-US HTTP/1.1
Host: localhost:13000
```

or in the request headers

```bash
GET / HTTP/1.1
Host: localhost:13000
X-Locale: en-US
```

## Suggested configuration

With English text as the key and translation as the value, this has the advantage that even if multiple languages are missing, it will be displayed in English and will not cause reading barriers, e.g.

```ts
i18n.addResources('zh-CN', 'your-namespace', {
  'Show dialog': '显示对话框',
  'Hide dialog': '隐藏对话框'
});
```

To make it easier to manage multilingual files, it is recommended to create a `locale` folder in the plugin and place all the corresponding language files in it: 

```bash
|- /my-plugin
  |- /src
    |- /server
      |- locale # Multi-language folder
        |- en-cn.ts
        |- en-US.ts
```

## Example

### Server-side error alert

For example, when a user places an order for a product in the store, if the product is not in stock, or not on the shelf, then the order interface should return the appropriate error when it is called.

```ts
const namespace = 'shop';

export default class ShopPlugin extends Plugin {
  async load() {
    this.app.i18n.addResources('zh-CN', namespace, {
      'No such product': '商品不存在',
      'Product not on sale': '商品已下架',
      'Out of stock': '库存不足',
    });

    this.app.resource({
      name: 'orders',
      actions: {
        async create(ctx, next) {
          const productRepo = ctx.db.getRepository('products');
          const product = await productRepo.findOne({
            filterByTk: ctx.action.params.values.productId
          productId });

          if (!product) {
            return ctx.throw(404, ctx.t('No such product'));
          }

          if (!product.enabled) {
            return ctx.throw(400, ctx.t('Product not on sale'));
          }

          if (!product.inventory) {
            return ctx.throw(400, ctx.t('Out of stock'));
          }

          const orderRepo = ctx.db.getRepository('orders');
          ctx.body = await orderRepo.create({
            values: {
              productId: product.id,
              quantity: 1,
              totalPrice: product.price,
              userId: ctx.state.currentUser.id
            }
          });

          next();
        }
      }
    });
  }
}
```