# Translating

OHIF supports internationalization using [i18next](https://www.i18next.com/)
through the npm package [@ohif/i18n](https://www.npmjs.com/package/@ohif/i18n),
where is the main instance of i18n containing several languages and tools.

### Installing

```bash
yarn add @ohif/i18n

# OR

npm install --save @ohif/i18n
```

### How it works

After installing `@ohif/i18n` npm package, the translation function
[t](https://www.i18next.com/overview/api#t) can be used [with](#with-react) or
[without](#without-react) React.

A translation will occur every time a text match happens in a
[t](https://www.i18next.com/overview/api#t) function.

The [t](https://www.i18next.com/overview/api#t) function is responsible for
getting translations using all the power of i18next.

E.g.

Before:

```html
<div>my translated text</div>
```

After:

```html
<div>{t('my translated text')}</div>
```

If the translation.json file contains a key that matches the HTML content e.g.
`my translated text`, it will be replaced automatically by the
[t](https://www.i18next.com/overview/api#t) function.

---

#### With React

This section will introduce you to [react-i18next](https://react.i18next.com/)
basics and show how to implement the [t](https://www.i18next.com/overview/api#t)
function easily.

##### Using HOCs

In most cases we used
[High Order Components](https://react.i18next.com/latest/withtranslation-hoc) to
share the `t` function among OHIF's components.

E.g.

```js
import React from 'react';
import { withTranslation } from '@ohif/i18n';

function MyComponent({ t, i18n }) {
  return <p>{t('my translated text')}</p>;
}

export default withTranslation('MyNameSpace')(MyComponent);
```

> Important: if you are using React outside the OHIF Viewer, check the
> [I18nextProvider](#using-outside-of-ohif-viewer) section, `withTranslation`
> HOC doesnt works without a I18nextProvider

##### Using Hooks

Also, it's possible to get the `t` tool using
[React Hooks](https://react.i18next.com/latest/usetranslation-hook), but it
requires at least React > 16.8 😉

#### Using outside of OHIF viewer

OHIF Viewer already sets a main
[I18nextProvider](https://react.i18next.com/latest/i18nextprovider) connected to
the shared i18n instance from `@ohif/i18n`, all extensions inside OHIF Viewer
will share this same provider at the end, you don't need to set new providers at all.

But, if you need to use it completely outside of OHIF viewer, you can set the
I18nextProvider this way:

```js
import i18n, { I18nextProvider } from '@ohif/i18n';
import App from './App';

<I18nextProvider i18n={i18n}>
  <App />
</I18nextProvider>;
```

After setting `I18nextProvider` in your React App, all translations from
`@ohif/i18n` should be available following the basic [With React](#with-react) usage.

---

#### Without React

When needed, you can also use available translations _without React_.

E.g.

```js
import { t } from '@ohif/i18n';
console.log(t('my translated text'));
console.log(t('$t(Common:Play) my translated text'));
```

---

# Main Concepts While Translating

## - Namespaces

Namespaces are being used to organize translations in smaller portions, combined
semantically or by use. Each `.json` file inside `@ohif/i18n` npm package
becomes a new namespace automatically.

- Buttons: All buttons translations
- CineDialog: Translations for the toll tips inside the Cine Player Dialog
- Common: all common jargons that can be reused like `t('$t(common:image)')`
- Header: translations related to OHIF's Header Top Bar
- MeasurementTable - Translations for the react-viewerbase Measurement Table
- UserPreferencesModal - Translations for the react-viewerbase Preferences Modal

### How to use another NameSpace inside the current NameSpace?
i18next provides a parsing feature able to get translations strings from any NameSpace,
 like this following example getting data from `Common` NameSpace:
```
$t(Common:Reset)
```

## - Extending Languages in @ohif/i18n

Sometimes, even using the same language, some nouns or jargons can change according to 
the country, states or even from Hospital to Hospital. 

In this cases, you don't need to set an entire language again, you can extend languages creating a new folder inside a pre existent language folder and @ohif/i18n will do the hard work.

This new folder must to be called with a double character name, like the `UK` in the following file tree:

```bash
 |-- src
    |-- locales
        |-- en
            |-- Buttons.json
            | UK
               |-- Buttons.js
            | US
               |-- Buttons.js
  ...
```

All properties inside a Namespace will be merged in the new sub language, e.g `en-US` and `en-UK` will merge the props with `en`.

This feature is based on i18next's fallback languages tool.

### - Extending languages dynamically

Once you have access to the i18n instance, you can use the 
[addResourceBundle](https://www.i18next.com/how-to/add-or-load-translations#add-after-init)
method to add and change language resources.

E.g.

```js
import { i18n } from '@ohif/i18n';
i18next.addResourceBundle('pt-BR', 'Buttons', {
  Angle: 'Ângulo',
});
```

---

### How to set a whole new language

To set a brand new language you can do it in two different ways:

- Opening a pull request for `@ohif/i18n` and sharing the translation with the
  community. 😍 Please see [Contributing](#contributing-with-new-languages) section
  for further information.
  
- Setting it only in your project or extension:

You'll need a folder structure like the following, which you can load using the `node context` and send it to `addLocales` method.

Folder structure:
```bash
 |-- ...
 |-- src
    |-- locales
        |-- en
            |-- Buttons.json
        |-- es
            | CO
               |-- Buttons.js
            |-- Buttons.json
  ...
```

E.g. of `addLocales` usage
```js
import { addLocales } from '@ohif/i18n';

const localesPath = './locales';
const context = require.context(localesPath, true, /\.json$/);
addLocales(context);
```

Also, [i18next](https://www.i18next.com/how-to/add-or-load-translations#add-after-init) provides a few methods to deal with languages, you have access to it's instance importing the default of @ohif/i18n;
Fell fre to play around with i18next like this:

```
import i18next from '@ohif/i18n';

i18next.addResourceBundle('en', 'namespace1', {
  key: 'hello from namespace 1'
});
   
```

---

## language Detections
@ohif/i18n uses [i18next-browser-languageDetector](https://github.com/i18next/i18next-browser-languageDetector) to manage detections, also exports a method called initI18n that accepts a new detector config as parameter.

### Changing the language
OHIF Viewer accepts a query param called `lng` in the url to change the language.

E.g. 
```
https://docs.ohif.org/demo/?lng=es-MX
```

### Language Persistence
The user's language preference is kept automatically by the detector and stored at a cookie called 'i18next', and in a localstorage key called 'i18nextLng'. 
These names can be changed with a new [Detector Config](https://github.com/i18next/i18next-browser-languageDetector).


## Debugging translations

There is an environment variable responsible for debugging the translations, called `REACT_APP_I18N_DEBUG`.

Run the project as following to get full debug information:

```bash
REACT_APP_I18N_DEBUG=true yarn run dev
```

### Contributing with new languages

Contributions of any kind are welcome! Please check the
[instructions](https://docs.ohif.org/contributing.html).
