## Source Code

### Backend

TODO

### Frontend

TODO

## Add translation

### Translation file

All translation files are in `packages/*/locale` directory. Those files are in yaml format. You can add a new language by creating a new file with the language id as the file name. For example, if you want to add a new language `ko_KR`, you can create a new file or edit the existing `packages/*/locale/ko_KR.yml` (not `ko-KR.yaml`), in the following format (all comments should be removed): 

```yaml
# packages/*/locale/ko_KR.yml
__id: ko_KR # If you are creating a new language, besure to add this language meta
__langname: 한국어 # Language name in the language itself
key1: value1 # translations
key2: value2
```

Please sort all keys in alphabetical order, ascending. If you are using vscode, you can select all file by Ctrl+A, then use Ctrl-Shift-P to open command palette, and use `sortLinesAscending` action.

Translation for each file should be put into each module seperately. Do not mix them together.

Currently we only accept translations from native speaker. **DO NOT USE MACHINE TRANSLATION.**

### Translation string

Substitution is supported in translation strings (both array-style and object-style).
Key and value should be quoted only when needed.

```yaml
Welcome to {0}, {1}: '{0} 오신 것을 환영합니다, {1}' # array style
Welcome to {place}, {name}: '{place} 오신 것을 환영합니다, {name}' # object style
```

Those translation strings will be used in the following format:

```js
// For backend (in template):
_('Welcome to {0}, {1}').format(place, name)
_('Welcome to {place}, {name}').format({ name, place })

// For backend (in code):
i18n('Welcome to {0}, {1}').format(place, name);
i18n('Welcome to {place}, {name}').format({ place, name });

// For frontend:
substitute(i18n('Welcome to {0}, {1}'), [place, name]);
substitute(i18n('Welcome to {place}, {name}'), { place, name });
```

### Fallback logic

Assume user's language is `ko_KR`. If there is no `ko_KR.yml` file, it will fallback to `ko.yml`. If there is no `ko.yml` file, it will fallback to `en.yml`. If there is no `en.yml` file, it will fallback to the key.