catstodon/app/javascript/mastodon/locales/locale-data/README.md

# Custom Locale Data

This folder is used to store custom locale data. These custom locale data are
not yet provided by [Unicode Common Locale Data Repository](http://cldr.unicode.org/development/new-cldr-developers)
and hence not provided in [react-intl/locale-data/*](https://github.com/yahoo/react-intl).

The locale data should support [Locale Data APIs](https://github.com/yahoo/react-intl/wiki/API#locale-data-apis)
of the react-intl library.

It is recommended to start your custom locale data from this sample English
locale data ([*](#plural-rules)):

```javascript
/*eslint eqeqeq: "off"*/
/*eslint no-nested-ternary: "off"*/

export default [
  {
    locale: "en",
    pluralRuleFunction: function(e, a) {
      var n = String(e).split("."),
        l = !n[1],
        o = Number(n[0]) == e,
        t = o && n[0].slice(-1),
        r = o && n[0].slice(-2);
      return a ? 1 == t && 11 != r ? "one" : 2 == t && 12 != r ? "two" : 3 == t && 13 != r ? "few" : "other" : 1 == e && l ? "one" : "other"
    },
    fields: {
      year: {
        displayName: "year",
        relative: {
          0: "this year",
          1: "next year",
          "-1": "last year"
        },
        relativeTime: {
          future: {
            one: "in {0} year",
            other: "in {0} years"
          },
          past: {
            one: "{0} year ago",
            other: "{0} years ago"
          }
        }
      },
      month: {
        displayName: "month",
        relative: {
          0: "this month",
          1: "next month",
          "-1": "last month"
        },
        relativeTime: {
          future: {
            one: "in {0} month",
            other: "in {0} months"
          },
          past: {
            one: "{0} month ago",
            other: "{0} months ago"
          }
        }
      },
      day: {
        displayName: "day",
        relative: {
          0: "today",
          1: "tomorrow",
          "-1": "yesterday"
        },
        relativeTime: {
          future: {
            one: "in {0} day",
            other: "in {0} days"
          },
          past: {
            one: "{0} day ago",
            other: "{0} days ago"
          }
        }
      },
      hour: {
        displayName: "hour",
        relativeTime: {
          future: {
            one: "in {0} hour",
            other: "in {0} hours"
          },
          past: {
            one: "{0} hour ago",
            other: "{0} hours ago"
          }
        }
      },
      minute: {
        displayName: "minute",
        relativeTime: {
          future: {
            one: "in {0} minute",
            other: "in {0} minutes"
          },
          past: {
            one: "{0} minute ago",
            other: "{0} minutes ago"
          }
        }
      },
      second: {
        displayName: "second",
        relative: {
          0: "now"
        },
        relativeTime: {
          future: {
            one: "in {0} second",
            other: "in {0} seconds"
          },
          past: {
            one: "{0} second ago",
            other: "{0} seconds ago"
          }
        }
      }
    }
  }
]

```

## Notes

### Plural Rules

The function `pluralRuleFunction()` should return the key to proper string of
a plural form(s). The purpose of the function is to provide key of translate
strings of correct plural form according. The different forms are described in
[CLDR's Plural Rules][cldr-plural-rules],

[cldr-plural-rules]: http://cldr.unicode.org/index/cldr-spec/plural-rules

#### Quick Overview on CLDR Rules

Let's take English as an example.

When you describe a number, you can be either describe it as:
* Cardinals: 1st, 2nd, 3rd ... 11th, 12th ... 21st, 22nd, 23nd ....
* Ordinals: 1, 2, 3 ...

In any of these cases, the nouns will reflect the number with singular or plural
form. For example:
* in 0 days
* in 1 day
* in 2 days

The `pluralRuleFunction` receives 2 parameters:
* `e`: a string representation of the number. Such as, "`1`", "`2`", "`2.1`".
* `a`: `true` if this is "cardinal" type of description. `false` for ordinal and other case.

#### How you should write `pluralRuleFunction`

The first rule to write pluralRuleFunction is never translate the output string
into your language. [Plural Rules][cldr-plural-rules] specified you should use
these as the return values:

  * "`zero`"
  * "`one`" (singular)
  * "`two`" (dual)
  * "`few`" (paucal)
  * "`many`" (also used for fractions if they have a separate class)
  * "`other`" (required—general plural form—also used if the language only has a single form)

Again, we'll use English as the example here.

Let's read the `return` statement in the pluralRuleFunction above:
```javascript
  return a ? 1 == t && 11 != r ? "one" : 2 == t && 12 != r ? "two" : 3 == t && 13 != r ? "few" : "other" : 1 == e && l ? "one" : "other"
```

This nested ternary is hard to read. It basically means:
```javascript
// e: the number variable to examine
// a: "true" if cardinals
// l: "true" if the variable e has nothin after decimal mark (e.g. "1.0" would be false)
// o: "true" if the variable e is an integer
// t: the "ones" of the number. e.g. "3" for number "9123"
// r: the "ones" and "tens" of the number. e.g. "23" for number "9123"
if (a == true) {
  if (t == 1 && r != 11) {
    return "one"; // i.e. 1st, 21st, 101st, 121st ...
  } else if (t == 2 && r != 12) {
    return "two"; // i.e. 2nd, 22nd, 102nd, 122nd ...
  } else if (t == 3 && r != 13) {
    return "few"; // i.e. 3rd, 23rd, 103rd, 123rd ...
  } else {
    return "other"; // i.e. 4th, 11th, 12th, 24th ...
  }
} else {
  if (e == 1 && l) {
    return "one"; // i.e. 1 day
  } else {
    return "other"; // i.e. 0 days, 2 days, 3 days
  }
}
```

If your language, like French, do not have complicated cardinal rules, you may
use the French's version of it:
```javascript
function (e, a) {
  return a ? 1 == e ? "one" : "other" : e >= 0 && e < 2 ? "one" : "other";
}
```

If your language, like Chinese, do not have any pluralization rule at all you
may use the Chinese's version of it:
```javascript
function (e, a) {
  return "other";
}
```