# tongue_tied
[](https://hex.pm/packages/tongue_tied)
[](https://hexdocs.pm/tongue_tied/)
A robust BCP47 language tag parser for Gleam. Parse and validate language tags according to RFC 5646 (BCP47) specification.
The test suite was copied from https://github.com/wooorm/bcp-47 (MIT licensed)
```sh
gleam add tongue_tied
```
## Usage
```gleam
import tongue_tied
pub fn main() -> Nil {
// Parse a simple language tag
let assert Ok(tag) = tongue_tied.parse_language_tag("en-US")
// Returns: LangTag(language: "en", script: None, region: Some("us"), variants: [], extensions: [], privateuse: None)
// Parse a complex language tag with script and variants
let assert Ok(complex) = tongue_tied.parse_language_tag("zh-Hant-HK")
// Returns: LangTag(language: "zh", script: Some("hant"), region: Some("hk"), variants: [], extensions: [], privateuse: None)
// Parse grandfathered tags
let assert Ok(grandfathered) = tongue_tied.parse_language_tag("i-klingon")
// Returns: Grandfathered("i-klingon")
// Parse private use tags
let assert Ok(private) = tongue_tied.parse_language_tag("x-custom-lang")
// Returns: PrivateUse("x-custom-lang")
}
```
## Features
- **Complete BCP47 Support**: Handles all language tag components including:
- Primary language subtags (2-8 letters)
- Extended language subtags
- Script codes (4 letters)
- Region codes (2 letters or 3 digits)
- Variant subtags
- Extension subtags
- Private use subtags
- **Grandfathered Tags**: Full support for both regular and irregular grandfathered tags like `i-klingon`, `en-GB-oed`, `zh-min-nan`
- **Private Use Tags**: Handles private use language tags starting with `x-`
- **Case Normalization**: Automatically normalizes case according to BCP47 conventions (lowercase language/region, title-case script)
- **Robust Parsing**: Comprehensive error handling and validation
## Language Tag Components
The parser returns different types based on the tag structure:
### `LangTag`
For well-formed language tags:
```gleam
LangTag(
language: String, // Required: "en", "zh-cmn", etc.
script: Option(String), // Optional: "Latn", "Hant", etc.
region: Option(String), // Optional: "US", "419", etc.
variants: List(String), // Optional: ["1901", "arevela"]
extensions: List(Extension), // Optional: Unicode/other extensions
privateuse: Option(String) // Optional: private use subtags
)
```
### `Grandfathered`
For grandfathered tags:
```gleam
Grandfathered(String) // "i-klingon", "en-GB-oed", etc.
```
### `PrivateUse`
For private use tags:
```gleam
PrivateUse(String) // "x-whatever", "x-custom-123"
```
## Examples
### Basic Language Tags
```gleam
// Simple language
tongue_tied.parse_language_tag("en")
// -> Ok(LangTag(language: "en", ...))
// Language with region
tongue_tied.parse_language_tag("fr-CA")
// -> Ok(LangTag(language: "fr", region: Some("ca"), ...))
// Language with script
tongue_tied.parse_language_tag("zh-Hant")
// -> Ok(LangTag(language: "zh", script: Some("hant"), ...))
```
### Extended Language Subtags
```gleam
// Chinese with Mandarin variant
tongue_tied.parse_language_tag("zh-cmn-Hans-CN")
// -> Ok(LangTag(language: "zh-cmn", script: Some("hans"), region: Some("cn"), ...))
```
### Variants and Extensions
```gleam
// German with historical variant
tongue_tied.parse_language_tag("de-CH-1901")
// -> Ok(LangTag(language: "de", region: Some("ch"), variants: ["1901"], ...))
// English with Unicode extension
tongue_tied.parse_language_tag("en-US-u-islamcal")
// -> Ok(LangTag(language: "en", region: Some("us"), extensions: [Extension(singleton: "u", subtags: ["islamcal"])], ...))
```
### Grandfathered and Private Use
```gleam
// Irregular grandfathered tag
tongue_tied.parse_language_tag("i-navajo")
// -> Ok(Grandfathered("i-navajo"))
// Private use tag
tongue_tied.parse_language_tag("x-my-custom-language")
// -> Ok(PrivateUse("x-my-custom-language"))
```
Further documentation can be found at <https://hexdocs.pm/tongue_tied>.
## Development
```sh
gleam run # Run the project
gleam test --target erlang # Run the tests
gleam test --target javascript # Run the tests
```
