languagetag.rs

#![feature(plugin)]
#![plugin(regex_macros)]
extern crate regex;
use regex::Regex;

const LANGUAGE_TAG_REGEX: Regex = regex!(r"(?ix)
(?P<language>[:alpha:]{2,3}(-(?P<extlang>[:alpha:]{3}(-[:alpha:]{3}){0,2}))?)
(?P<script>-[:alpha:]{4})?
(?P<region>-([:alpha:]{2}|[:digit:]{3}))?
(?P<variant>-([:alnum:]{5,8}|[:digit:][:alnum:]{3}))*
(?P<extension>-(?P<singleton>[0-9a-wy-z])(-[:alnum:]{2,8})+)*
(?P<privateuse>-x(-[:alnum:]{1,8})+)?
");
// produces compiler error:
// src/languagetag.rs:8:35: 15:3 error: constants cannot refer to other statics, insert an intermediate constant instead [E0013]
// src/languagetag.rs: 8 const LANGUAGE_TAG_REGEX: Regex = regex!(r"(?ix)
// src/languagetag.rs: 9 (?P<language>[:alpha:]{2,3}(-(?P<extlang>[:alpha:]{3}(-[:alpha:]{3}){0,2}))?)
// ..

///////////
// const LANGUAGE_TAG_RE: &'static strt = r"(?ix)
// (?P<language>[:alpha:]{2,3}(-(?P<extlang>[:alpha:]{3}(-[:alpha:]{3}){0,2}))?)
// (?P<script>-[:alpha:]{4})?
// (?P<region>-([:alpha:]{2}|[:digit:]{3}))?
// (?P<variant>-([:alnum:]{5,8}|[:digit:][:alnum:]{3}))*
// (?P<extension>-(?P<singleton>[0-9a-wy-z])(-[:alnum:]{2,8})+)*
// (?P<privateuse>-x(-[:alnum:]{1,8})+)?
// ";
// const RE: Regex = regex!(LANGUAGE_TAG_RE);
// produces compiler error:
// src/languagetag.rs:16:42: 16:54 error: expected string literal but got `LANGUAGE_TAG_RE`
// src/languagetag.rs:16 const LANGUAGE_TAG_REGEX: Regex = regex!(LANGUAGE_TAG_RE);
//                                                                ^~~~~~~~~~~~

pub struct LanguageTag<'a> {
    language: &'a str
}

impl<'a> LanguageTag<'a> {
    pub fn new(lt: &'a str) -> Result<LanguageTag, &'static str> {
        if Self::is_well_formed(lt) {
            Ok(Self::canonicalize(lt))
        } else {
            Err(NOT_WELL_FORMED)
        }
    }

    fn is_well_formed(lt: &'a str) -> bool {
        return LANGUAGE_TAG_REGEX.is_match(lt)
    }

    fn canonicalize(lt: &'a str) -> LanguageTag {
        // stub
        LanguageTag {
            language: lt
        }
    }
}