tools/publish/src/rdf/conversion.rs

use oxigraph::model::{NamedNode, Quad, Term};
use oxigraph::model::vocab::{rdf, xsd};
use oxilangtag::LanguageTag;

pub fn quad_into_term(quad: Quad) -> Term {
    quad.object
}

pub fn term_to_named_node(term: &Term) -> Option<&NamedNode> {
    if let Term::NamedNode(node) = term {
        Some(node)
    } else {
        None
    }
}

pub fn term_into_string(term: Term) -> Option<String> {
    term_as_str(&term).map(String::from)
}

pub fn term_as_str(term: &Term) -> Option<&str> {
    if let Term::Literal(literal) = term {
        match literal.datatype() {
            xsd::STRING | xsd::NORMALIZED_STRING | rdf::LANG_STRING | rdf::DIR_LANG_STRING => {
                Some(literal.value())
            }
            _ => None,
        }
    } else {
        None
    }
}

/*pub fn term_to_tagged_string(term: &Term) -> Option<(String, Option<LanguageTag<String>>)> {
    term_as_str(&term).and_then(|value| {
        if let Term::Literal(literal) = term {
            literal.language()
                .map(|language| {
                    let tag = LanguageTag::parse(language.to_string()).ok();
                    (value.to_string(), tag)
                })
        } else { None }
    })
}*/

pub fn term_to_boolean(term: &Term) -> Option<bool> {
    if let Term::Literal(literal) = term {
        if literal.datatype() == xsd::BOOLEAN {
            literal.value().parse().ok()
        } else {
            None
        }
    } else {
        None
    }
}

pub fn term_to_u64(term: &Term) -> Option<u64> {
    if let Term::Literal(literal) = term &&
        (literal.datatype() == xsd::NON_NEGATIVE_INTEGER || literal.datatype() == xsd::INTEGER) {
        let value: u64 = literal.value().parse().expect("Failed to parse u64 from ontology. It ought to be a non-negative integer.");
        Some(value)
    } else { None }
}