use oxigraph::model::{NamedNode, NamedNodeRef, Term, TermRef};
use oxigraph::model::vocab::xsd;
use crate::vocab::rdf;

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

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