Function context_get_variable

src/navigate.rs:265–311

FIX: think of a better place to put this, and maybe a better interface

(context: &Context<'c>, var_name: &str, mathml: Element<'c>)

// FIX: think of a better place to put this, and maybe a better interface
pub fn context_get_variable<'c>(context: &Context<'c>, var_name: &str, mathml: Element<'c>) -> Result<(Option<String>, Option<f64>)> {
    // First return tuple value is string-value (if string, bool, or single node) or None
    // Second return tuple value is f64 if variable is a number or None
    // This is ridiculously complicated for what in the end is a hashmap lookup
    // There isn't an API that lets us get at the value, so we have to setup/build/evaluate an xpath
    // Note: mathml can be any node. It isn't really used but some Element needs to be part of Evaluate() 
    let factory = Factory::new();
    match factory.build(&("$".to_string() + var_name)) {
        Err(_) => bail!("Could not compile XPath for variable: {}", var_name),
        Ok(xpath) => match xpath.unwrap().evaluate(context, mathml) {
            Ok(val) => return Ok( match val {
                Value::String(s) => (Some(s), None),
                Value::Number(f) => (None, Some(f)),
                Value::Boolean(b) => (Some(format!("{}", b)), None),
                Value::Nodeset(nodes) => {
                    if nodes.size() == 1 {
                        if let Some(attr) = nodes.document_order_first().unwrap().attribute() {
                            return Ok( (Some(attr.value().to_string()), None) );
                        }
                    };
                    let mut error_message = format!("Variable '{}' set somewhere in navigate.yaml is nodeset and not an attribute: ", var_name);
                    if nodes.size() == 0 {
                        error_message += &format!("0 nodes (false) -- {} set to non-existent (following?/preceding?) node", var_name);
                    } else {
                        let singular = nodes.size()==1;
                        error_message += &format!("{} node{}. {}:",
                                nodes.size(),
                                if singular {""} else {"s"},
                                if singular {"Node is"} else {"Nodes are"});
                        nodes.document_order()
                            .iter()
                            .enumerate()
                            .for_each(|(i, node)| {
                                match node {
                                    sxd_xpath::nodeset::Node::Element(mathml) =>
                                        error_message += &format!("#{}:\n{}",i, mml_to_string(mathml)),
                                    _ => error_message += &format!("'{:?}'", node),
                                }   
                            })    
                    };
                    bail!(error_message);
                },
            } ),
            Err(_) => bail!("Could not find value for navigation variable '{}'", var_name),
        }
    }
}

/// Given a key code along with the modifier keys, the current node is moved accordingly (or value reported in some cases).]
/// The spoken text for the new current node is returned.